This document summarizes research on using metallic nanostructures to enhance fluorescence. Specifically, it proposes using "stair-gratings" - nanostructures with corrugations that have an excavated rectangular section to create a stair-like profile. Experiments show that stair-gratings provide higher fluorescence enhancement and narrower emission directionality compared to conventional gratings, covering both the excitation and emission bands of fluorophores. Finite-difference time-domain simulations agree with experimental results, demonstrating the potential of stair-gratings for applications requiring enhanced and directional single-molecule fluorescence.
The document discusses luminescence and phosphorescence spectroscopy. It defines luminescence as light emission from a substance when an electron returns to the ground state from an excited state. Phosphorescence is luminescence from a triplet excited state with a longer lifetime than fluorescence which occurs from a singlet state. The document describes various types of luminescence and provides details on instrumentation, sample preparation, and applications of phosphorescence spectroscopy in different fields such as pharmaceutical, clinical, environmental, and forensic analyses.
The document proposes several ideas for a laparoscopic device that avoids using a port to insert a separate light source. Idea 1 involves using photoluminescence to illuminate instruments through the skin. Idea 2 is to use bioluminescent enzymes inserted through a keyhole that would react and emit light. Idea 3 stores chemiluminescent materials in an elastic material inside the body. Idea 4 uses a magnet to control a light source inserted into the peritoneal cavity. The final idea is a mechanical system with extendable branches containing light sources that can be manipulated during surgery. The goal is to minimize ports and scarring while providing adequate illumination for laparoscopic procedures.
CVB222 UV-vis Absorption and Fluorescence LectureMark Selby
- The document discusses absorption and fluorescence spectroscopy techniques. It covers fundamental concepts like Beer's law, deviations from Beer's law, instrumentation for absorption and fluorescence measurements, and applications like drug and pollutant analysis.
- Key concepts covered include energy level diagrams to explain fluorescence and phosphorescence, factors that influence fluorescence intensity, and examples of fluorescent molecules and how their structure impacts fluorescence properties.
- Applications discussed are determination of carcinogenic polyaromatic hydrocarbons like benzo(a)pyrene and fluorimetric analysis of drugs like quinine and LSD.
3.2 molecular fluorescence and phosphorescence spectroscopyGaneshBhagure2
This document discusses molecular fluorescence and phosphorescence spectroscopy. It begins with an introduction to the principles and terms, explaining that fluorescence occurs when emission takes place within 10-8 seconds of absorption, while phosphorescence occurs after more than 10-8 seconds. The document then covers electronic transitions, factors that affect fluorescence and phosphorescence like temperature, pH, and solvent, and instrumentation including components of fluorimeters.
This document discusses different types of photoluminescence including fluorescence, phosphorescence, and phosphor thermometry. Fluorescence involves light emission from a substance that has absorbed light or electromagnetic radiation at a higher energy level, and re-emits light at a lower energy level. Phosphorescence differs in that the re-emission of light occurs over longer time scales from "forbidden" energy state transitions. Phosphor thermometry uses characteristics of phosphor luminescence emissions like brightness or color that change with temperature for temperature measurement applications. Common phosphors used include zinc sulfide doped with copper or rare earth doped aluminosilicates.
Photoluminescence is light emission from matter after absorbing photons. Following photon absorption, various relaxation processes occur where photons are re-emitted. Photoluminescence can be classified by excitation energy relative to emission energy. Resonant excitation involves equivalent absorption and emission photon energies, while fluorescence involves energy loss so emitted photons have lower energy. Phosphorescence also involves energy loss but through a spin-forbidden transition, making it a slower process. Photoluminescence is used to measure semiconductor purity and disorder.
The document discusses luminescence and phosphorescence spectroscopy. It defines luminescence as light emission from a substance when an electron returns to the ground state from an excited state. Phosphorescence is luminescence from a triplet excited state with a longer lifetime than fluorescence which occurs from a singlet state. The document describes various types of luminescence and provides details on instrumentation, sample preparation, and applications of phosphorescence spectroscopy in different fields such as pharmaceutical, clinical, environmental, and forensic analyses.
The document proposes several ideas for a laparoscopic device that avoids using a port to insert a separate light source. Idea 1 involves using photoluminescence to illuminate instruments through the skin. Idea 2 is to use bioluminescent enzymes inserted through a keyhole that would react and emit light. Idea 3 stores chemiluminescent materials in an elastic material inside the body. Idea 4 uses a magnet to control a light source inserted into the peritoneal cavity. The final idea is a mechanical system with extendable branches containing light sources that can be manipulated during surgery. The goal is to minimize ports and scarring while providing adequate illumination for laparoscopic procedures.
CVB222 UV-vis Absorption and Fluorescence LectureMark Selby
- The document discusses absorption and fluorescence spectroscopy techniques. It covers fundamental concepts like Beer's law, deviations from Beer's law, instrumentation for absorption and fluorescence measurements, and applications like drug and pollutant analysis.
- Key concepts covered include energy level diagrams to explain fluorescence and phosphorescence, factors that influence fluorescence intensity, and examples of fluorescent molecules and how their structure impacts fluorescence properties.
- Applications discussed are determination of carcinogenic polyaromatic hydrocarbons like benzo(a)pyrene and fluorimetric analysis of drugs like quinine and LSD.
3.2 molecular fluorescence and phosphorescence spectroscopyGaneshBhagure2
This document discusses molecular fluorescence and phosphorescence spectroscopy. It begins with an introduction to the principles and terms, explaining that fluorescence occurs when emission takes place within 10-8 seconds of absorption, while phosphorescence occurs after more than 10-8 seconds. The document then covers electronic transitions, factors that affect fluorescence and phosphorescence like temperature, pH, and solvent, and instrumentation including components of fluorimeters.
This document discusses different types of photoluminescence including fluorescence, phosphorescence, and phosphor thermometry. Fluorescence involves light emission from a substance that has absorbed light or electromagnetic radiation at a higher energy level, and re-emits light at a lower energy level. Phosphorescence differs in that the re-emission of light occurs over longer time scales from "forbidden" energy state transitions. Phosphor thermometry uses characteristics of phosphor luminescence emissions like brightness or color that change with temperature for temperature measurement applications. Common phosphors used include zinc sulfide doped with copper or rare earth doped aluminosilicates.
Photoluminescence is light emission from matter after absorbing photons. Following photon absorption, various relaxation processes occur where photons are re-emitted. Photoluminescence can be classified by excitation energy relative to emission energy. Resonant excitation involves equivalent absorption and emission photon energies, while fluorescence involves energy loss so emitted photons have lower energy. Phosphorescence also involves energy loss but through a spin-forbidden transition, making it a slower process. Photoluminescence is used to measure semiconductor purity and disorder.
Fluorescence occurs when a molecule absorbs high-energy electromagnetic radiation, usually UV light, and re-emits it as lower-energy, visible light. The energy difference between the absorbed and emitted photons is released as heat. Fluorescence is found in many materials in nature like certain gems and minerals, and it is used in fluorescent lighting, fluorescence spectroscopy, microscopy, and biomedical applications.
This document discusses fluorimetry and phosphorimetry. It defines them as measurement techniques, with fluorimetry measuring fluorescence intensity at a particular wavelength, and phosphorimetry measuring phosphorescence in conjunction with pulsed radiation. It describes the principles behind photoluminescence, including fluorescence and phosphorescence. Factors affecting these processes and instrumentation used are summarized, including light sources, filters, monochromators, and detectors. Applications in pharmaceutical, clinical, environmental, and entertainment fields are also briefly outlined.
