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Nanostructures - Dimension Effect nano biotechnology. pptx
- 1. Lecture Plan S. No Lecture Title Delivery Date 1 Introduction; interface between nanotechnology and bio-nanotechnology. 21.2 – 22.2 2 Manipulating molecules / Nanostructures Carbon fullerenes and nanotubes; non-carbon nanotubes and fullerene-like materials; quantum dots; nanowires, nanorods and other nanomaterial’s; magnetic nanoparticles 28.2 - 29.2 3 Natural biological assembly at the nanoscale and nanometric biological assemblies (complexes); 4 Nanobionics and bio-inspired nanotechnology. 5 Applications of biological assemblies in nanotechnology; medical, cosmetics, agriculture, water and other applications of nano-biotechnology. 6 Prospects of nano-biotechnology. 7 The use of nanotechnology for diagnosing and curing disease. Dr. Munezza Khan
- 4. VACANT “d” Orbitals The number of vacant orbitals increases the density of states and discretized it. Dr. Munezza Khan
- 6. Dr. Munezza Khan (Coercivity) Coercivity the resistance of a magnetic material to changes in magnetization, equivalent to the field intensity necessary to demagnetize the fully magnetized material. Unit: Amp/m or cgs (Oersteds)
- 7. Type of Magnetic NPs Schematic description of different magnetic properties. (A) Schematic orientation of magnetic moments (spins) of ferromagnetic, antiferromagnetic, ferrimagnetic, and paramagnetic materials are shown. (B) Broadening and dissipation of Weiss domains of a ferromagnetic material through an increasing, external magnetic field is shown from left to right. (C) Schematic graph of coercivity versus particle size. Superparamagnetic particles show no coercivity, coercivity increases for single-domain particles with increasing size until a maximum, when a switch to the energetically more favorable multi-domain state occurs. (D) Schematic sample of superparamagnetic particles is shown. Without an external magnetic field, particles show random orientation that leads to no net magnetization of the sample. With an external magnetic field, magnetic moments orient parallel toward the source of the magnetic field. (E) Schematic depiction of magnetization curves and their extractable information on magnetic properties of a sample. Temperature (inlet) and magnetic field strength dependency in SQUID magnetometry measurements shown. Ferro- and ferrimagnetic materials usually show similar curves, only ferromagnetism is shown. Inlet: Magnetic susceptibility versus temperature graph is shown. Based on the changing magnetic susceptibility at rising temperature, one can differentiate antiferromagnetic, ferromagnetic, or paramagnetic properties of a sample. Magnetic susceptibility decreases exponentially with increasing temperature for paramagnetic samples. Until TN, antiferromagnetic samples show an increase in magnetic susceptibility with temperature. Near TC, ferro- and ferrimagnetic samples show a steep decrease in magnetic susceptibility with temperature. Then, above TN and TC paramagnetic behavior is visible for ferro-, ferri-, and antiferromagnetic samples. Main graph: Sample magnetization versus strength of external magnetic field. Non-magnetized samples start at zero magnetization without an external magnetic field. Measurement allows to find coercivity points as marked for hysteresis curve of ferro- and ferrimagnetic samples that arises from moving/dissipating Weiss domains with magnetic field strength. No coercivity and hysteresis is usually visible for superparamagnetic particles. A linear course of sample magnetization is common for paramagnetic and diamagnetic samples. Plateau of sample magnetization marks saturation magnetization of sample, where no distinct Weiss domains exist in multi-domain state particles and is used as a mean to compare magnetic potency of a sample. Dr. Munezza Khan
- 8. Materials Properties @ Nanoscale SIZE DEPENDENT MAGNETIC PROPERTIES Domains are regions where all the atoms contribute their magnetic moment in the same direction. Dr. Munezza Khan
- 10. Anisotropic Nanomaterials Geometry of the nanomaterials adds anisotropy; Direction Dependent properties
- 11. Unit cell is the single repeating unit in the lattice, and it is defined by it lattice constants i.e. length of edges and its angles. Dr. Munezza Khan
- 12. Unit cell is the single repeating unit in the lattice, and it is defined by it lattice constants i.e. length of edges and its angles. Dr. Munezza Khan
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- 15. Dr. Munezza Khan Bravais Lattice refers to the 14 different 3- dimensional configurations into which atoms can be arranged in crystals. The smallest group of symmetrically aligned atoms which can be repeated in an array to make up the entire crystal is called a unit cell.
- 16. Dr. Munezza Khan Kusior, Anna, Milena Synowiec, Katarzyna Zakrzewska, and Marta Radecka. "Surface-controlled photocatalysis and chemical sensing of TiO2, α-Fe2O3, and Cu2O nanocrystals." Crystals 9, no. 3 (2019): 163. Figure illustrates the idea of the facet-dependent photocatalysis and (bio)chemical sensing of metal oxide semiconductor (MOS) using as an example anatase TiO2 crystals that are normally dominated by the thermodynamically stable {101} facets (more than 94% according to the Wulff construction rather than much more reactive {001} facets. However, an exposure of the more reactive {001} facets has a tremendous impact on both photocatalysis and gas sensing mechanism.
