Dissertations / Theses on the topic 'Nanomaterials - Gas Sensing'

The aim of this research is to develop high performance gas sensors with low power consumption and high portability. This was achieved by synthesizing carbon nanomaterials decorated with alkali-metal dopants and metal oxides, and by optimizing ultrathin layer of carbon nanobutes coupled to a new deposition technique. These materials demonstrated excellent sensitivity at room temperature to both nitrogen dioxide and ammonia, down to ppm level, providing a new pathway to realise room temperature gas sensors. Our fabrication methods are highly scalable and do not involve the use of expensive equipment which makes them excellent candidates for mass production.

The birth of nanotechnology era has revolutionized materials science, catalysis and field of optoelectronics. Novel and unique phenomena emerge when material dimensions are reduced to ultra-small size regime and enter nanometre (2-100 nm) realm. Such novel materials are expected to replace bulk materials, offering lower cost of manufacturing and enabling progress in many areas such as solar cell, drug delivery, quantum communication and computing, catalysis and sensing applications. With the progress in nanomaterial synthesis and fabrication, the need for the state-of-art characterization techniques became obvious; such techniques help to establish a complete understanding of the nature and interactions of nanosized materials. In this thesis, the first part focuses on the synthesis of gold and ruthenium clusters, namely Au8, Au9, Au101, Ru3, Ru4 and AuRu3, using the well-established synthetic protocols in the literature. Apart from the standard lab-based characterization techniques such as nuclear magnetic resonance (NMR), UV-visible spectroscopy (UV-vis) and Fourier Transform Infra-red (FTIR), a less explored but useful technique far infra-red (far IR) spectroscopy, available at the Australian Synchrotron (AS), was employed to investigate the vibrational modes in these clusters. Peaks in the experimental far IR spectra were assigned unambiguously to specific vibrations by comparing with the ones generated via DFT calculations with the help of collaborators, group of Professor Gregory Metha, University of Adelaide. For the Au9 cluster, three significant gold core vibrations are observed at 157, 177 and 197 cm-1 in the experimental spectrum. In the case of the Ru3 cluster, only a single ruthenium core vibration is identified within the spectrum, at 150 cm-1 with the calculated force constant, k = 0.33 mdyne/Å. The Ru4 cluster exhibits two metal core vibrations at 153 and 170 cm-1 with force constants of 0.35 and 0.53 mdyne/Å, respectively. Substitution with a gold atom yielding a mixed metal AuRu3 cluster shifts the core transitions toward higher wavenumbers at 177 and 299 cm-1 with an increase in force constants to 0.37 and 1.65 mdyne/Å, respectively. This is attributed to the change in chemical composition and geometry of the metal cluster core. A combination of the DFT calculations and high quality synchrotron-based experimental measurements allowed the full assignment of the key transitions in these clusters. Next, these clusters were fabricated into heterogeneous catalysts by depositing on different metal oxide nanopowders. Synchrotron X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies were performed at the Australian Synchrotron and the Photon Factory synchrotron in Japan to investigate the electronic structure of Au8, Au9 and Au101 on TiO2 catalysts. The XPS analysis reveals that “as-deposited” Au8 and Au9 retain some un-aggregated clusters while Au101 show bulk-like gold. These findings are in line with TEM observations, where the aggregates (large particles, > 2 nm) of Au8, Au9 and Au101 are hardly seen under HRTEM. UV-visible diffuse reflectance spectroscopy (UV-vis DRS) studies show the absence of localised surface plasmon resonance (LSPR) peaks in these “as-deposited” clusters, suggesting they are below 2 nm in size. Importantly, the XAS spectrum of “as-deposited” Au9 clusters estimates that 60% of pure, un-aggregated Au9 clusters and 40% of bulk gold in the sample. Upon calcination under O2 and combined O2 and H2 (O2-H2), Au8, Au9 and Au101 clusters form larger nanoparticles (> 2 nm) with the appearance of LSPE peak in UV-vis DR spectra. In addition, majority of the phosphine ligands (that stabilise the gold core) dislodge and form phosphine oxide-like species by interacting with oxygen on the TiO2 surface. The third part focused on testing the catalytic performance of the supported Au8, Au9, Au101, Ru3, Ru4 and AuRu3 clusters on different TiO2, SiO2, ZnO and ZrO2 in benzyl alcohol oxidation. Au101-based catalysts display the highest catalytic activity with a turn-over frequency (TOF) up to 0.69 s-1. The high catalytic activity is attributed to the formation of large Au nanoparticles (> 2 nm) that coincides with the partial removal of capping ligands. Au8 and Au9 clusters which contain NO3- counter anions are found to be inactive in benzyl alcohol oxidation. Further work shows that the presence of NO3- species diminishes the catalytic activity. Monometallic ruthenium clusters, Ru3 and Ru4, are found to be inactive yet the bimetallic AuRu3 clusters are active in benzyl alcohol oxidation, suggesting the synergistic effect between ruthenium and gold metal. Investigation of catalytic testing parameters reveals that tuning selectivity of the product is possible through manipulating the reaction temperature. Finally, a joint experiment with Prof. Wojtek Wlodarski’s group at RMIT, Melbourne was undertaken to test the sensing ability of Au9 clusters for hydrogen detection. Au9 clusters were deposited onto radio-frequency (RF) sputtered WO3 films at two different concentrations; 0.01(S1) and 0.1(S2) mg/mL. It was found that the optimal temperatures for sensor S1 and S2 were 300 °C and 350 °C, respectively. The sensor with lower Au9 concentration (S1) displays a faster response and recovery time, and a higher sensitivity toward H2. HRTEM studies reveal that the sensor S1 contain a significant population of sub-5 nm Au nanoparticles which might be responsible for a faster rate of H2 adsorption and dissociation. The key finding in this study suggest that the addition of catalytic layer such as ultra-small Au9 clusters results in improved sensitivity and dynamic performance (response and recovery time) of H2 sensors. In summary, this thesis demonstrated that cluster-based nanomaterials have wide range of applications spanning from catalysis to sensing. Further improvements in material synthesis and use of multiple complimentary characterization techniques allowed better understanding of the nature of the key active species (metal nanoparticles) assisting design of catalysts and sensors with enhanced performance.