Fluorimetry involves measuring fluorescence intensity at a particular wavelength using a fluorimeter or spectrofluorimeter. Fluorescence occurs when molecules absorb radiation and electrons are excited to a higher energy state. As electrons return to the ground state, they emit radiation. Factors like concentration, pH, and temperature can affect fluorescence intensity. Instrumentation includes a light source, filters/monochromators, sample cells, and detectors. Applications include determining inorganic/organic substances and compounds in pharmaceutical analysis.
This document provides an overview of fluorescence spectroscopy. It begins with a brief introduction to fluorescence as a type of luminescence involving emission of light from electronically excited states. It then discusses the Jablonski diagram, which provides the scientific foundation for fluorescence. Several key characteristics of fluorescence emission are described, including Stokes shift and Kasha's rule. The document outlines some common applications of fluorescence spectroscopy and describes the basic components and operation of fluorescence spectrometers, including light sources, monochromators, and photomultiplier tubes. It concludes by noting that fluorescence intensity can decrease at extremely high sample concentrations due to factors like self-quenching.
The document discusses spectrofluorimetry and luminescence spectroscopy. It defines fluorescence and phosphorescence as types of photoluminescence that occur when a molecule absorbs radiation and then emits light as it relaxes to the ground state. Fluorescence emission occurs from the lowest excited singlet state on a timescale of 10-9 to 10-7 seconds, while phosphorescence emission occurs from the lowest triplet excited state on a longer timescale of 10-6 to 10 seconds. The document also provides examples of applications including the analysis of polyaromatic hydrocarbons like benzo(a)pyrene and fluorimetric drug analysis including the detection of LSD.
Principles and application of fluorescence spectroscopyruthannfrimpong1
Fluorescence spectroscopy is a technique that measures the fluorescence from samples to determine their composition. It involves exciting a sample with light and measuring the wavelengths of the light emitted. The document discusses the principles of fluorescence, the components of fluorescence spectrometers, factors that influence fluorescence measurements, and applications to food analysis like detecting heat treatments of milk and quantifying nutrients. Case studies demonstrate how fluorescence spectra can distinguish between raw and processed milk.
This chapter discusses fluorometry, which uses fluorescence to perform sensitive analyses. Fluorescence occurs when molecules absorb ultraviolet or visible light and emit light of a lower energy as they return to the ground state. Factors that influence fluorescence intensity include concentration, presence of other solutes, pH, temperature, and chemical structure. Fluorometry is compared to spectrophotometry, with fluorometry typically being more sensitive but less specific. Applications of fluorometry to pharmaceutical analysis are discussed, particularly for analyzing drugs and metabolites in biological samples.
This document discusses phosphorescence spectroscopy and provides information about molecular luminescence, including fluorescence and phosphorescence. It describes the basic principles, including how molecules are excited to higher energy states and then emit light as they relax to lower energy states. Singlet and triplet states are defined, along with electronic and vibrational energy levels. Electron transitions like internal conversion, intersystem crossing, and vibrational relaxation are explained. Instrumentation for measuring phosphorescence is also summarized, including components like light sources, monochromators, sample cells, and detectors. Some applications of phosphorescence are mentioned, such as in television screens, pigments, and glow-in-the-dark toys.
Photoluminescence Spectroscopy for studying Electron-Hole pair recombination ...RunjhunDutta
Description of Photoluminescence Spectroscopy: Principle, Instrumentation & Application.
Three research papers have been summarized which lay stress on Photoluminescence Study for Electron-Hole Pair Recombination for characterizing the properties of semiconductors used in Photoelectrochemical Splitting of Water.
This document discusses fluorimetric analysis. It begins with defining fluorescence and the different types of luminescence. Excited electrons return to the ground state and emit photons. Factors affecting fluorescence include the nature of the molecule, substituents, concentration, pH, temperature, and viscosity. Instrumentation includes light sources, filters, monochromators, sample cells, and detectors like photomultiplier tubes. Applications of fluorescence include determining inorganic substances, using fluorescent indicators, organic analysis, pharmaceutical analysis, and liquid chromatography.
This document discusses fluorescence spectroscopy. It defines fluorescence spectroscopy as a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It describes the basic principles of how fluorescence spectroscopy works, including how molecules are excited to higher energy states and then emit photons as they fall to lower energy states. It also outlines the key components of a fluorescence spectroscopy system, including light sources, wavelength selection tools, detectors, and read-out devices. Finally, it discusses some common applications of fluorescence spectroscopy and some limitations.
Fluorescence as a phenomenon is part of a larger family of related luminescent processes in which a susceptible substance absorbs light, only to reemit light (photons) from electronically excited states after a given time.
Photo luminescent processes that are generated through excitation, whether this is via physical, mechanical, or chemical mechanisms, can generally be subdivided into fluorescence and phosphorescence. Absorption of a light quantum (blue) causes an electron to move to a higher energy orbit. After residing in this “excited state” for a particular time, the fluorescence lifetime, the electron falls back to its original orbit and the fluorochrome dissipates the excess energy by emitting a photon (green).
Compounds that display fluorescent properties are generally termed fluorescent probes or dyes. Often ‘fluorochrome’ and ‘fluorophore’ are used interchangeably. The term ‘fluorophore’ refers to fluorochromes that are conjugated covalently or through adsorption to biological macromolecules, such as nucleic acids, lipids, or proteins. Fluorochromes come in different flavors and include organic molecules (dyes), inorganic ions (e.g., lanthanide ions such as Eu, Tb, Yb, etc.)fluorescent proteins (e.g., green fluorescent protein) atoms (such as gaseous mercury in glass light tubes).
Recently, inorganic luminescent semiconducting nanoparticles, quantum dots, have been introduced as labels for biological assays, bio-imaging applications, and theragnostic purposes (the combination of diagnostic and therapeutic modalities in one and the same particle).
Fluorescence microscopy provides an efficient and unique approach to study fixed and living cells because of its versatility, specificity, and high sensitivity.
Fluorescence microscopes can both detect the fluorescence emitted from labeled molecules in biological samples as images or photometric data from which intensities and emission spectra can be deduced. By exploiting the characteristics of fluorescence, various techniques have been developed that enable the visualization and analysis of complex dynamic events in cells, organelles, and sub-organelle components within the biological specimen.
The most common techniques are
Fluorescence recovery after photo bleaching (FRAP)
Fluorescence loss in photo bleaching (FLIP)
Fluorescence localization after photo bleaching (FLAP)
Fluorescence resonance energy transfer (FRET)
Fluorescence spectroscopy involves three main processes: excitation, where a molecule absorbs a photon and reaches an excited state; internal conversion and vibrational relaxation in the excited state; and fluorescence emission, where the molecule returns to the ground state and emits a photon. It has many applications including structural elucidation of molecules, monitoring molecular interactions and conformational changes, and tracking ions and biomolecules in cells. Specifically, intrinsic protein fluorescence relies on tryptophan residues, while extrinsic labels are often used for non-fluorescent compounds. Fluorescence resonance energy transfer (FRET) also allows measuring distances between fluorophores to study biomolecular interactions and conformational dynamics.
