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  1. 1. Nanotechnology and its applications in crop improvement
  2. 2. Nanotechnology and its applications in crop improvement Abstract Nanotechnology is the Design, Fabrication and Utilization of materials, devicesand systems through control of matter on the nanometer length scale and exploitation ofnovel phenomena and properties (physical, chemical, biological) at that length scale. It isnow more properly labeled as "molecular nanotechnology" (MNT) or "nano-scaleengineering”. By taking advantage of quantum-level properties, nanotechnology allowsfor unprecedented control of the material world, at the nanoscale, providing the means bywhich systems and materials can be built with exact specifications and characteristics,allowing materials to be lighter, stronger, smarter, cheaper, cleaner and more precise.Nanotechnology has the potential to advance agricultural productivity through geneticimprovement of plants, delivery of genes and drug molecules to specific sites at cellularlevels, and nano-array based gene-technologies for gene expressions in plants andanimals under stress conditions. The potential is increasing with suitable techniques andsensors being identified for precision agriculture, natural resource management, earlydetection of pathogens and contaminants in food products, smart delivery systems foragrochemicals like fertilizers and pesticides, smart systems integration for foodprocessing, packaging and other areas like monitoring agricultural and food systemsecurity. Further developments in nanotechnology in this sector can be expected tobecome the main economic driving forces in the long run and benefit consumers,producers, farmers, ecosystems, and the general society at large. In India, the importance of research and development in nanotechnology has beenrecognized as of paramount importance. If Indian agriculture is to attain its broad nationalgoal of sustainable agricultural growth of over 4%, it is important that thenanotechnology research is extended to the agricultural total production-consumptionsystem, that is, across the entire agricultural value chain. Nanotechnology will give rise to a host of novel social, ethical, philosophical andlegal issues. It is important to have a regulatory mechanism in place to predict and workto alleviate anticipated problems.INTRODUCTION Imagine a supercomputer a billion times more powerful than today’s and yet sosmall it would be barely visible by a light microscope. Fleets of medical robots smallerthan a cell roaming our bodies eliminating bacteria, clearing out clogged arteries,reversing the ravages of old ages and effectively making us immortal. Clean factoriesmanufacturing without having to worry about pollution choking up the environment.Cheap and abundant solar energy replacing conventional fossil fuels like oil, coal andgas. Building materials that are stronger, lighter and cheaper than the ones used in today’s 2
  3. 3. rockets, making lunar vacations no more expansive than says a trip to South Pole. Aworld where material abundance for all the people becomes a reality. Sounds too good to be true? Not for the new breed of scientists who believe that stthe 21 century could see all these science fiction dreams come true thanks tonanotechnology, a hybrid of chemistry and engineering that has opened up a whole newworld of possibilities which If taken to their logical conclusion would completely changeus and the world as we know it today. Indeed, so exciting are the prospects of thisrevolutionary science that countries all over the world are investing in the research anddevelopment of nanotechnology. Clearly nanotechnology is slowly but surely capturingthe attention of the scientific community, the media and no the public. But just whatexactly is nanotechnology and why everyone talking about it?WHAT IS NANOTECHNOLOGY? Nanos: Greek term for dwarf, Technology: visualize, characterize, produce andmanipulate matter of the size of 1 – 100 nm. Nanotechnology is manufacturing at the molecular level- building things fromNano-scale components. Nanotechnology proposes the construction of novel Nano-scaledevices possessing extraordinary properties. Through the developments of suchinstruments and technique it is becoming possible to study and manipulate individualatoms. At present, conventional manufacturing techniques manipulate billions of atomsat a time using large scale deformation methods like pounding and chipping. In thefuture, Molecular nanotechnology” will allow very complete control over the placementof individual atoms. Nanotechnology is often referred to as “bottom up” manufacturing because itaims to start with the smallest possible building materials, atoms using them to create adesired product. Working with individual atoms allow “atom –by –atom “design ofstructures. Nanotechnology can eliminate unwanted byproducts. Nanotechnology wouldallow us to get essentially every atom in the right place, make almost any structureconsistent with the most of law of physics and chemistry that we can specify in atomicdetail and have manufacturing costs not greatly exceeding the cost of the required rawmaterials and energy. Related and interwoven fields include, but are not limited to: Nanomaterials,Nanomedicine, Nanobiotechnology, Nanolithography, Nanoelectronics, Nanomagnetics,Nanorobots, Biodevices [biomolecular machinery], AI, MEMS [MicroElectroMechanicalSystems], NEMS [Nano Electro Mechanical Systems], Biomimetic Materials, Microencapsulation, and many others.DEFINITION 3
  4. 4. • “Nanotechnology is the Design, Fabrication and Utilization Of materials, Structures, devices and systems through control of matter on the nanometer length scale and exploitation of novel phenomena and properties (physical, chemical, biological) at that length scale In At Least One Dimension”. • “A manufacturing technology able to inexpensively fabricate most structures consistent with natural laws and to do so with molecular precision”. • “The precision, placement, measurement, manipulation and modeling of nanometer scale matter”. • “The interactions of cellular and molecular components and engineered materials typically cluster of atoms, molecules and molecular fragments at the most elemental level of biology”. • “By taking advantage of quantum-level properties, MNT allows for unprecedented control of the material world, at the nanoscale, providing the means by which systems and materials can be built with exact specifications and characteristics”.Emergence of Nanotechnology The first so-called scientific study of nanoparticles took place way back in 1831,when Michael Faraday investigated the ruby red colloids of gold and made public that thecolor was due to the small size of the metal particles. Gold and silver have found theirway into glasses for over 2000 years, usually as nanoparticles. They have most frequentlybeen employed as colorants, particularly for church windows. Until 1959, nobody hadthought of using atoms and molecules for fabricating devices. It was first envisioned byNobel Laureate Physicist Richard Feynman at a lecture entitled “There is plenty of roomat the bottom”. It was much later in 1974 that Norio Taniguchi, a researcher at theUniversity of Tokyo, Japan used the term “nanotechnology” while engineering thematerials precisely at the nanometer level. The primary driving force for miniaturizationat that time came from the electronics industry, which aimed to develop tools to createsmaller electronic devices on silicon chips of 40–70 nm dimensions. The use of this term,“nanotechnology” has been growing to mean a whole range of tiny technologies, such asmaterial sciences, where designing of new materials for wide-ranging applications areconcerned; to electronics, where memories, computers, components and semiconductorsare concerned; to biotechnology, where diagnostics and new drug delivery systems areconcerned.THE PIONEERS: 4