En aquesta tesis utilitzant principalment Aerosol Assited Chemical Vapor Deposition, AACVD, com a metodologia de síntesis d'òxid de tungstè nanoestructurat s'han fabricat diferents sensors de gasos. Per tal d'estudiar la millora en la selectivitat i la sensibilitat dels sensors de gasos basats en òxid de tungstè aquest s'han decorat, via AACVD, amb nanopartícules d'altres òxids metàl·lics per a crear heterojuncions per tal d'obtenir un increment en la sensibilitat electrònica, les propietats químiques del material o bé ambdues. En particular, s'han treballat en diferents sensors de nanofils d'òxid de tungstè decorats amb nanopartícules d'òxid de níquel, òxid de cobalt i òxid d'iridi resultant en sensors amb un gran increment de resposta i selectivitat cap al sulfur d'hidrogen, per a l'amoníac i per a l'òxid de nitrogen respectivament a concentracions traça. A més a més, s'han estudiat els mecanismes de reacció que tenen lloc entre les espècies d'oxigen adsorbides a la superfície del sensor quan interactua amb un gas. I també s'ha treballat en intentar controlar el potencial de superfície de les capes nanoestructurades per tal de controlar la deriva en la senyal al llarg del temps, quan el sensor està operant, a través d'un control de temperatura.
En esta tesis utilizando principalmente Aerosol Assited Chemical Vapor Deposition, AACVD, como metodología de síntesis de óxido de tungsteno nanoestructurado se han fabricado diferentes sensores de gases. Para estudiar la mejora en la selectividad y la sensibilidad de los sensores de gases basados en óxido de tungsteno estos se han decorado, vía AACVD, con nanopartículas de otros óxidos metálicos para crear heterouniones para obtener un incremento en la sensibilidad electrónica, las propiedades químicas del material o bien ambas. En particular, se han trabajado en diferentes sensores de nanohilos de óxido de tungsteno decorados con nanopartículas de óxido de níquel, óxido de cobalto y óxido de iridio resultante en sensores con un gran incremento de respuesta y selectividad hacia el sulfuro de hidrógeno, para el amoníaco y para el óxido de nitrógeno respectivamente a concentraciones traza. Además, se han estudiado los mecanismos de reacción que tienen lugar entre las especies de oxígeno adsorbidas en la superficie del sensor cuando interactúa con un gas. Y también se ha trabajado en intentar controlar el potencial de superficie de las capas nanoestructuradas para controlar la deriva en la señal a lo largo del tiempo, cuando el sensor está trabajando, a través de un control de temperatura.
In this thesis, using mainly Aerosol Assited Chemical Vapor Deposition, AACVD, as a synthesis methodology for nanostructured tungsten oxide, different gas sensors have been manufactured. To study the improvement in the selectivity and sensitivity of gas sensors based on tungsten oxide, they have been decorated, via AACVD, with nanoparticles of other metal oxides to create heterojunctions to obtain an increase in electronic sensitivity, in the chemical properties of the material or at the same time in both. Particularly, we have worked on different tungsten oxide nanowire sensors decorated with nanoparticles of nickel oxide, cobalt oxide and iridium oxide resulting in sensors with a large increase in response and selectivity towards hydrogen sulfide, for ammonia. and for nitrogen oxide respectively at trace concentrations. In addition, the reaction mechanisms that take place between oxygen species adsorbed on the sensor surface when it interacts with a gas have been also studied. Furthermore, efforts have been put on trying to control the surface potential of the nanostructured layers to control the drift in the signal over time, when operating the sensors, through temperature control.