This document discusses fluorescence, phosphorescence, and chemiluminescence. It describes the theory behind these processes, including excitation of electrons, re-emission of light, and differences in singlet and triplet states. Diagrams are shown to illustrate energy levels. Various deactivation processes are outlined, and factors that influence fluorescence such as temperature, concentration, and solvent effects are examined. Applications for detecting inorganic ions and biochemical systems are provided, along with examples of fluorescent compounds and their emission wavelengths. Instrumentation for measurement including fluorometers and spectrofluorometers is also detailed.
This document presents an overview of fluorimetry. It discusses that fluorimetry is the measurement of emitted fluorescence light. When certain substances are exposed to light, they emit visible light or radiation, known as fluorescence. Fluorescence occurs immediately after light absorption and stops when the light is removed. Phosphorescence is delayed fluorescence that continues after light removal. Fluorimetry works by exciting substances from their singlet ground state to a singlet excited state, then measuring the wavelength of light emitted as they return to the ground state.
This document provides an overview of fluorimetry. It defines fluorescence as the emission of light from a substance when electrons return to the ground state after absorbing UV or visible light. Factors that affect fluorescence include the nature of the molecule, substituents, concentration, oxygen, pH, and temperature. Fluorimeters contain a light source, filters, sample cells, and detectors such as photomultiplier tubes. Applications of fluorimetry include determining inorganic substances, use in nuclear research and as indicators in titrations. Recent developments include using laser-induced fluorescence for fast environmental virus analysis.
Fluorescent dyes are molecules that absorb light at one wavelength and emit it at a longer wavelength. They are useful for labeling and studying biomolecules. Some common fluorescent dyes include fluorescein, rhodamine, and GFP. Fluorescent dyes have many applications, such as cancer research where they allow over 1500 protein spots to be detected from microdissected tissue, physiological sensing inside deep tissue, monitoring acidified organelles during autophagy, and assessing contamination during drilling operations. The Jablonski diagram illustrates the excited states involved in the fluorescent process.
The document describes a study that developed an inquiry-based approach for undergraduate students to isolate and characterize natural Vibrio fischeri symbionts from the Hawaiian bobtail squid. Each semester, students isolated multiple strains directly from the light organ of a wild-caught squid. Phenotypic assays found variation in bioluminescence responses and motility rates among strains. Genetic sequencing revealed diversity in the luxIR intergenic region. Phylogenetic analysis classified strains into genetically distinct groups. Colonization experiments showed all strains could colonize juvenile squid, though colonization efficiency varied. This inquiry-based approach effectively characterized the phenotypic and genetic diversity of natural V. fischeri symbionts.
This document provides information about bioluminescence. It begins with an acknowledgement and introduction defining bioluminescence. The document then discusses the history of bioluminescence research, how it evolved in different organisms, and how the bioluminescence reaction works on a chemical level. It lists several bioluminescent organisms and describes some uses of bioluminescence in nature for camouflage, attraction, defense, warning, and communication. The document also outlines several modern applications of bioluminescence in fields like biology, medicine, the environment, and industry. It distinguishes between bioluminescence and biofluorescence and briefly describes two recent research papers on biol
Fluorescence occurs when a molecule absorbs high-energy electromagnetic radiation, usually UV light, and re-emits it as lower-energy, visible light. The energy difference between the absorbed and emitted photons is released as heat. Fluorescence is found in many materials in nature like certain gems and minerals, and it is used in fluorescent lighting, fluorescence spectroscopy, microscopy, and biomedical applications.
This document discusses fluorimetry and phosphorimetry. It defines them as measurement techniques, with fluorimetry measuring fluorescence intensity at a particular wavelength, and phosphorimetry measuring phosphorescence in conjunction with pulsed radiation. It describes the principles behind photoluminescence, including fluorescence and phosphorescence. Factors affecting these processes and instrumentation used are summarized, including light sources, filters, monochromators, and detectors. Applications in pharmaceutical, clinical, environmental, and entertainment fields are also briefly outlined.
Fluorimetry involves measuring fluorescence intensity at a particular wavelength using a fluorimeter or spectrofluorimeter. Fluorescence occurs when molecules absorb radiation and electrons are excited to a higher energy state. As electrons return to the ground state, they emit radiation. Factors like concentration, pH, and temperature can affect fluorescence intensity. Instrumentation includes a light source, filters/monochromators, sample cells, and detectors. Applications include determining inorganic/organic substances and compounds in pharmaceutical analysis.
This document provides an overview of fluorescence spectroscopy. It begins with a brief introduction to fluorescence as a type of luminescence involving emission of light from electronically excited states. It then discusses the Jablonski diagram, which provides the scientific foundation for fluorescence. Several key characteristics of fluorescence emission are described, including Stokes shift and Kasha's rule. The document outlines some common applications of fluorescence spectroscopy and describes the basic components and operation of fluorescence spectrometers, including light sources, monochromators, and photomultiplier tubes. It concludes by noting that fluorescence intensity can decrease at extremely high sample concentrations due to factors like self-quenching.
The document discusses spectrofluorimetry and luminescence spectroscopy. It defines fluorescence and phosphorescence as types of photoluminescence that occur when a molecule absorbs radiation and then emits light as it relaxes to the ground state. Fluorescence emission occurs from the lowest excited singlet state on a timescale of 10-9 to 10-7 seconds, while phosphorescence emission occurs from the lowest triplet excited state on a longer timescale of 10-6 to 10 seconds. The document also provides examples of applications including the analysis of polyaromatic hydrocarbons like benzo(a)pyrene and fluorimetric drug analysis including the detection of LSD.
Principles and application of fluorescence spectroscopyruthannfrimpong1
Fluorescence spectroscopy is a technique that measures the fluorescence from samples to determine their composition. It involves exciting a sample with light and measuring the wavelengths of the light emitted. The document discusses the principles of fluorescence, the components of fluorescence spectrometers, factors that influence fluorescence measurements, and applications to food analysis like detecting heat treatments of milk and quantifying nutrients. Case studies demonstrate how fluorescence spectra can distinguish between raw and processed milk.
This chapter discusses fluorometry, which uses fluorescence to perform sensitive analyses. Fluorescence occurs when molecules absorb ultraviolet or visible light and emit light of a lower energy as they return to the ground state. Factors that influence fluorescence intensity include concentration, presence of other solutes, pH, temperature, and chemical structure. Fluorometry is compared to spectrophotometry, with fluorometry typically being more sensitive but less specific. Applications of fluorometry to pharmaceutical analysis are discussed, particularly for analyzing drugs and metabolites in biological samples.
This document discusses phosphorescence spectroscopy and provides information about molecular luminescence, including fluorescence and phosphorescence. It describes the basic principles, including how molecules are excited to higher energy states and then emit light as they relax to lower energy states. Singlet and triplet states are defined, along with electronic and vibrational energy levels. Electron transitions like internal conversion, intersystem crossing, and vibrational relaxation are explained. Instrumentation for measuring phosphorescence is also summarized, including components like light sources, monochromators, sample cells, and detectors. Some applications of phosphorescence are mentioned, such as in television screens, pigments, and glow-in-the-dark toys.
Photoluminescence Spectroscopy for studying Electron-Hole pair recombination ...RunjhunDutta
Description of Photoluminescence Spectroscopy: Principle, Instrumentation & Application.
Three research papers have been summarized which lay stress on Photoluminescence Study for Electron-Hole Pair Recombination for characterizing the properties of semiconductors used in Photoelectrochemical Splitting of Water.