  5. 5. The word “Nanotechnology” coined in 1974 by Norio Taniguchi at theUniversity of Tokyo. During the 1950s Arthur von Hippel, an electrical engineer fromthe Massachussetts Institute of Technology (MIT) coined the term “molecularengineering” and predicted the feasibility of constructing nanomolecular devices.However it was in December 29, 1959, the American physicist Richard Feynman gave aseminal lecture to the American Physical Society entitled “There’s Plenty of Room atthe Bottom”. In this he discussed the benefits to society that would accrue if we wereable to manipulate matter and manufacture artifacts with precision on a scale of a fewatoms across, which corresponds to a dimension of about one nanometer. He correctlyforesaw, for example, the impact that miniaturization would have on the capabilities ofelectronic computers; he also predicted the development of the methods that are nowused to make integrated circuits and the emergence of techniques for writing extremelyfine patterns with beams of electrons. He even mooted the possibilities of makingmachines at the molecular scale, which would enable us to manipulate chemical andbiological molecules. Forty years on from this lecture, technologists working in the fieldof nanotechnology are starting to realize some of the ideas originally propounded byFeynman, and many others that were not foreseen at that time. Greg Binnig and Heinrich Rohrer in 1985 invented the scanning tunnelingmicroscope. Eric Drexler, chairman of the Foresight Institute (1970s) in his book “Engine 5
  6. 6. of creation” has been written that future was one where everything would be built fromthe bottom up by tiny machines “nanomachines” or “assemblers” that would be able tobuild large scale objects that were perfect on the atomic scale.Consequences of Miniaturization Every substance regardless of composition exhibits new properties when the sizeis reduced to less than 100 nm. The electronic structure of a nanocrystal criticallydepends on its size. For small particles, the electronic energy levels are not continuous asin bulk materials, but discrete. This arises primarily due to confinement of electronswithin particles of dimension smaller than the bulk electron delocalization length; thisprocess is termed as quantum confinement. Noble metal and semiconductor nanoparticlesare unique examples of this principle. Thus, the properties of traditional materials changeat nano level due to the quantum effect and the behavior of surfaces start to dominate thebehavior of bulk materials. The optical, electrical, mechanical, magnetic, and chemicalproperties can be systematically manipulated by adjusting the size, composition, andshape of the nanoscale materials. Nanomaterials have tremendous potential applicationsin catalysis, photocatalysis,optoelectronics, single-electron transistors, light emitters,nonlinear optical devices, hyperthermia treatment for malignant cells, magnetic memorystorage devices, magnetic resonance imaging enhancement, cell labeling, cell tracking, invivo imaging, and DNA detection. The wide range of applications shown bynanomaterials is mainly due to (i) large surface area and (ii) small size. Electrontransport, manifested in phenomena like Coloumb blockade, as well as the catalytic andthermodynamic properties of structures can be tailored when one can rationally designmaterials on this length scale. Therefore, analytical tools and synthetic methods allow oneto control composition and design on this nanometer range and will undoubtedly yieldimportant advances in almost all fields of science. NOBEL PRIZES FOR ELUCIDATING ATOMS AND SUBATOMIC PARTICLES. NOBELS. No. WINNERS ACHIEVEMENT PRIZE1. Gerd Binnig, Scanning Tunneling Microscope. 1986 Heinrich Rohrer.2. Hans Dehmelt, Traps to isolate atoms and subatomic species. 1989 Wolfgang Paul.3. George Charpak Subatomic Particle detectors 1992 6
  7. 7. 4. Clifford Schull, Neutron Diffraction technique for Structure 1994 Bertram Brockhouse. determination5. Steven Chu, Claude Methods to cool and trap atoms with Laser light 1997 Cohen -Tannoudji, William PhillipsHOW BIG IS NANOTECHNOLOGY? "Nanometer" (abbreviated nm), derived from the Greek word for midget,"NANO" is a metric prefix and indicates a billionth part (10-9). A micron is a millionth ofa meter, which is the scale that is relevant to building computers, computer memory, andlogic devices. A nanometer is one thousandth of a micron, and a thousandth of a millionthof a meter (a billionth of a meter). A nanometer is about the width of six bonded carbonatoms, and approximately 40,000 are needed to equal the width of an average human hair. Sizes of nanoscale objects –Nature vs. fabrication Object Diameter Hydrogen atom 0.1nm Buckminsterfullerene (C60 ) 1.0 nm Six carbon atoms aligned 1.0 nm DNA (width) 2.0 nm Nanotube 3-30 nm Proteins 5-50 nm Quantum Dots (of CdSe) 8.0 nm Dip pen nanolithography features 10-15 nm Dendrimers 10 nm Microtubules 25nm Ribosome 25 nm Virus 75-100 nm Nanoparticles range from 1-100 nm Semiconductor chip features 90 nmWHY NANOTECHNOLOGY? It would enable computer designers to break through the Moore’s law, Intel co-founder Dr. Gordon Moore predicted that technology that went into integrated circuitswould roughly double in power every 12-18 months. That is why the latest Pentium Vchip clocking 3.2 gigahertz is about 25,000 times faster and packs 25,000 as the first 7
  8. 8. ever microchip, the Intel 4004 of 1971. Physicists say it will takes at least 10 years at themost before we are able to dream up a bigger, better, microchip on that slab of silicon.And that is where nanotechnology comes in: the ability to fashion electronic circuits–entire computers –with atom length nanowires or nanotubes, made from carbon ratherthan silicon may allow computer hardware to progress beyond physical barriers ofMoore’s law. • Limitations of resources: Waste problem. • Necessity: Increasing population, density increases and demand for new technology.NANOTECHNOLOGY IS MULTIDISCIPLINARYWHAT IS UNIQUE ABOUT NANOTECHNOLOGY? • Small size (High surface to volume ratio), therefore requires self assemblers. • Significantly higher hardness, breaking strength and toughness at low temperatures and super plasticity at high temperatures, the emergence of additional electronic states, high chemical selectivity of surface sites and significantly increased surface energy. 8