This thesis deals with one-dimensional (1D) and two-dimensional nanomaterials (2D) in terms of their utilization for new types of gas sensors. Thesis focuses on study of sensing elements for gas sensors based on semiconductor metal oxide materials (MOX) and their manufacturing technology. The objective of the thesis is the design and implementation of a sensing elements formed by selected nanomaterials based on the structure of interdigital electrodes. The result of the practical part of the thesis is the characterization and comparison of materials in terms of their detection parameters in the presence of selected test gases. The first part of thesis hierarchically defines chemoresistive gas sensor, characterizes and explains its operation principle. Second part studies 1D and 2D nanomaterials of sensing elements for MOX chemoresistive gas sensors, contains a research of their properties and describes their methods of manufacturing and implementation. The last part deals with the implementation of the sensitive layer of the sensor with selected nanomaterials, characterizes and compares their detection properties.

The popularity of graphene owing to its unique properties has triggered huge interest in other two-dimensional (2D) nanomaterials. Among them, silicene shows considerable promise for electronic devices due to the expected compatibility with silicon electronics. However, the high-end potential application of silicene in electronic devices is limited owing to the lack of an energy band gap. Hence, the principal objective of this research is to tune the electronic and magnetic properties of silicene related nanomaterials through first-principles models. I first explored the impact of edge functionalization and doping on the stabilities, electronic, and magnetic properties of silicene nanoribbons (SiNRs) and revealed that the modified structures indicate remarkable spin gapless semiconductor and half-metal behaviors. In order to open and tune a band gap in silicene, SiNRs were perforated with periodic nanoholes. It was found that the band gap varies based on the nanoribbon’s width, nanohole’s repeat periodicity, and nanohole’s position due to the quantum confinement effect. To continue to take advantage of quantum confinement, I also studied the electronic and magnetic properties of hydrogenated silicene nanoflakes (SiNFs). It was discovered that half-hydrogenated SiNFs produce a large spin moment that is directly proportional to the square of the flake’s size. Next, I studied the adsorption behavior of various gas molecules on SiNRs. Based on my results, the SiNR could serve as a highly sensitive gas sensor for CO and NH3 detection and a disposable gas sensor for NO, NO2, and SO2. I also considered adsorption behavior of toxic gas molecules on boron carbide (BC3) and found that unlike graphene, BC3 has good sensitivity to the gas molecules due to the presence of active B atoms. My findings divulged the promising potential of BC3 as a highly sensitive molecular sensor for NO and NH3 detection and a catalyst for NO2 dissociation. Finally, I scrutinized the interactions of CO2 with lithium-functionalized germanene. It was discovered that although a single CO2 molecule was weakly physisorbed on pristine germanene, a significant improvement on its adsorption energy was found by utilizing Li-functionalized germanene as the adsorbent. My results suggest that Li-functionalized germanene shows promise for CO2 capture.