This document discusses fluorimetric analysis. It begins with defining fluorescence and the different types of luminescence. Excited electrons return to the ground state and emit photons. Factors affecting fluorescence include the nature of the molecule, substituents, concentration, pH, temperature, and viscosity. Instrumentation includes light sources, filters, monochromators, sample cells, and detectors like photomultiplier tubes. Applications of fluorescence include determining inorganic substances, using fluorescent indicators, organic analysis, pharmaceutical analysis, and liquid chromatography.
This document discusses fluorescence spectroscopy. It defines fluorescence spectroscopy as a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It describes the basic principles of how fluorescence spectroscopy works, including how molecules are excited to higher energy states and then emit photons as they fall to lower energy states. It also outlines the key components of a fluorescence spectroscopy system, including light sources, wavelength selection tools, detectors, and read-out devices. Finally, it discusses some common applications of fluorescence spectroscopy and some limitations.
Fluorescence as a phenomenon is part of a larger family of related luminescent processes in which a susceptible substance absorbs light, only to reemit light (photons) from electronically excited states after a given time.
Photo luminescent processes that are generated through excitation, whether this is via physical, mechanical, or chemical mechanisms, can generally be subdivided into fluorescence and phosphorescence. Absorption of a light quantum (blue) causes an electron to move to a higher energy orbit. After residing in this “excited state” for a particular time, the fluorescence lifetime, the electron falls back to its original orbit and the fluorochrome dissipates the excess energy by emitting a photon (green).
Compounds that display fluorescent properties are generally termed fluorescent probes or dyes. Often ‘fluorochrome’ and ‘fluorophore’ are used interchangeably. The term ‘fluorophore’ refers to fluorochromes that are conjugated covalently or through adsorption to biological macromolecules, such as nucleic acids, lipids, or proteins. Fluorochromes come in different flavors and include organic molecules (dyes), inorganic ions (e.g., lanthanide ions such as Eu, Tb, Yb, etc.)fluorescent proteins (e.g., green fluorescent protein) atoms (such as gaseous mercury in glass light tubes).
Recently, inorganic luminescent semiconducting nanoparticles, quantum dots, have been introduced as labels for biological assays, bio-imaging applications, and theragnostic purposes (the combination of diagnostic and therapeutic modalities in one and the same particle).
Fluorescence microscopy provides an efficient and unique approach to study fixed and living cells because of its versatility, specificity, and high sensitivity.
Fluorescence microscopes can both detect the fluorescence emitted from labeled molecules in biological samples as images or photometric data from which intensities and emission spectra can be deduced. By exploiting the characteristics of fluorescence, various techniques have been developed that enable the visualization and analysis of complex dynamic events in cells, organelles, and sub-organelle components within the biological specimen.
The most common techniques are
Fluorescence recovery after photo bleaching (FRAP)
Fluorescence loss in photo bleaching (FLIP)
Fluorescence localization after photo bleaching (FLAP)
Fluorescence resonance energy transfer (FRET)
Fluorescence spectroscopy involves three main processes: excitation, where a molecule absorbs a photon and reaches an excited state; internal conversion and vibrational relaxation in the excited state; and fluorescence emission, where the molecule returns to the ground state and emits a photon. It has many applications including structural elucidation of molecules, monitoring molecular interactions and conformational changes, and tracking ions and biomolecules in cells. Specifically, intrinsic protein fluorescence relies on tryptophan residues, while extrinsic labels are often used for non-fluorescent compounds. Fluorescence resonance energy transfer (FRET) also allows measuring distances between fluorophores to study biomolecular interactions and conformational dynamics.
This document discusses fluorescence, phosphorescence, and chemiluminescence. It describes the theory behind these processes, including excitation of electrons, re-emission of light, and differences in singlet and triplet states. Diagrams are shown to illustrate energy levels. Various deactivation processes are outlined, and factors that influence fluorescence such as temperature, concentration, and solvent effects are examined. Applications for detecting inorganic ions and biochemical systems are provided, along with examples of fluorescent compounds and their emission wavelengths. Instrumentation for measurement including fluorometers and spectrofluorometers is also detailed.
This document presents an overview of fluorimetry. It discusses that fluorimetry is the measurement of emitted fluorescence light. When certain substances are exposed to light, they emit visible light or radiation, known as fluorescence. Fluorescence occurs immediately after light absorption and stops when the light is removed. Phosphorescence is delayed fluorescence that continues after light removal. Fluorimetry works by exciting substances from their singlet ground state to a singlet excited state, then measuring the wavelength of light emitted as they return to the ground state.
This document provides an overview of fluorimetry. It defines fluorescence as the emission of light from a substance when electrons return to the ground state after absorbing UV or visible light. Factors that affect fluorescence include the nature of the molecule, substituents, concentration, oxygen, pH, and temperature. Fluorimeters contain a light source, filters, sample cells, and detectors such as photomultiplier tubes. Applications of fluorimetry include determining inorganic substances, use in nuclear research and as indicators in titrations. Recent developments include using laser-induced fluorescence for fast environmental virus analysis.
Fluorescent dyes are molecules that absorb light at one wavelength and emit it at a longer wavelength. They are useful for labeling and studying biomolecules. Some common fluorescent dyes include fluorescein, rhodamine, and GFP. Fluorescent dyes have many applications, such as cancer research where they allow over 1500 protein spots to be detected from microdissected tissue, physiological sensing inside deep tissue, monitoring acidified organelles during autophagy, and assessing contamination during drilling operations. The Jablonski diagram illustrates the excited states involved in the fluorescent process.
The document describes a study that developed an inquiry-based approach for undergraduate students to isolate and characterize natural Vibrio fischeri symbionts from the Hawaiian bobtail squid. Each semester, students isolated multiple strains directly from the light organ of a wild-caught squid. Phenotypic assays found variation in bioluminescence responses and motility rates among strains. Genetic sequencing revealed diversity in the luxIR intergenic region. Phylogenetic analysis classified strains into genetically distinct groups. Colonization experiments showed all strains could colonize juvenile squid, though colonization efficiency varied. This inquiry-based approach effectively characterized the phenotypic and genetic diversity of natural V. fischeri symbionts.
This document provides information about bioluminescence. It begins with an acknowledgement and introduction defining bioluminescence. The document then discusses the history of bioluminescence research, how it evolved in different organisms, and how the bioluminescence reaction works on a chemical level. It lists several bioluminescent organisms and describes some uses of bioluminescence in nature for camouflage, attraction, defense, warning, and communication. The document also outlines several modern applications of bioluminescence in fields like biology, medicine, the environment, and industry. It distinguishes between bioluminescence and biofluorescence and briefly describes two recent research papers on biol
Historically architecture has likened the city as an organism and looked to nature for design inspiration. Until recently the tools that have enabled architects to engage with what R. Buckminster Fuller called the ‘drivers of biology’, have not been available and architects use biological systems in a symbolic way called biological ‘formalism’ where aesthetics are prioritized over function. Recent developments in Synthetic Biology, which were demonstrated at Artificial Life XI suggested it was possible to design and engineer materials that meet the requirements necessary for a new generation of smart materials.
Presentación del evento #BIGTOURISM #WTC2014 @CIBBVA @SEGITTUR en BBVA Innovation Center, el día 13 de Noviembre 2014.