  9. 9. • New entry ways (high mobility in human body, plants and environment).Applications of Nanotechnology in Agriculture  Crop improvement  Nanobiotechnology  Analysis of gene expression and Regulation  Soil management  Plant disease diagnostics  Efficient pesticides and fertilizers  Water management  Bioprocessing  Post Harvest Technology  Monitoring the identity and quality of agricultural produce  Precision agricultureNanotechnology for Crop ImprovementDNA in Nano World The DNA molecule has appealing features for use in nanotechnology: itsminuscule size, with a diameter of about 2 nanometers, its short structural repeat (helicalpitch) of about 3.4–3.6 nm, and its ‘stiffness’, with a persistence length (a measure ofstiffness) of round 50 nm. There are two basic types of nanotechnological construction:‘top-down’ systems are where microscopic manipulations of small numbers of atoms ormolecules fashion elegant patterns, while in ‘bottom-up’ constructions, many moleculesself-assemble in parallel steps, as a function of their molecular recognition properties. Asa chemically based assembly system, DNA will be a key player in bottom-upnanotechnology. The origins of this approach date to the early 1970s, when in vitrogenetic manipulation was first performed by tacking together molecules with ‘sticky 9
  10. 10. ends’. A sticky end is a short single-stranded overhang protruding from the end of adouble-stranded helical DNA molecule. Like flaps of Velcro, two molecules withcomplementary sticky ends — that is, their sticky ends have complementaryarrangements of the nucleotide bases adenine, cytosine, guanine and thymine — willcohere to form a molecular complex. Sticky-ended cohesion is arguably the best exampleof programmable molecular recognition: there is significant diversity to possible stickyends (4N for N-base sticky ends), and the product formed at the site of this cohesion is theclassic DNA double helix. Likewise, the convenience of solid support-based DNAsynthesis3 makes it is easy to program diverse sequences of sticky ends. Thus, stickyends offer both predictable control of intermolecular associations and predictablegeometry at the point of cohesion. Perhaps one could get similar affinity properties fromantibodies and antigens, but, in contrast to DNA sticky ends, the relative three-dimensional orientation of the antibody and the antigen would need to be determined forevery new pair. The nucleic acids seem to be unique in this regard, providing a tractable,diverse and programmable system with remarkable control over intermolecularinteractions, coupled with known structures for their complexes.Nanobiotechnology: Molecular biology complementing Nanotechnology The credit for the term "nanobiotechnology" goes to Lynn W. Jelinski, abiophysicist at Cornell University. Nanobiotechnology joins the breakthroughs innanotechnology to those in molecular biology. Molecular biologists helpnanotechnologists understand and access the nanostructures and nanomachines designedby 4 billion years of natural engineering and evolution — cell machinery and biologicalmolecules. Exploiting the extraordinary properties of biological molecules and cellprocesses, nanotechnologists can accomplish many goals that are difficult or impossibleto achieve by other means. For example, rather than build silicon scaffolding fornanostructures, DNAs ladder structure provides nanotechnologists with a naturalframework for assembling nanostructures; and its highly specific bonding propertiesbring atoms together in a predictable pattern to create a nanostructure. Nanotechnologistsalso rely on the self-assembling properties of biological molecules to createnanostructures, such as lipids that spontaneously form liquid crystals. DNA has been used not only to build nanostructures but also as an essentialcomponent of nanomachines. Most appropriately, DNA, the information storagemolecule, may serve as the basis of the next generation of computers. As microprocessorsand microcircuits shrink to nanoprocessors and nanocircuits, DNA molecules mountedonto silicon chips may replace microchips with electron flow-channels etched in silicon.Such biochips are DNA-based processors that use DNAs extraordinary information 10
  11. 11. storage capacity. Conceptually, they are very different from the DNA chips discussedbelow. Biochips exploit the properties of DNA to solve computational problems; inessence, they use DNA to do math. Scientists have shown that 1,000 DNA molecules cansolve in four months computational problems that require a century for a computer tosolve. Other biological molecules are assisting in our continual quest to store and transmitmore information in smaller places. For example, some researchers are using light-absorbing molecules, such as those found in our retinas, to increase the storage capacityof CDs a thousand-fold. Nanobiotechnology is an emerging area of opportunity that seeks to fusenano/microfabrication and biosystems to the benefit of both. It relates to all applicationsof genomics including mammalian, plant and microbial. It provides the basic tools andsubsequently the technology for gathering sequence information and designinginnovative devices to probe questions related to the biological importance of the genomicinformation and the application of this knowledge in diverse fields, particularly medicineand agriculture.Potential Applications of Nanobiotechnology in Agriculture• High throughput DNA sequencing and nanofabricated gel-free systems• Microarrays and expression profiling• Increasing the speed and power of disease diagnostics• Creating bio-nanostructures for getting functional molecules into cells• Miniaturizing biosensorsThe impact of nanobiotechnology may be immediately felt in the following areas:Nanofabricated Gel-free Systems and High Throughput DNA Sequencing As a central process, DNA sequencing needs to be improved in terms of itsthroughput and accuracy. Nanofabrication technology will be critical toward this goalboth in terms of improving existing methods as well as delivering novel approaches forsequence detection. The scaling down in size of the current sequencing technology allowsthe process to be more parallel and multiplex. Research in nanobiotechnology isadvancing toward the ability to sequence DNA in nanofabricated gel-free systems, whichwould allow for significantly more rapid DNA sequencing. Coupled with powerfulapproaches such as association genetic analysis, DNA sequencing data of the cropgermplasm, including the cultivated crop gene pool and the wild relatives can potentiallyprovide highly useful information about molecular markers associated withagronomically and economically important traits. Thus, nanobiotechnology can enhancethe pace of progress in molecular marker-assisted breeding for crop improvement. 11