Investigations into a number of hetero-junction and nanoceramic materials systems for metal oxide semiconductor (MOS) gas sensing for potential environmental and bio-sensing applications are presented. The hetero-junction study encompasses investigations into various composite n-n hetero-contact systems such as WO3-ZnO and SnO2-ZnO and a p-n hetero-contact system, specifically CTO (Chromium Titanium Oxide) - ZnO. The facile fabrication of various arrays of hetero-junction MOS gas sensor devices has been demonstrated. A simple change in the compositional contribution of an individual metal oxide within a composite, exhibits the ability to tune the composite’s responsivity and selectivity. The hetero-junction systems were characterized by various techniques including Scanning Electron Microscopy (SEM), Raman spectroscopy, X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) and the influence of the physical and chemical properties of these materials towards the associated gas sensing properties, deduced. Further, the influence of fundamental properties of junctions such as contact potential and packing structure, towards the sensing properties, are also discussed. The nanomaterials study encompasses investigation into ZnO semiconducting oxides fabricated by various emerging fabrication technologies including Continuous Hydrothermal Flow Synthesis (CHFS) and other relatively high temperature routes. The chemical and physical properties of the nanoceramics have been investigated by various techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET) surface area measurements. The investigation demonstrates emerging techniques for the production of nanomaterials, which can be successfully used in MOS gas sensing for the desired applications. Further, the study shows that the behaviour of the nanomaterials is complex and material surface area is not the only deterministic factor of enhanced responsivities, but microstructural factors such as morphology and particle size, as well as heat-treatment conditions are all influential over the overall sensing properties. This thesis presents an overview of emerging material systems for MOS gas sensing applications.

博士
國立清華大學
材料科學工程學系
105
The scope of this thesis covers the fabrication of a single titanium oxide nanodot (ND) by atomic force microscopy (AFM) nanolithography, growth of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) and applications for ultraviolet (UV) light and NO gas sensing. In the first part of thesis, we report on the fabrication of a single titanium oxide ND UV sensor by AFM nanolithography. A single titanium NW is first fabricated by AFM nanomachining and gold contact electrodes are then created by photolithography. By subsequent AFM nano-oxidation, a single titanium oxide ND sensor is produced. Two types of ND sensors, namely ohmic contact and Schottky contact, have been obtained and the sensitivities are around 0.25 and 320, respectively, under ultraviolet illumination. The rise and the reset times of the Schottky contact sensor are also significantly faster. In the second part of thesis, gas sensing using the titanium oxide ND sensor is realized by the photo-activation and the photo-recovery approaches. It is found that a senor with a smaller ND has better performance than a larger one. A response of 31%, a response time of 91 s, and a recovery time of 184 s have been achieved at a concentration of 10 ppm for a ND with a size of around 80 nm. The present work demonstrates the potential application of single metal oxide NDs for gas sensing with performance that can be compared with metal oxide nanowire gas sensors. In the third part of thesis, we report on the NO gas sensing performance of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) under ambient environment. ZnO NWs are grown on Si substrates using a solution method and then modified with Cu2O NPs by photoreduction. The response of the NP modified NWs sensor to 1 ppm NO gas is 353%, which is 14.7 times as high as that of unmodified NW sensor. A response of 8.5% has been achieved at 60 ppb, showing the good potential for low concentration NO sensing.

碩士
國立臺北科技大學
製造科技研究所
102
In this study, the one-dimension tungsten oxide nanomaterials were prepared using DC magnetron sputtering, followed by annealing treatment. We adjusted various fabricated parameters such as the stable power dessity (1 Wcm-2), substrate heating (25-250℃), thickness of thin films (150, 300 and 500 nm) and annealing duration (1-2 hr) to investigate their impact on the morphology, phase, microstructure and NO2 gas sensing. During this research, we observed that the tungsten thin films which the heating substrate at 250℃ was a better preparation way for nanowire than them without substrate heating, and they were synthesized to transform into an one-dimensional structure of tungsten oxide with annealing treatment of 700℃. The length of nanowires gradually increased with longer annealing duration time, and the diameter of nanowires also had good growth trend. The results of microstructure analysis indicated that the one-dimension tungsten oxide nanomaterials present W18O49 phase with (010) growth plane. After HRTEM analysis, the d-spacing of (010) plane was 0.378 nm. In Raman analysis, we observed that the Raman spectrum of tungsten oxide nanowires appeared Raman shift at two main regions (200~500 cm-1 and 500~1000 cm-1). It indicate that the W18O49 nanowires were monoclinic structure. In gas sensing results, we found out the optimum working temperature of 150℃, and using different concentrations (10~100 ppm) to do experiments for NO2 gas sensing properties, and found out the nanowire with substrate heating had the best sensing properties. Finally, we got the conclusion that gas sensing sensitivity (2.22 to 3.13) increased with the concentration also showed a linear growth.