Su Streaming lo puedes ver en: https://www.centrodeinnovacionbbva.com/eventos/evento-big-tourism-we-are-all-tourists-1ajornada
This document summarizes information about the Fortissimo 2 project and its first open call for applications. Fortissimo 2 builds on the previous Fortissimo project to provide SMEs with access to advanced simulation services through an HPC cloud. It aims to establish a marketplace for HPC expertise and services. The first open call seeks new experiments involving modeling of coupled phenomena or high-performance data analytics to benefit manufacturing SMEs. Proposals are due by May 18, 2016 and selected experiments will receive up to €250,000 in funding to participate between November 2016 and April 2018. The call details funding models and evaluation criteria for the proposed experiments.
AWSome Day Barcelona 26 Feb 2015 - Opening Keynotelanfranf
This document outlines the agenda for an AWS conference in Barcelona on February 26, 2015. It begins with acknowledging Intel as the global sponsor and Capside as the training partner. The agenda then lists the schedule of presentations and demos on AWS services from 9:00am to 5:00pm, including introductions, storage, compute, managed services, databases, deployment and management. Breaks are scheduled between sessions. Quotes highlight how enterprises are increasingly adopting cloud computing on AWS for agility, the breadth of AWS platforms, continual innovation, and cost savings. The document concludes by thanking attendees and wishing them to enjoy the conference.
Este documento describe la innovación abierta y sus principios. Explica que la innovación abierta implica que tanto agentes internos como externos a la organización participan en el proceso de innovación. También discute cómo las organizaciones pueden abrir su innovación a proveedores, clientes, centros tecnológicos y otros aliados externos.
Este documento trata sobre la innovación abierta, un nuevo enfoque estratégico donde las empresas cooperan con profesionales externos para innovar. Se define la innovación abierta como un proceso donde las oportunidades de innovación se pueden dar en cada etapa. También se presentan ejemplos de cómo funciona a través de estudios de caso y se discuten los desafíos y beneficios de esta estrategia. Finalmente, se enfatiza la importancia de hacer preguntas correctas para encontrar soluciones innovadoras.
El documento habla sobre la innovación abierta. Define conceptos como dentro-fuera y modelos mentales. Explica que la innovación es un proceso multidisciplinar, incierto y acumulativo. También describe diferentes tipos de innovación como disruptiva y los círculos de causalidad que influyen en los procesos innovadores.
El documento describe cómo la innovación puede lograrse a través del compromiso (engagement). Explica que el compromiso no son solo "me gusta" en Facebook, sino vínculos reales entre personas. Señala tres formas de lograr innovación a través del compromiso: 1) compromiso entre la organización y cada empleado, 2) innovación abierta entre emprendedores, y 3) crowdsourcing entre la organización y miles de personas. El documento argumenta que las personas son el motor de la innovación y que el compromiso es la mejor estrategia para producir innovación.
This document discusses the principles and clinical applications of chemiluminescent assays. Chemiluminescence involves the emission of light from a chemical reaction and can be enhanced through the use of enzymes like horseradish peroxidase. Chemiluminescent assays are commonly used for immunoassays and have higher sensitivity than ELISA or radioimmunoassays. The document outlines the mechanisms and substrates involved in chemiluminescence and lists many clinical applications for measuring markers of thyroid function, tumor progression, anemia, cardiac function, hormone levels, therapeutic drug monitoring, hepatitis, and diabetes.
Diaporama ProgrèS Technique Et Croissance 2007 2008guestf961ba
Ce diaporama présentant les liens entre croissance et déprogrès technique reprend :
1 - le diaporama de T Larribe sur robinson (remarquable comme toujours)
2 - il s'appuie sur des éléments à une diaporama d'HEC
3 Il emprunte des animations à mr Rodriguez
Pression économique sur les coûts, vitesse accélérée, nouvelles frontières, fournisseurs moins pertinents… il semble urgent de reconsidérer les activités de la DSI et de faire évoluer son modèle !
intoduction to lumiscence
introduction and principle of chemilumiscence
different types of lumiscence
detail of the electrochemilumiscence, working, principle, instrumentation, measurin.
application in medical field
difference between chemilumiscence and elecrochemiluminescence
Nanobiosensors use biological components on the nano-scale to detect target molecules. They consist of a bioreceptor element for molecular recognition connected to a transducer that converts the biological response into a measurable signal. Common transduction methods include optical, electrochemical and mechanical. Examples are nanowire field effect sensors that detect binding as a change in electrical conductivity, and cantilever sensors that detect binding as a change in resonant frequency through surface stress. Nanobiosensors show potential for applications in healthcare diagnostics, environmental monitoring, and more.
The document discusses different types of luminescence including bioluminescence used by deep sea organisms. It then describes how luminol is used by crime scene investigators to detect trace amounts of blood, even if cleaning products were used. Finally, it mentions green fluorescent protein (GFP) which was used to win the 2008 Nobel Prize in Chemistry and is now used in medical research to track proteins in diseases like cancer and Alzheimer's.
This document discusses a new design of plasmonic nanoantenna with a slant gap that can enhance optical chirality. The slant gap provides an enhanced electric field parallel to an external magnetic field with a phase delay of π/2, resulting in enhanced optical chirality in the near field. Numerical simulations show this nanoantenna design can generate a near field with enhanced optical chirality when excited by linearly polarized light. This enhanced optical chirality could allow for circular dichroism analysis using linearly polarized light and may find applications in analyzing the chirality of surface-bound matter.
This document summarizes research on using localized surface plasmons generated by gold nanoparticles to optically switch liquid crystals. When gold nanoparticles are excited by laser light at their surface plasmon resonance, they generate strong localized electric fields. These electric fields are able to reversibly switch the orientation of nearby nematic liquid crystals from homeotropic to planar alignment at room temperature with low excitation intensities under 0.03 W/cm^2. The direction of planar alignment can also be controlled by changing the polarization of the excitation light. This provides a new approach for all-optical switching and control of liquid crystals using plasmonic heating and electric fields from gold nanoparticles.
1. The document summarizes Tijmen G. Euser's research activities and publications. As a PhD student, he studied dynamic changes in light propagation in photonic crystals and demonstrated optical switching of photonic band gap crystals.
2. As a postdoc, his research included developing hollow-core photonic crystal fibers for optofluidic microreactors, waveguide-based micromanipulation techniques, and spatial light modulation applications. This work enabled new experiments in fields like photochemistry, microparticle transport, and fiber-based spectroscopy.
3. His publications include over 40 peer-reviewed papers investigating topics like optofluidic reactors, optical trapping and propulsion in fibers, spatial mode control
Graphene plasmonic couple to metallic antennaxingangahu
1. The document proposes a novel nanoantenna configuration using a metallic dipole antenna on top of an insulator layer, with a graphene sheet attached below the insulator.
2. By modifying the chemical potential of the graphene sheet using an applied gate voltage, the dispersion relation and optical conductivity of graphene can be tuned.
3. This allows the in-phase and out-of-phase coupling between the metallic plasmonics and graphene plasmonics to modify characteristics of the metal-graphene nanoantenna like its resonance frequency, near-field and far-field responses.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
Alexandru Marcu - "Faculty of physics, University of Cluj"SEENET-MTP
Prof. Alexandru Marcu presented Faculty of Physics, Babes-Bolyai University, Cluj-Napoca (Romania) at the SEENET-MTP RC & EC meeting held in Timisoara (Romania), November 22, 2014.