- 17. Dr. Munezza Khan Unit cells of the iron oxides. a) Magnetite (Fe3O4) in an inverse spinel crystal structure with equal and opposite spins from Fe³⁺ ions in octahedral and tetrahedral sites, and unbalanced spins from Fe²⁺ in octahedral sites to form an overall magnetic structure. b) Wüstite (FeO) in a rock salt crystal structure. c) Hematite (α‐Fe2O3) in a rhombohedral crystal structure. d) Maghemite (γ‐Fe2O3) in an inverse spinel crystal structure. Morphology effect in Magnetic Materials Maghemite saturation magnetization (76 emu/g) is lower than magnetite (92 emu/g) and more than hematite (0.1-0.4 emu/g).
- 18. Shape controlled Properties 1. Catalysis 2. Plasmonics 3. Biological Sensing 4. Therapeutics 5. Biological Imaging Dr. Munezza Khan
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- 24. Dr. Munezza Khan Reference: Guo, Zhongnan, et al. "High active crystalline {1 1 0} facets with high surface energy in Tin monoxide photocatalyst." Inorganic Chemistry Communications 134 (2021): 109043.
- 25. Dr. Munezza Khan Shape Control growth of Gold Nanoparticles
- 26. Dr. Munezza Khan Critical micelle formation concentration explained - DataPhysics Instruments (dataphysics- instruments.com) Use of Surfactant as Dimension Control Factor during Nanocrystal Growth
- 27. Dr. Munezza Khan New seeds or units are added in the preferable crystallographic planes which define the shape/ geometry or dimensional growth of a crystal.
- 28. Dr. Munezza Khan Change in Gibb’s free energy with the addition of mixture components.
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- 30. Facet-selective design rule: Facets with higher surface energies grow at lower ∆ Dr. Munezza Khan
- 31. pecific exposed facet design rule: Facets with higher surface energies are exposed at higher ∆μ Dr. Munezza Khan
- 32. Dr. Munezza Khan
Editor's Notes
- It is possible to remove the internally created magnetic field by raising the temperature of the ferromagnet. As temperature increases, the atoms (and domains) vibrate more until exchange coupling ceases and the domains can no longer maintain their non-random alignment. This temperature is called the Cure temperature. Above the Curie temperature, ferromagnetic materials become paramagnetic.
- Anisotropic nanomaterials are a class of materials, in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Most of the traditional nanomaterials are spheres, in which properties are isotropic in all directions. Anisotropic particles exist in the form of rods, wires, tubes, plates, stars, tetrapods, etc. They can also be classified as one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) materials, depending on the dimensional units required to describe them.
- The design of photocatalytic and gas sensing materials is to use the shape-controlled nanocrystals with well-defined facets exposed to light or gas molecules. An abrupt increase in several papers on the synthesis and characterization of metal oxide semiconductors such as a TiO2, α-Fe2O3, Cu2O of low-dimensionality, applied to surface-controlled photocatalysis and gas sensing, has been recently observed A brilliant idea to expose highly reactive facets of well-defined crystals to external stimuli such as light, gas, or organic pollutants in order to enhance the efficiency of processes governed by the surface chemistry Single crystals are usually terminated with the low Miller index facets that allow minimizing their surface energy. During the crystal growth, the rate, at which the high Miller index facets evolve, is very fast, eliminating them in the final state. Photocatalysis requires a control over three basic steps, as shown in Figure 1—left, concerning the charge, electrons e−, and holes h+: generation upon photoexcitation, transfer to the surface of the photocatalytic crystal, participation in redox reactions taking place at the active surface. Charge kinetics in all these processes decides about the overall efficiency of the photocatalysis while in the case of shape-controlled crystals, the transfer of electrons and holes to different facets may help in avoiding too fast recombination, being detrimental to the efficiency of the process. The exposed facets may affect the photocatalytic performance through multiple effects. Gas sensing by metal oxide semiconductors, MOS, is usually based on the changes in the electrical resistance caused by at least two consecutive processes of chemisorption
- we indicate that the {1 1 0} facets of SnO show higher activity than those of {1 0 0} and {1 0 1}, which is resulted from the higher surface energy. The high active crystalline facets of SnO were determined. SnO single crystals with two different shapes were synthesized. The truncated bipyramid crystals shows {1 0 1} exposed facets whereas the diskette shows {1 0 0} and {1 1 0} facets. The {1 1 0} facets exhibit higher photocatalytic activity than {1 0 0} and {1 0 1} due to higher surface energy The activity of SnO photocatalyst with different exposed facets has been investigated based on the micrometer-sized SnO single-crystals with two different shapes. Truncated bipyramid crystals with {1 0 1} exposed facets and diskette-shaped crystals exhibiting {1 0 0} and {1 1 0} planes have been synthesized by hydrothermal method with different reacting temperatures. We demonstrated higher photocatalytic performance of {1 1 0} facets of SnO compared to those of {1 0 0} and {1 0 1}, which is ascribed to the high surface energy of {1 1 0} facets. Our work suggests that the {1 1 0} facets are the high active facets of layered SnO, and this can guide the crystal facet engineering of this good semiconducting material.