  12. 12. Microarrays and Expression Profiling Microarray-based hybridization methods allow to simultaneously measure theexpression level for thousands of genes. Such measurements contain information aboutmany different aspects of gene regulation and function, and indeed this type ofexperiments has become a central tool in biological research. The development of novelformats for sequence determination and patterns of genomic expression which can havesignificantly higher throughput than current technologies is vital. Thousands of DNA orprotein molecules are arrayed on glass slides to create DNA chips and protein chips,respectively. Recent developments in microarray technology use customized beads inplace of glass slides. Overall, nanofabrication techniques can be used, for example, topattern surface chemistry for a variety of biosensor and biomedical applications.Three areas which exemplify this are:• Determination of new genomic sequences• Scanning of genes for polymorphism that might have an impact on phenotype• Comprehensive survey of the pattern of gene(s) expression in organisms when exposed to biotic/abiotic stress.The fundamental principle underlying the microarray technology has inspired researchersto create many types of microarrays to answer scientific questions and discover newproducts.DNA Microarrays: DNA microarrays are being used to:• detect mutations in disease-related genes• monitor gene activity• identify genes important to crop productivity• improve screening for microbes used in bioremediationGene sequence and mapping data mean little until we determine what those genes do—which is where protein arrays come in.Protein Microarrays: While going from DNA arrays to protein arrays is a logical step, itis by no means simple to accomplish. The structures and functions of proteins are muchmore complicated than that of DNA, and proteins are less stable than DNA. Each celltype contains thousands of different proteins, some of which are unique to that cells job.In addition, a cells protein profile varies with its health, age, and current and pastenvironmental conditions. 12
  13. 13. Protein microarrays are being used to:• discover protein biomarkers that indicate disease stages• assess potential efficacy and toxicity of pesticides (natural and synthetics)• measure differential protein production across cell types and developmental stages, and in both healthy and diseased states• study the relationship between protein structure and function evaluate binding interactions between proteins and other moleculesAtomically Modified Seeds: In March 2004, ETC Group reported on a nanotech research initiative in Thailandthat aims to atomically modify the characteristics of local rice varieties. In a three-yearproject at Chiang Mai University’s nuclear physics laboratory, researchers “drilled” ahole through the membrane of a rice cell in order to insert a nitrogen atom that wouldstimulate the rearrangement of the rice’s DNA. So far, researchers have been able to alterthe colour of a local rice variety from purple to green. In a telephone interview, Dr.Thirapat Vilaithong, director of Chiang Mai’s Fast Neutron Research Facility, toldBiodiversity Action Thailand (BIOTHAI) that their next target is Thailand’s famousJasmine rice. The goal of their research is to develop Jasmine varieties that can be grownall year long, with shorter stems and improved grain colour. One of the attractions of thisnano-scale technique, according to Dr. Vilaithong, is that, it does not require thecontroversial technique of genetic modification. “At least we can avoid it.” Low-energy ion beam bombardment at energy levels in the range of 60–125 keVand ion fluences (dose) of 1×1016–5×1017 ions/cm2 was chosen for mutation inductionin Thai jasmine rice (Oryza sativa L. cv. KDML 105) at Chiang Mai University. One ofthe rice mutants designated BKOS6 was characterized. The rice mutant was obtainedfrom KDML 105 rice embryos bombarded with N++N2+ ions at an energy level of 60 keVand ion fluence of 2×1016 ions/cm2. Phenotypic variations of BKOS6 were short instature, red/purple color in leaf sheath, collar, auricles, ligule, and dark brown stripes onleaf blade, dark brown seed coat and pericarp. The mutants reproductive stage was foundin off-season cultivation (March–July). HAT-RAPD (High Annealing Temperature-Random Amplified Polymorphic DNA) was applied for analysis of genomic variation inthe mutant. Of 10 primers, two primers detected two additional DNA bands at 450 bp and400 bp. DNA sequencing revealed that the 450 bp and the 400 bp fragments were 60%and 61% identity to amino acid sequence of flavanoid 3′hydroxylase and cytochromeP450 of O. sativa japonica, respectively. 13
  14. 14. Figure: The rice mutants designated BKOS6 was derived by bombardment with N++N2+ ions from KDML 105 rice embryos.Synthetic Tree In trees, evaporation of water from leaf cells called spongy mesophyll pulls water up through hollow cells in the trunk 14
  15. 15. (spongy mesophyll is the tissue in the lower half of this picture, a cross-section through aleaf). The strong, cohesive properties of water, responsible for its powerful surfacetension, allow the water to exist at large negative pressures. But even the smallest bubblewould explosively expand into the water, disrupting its flow in a process known ascavitation. The interface between the plant’s water system and the air, formed by thespongy mesophyll, must allow water to pass, but not the gas molecules that would causecavitation. Figure: The synthetic hydrogel mimics the trnaspiartion pattern of a typical plant system. Trees grow many times taller - more than 100 metres in the case of the tallestredwoods. Yet they supply their leaves with a constant flow of water. They achieve thisfeat by keeping the water high up in their trunks under pressures many atmospheresbelow that of a vacuum. Wheeler and Stroock report a duplication of this trick: they have created a tiny‘synthetic tree’ through whose trunk water flows at pressures of around -10 atmospheres.To create their tree, Wheeler and Stroock use a hydrogel, which mimics the mesophyll byholding water in molecular-scale pores, smaller than those of other porous solids. As theirrespective ‘root’ and ‘leaf’, the authors formed two networks of channels, 10 micrometresin diameter, in a sheet of poly(hydroxyethyl methacrylate), and connected them by asingle channel, the ‘trunk’. With the ‘root’ exposed to a source of water and the ‘leaf’ to astream of damp air, water flows through the system powered solely by ‘leaf’ evaporation.The pressures developed in the trunk are some 15 times more negative than in anypreviously reported pumping system. The device is shown in Figure of the paper. It is just 5 cm long, and the flow is alittle over 2 micrograms of water per second — but from such small acorns do mightyoaks grow. The synthetic tree can provide a test device for theories of tree physiologyand, scaled-up, the technology could find uses in passive pumps or cooling devices —evaporation makes the ‘leaf’ a heat sink. Also, the large negative pressures developedmight be used to drag water out of even quite dry soils, simultaneously filtering outimpurities by passage through the ‘root’ hydrogel. This process, which the authors dub“reverse reverse osmosis”, could form the basis of solar-powered mining of pure water inarid or contaminated environments.Silica beaks Plant Cell Imagine a tiny bundle of parallel tubes with each tube containing liquid andhaving a cap that is removable at will. How useful might these objects be in 15