Percolation of light through whispering gallery modes in 3D lattices of coupl...Shashaanka Ashili
This document summarizes research on 3D lattices of coupled microspheres with whispering gallery modes (WGMs). Key points:
1) The researchers synthesized 3D lattices of dye-doped fluorescent polystyrene spheres with controlled thickness from one to 43 monolayers using flow-assisted self-assembly.
2) Optical transmission spectra of the lattices showed signatures of coupling between spheres, including WGM peak splitting and anomalously high transmission at peak wavelengths.
3) The observed WGM transport is interpreted using an analogy to percolation theory, where optical "bonds" connect lattice sites depending on size dispersion. Near-perfect lattices could enable resonant sensing and light emission applications
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docxRAHUL126667
Calculation of Optical Properties of Nano Particle
PHYSICS 5535- Optical Properties Matter-Spring 2017
Raznah Yami
Outline
1. Introduction: this part gives a precise overview of the whole paper. It begins by illustrating a brief introduction and importance of Nano Particles and the theoretical approaches used for their calculation.
2. Main idea: this section provides a step-by-step in-depth analysis of recently developed theories the calculation of optical properties of nanoparticles. It also provides calculation and equations employed these approaches.
2.1 Optical Properties of Nanoparticles: this section talks about the basics principles and governing the optical behavior of Nano particles and provides in-depth knowledge of different phenomena observed while dealing with optical properties of Nano particles.
2.2 Mie-Theory: the research provides exhaustive information the study optical properties of nanoparticles using Mie theory. This research focuses on Mie theory for the calculation of optical properties of Nano particle according to which we can calculate the place of surface Plasmon resonance in optical spectra of metallic spherical nanoparticle.
2.3 Discrete Dipole Approximation method: this section enumerates sufficient information about the calculation of absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold Nano spheres, silica-gold Nano shells, and gold Nano rods and we examine the magneto-optical scattering from nanometer-scale structures using a discrete dipole approximation.
3. Conclusion: This section provides a summary of the most important points, which presents an overview of the practical application and calculation methods of optical properties of Nano particles talking about core principles, which therefore explain the behavior exhibited by nanoparticles.
List of figures:
Figure 1: Localized surface Plasmon resonance ,resulting from the collective oscillations of delocalized electrons in response to an external electric field
Figure 2: Absorption spectra of semiconductor nanoparticles of different diameter. Right-nanoparticles suspended in solution.
Figure 3: Comparison of absorbance along increasing wavelength between Nano GaAs (7-15 nm) and Bulk GaAs showing an apparent blue shift
Figure 4: Showing the effect of blue shift because of quantum confinement as the wavelength shifts from 1100 nm to 2000 nm when we move from particle size of 9nm to parcile size of 3 nm.
Figure 5: Emission spectra of several sizes of (Cdse) Zns core-shell quantum dots.
Figure 6: The optical spectra and transmission electron micrographs for the particles in vials 1–5 are also shown. Scale bars in micrographs are all 100 nm
Figure7: Shows the effect of varying relative core and shell thickness of gold Nano Shells, there is an apparent blue shift as the frequency increases
References:
1. . P. S. Per ...
The effects of inter-cavity separation on optical coupling in dielectric bisp...Shashaanka Ashili
The optical coupling between two size-mismatched spheres was studied by using one sphere as a local source of light with whispering gallery modes (WGMs) and detecting the intensity of the light scattered by a second sphere playing the part of a receiver of electromagnetic energy. We developed techniques to control inter-cavity gap sizes between microspheres with ~30nm accuracy. We demonstrate high efficiencies (up to 0.2-0.3) of coupling between two separated cavities with strongly detuned eigenstates. At small separations (<1 μm) between the spheres, the mechanism of coupling is interpreted in terms of the Fano resonance between discrete level (true WGMs excited in a source sphere) and a continuum of “quasi”-WGMs with distorted shape which can be induced in the receiving sphere. At larger separations the spectra detected from the receiving sphere originate from scattering of the radiative modes.
X-ray powder diffraction is a nondestructive technique used to characterize both organic and inorganic materials. It can be used to identify crystal phases, perform quantitative analysis, and determine structural imperfections in samples from fields like geology, polymers, pharmaceuticals, and forensics. In geology specifically, XRD is widely used for quantitative analysis and can identify clay-rich minerals and other fine-grained minerals that are difficult to analyze optically, providing information about mineral composition and properties.
This document proposes using a thin layer of chalcogenide phase change material like Ge2Sb2Te5 to optically tune the EIT-like response of an all-dielectric metasurface. The metasurface consists of silicon nanoresonators that support an EIT-like resonant response at 1550nm when the phase change material is amorphous. Switching the material to crystalline shifts the EIT response to higher wavelengths due to increased losses. This provides a reversible tuning mechanism for the metasurface response with nanosecond laser pulses, allowing dynamic control over transmission and dispersion properties.
This document summarizes several recent research papers on topics related to biophotonics, quantum optics, quantum dots, and plasmonics. It discusses the following key points:
1) Scientists created rings of living cells that act as optically-controlled oscillators for electrical waves, which could store topological bits of information.
2) Researchers experimentally demonstrated that resonance fluorescence is modified using squeezed light, confirming 30-year old predictions.
3) A device was developed that can sort photons by number and polarization using a quantum dot in a microcavity.
4) Improved characterization of silver's optical constants was reported to reduce underestimation of plasmonic loss.
Study of highly broadening Photonic band gaps extension in one-dimensional Me...IOSR Journals
This document discusses the theoretical study of enhancing the reflectance spectra of one-dimensional metallo-organic multilayer photonic structures. It examines structures composed of alternating thin layers of silver and the organic material N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine. The transfer matrix method is used to calculate the reflectance spectra for different configurations of layer thicknesses and incident angles of light. Tuning of the photonic band gap is observed by varying the thickness of either the metal or organic layers. Broadening and shifting of the band edges from ultraviolet to visible and infrared regions occurs due to the optical absorption properties of both the
Tem Crams of Distinctive NLO Material (Second Harmonic Generative Type) Bariu...msejjournal
Single crystals of Barium para nitrophenolate sample has been grown by solution growth method and Microscopic analysis - TEM is carried out for proper internal analysation and given here for reference. The specimen has a special specification of SHG efficiency of more than 16 times than KDP [1] the single XRD data also given here for comparison and analysation of the materials.
TEM CRAMS OF DISTINCTIVE NLO MATERIAL (SECOND HARMONIC GENERATIVE TYPE) BARIU...msejjournal
Single crystals of Barium para nitrophenolate sample has been grown by solution growth method and
Microscopic analysis - TEM is carried out for proper internal analysation and given here for reference.
The specimen has a special specification of SHG efficiency of more than 16 times than KDP [1] the single
XRD data also given here for comparison and analysation of the materials.
X-ray crystallography is a technique used to determine the three-dimensional atomic structure of crystals. X-rays are diffracted by the crystal and the diffraction pattern is collected on a detector. By analyzing the diffraction pattern using Bragg's law and Fourier transforms, scientists can construct electron density maps and refine protein structures at high resolution. Key aspects of X-ray crystallography include generating X-rays, collecting diffraction data, solving protein structures, and refining models using computational methods. This technique has provided atomic level insights into protein structure and been instrumental in numerous scientific discoveries through applications like determining unknown material structures.