- The chemical potential tells how the Gibbs function will change as the composition of the mixture changes. Therefore, by adjusting the ∆ of the growth solution, specific curvature-selective energy windows can be attained, enabling corner- and edge-selective nucleation (Fig. 1A). Experimentally, we can tune ∆ of the growth solution by changing the reaction conditions. For example, increasing the concentration of the reducing agent ascorbic acid (AA), decreasing the reduction potential of the reduction agent, or decreasing the concentration of the ligand adsorbate hexadecyltrimethylammonium bromide (CTAB) all result in increased ∆. The length and binding affinity of the ligands are key parameters that affect the E profiles and growth selectivity. When a weakly binding ligand is used (e.g., CTAB), the E values and their differences are negligible, resulting in uniform growth of the nanoprism into a larger nanoprism (fig. S2). In other words, when only CTAB is used, secondary nucleation does not occur and growth selectivity cannot be achieved.
- NCs of various polyhedral shapes are used as seeds. Octahedral and concave rhombic dodecahedral gold seeds (Fig. 2, A and B) have corners and edges with different curvatures. Regardless of the polyhedral geometry of the seeds, subsequent site-specific gold deposition only on the corners (Fig. 2, D and E) or only the edges (Fig. 2, H and I) can be obtained by changing the Ascorbic Acid concentration to tune the ∆ relative to E. When a seed NC has multiple types of corners (or edges)
- In addition to the curvature differences, facet energy () differences also play an important role in influencing the corresponding E profiles for subsequent NC nucleation. To decouple the effects of differing facets from that of curvature, the side faces of nanorods with no curvature difference, which are bound by alternating {100} and {110} facets (33), are used as a model system. The higher the (resulting from the lower coordination number), the lower the E (nucleation energy barrier) and the easier it is for solutes to access sites for subsequent nucleation. Specifically, {110} > {100} such that E{110} is less than E {100}. < E{100} (Fig. 3, B and C).>Therefore, subsequent gold atoms were only selectively deposited on the four {110} facets of the nanorods’ side faces when only surmounts E{110} (Fig. 3, D and E).
- On the basis of the Thomson-Gibbs equation (32) in a growing crystal, facets with higher surface energies will appear when the ∆ of the growth solution is higher (detailed discussion in the Supplementary Materials). For example, in the case of gold nanocubes and octahedra, the surface energy of {100} in dark green is higher than that of {111} in light green (Fig. 4A). Therefore, using corner nucleated octahedra as seeds (Fig. 4, B and E), growth occurs almost exclusively on the existing nuclei on the corners. The corners are bound by {111} facets at lower ∆ (100 mM CTAB) (Fig. 4, B and F), while the {100} facets begin to appear on the corners at higher ∆ (10 mM CTAB) (Fig. 4, B and G). Moreover, when edge-nucleated nanocubes are used as seeds (Fig. 4, C and I), subsequent growth only occurs on the existing nuclei along the edges. The edges are bound by {100} facets at higher ∆ (10 mM CTAB) (Fig. 4, C and J), while the {111} facets begin to appear along the edges at lower ∆ (100 mM CTAB) (Fig. 4, C and K, and fig. S8). Higher concentration of surfactant lowers chemical potential of the growth solution Lower concentration of surfactant increases chemical potential of the growth solution
- Based on their dimensionality and the overall shape of these materials, NMs can be further divided into four classes. Zero-dimensional nanomaterials (0D) have all their dimensions in nanoscale, i.e., sized below 100 nm. 0D includes spherical NMs, cube, nanorod, polygon, hollow sphere, metal, and core–shell NMs as well as quantum dots (QDs). One-dimensional nanomaterials (1D) are materials with one dimension not in nanoscale while the other two dimensions are in nanoscale. 1D includes metallic, polymeric, ceramic, nanotube, and nanorod filament or fiber, nanowires, and nanofibers. Two-dimensional nanomaterials (2D) contain only one dimension in nanoscale while the other two are not. 2D includes single-layered and multi-layered, crystalline or amorphous, thin films, nanoplates, and nanocoating. Three-dimensional (3D) materials have various dimensions beyond 100 nm. 3D NMs combine multiple nanocrystals in different directions. Examples of the same are foams, fibers, carbon nanobuds, nanotubes, fullerenes, pillars, polycrystals, honeycombs, and layer skeletons