  16. 16. biotechnology? François Torney, Brian Trewyn and colleagues1 at Iowa State Universitydescribe the use of mesoporous silica nanoparticles (MSNs) to deliver foreign geneticmaterial into plant cells in a process known as transformation. They further show that thenanoparticles can carry and release effectors - small molecules that induce the expressionof genes - within the plant cells in a controlled fashion. Figure. Delivering DNA and theireffector molecules into intact plant cells using mesoporous silica nanoparticles. a) Atypical plant cell, illustrating the thick cell wall (cw). b) After action of the gene gun,MSNs (small circles), carrying the small effector molecule (β-estradiol) within the gold-capped structure and externally coated with plasmid DNA, penetrate the cell wall and, insome cases, enter the cytoplasm. Torney and co-workers explored both the surface attachment and encapsulationproperties of MSNs, using plant cells as the test-bed. Plants have a thick cell wall thatimpedes delivery of materials from the exterior (Fig. a). In preliminary experiments,Torney and colleagues incubated protoplasts — plant cells whose cell walls are removed-with fluorescently labelled MSNs. It was found that modifying the MSN surface withtriethylene glycol was necessary for MSNs to penetrate the cells. This surface 16
  17. 17. modification also allowed DNA plasmids (cloned DNA segments) to adsorb onto theMSN surface. Figure. Designer nanotubes based on mesoporous silica can now penetrate thethick cell walls of plants and deliver DNA and their activators. This opens the way toprecisely manipulate gene expression in plants at the single-cell level. After entering the protoplasts, the plasmid DNA was released from the MSNs andthe green fluorescent protein (GFP) marker encoded in the DNA was expressed in thecells and detected by microscopy. Delivery is efficient because the minimum amount ofDNA required to detect marker expression was 1,000-fold lower than that required whenusing conventional methods to deliver DNA into protoplasts. It seems that using MSNs asa means to deliver DNA in this way should gain popularity for protoplast-based geneexpression studies. Although delivering material into protoplasts is important, it is not a particularlycommon approach in plant biotechnology because the cell walls must first be removed. Apopular tool used to deliver materials into plants with intact cell walls is the ‘gene gun’.The carrier particles, usually coated with DNA, enter the cells through the walls bybombardment using high-pressure gases or, less commonly, explosive rounds. Despite the destructive nature of this method, recovery is efficient enough toallow the DNA to be expressed in the plants. The advantage of using MSNs with the genegun is that both the DNA and small effector molecules can be delivered at the same time.This work stimulates a number of questions. What might be the effect of includingcombinations of effector molecules within the MSNs, and/or combinations of plasmidDNA on their surfaces? Can MSNs be designed to uncap under more selective conditions(for example, using laser light or in response to chemical changes in the plant cells)? CanMSNs be designed so they can be recapped? Answering these questions is by no means 17
  18. 18. easy, but the promise shown by MSNs in general, and this work in particular, suggestsmany more breakthroughs will emerge in this area.Hormone and Antibiotics Delivery in plants Protein and nucleic acid drugs usually have poor stability in physiologicalconditions. It is therefore essential for these drugs to be protected en route to their targetdisease sites in the body. Controlled release involves thecombination of a biocompatible material ordevice with a drug to be delivered in a way thatit can be delivered to and released at diseasedsites in a designed manner. Drug-deliverysystems may rescue potential drug candidatesby increasing solubility and stability by theapplication of coating of polymerdrugconjugates, polymeric micelles, polymericnanospheres and nanocapsules, and polyplexes. Polymer-drug conjugates (520nm) represent the smallest nanoparticulate deliveryvehicles. The polymers used for such purposes are usually highly water-soluble and includesynthetic polymers (for example, poly(ethylene glycol) (PEG)) and natural polymers (such asdextran). E.g. a cyclodextrin-based polymer developed at Insert Therapeutics increases the slowand sustained release of streptomycin, in plants against viruses.Nanofuels Levesque’s lab (University of Otawwa) is working on nanoconversion ofagricultural materials into valuable products. The design and development of newnanocatalysts for the conversion of vegetable oils into biobased fuels and biodegradablesolvents is already under scientific examination, and could be greatly enhanced with thehelp of nanotechnological abilities. This is based on the concept that the organic fuels atnano scale would be able to give greater energy with lesser energy loss duringconversion.Particle Farming Nanoparticles may not be produced in a laboratory, but grown in fields ofgenetically engineered crops – what might be called “particle farming.” 18
  19. 19. Research from the University of Texas-El Paso confirms that plants can also soakup nanoparticles that could be industrially harvested. In one particle farming experiment,alfalfa plants were grown on an artificially gold-rich soil; gold nanoparticles in the rootsand along the entire shoot of the plants that had physical properties like those producedusing conventional chemistry techniques, which are expensive and harmful to theenvironment. The metals are extracted simply by dissolving the organic material. National Chemistry Laboratory in Pune, India have been carrying out similarwork with geranium leaves immersed in a gold-rich solution.Seeding Iron Russian Academy of Sciences reports that they have been able to improve thegermination of tomato seeds by spraying a solution of iron nanoparticles on to fields.They report that application of nano-disperse iron at the rate of 10-30 µg/ml on Tomatoseeds var. Gribovskii leads to stimulator of growth and hastens the process of germinationof seeds simultaneously stimulating the development of the root system. This waspresented by A.M. Prochorov et al., “The influence of very minute doses of nano-disperse iron on seed germination,” presentation given at the Ninth Foresight Conferenceon Molecular Nanotechnology, 2001.Using Nanosensors on Crops and Nanoparticles in Fertilisers Tiny sensors offer the possibility of monitoring pathogens on