Currently, there is an enormous demand for the development of high performance nitrogen dioxide (NO2) gas sensors for environmental pollution monitoring. Hence, there is a constant quest to replace traditional metal oxide nanostructures as gas sensing materials due to the challenges associated with high temperature working condition. Carbon nanomaterials, particularly graphene because of its unique properties have recently attracted a great deal of interests for gas sensing applications. Abundant defects and functional groups on reduced graphene oxide (rGO), a derivative of graphene, not only facilitate gas adsorption but also provide the ease of selective functionalization with specific organic and inorganic groups for achieving selectivity. The interfacial interactions at the junctions of rGO and nanostructures support the modulation of electronic properties, making the graphene hybrid highly responsive to external chemical perturbations. A chemiresistor device based on Sr nanoparticles (NPs) decorated rGO (rGO-Sr) is presented for detecting NO2 gas over a wide concentration range of 500 ppb to 104 ppm. It is a unique study using hybrid of rGO with a low work function alkaline earth metal. At a concentration of 1 ppm, rGO-Sr exhibited an approximate 222% increase in response as compared to rGO. The calculated detection limit (DL) of the sensor was 478 ppb that is close to the experimentally observed limit. The hybrid sensor was also highly selective to NO2 amongst other gases like CO, SO2, CH4, NH3 and exhibited good sensing responses at different humidity conditions at room temperature, thus presenting it as a promising candidate for selective NO2 sensing at room temperature. Electron transfer from Sr to rGO is induced by work function difference due to which more electrons populate the rGO, thus facilitating rapid charge transfer to electrophilic NO2. Also, Sr NPs, possess high adsorption energy for NO2 which plays an important role in fast and selective adsorption of NO2 at room temperature. Thus, engineering the work function of rGO triggered by the work function differences in graphene hybrid can efficiently create a highly sensitive and selective NO2 sensor. The study was further extended to develop interfaces of rGO with semiconductor, molybdenum disulphide (MoS2) and a noble metal, silver (Ag). Thus, chemiresistive devices based on rGO-MoS2 hybrid (GM) and rGO-MoS2-Ag (GMA) were fabricated for NO2 interaction over a wide concentration range. Both the devices showed much higher sensor responses than rGO alone. Also, both the devices revealed an approximate 500% increase in response to NO2 exposure than rGO device at a concentration of 1 ppm. Moreover, the calculated DL of the GM and GMA sensors were 147 ppb and 70 ppb, respectively. The increased sensor performance of GM compared to rGO is attributed to the defect-dominated adsorption of NO2 molecules on rGO and MoS2. Also, modulation of fermi level at the p-p interface of rGO and MoS2 on NO2 exposure provides enhanced sensitivity. Further, on integration of Ag NPs onto rGO-MoS2 matrix, an interfacial electron transfer occurs from Ag to rGO and MoS2 induced by the work function differences, thus facilitating electron withdrawal by NO2. Moreover, the Ag NPs provide catalytic effect due to which more active intermediate species like NO- and O- are formed that are adsorbed on both rGO and MoS2 thus leading to enhanced sensitivity. Again, such an approach effectively pave the way for engineering nanostructures for tailoring sensitivity and selectivity. Various allotropes of carbon facilitate a unique study on the effect of size on the gas interaction. Thus, the interaction of NO2 gas with zero dimensional carbon nanodots (CNDs) has been further exploited. It is observed that the reduction in dimension of carbon structure, from two-dimensional rGO to zero-dimensional CND has a great impact on the electronic interaction process with NO2. The usual charge transfer sensing mechanism observed in rGO was found hindered in CNDs on exposure to NO2, because charge traps induced by water molecules screen any charge transfer due to NO2 molecules. The functional groups on the surface of CNDs attract ambient water molecules, which in turn act as charge traps and thus, result in the hysteresis in the current–voltage response, where area of hysteresis revealed a strong dependence on gas interaction time. Thus, this study leads to not only develop a deep understanding on the effect of size but also a novel functionality is presented on the gas interaction at small scale interfaces.