Complete Photoproduction Experiments - 12th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, Virginia, USA, 31 May-4 June 2010. AIP Conference Proceedings, October 2011, Vol. 1374, pp. 17-22, ISSN: 0094-243X, doi: 10.1063/1.3647092
di A. D’Angelo, K. Ardashev, C. Bade, O. Bartalini, V. Bellini, M. Blecher, J. P. Bocquet, M. Capogni, A. Caracappa, L. E. Casano, M. Castoldi, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, C. Gibson, B. Girolami, A. Giusa, H. Glu, K. Hicks, S. Hoblit, A. Honig, T. Kageya, M. Khandaker, O. C. Kistner, S. Kizilgul, S. Kucuker, A. Lapikf, A. Lehmann, P. Levi Sandri, A. Lleres, M. Lowry, M. Lucas, J. Mahon, F. Mammoliti, G. Mandaglio, M. Manganaro, L. Miceli, D. Moricciani, A. Mushkarenkovf, V. Nedorezovf, B. Norum, M. Papb, B. Preedom, H. Seyfarthb, C. Randieri, D. Rebreyend, N. Rudnevf, G. Russo, A. Sandorfi, C. Schaerf, M. L. Sperduto, H. Stroher, M. C. Sutera, C. E. Thorn, A. Turingef, V. Vegna, C. S. Whisnanth, K. Wang, X. Wei (2011)
Abstract
The extraction of resonance parameters from meson photo-reaction data is a challenging effort, that would greatly benefit from the availability of several polarization observables, measured for each reaction channel on both proton and neutron targets. In the aim of obtaining such complete experiments, polarized photon beams and targets have been developed at facilities, worldwide. We report on the latest results from the LEGS and GRAAL collaborations, providing single and double polarization measurements on pseudo-scalar meson photo-production from the nucleon.
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1. Introduction
Molecular fluorescence detection has various applications in many fields such as biosensors,
early diagnosis, bioimaging, single photon source and so on [1,2]. However, the low signal to
noise ratio (SNR) limits the detection efficiency of single molecule fluorescence. Thus, how
to control the photoluminescence process, which can be divided into excitation and emission
processes, becomes a main topic in this field. As we know, metallic nanostructures have
novel characteristics, i.e. surface plasmon (SP) and localized surface plasmon (LSP) [3,4],
which can be exploited to modify the photoluminescence process strongly [5–7]. For instance,
metallic nano-apertures are able to confine electromagnetic field within the aperture due to
LSP effect, and the resulted high intensity field can enhance the excitation efficiency. Also,
the nano-apertures have an extra advantage of suppressing background [8–10]. In addition,
plasmonic gratings have attracted many attentions due to their unique SP characteristic. The
plasmonic gratings cannot only enhance specific SP mode but also modify its propagation
direction. For example, plasmonic gratings are able to modify the light transmission from
single nano-aperture [11]. Moreover, the hybrid nanostructure of plasmonic gratings and
nano-aperture have been extensively investigated for single molecule fluorescence
enhancement [12–16]. When the gratings coupling with the nano-aperture, it cannot only
enhance the near-field excitation rate but also it can modify the emission rate and the far-field
radiation pattern of the molecular fluorescence. It is also found that the resonance wavelength
is dependent on their geometry parameters, such as the groove depth and grating period,
which provide a way to optimize the optical response corresponding to specific fluorescence
molecule [17,18]. While conventional plasmonic gratings response effectively only in a
narrow spectral band. Therefore, there is a tradeoff between the excitation and emission
processes when the Stokes shift of the photoluminescence process is relatively large.
Although asymmetric dual-face grating antenna was proposed in theory to control the local
excitation enhancement, the collection efficiency, and the quantum efficiency separately, the
goals to optimize the fluorescence enhancement still remain an open challenge in experiment.
In this study, we demonstrated that the nano-apertures associated with stair-gratings have
high surface enhancement factor and better beaming effect in comparison to the conventional
ones. In contrast to the conventional gratings, we propose to excavate a rectangle part of
corrugations and make the cross profile likes a stair-grating. The schematic of stair-gratings is
shown in Fig. 1 as a hybrid of two gratings with different period or depth. Thus, a new
periodic parameter is introduced into the plasmonic grating, which could increase the optical
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19568
3. response both at the excitation and emission bands simultaneously. In experiment, we used
fluorescence correlation spectroscopy (FCS) to analyze the fluorescence trace and the
fluorescence count rate per molecule. The nano-apertures with stair-gratings truly presented
higher enhancement effect. In addition, the emission angular patterns were measured with the
back focal plane (BFP) imaging method, presenting a narrower directionality for the stair-
gratings. By employing finite-difference time-domain (FDTD), the directional emission
patterns and near-field enhancement were calculated. The numerical simulations are in good
agreement with the experiments. The proposed stair gratings provide a flexible way to control
the enhancement and beaming effect of the molecule fluorescence.
Fig. 1. Schematic of proposed stair-gratings. We excavate a rectangle part of the corrugations
and make it like a stair. There are two new geometry parameters which can use to tune the
optical response. (b) and (c) SEM cross profile of the common grating and stair-grating
separately.
2. Experimental methods
In the experiment, optical measurement methods are set up on an integrated microscopy
system (NTEGRA Spectra, NT-MDT). The schematic of optical setup is shown in Fig. 2(a).
We can measure white light dark-field scattering [19,20], photoluminescence(PL), FCS
[12,21], and fluorescence radiation patterns [22,23] of the same single nano-aperture in situ.
In all measurements, we used an oil-immersion objective lens (N.A. 1.49, 60 × , TIRF,
Olympus). And the angular patterns of the fluorescence emission were obtained with the back
focal plane (BFP) imaging method. A CW laser at wavelength of 632.8 nm was used as the
excitation light with excitation power of ~60 μW. On the other hand, we used Alexa 647 in
the solution with concentration of ~1μM. To prevent from molecular adsorption due to the
local charges, we used phosphate aqueous buffered solution. To prepare the metallic
nanostructures, there are four steps as shown in Fig. 2(c): (1) Deposit Au thin film on the
cover glass by using magnetic sputtering; (2) Use focus ion beam (FIB) to penetrate through
the Au film and etch into the glass to fabricate the corrugations of the gratings; (3) Deposit
Au film again onto the samples in order to fill the corrugations; (4) Fabricate the central nano-
aperture with FIB milling. By using the Pt deposition which is integrated in the FIB system,
we can easily identify the fabricated nanostructure under the SEM. The SEM images of the
common and stair gratings are shown in Figs. 1(b) and 1(c) separately. We find that the
corrugations of the stair-gratings and the common gratings can be fabricated well as expected.
In our experiments: the corrugation groove depth d = 200 nm, width a = 220 nm, the height of
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19569
4. the excavated part d2 = 100 nm, the width of the excavated part a2 = 110, the central aperture
diameter (same with bare aperture) D = 250 nm, there are 5 grooves for both the stair and
common gratings, and Au film thickness H = 300 nm.
Fig. 2. (a) Schematic of optical experiment setup. (b) Optical confocal scanning image of a
sample containing bare apertures, nano-apertures surrounded with common and stair grating.
(c) Fabrication procedure of the nano-apertures with stair-gratings.