crops and livestockas well as measuring crop productivity. In addition, nanoparticles could increase theefficiency of fertilisers. However, the Swiss insurance company SwissRe warned in areport in 2004 that they could also increase the ability of potentially toxic substances,such as fertilisers, to penetrate deep layers of the soil and travel over greater distances. A nanotech research initiative in Thailand aims to atomically modify thecharacteristics of local rice varieties - including the countrys famous jasmine rice- and tocircumvent the controversy over Genetically Modified Organisms (GMOs). Nanobiotechtakes agriculture from the battleground of GMOs to the brave new world of AtomicallyModified Organisms (AMOs).Nanocides: Pesticides via Encapsulation Pesticides containing nano-scale active ingredients are already on the market, andmany of the world’s leading agrochemical firms are conducting R&D on the developmentof new nano-scale formulations of pesticides (see below, Gene Giants: EncapsulationR&D). For example: BASF of Germany, the world’s fourth ranking agrochemical 19
  20. 20. corporation (and the world’s largest chemical company), recognizes nanotech’s potentialusefulness in the formulation of pesticides. BASF is conducting basic research and hasapplied for a patent on a pesticide formulation, “Nanoparticles Comprising a CropProtection Agent,” that involves an active ingredient whose ideal particle size is between10 and 150 nm. The advantage of the nano-formulation is that the pesticide dissolvesmore easily in water (to simplify application to crops); it is more stable and the killing-capacity of the chemical (herbicide, insecticide or fungicide) is optimized. Bayer CropScience of Germany, the world’s second largest pesticide firm, has applied for a patent onagrochemicals in the form of an emulsion in which the active ingredient is made up ofnanoscale droplets in the range of 10-400 nm. (An emulsion is a material in which oneliquid is dispersed in another liquid – both mayonnaise and milk are emulsions.) The company refers to the invention as a “microemulsion concentrate” withadvantages such as reduced application rate, “a more rapid and reliable activity” and“extended long-term activity.” Syngenta, headquartered in Switzerland, is the world’slargest agrochemical corporation and third largest seed company. Syngenta already sellspesticide products formulated as emulsions containing nano-scale droplets. Like Bayer Crop Science, Syngenta refers to these products as microemulsionconcentrates. For example, Syngenta’s Primo MAXX Plant Growth Regulator (designedto keep golf course turf grass from growing too fast) and its Banner MAXX fungicide(for treating golf course turf grass) are oil-based pesticides mixed with water and thenheated to create an emulsion. Syngenta claims that both products’ extremely smallparticle size of about 100 nm (or 0.1 micron) prevents spray tank filters from clogging,and the chemicals mix so completely in water that they won’t settle out in the spray tank.Banner MAXX fungicide will not separate from water for up to one year, whereasfungicides that contain larger particle size ingredients typically require agitation everytwo hours to prevent misapplications and clogging in the tank. Syngenta claims that theparticle size of this formulation is about 250 times smaller than typical pesticide particles.According to Syngenta, it is absorbed into the plant’s system and cannot be washed off byrain or irrigationSoil Binder - Using Chemical Reactions at the Nanoscale to Bind Soil Together In 2003, ETC Group reported on a nanotech-based soil binder called SoilSetdeveloped by Sequoia Pacific Research of Utah (USA). SoilSet is a quick-setting mulchwhich relies on chemical reactions on the nanoscale to bind the soil together. It wassprayed over 1,400 acres of Encebado mountain in New Mexico to prevent erosionfollowing forest fires, as well as on smaller areas of forest burns in Mendecino County,California. 20
  21. 21. Soil Clean-Up Using Iron Nanoparticles A number of approaches are being developed to apply nanotechnology andparticularly nanoparticles to cleaning up soils contaminated with heavy metals and PCBs.Dr. Wei-Xang Zhang has pioneered a nano clean-up method of injecting nano-scale ironinto a contaminated site. The particles flow along with the groundwater anddecontaminate en route, which is much less expensive than digging out the soil to treat it.Dr. Zhang’s tests with nano-scale iron show significantly lower contaminant levels withina day or two. The tests also show that the nano-scale iron will remain active in the soil forsix to eight weeks, after which time it dissolves in the groundwater and becomesindistinguishable from naturally occurring iron.Consumer products: • Nanoscale powders, in their free form, without consolidation or blending, used by cosmetics manufacturers: – Titanium Dioxide and Zinc Oxide powders for facial base creams and sunscreen lotions. – Iron Oxide powders as base material for rouge and lipstick. • Improved wear and corrosion resistance. Nanocomposite materials, with increased impact strength, for automobiles.Disease diagnosis: • Sample Retrieval: Develop retrieval nanosystems for sampling specific components (from air, plant and animal organisms, water, and soil). • Pathogen Detection: Develop methods of near real time pathogen detection and location reporting using a systems approach, integrating nanotechnology micro- electromechanical systems (MEMS), wireless communication, chip design, and molecular biology for applications in agricultural security (economic, agricultural terrorism, agricultural forensics) and food safetyQuality maintain Identity Preservation (IP) is a system that creates increased value by providingcustomers with information about the practices and activities used to produce a particularcrop or other agricultural product. Certifying inspectors can take advantage of IP as a 21
  22. 22. more efficient way of recording, verifying, and certifying agricultural practices. Today,through IP it is possible to provide stakeholders and consumers with access toinformation, records and supplier protocols regarding such information as farm of origin,environmental practices used in production, food safety and quality and informationregarding animal welfare issues. Some food or processed agricultural products may bestored for years, with intermittent samplings for storage pathogens or environmentalstorage problems. Each day shipments of food and other agricultural products are movedall over the world. Currently, there are financial limitations in the numbers of inspectorsthat can be employed at critical control points for the safe production, shipment andstorage of food and other agricultural products. Quality assurance of agriculturalproducts’ safety and security could be significantly improved through IP at the nanoscale.Nanoscale IP holds the possibility of the continuous tracking and recording of the historywhich a particular agricultural product experiences. We envision nanoscale monitorslinked to recording and tracking devices to improve identity preservation of food andagricultural products.Smart Treatment Delivery Systems Today, application of agricultural fertilizers, pesticides, antibiotics, probiotics andnutrients is typically by spray or drench application to soil or plants, or through feed orinjection systems to animals. Delivery of pesticides or medicines is either provided as“preventative” treatment, or is provided once the disease organism has multiplied andsymptoms are evident in the plant or animal. Nanoscale devices are envisioned thatwould have the capability to detect and treat an infection, nutrient deficiency, or otherhealth problem, long before symptoms were evident at the macro-scale. This type oftreatment could be targeted to the area affected. “Smart Delivery Systems” for agriculture can possess any combination of thefollowing characteristics: time-controlled, spatially targeted, self regulated, remotelyregulated, preprogrammed, or multifunctional characteristics to avoid biological barriersto successful targeting. Smart delivery systems also can have the capacity to monitor theeffects of the delivery of pharmaceuticals, nutraceuticals, nutrients, food supplements,bioactive compounds, probiotics, chemicals, insecticides, fungicides, vaccinations, orwater to people, animals, plants, insects, soils and the environment.Nanotechnology and Indian Initiatives 22
  23. 23. At present, USA leads with a 4 year, 3.7 billion USD investment through itsNanotechnology Development Programme (NDP). The market for the nanotechnology was 7.6 billion USD in 2003 and is expectedto be 1 trillion USD in 2011 However, the full potential of nanotechnology in the agricultural and foodindustry has still not been realised. 23
  24. 24. 24
  25. 25. Present area of activities in the field of Nanotechnology in IndiaThe priority areas identified in Agriculture are: • Detecting contamination in raw agriculture products • Development of nano tubes devices to diagnoses diseases in agriculture crops. • To detect carcinogenic pathogens and bio sensors for improved and contamination free agriculture products. • Use of nano particles with bio compatible ChitosanNational Challenge Program on Nanobiotechnology and Food andHealth SecurityNational Physical Laboratory, New Delhi has been entrusted as the nodal organization • To meet the Millennium Development Goal of UN 25
  26. 26. • To prioritize the area of research and to measure the research outlay and scientific and social outcome • To coordinate the research between ICAR, CSIR, ICMR, DST and DBT organizations.DST has invested approx. $20million for the period 2004-2009.OBSTACLES: Unlike building with traditional materials that stay where you put them, atomsand molecules are volatile and will rearrange themselves constantly to maintain stability.So positional Control: must be achieved, and self-replication is necessary to reduce costs.It will also allow atoms to be placed precisely without parts bumping into each other inthe wrong way. Eric Drexler has proposed a robotic arm to control the placement ofatoms. The Stewart platform, which is stiffer and simpler than Drexler’s robotic arm, hasalso been proposed.Nanotechnology : A Friend or Monster in The Making ?Current status Nanobiotechnology is still at its early stages of development the development ismulti-directional and fast-paced. Universities are forming nanotechnology centers and thenumber of papers and patent applications in the area is rising quickly. Realistically, some of these newly developed tools might not have viableapplications and could end-up on the ‘technology shelf’ in the future but offcorse thereare definite benefits. Nanobiotechnology is interdisciplinary and brings together life scientists andengineers. This, in turn, fuels further growth of ideas, which would not occur withoutthese interdisciplinary interactions.Future trends Developments will gradually become more ordered and develop sharp focus asapplications mature to produce useful and validated technologies.The question that whether the coming age of Nanotechnology is the Next technologicalrevolution everyone talking about is still to be answered?There is great optimism among scientists, politicians and policy makers who anticipatesignificant job creation. 26
  27. 27. Opportunities for developing new materials and methods that will enhance our ability todevelop faster, more reliable and more sensitive analytical systems.Overall the scenario presents us with the view that nanotechnology is here to stay!Political, social or ethical concerns related to nanotechnologydevelopment • Is Nanotechnology more acceptable compared to genetically modified products? • The potential risks in using nanoparticles in agriculture are no different than those in any other industry. • Proprietary issues associated with the nano-products. • Since there is no standardization for the use and testing of nanotechnology, products incorporating the nanomaterials are being produced without check.ConclusionsSome of the important conclusions that can be drawn are • Nanotechnology is the engineering of tiny machines i.e. the ability to build things from the “bottom up”, manufacturing because it aims to start with the smallest possible building materials, ATOMS using them to create a desired product. • By taking advantage of quantum-level properties, MNT allows for unprecedented control of the material world, at the nanoscale, providing the means by which systems and materials can be built with exact specifications and characteristics. • Nanotechnology has wider uses in biotechnology, genetics, plant breeding, disease control, fertilizer technology, precision agriculture, and allied fields, etc. SUMMARY: NANOTECHNOLOGY IN A NUTSHELL NEW TECHNOLOGY : ATOMIC ENGINEERING : NEW MATERIALS : NEW PROPERTIES SIGNIFICANTS BENEFITS : CLEAN ENERGY : IMPROVED EFFICIENCY : BETTER WASTE TTREATMENT POTENTIAL RISKS : HIGH MOBILITY ? : NOVEL TOXICITY ? : CORPORATE LIABILITY ? 27
  28. 28. So careful developments to achieve benefits and manage risks requires: • CLEAR REGULATIONS • RISK IDENTIFICATION RESEARCH • RISK MANAGEMENT STANDARDS • "Nanotechnology will give rise to a host of novel social, ethical, philosophical and legal issues. It will be important to have a group in place to predict and work to alleviate anticipated problems”. • Both the government and the private sector have to join hands and form a “Nano tech Enterprise". If we take up a mission mode with a clear cut vision, the country will reap the benefits of Nanoscience and technology.“Our future lies in Nanotechnology” We believe that nanotechnology would give us an opportunity, if we takeappropriate and timely action to become one of the important technological nations in theworld. The world market in 2005 is for nano materials, nano tools, nano devices and nanobiotechnology, which put together, is expected to be over hundred billion dollars.Nanotechnology is a new technology that is knocking at doors. (Source: presidentaddress to scientist and technologists in April 2005 in Delhi.) 28