3. Results and discussion
First of all, we use the white light dark-field scattering method to characterize the response of
the nanostructures. The results are shown in Fig. 3(a). As we can see, in the range from 625
nm to 675 nm, both the stair-gratings (red line) and the common gratings (blue line) present a
broad resonance. Obviously, the stair-gratings have higher scattering intensity which implies
it has stronger optical response when comparing to the common gratings. Correspondingly,
the Alexa 647 dye molecules used in the present experiment also emits in this range. Thus,
spectral response of the nanostructures covers not only the excitation wavelength of 632.8 nm
but also the emission spectral range of 640 ~700 nm. Figure 3(b) shows the fluorescence
spectra of the molecules being confined within the nano-apertures. The results from three
kinds of nanostructures are compared: bare nano-apertures, nano-apertures with common
gratings, and nano-apertures with stair-gratings. As shown in Fig. 3(b), the nano-apertures
with gratings modify the fluorescent spectral shape slightly when comparing to the
fluorescence spectrum obtained from the dye molecules in free solution (data not shown). At
wavelength ~700 nm, there is a “shoulder” for both the common and stair gratings. This
spectral variation can be due to the strong interaction between the dye molecules and the
nanostructures [10]. The PL spectrum of the dye molecules in free solution is also plotted for
comparison.
In order to obtain normalized fluorescence count rate per molecule, it is necessary to
obtain the average number of the dye molecules in the nano-apertures. In the following, we
measured the fluorescence intensity from single nano-apertures with two avalanche
photodiodes (SPCM-AQRH-16-FC, PerkinElmer) and obtained the FCS curves through
cross-correlation to suppress after-pulsing (correlator.com, US). The results are shown in Fig.
4(a). The FCS curves of three kinds of nanostructures have little difference, which means that
the average number of the molecules is almost the same because the different nanostructures
actually have the same nano-aperture size. Nevertheless, we notice that the result of the bare
aperture has a slightly higher G(0) which probably due to less background noise than the
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19570
5. others. According to three dimensional Brownian diffusion model, we have the formula:
( ) ( )
12
1/221
1 1 1 1 1 /T d
bT d
B
G n exp s
N F
τ τ
τ τ τ
τ τ
−
−
= + − + − + +
[8,10,21], where N is the
total number of molecules, F the total signal, B the background noise, nT the amplitude of the
dark state population, bT the dark state blinking time, τd the mean diffusion time, and s the
ratio of transversal to axial dimensions of the analysis volume. We used this formula to fit the
FCS curves and calculate the average number of molecules. After fitting the curves, we
obtained the fluorescence count rate per molecule. As shown Fig. 4(c), we provide the
averaged count rate and standard deviation in different structures, summarized from three
stair-gratings, four common gratings and four bare apertures. In average, in comparing to the
bare aperture, the stair-gratings can reach 2-fold fluorescence enhancement factor. And the
stair-gratings perform better than common gratings. The stair-gratings have the highest count
rate, i.e. the stair-gratings can still promote 20% of the count rate than the common ones.
Both the count rate of the common gratings and the stair-gratings are much higher than that of
the bare nano-apertures. It implies that the stair-gratings are able to significantly enhance the
fluorescence.
Fig. 3. (a) Scattering spectra of nano-aperture with stair and common gratings. (b)
Fluorescence spectra of the molecules within different nanostructures: stair-gratings, common
gratings and bare aperture. PL spectrum in free solution is also plotted for comparison.
Fig. 4. (a) Fluorescence correlation spectroscopy curves of three different nanostructures. (b)
Normalized representative fluorescence intensity trace, and (c) Normalized fluorescence count
rate per molecule for different structures.
Additionally, it is necessary to discuss the molecular far-field radiation pattern modified
by the different nanostructures, since it is another important factor to determine the collection
efficiency during the surface enhanced fluorescence. Figure 5 shows the fluorescence far-field
radiation patterns with the BFP imaging method, and all images with the same color bar.
Figure 5(a) shows the results of the bare apertures and the distribution of the pattern is
homogeneous. It implies that the molecular radiation within the bare aperture spread in a
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19571
6. broad solid angle. The patterns of the common gratings are shown in Fig. 5(b). As we can see,
the fluorescence signals concentrate more in the center, which means that the common
gratings are able to boost the collection efficiency. Furthermore, as shown in Fig. 5(c), we
find that the fluorescence signals are highly confined in the center when comparing to the
former two nanostructures. These results imply that the stair-gratings can confine the
molecular radiation in a narrower solid angles. We notice that the experimental results above
are based on the use of the high N.A. objective (N.A. = 1.49) which can collect the
fluorescence signal very efficiently. Hence, we can obtain a higher enhancement factor if we
use an air objective to replace the oil immersion objective.
Fig. 5. Molecular radiation patterns from different structures (a) Bare nano-aperture (b) Nano-
aperture with common gratings (c) Nano-aperture with stair-gratings.
Fig. 6. Simulated far-field radiation patterns at different wavelengths for (a) Bare nano-
aperture (b) Nano-aperture with common gratings (c) Nano-aperture with stair-gratings, and
near-field intensity enhancement indicated in each top-right corner correspondingly.
Furthermore, we employed the FDTD method to simulate the phenomena qualitatively
[24]. In our simulations: the corrugations height d = 200 nm, width a = 220 nm, the height of
the excavated part d2 = 100 nm, the width of the excavated part a2 = 110, the central aperture
diameter (same with bare aperture) D = 250 nm, Au film thickness H = 300 nm. For the
wavelength from 633 nm to 672 nm, we calculated the near-field enhancement factor within
the nano-apertures and the far-field radiation patterns. It should be note that we only present
the results for the dipole is parallel to the Au film, because such orientation is dominated over
the perpendicular ones. For instance, the power radiative of parallel dipole is about two order
of magnitudes higher than the perpendicular one. As shown in Fig. 6(b), the common gratings
perform well at the wavelength of 633 nm, but the efficiency of the common gratings
decrease for longer wavelength significantly. It is due to the width of the spectral response is
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19572
7. narrower. In contrast, as shown in Fig. 6(c), the stair-gratings perform well at the wavelength
of 633 nm. And the performance of the stair-gratings at wavelength of 650 ~670 nm are still
good enough for good beaming effect although the excitation enhancement factor is lower
slightly. These simulation results are in good agreement with the experiments, i.e. the stairs-
gratings can confine the radiation better than the common gratings. It should be noted that the
groove depth in the present study is pretty deep according previous studies [12,25]. It is still
necessary to optimize the parameters of the stair grating, e.g. groove depth and geometry of
excavated part so on, for better performance. Nevertheless, based on current experimental and
numerical simulations, it is reliable to conclude that the stair grating can work better rather
than the common grating.
4. Conclusions
In conclusion, we design a new type of gratings called as stair-gratings and combine them
with nano-aperture for surface enhanced fluorescence detection. In comparison with the
conventional ones, we find that the detected fluorescent intensity by the stair-gratings is
higher than the common grating. And narrower directionality by the stair-gratings would
enable the detection of molecular fluorescence with low N.A. objective. All these factors
allow a higher SNR and higher detection efficiency of single molecule fluorescence. We also
employed the FDTD method to simulate the near-field enhancement and far-field radiation
patterns. The simulation results are in good agreement with the experimental results. Our
research contributes to understanding to the plasmonic gratings for optimizing the surface
enhancement process of photoluminescence process.
Funding
This work was supported by the National Key Basic Research Program of China (grant no.
2013CB328703) and the National Natural Science Foundation of China (NSFC) (grant nos.
61422502, 11374026, 61521004, 11527901)
Vol. 24, No. 17 | 22 Aug 2016 | OPTICS EXPRESS 19573