  29. 29. Reference:-A. Malato, J. Blanco, A. Vidal and C. Richter, “Photocatalysis with solar energy at a pilot-plant scale: an overview”, (2002), Applied Catalysis B: Environmental, Vol. 37, 1–15.A. Mills, L. Punte, and M. Stephan, “An overview of semiconductor photocatalysis”, (1997), J. Photochem. Photobiol. A., Vol. 108, 1-35.A. Sugunan, H. C. Warad, C. Thanachayanont, J. Dutta And H. Hofmann, “Zinc oxide nanowires on non-epitaxial substrates from colloidal processing for gas sensing applications”, Nanostructured and Advanced Materials for Applications in Sensor, Optoelectronic and Photovoltaic Technology, NATO- Advance Study Institute, Sozopol, Bulgaria, 6-17th September 2004A.M. Prochorov et al., “The influence of very minute doses of nano-disperse iron on seed germination,” presentation given at the Ninth Foresight Conference on Molecular Nanotechnology, 2001.Annonymous, 2004. Down on the farm: The impact of nano-scale technologies on food and agriculture. Action Group on Erosion Technology Concentration, Ottawa, Canada. www.etcgroup.orgB. Phanchaisri, R. Chandet, L.D. Yu, T. Vilaithong, S. Jamjod, S. Anuntalabhochai. Low-energy ion beam-induced mutation in Thai jasmine rice (Oryza sativa L. cv. KDML 105) Surface & Coatings Technology 201 (2007) 8024–8028.C.F., Chau, Wu, Shiauan-Huei and Gow-Chin Yen. 2007. The development of regulations for food nanotechnology. Trends in Food Science and Technology. 18:269-280.C.I. Moraru, 2003. Nanotechnology: A new frontier in food science. Food Technology 57(12):24-29.D. Li, H. Haneda, “Morphologies of zinc oxide particles and their effects on photocatalysis’, (2003), Chemosphere, Vol. 51(2), 129-37 29
  30. 30. D. Maysinger, 2007. Nanoparticles and cells: Good companions and doomed partnerships. Org. Biomol. Chem. 5:2335-2342.D. S. Bhatkhande, V. G. Pangarkar and A. A. C. M. Beenackers, “Photocatalytic degradation for environmental applications – A Review”, (2001), J. Chem. Technol. Biotechnol, Vol. 77, 102- 116E. C. Alocilja and S. M. Radke, ‘Market analysis of biosensors for food safety’, Biosensors and bielectronics, (2003), Vol. 18, 841-846.ETC Group News Release, “Atomically Modified Rice in Asia?” 25 March 2004. Available on the Internet: Kulzer and M. Orrit, “Single-Molecule Optics”, (2004), Annual Review of Physical Chemistry, Vol. 55, 585-611F.R.R. Teles, L.P. Fonseca, Talanta (2008) Trends in DNA biosensors, Article in press doi:10.1016/j. Talanta.2008.07.024F.X., Redl, Cho, K.S., Murray, C. B. and O’Brien, S. (2003). Three dimensional binary super lattices of magnetic nanocrystal &semiconductor quantum dots. Nature 424(6943), 968-971.H. C. Warad, S. C. Ghosh, C. Thanachayanont and J. Dutta, ‘Highly Luminescent Manganese Doped ZnS Quantum Dots for Biological Labeling’, conference proceedings ‘Smart/Intelligent Materials and Nanotechnology’, Chiang Mai, Thailand, 1-3 December 2004. Dutta and H. Hofmann, “Self-Organization of Colloidal Nanoparticles”, (2004) Encyclopedia of Nanoscience and Nanotechnology, Vol. 9, 6 17-640.J. M. Herrmann, “Heterogeneous photocatalysis: fundamentals and applications to the removal of various types of aqueous pollutants, (1999), Catalysis Today Vol. 53, 115–129. 30
  31. 31. J. Peral, X. Domenech and D. F. Ollis, “Heterogeneous photocatalysis for purification, decontamination and deodorization of air”, (1997), J. Chem. Technol. Biotechnol, Vol. 70, 117-140.K. Yuen, U. Muller, and J. Lahiri, "Rare earth-doped glass microbarcodes",(2003), PNAS, Vol. 100, 389-393Kroto, H. W., Heath, J. R., O’Brian, S. C., Curl, R. F. and Smalley, R. E., Nature, 1985, 318, 162–163.L. C. Torres-Martínez, L. Nguyen, R. Kho, W. Bae, K. Bozhilov, V. Klimov and R. K Mehra, “Biomolecularly capped uniformly sized nanocrystalline materials: glutathione-capped ZnS nanocrystals”, (1999), Nanotechnology Vol. 10, 340-354L. Vayssieres, K. Keis, S. E. Lindquist and A. Hagfeldt, “Purpose-Built Anisotropic Metal Oxide material: 3D Highly Oriented Microrod Array of ZnO” (2001), J Phys. chem. 105, 3350-3352M. A., Poggi, Bottomley, L. A. and Lillehi, P.T. (2002). Scanning probe microscopy. Anal. chem. 74, 2851-2862.M. Blake, “Bibliography of Work on Photocatalytic Removal of Hazardous Compounds from Water and Air”, (1997), NREL/TP- 430-22197, National Renewable Energy Laboratory, Golden.M. C., Roco, Williams, R. S., Alivasatos, P., Eds. Nanotechnology Research Directions: IWGN Workshop Report, Kluwer Academic Publishers: Norwell, MA, 1999.M. H. Huang, Y Wu, H. Feick, N. Tran, E. Weber and P. Yang, "Catalytic . Growth of Zinc Oxide Nanowires by Vapor Transport" (2001), Adv. Mater., Vol. 13, 113-1 16.M. J. Dejneka, A. Streltsov, S. Pal, A. G. Frutos, C. L. Powell, K. Yost, P. Nanomaterials by J. Dutta and H. Hofmann, Text book in preparation.M. K. Hossain, S. C. Ghosh, Y Boontongkong C. Thanachayanont and . J. Dutta, “Growth of zinc oxide nanowires and nanobelts for gas sensing applications”, (2005), Journal of Metastable and Nanocrystalline Materials, Vol. 23, 27-30 31
  32. 32. M. Reches, and E. Gazit. (2003). Casting metal nano-wires within discrete self-assembled peptide noontides. Science. 300, 625- 627.P. D. Patel, “(Bio) sensors for measurement of analytes implicated in food safety: a review” (2002) Trends in analytical chemistry, Vol. 21, 96-115P. Liu, Y.W. Zhang and C. Lu, “Finite element simulations of the self- organized growth of quantum dot superlattices”, (2003), Phys. Rev. 68, 195314.P.A. Troshin, R.N. Lyubovskaya, I.N. Ioffe, N.B. Shustova, E. Kemnitz, S.I. Troyanov, Angew. Chem. Int. Ed. Engl. 44, 234 (2005).P.M. Ajayan, Nanotechnology how does a nanofibre grow? (2004). Nature. 427, 402-403.R. F., Curl, Angew. Chem., Int. Ed. Engl., 1997, 36, 1566– 1576; Kroto, R., Angew. Chem., Int. Ed. Engl., 1997, 36, 1578–1593;R. Vacassy, S. M. Scholz, , J. Dutta, C. J. G. Plummer, R. Houriet and H. Hofmann , “Synthesis of controlled spherical Zinc Sulfide Particles by Precipitation from Homogeneous Solutions”, (1998), Journal of American Ceramic Society Vol. 81, 2699-2705S. R. Nicewarner-Pena, R. G. Freeman, B. D. Reiss, L. He, D. J. Pena, I. D. Walton, R. Cromer, C. D. Keating and M. J. Natan, “Submicrometer metallic barcodes” (2001), Science, Vol. 294 (5540), 137-41T.D. Wheeler, & Stroock, A.D. 2008. The transpiration of water at negative pressures in a synthetic tree. Nature. 455:208-212.W., Ranjana. “Thailand embarks on the nano path to better rice and silk,” Bangkok Post, Jan. 21, 2004. Available on the Internet: 7266X. L. Su, Y Li, “Quantum dot biolabeling coupled with . immunomagnetic separation for detection of Escherichia coli O157:H7” (2004), Anal Chem. Vol. 76 (16), 4806-10. 32
  33. 33. Y A. Cao, X. T. Zhang, W. S. Yang, H. Du, Y B. Bai, T. J. Li, J. N. Yao, . . “Bicomponent TiO2/SnO2 particulate film for photocatalysis”, (2002), Chem. Mater., Vol. 12, 3445.Y Xia, Yang, P., Sun, Y Wu, Y Mayers, B., Gates, B., Yin, Y Kim, F., and ., ., ., ., Yan, H. (2003).One dimensional nanostructures: synthesis, characterization and application. Adv. Mater.15 (5), 353-389. 33