This thesis deals with the research work carried out for the development of novel applications by integrating biomolecules with various nanostructures. The thesis is organized as follows: Chapter 1 reviews the properties of nanomaterials which are important to consider while developing them for various biological and other applications. It discusses the factors which affect the cytotoxicity of nanocrystals towards living cells, photocatalytic mechanisms of nanocrystals that work behind the inactivation of bacterial cells and gas sensing properties of nanocrystals. It also mentions about the integration of biomolecules with nanomaterials which is useful for the development of biosensors, materials that are presently used for fabricating biosensors and the challenges associated with designing successful biosensors. Chapter 2 presents the antibacterial and anticancer properties of ZnO/Ag nanohybids. In this study a simple route to synthesize ZnO/Ag nanohybrids by microwave synthesis has been established where ZnO/Ag nanohybrids have shown synergistic cytotoxicity towards mammalian cells. The observed synergism in the cytotoxicity of ZnO/Ag nanohybrids could lead to the development of low dose therapeutics for cancer treatment. Chapter 3 presents photocatalytic inactivation of bacterial cells by pentavalent bismuthates class of materials. AgBiO3 which was obtained from KBiO3 by ion-exchange method was investigated for its photocatalytic inactivation properties towards E.coli and S.aureus cells under dark and UV illumination conditions. Chapter 4 presents the integration of DNA molecules with ZnO nanorods for the observation of Mott-Gurney characteristics. In this study, ZnO nanorods were synthesized hydrothermally and were characterized by TEM and XRD analysis. DNA molecules were immobilized over ZnO nanorods which were confirmed by UV-Vis spectroscopy and confocal florescence microscopy. Solution processed devices were fabricated by using these DNA immobilized nanostructures and I-V characteristics of these devices were taken in dark and under illumination conditions at different wavelengths of light at fixed intensity. Interestingly, Mott-Gurney law was observed in the I-V characteristics of the devices fabricated using DNA immobilized ZnO nanorods. Chapter 5 presents the chemical synthesis of molecular scale ultrathin Au nanowires. These nanostructures were then used for fabricating electronic biosensors. In this study, the devices were fabricated over Au nanowires by e-beam lithography and a methodology to functionalize Au nanowires and then characterize them by florescence microscopy as well as AFM has been established. The fabricated biosensors were employed for the label free, electrical detection of DNA hybridization process. Chapter 6 presents a simple, cost effective and solution processed route to fabricate devices using ultrathin Au nanowires. The devices were then used for sensing ethanol, H2 and NH3. An important property of these devices is that they can sense these gases at room temperature which reduce their operation cost and makes them desirable to use under explosive conditions.

This thesis deals with the research work carried out for the development of novel applications by integrating biomolecules with various nanostructures. The thesis is organized as follows: Chapter 1 reviews the properties of nanomaterials which are important to consider while developing them for various biological and other applications. It discusses the factors which affect the cytotoxicity of nanocrystals towards living cells, photocatalytic mechanisms of nanocrystals that work behind the inactivation of bacterial cells and gas sensing properties of nanocrystals. It also mentions about the integration of biomolecules with nanomaterials which is useful for the development of biosensors, materials that are presently used for fabricating biosensors and the challenges associated with designing successful biosensors. Chapter 2 presents the antibacterial and anticancer properties of ZnO/Ag nanohybids. In this study a simple route to synthesize ZnO/Ag nanohybrids by microwave synthesis has been established where ZnO/Ag nanohybrids have shown synergistic cytotoxicity towards mammalian cells. The observed synergism in the cytotoxicity of ZnO/Ag nanohybrids could lead to the development of low dose therapeutics for cancer treatment. Chapter 3 presents photocatalytic inactivation of bacterial cells by pentavalent bismuthates class of materials. AgBiO3 which was obtained from KBiO3 by ion-exchange method was investigated for its photocatalytic inactivation properties towards E.coli and S.aureus cells under dark and UV illumination conditions. Chapter 4 presents the integration of DNA molecules with ZnO nanorods for the observation of Mott-Gurney characteristics. In this study, ZnO nanorods were synthesized hydrothermally and were characterized by TEM and XRD analysis. DNA molecules were immobilized over ZnO nanorods which were confirmed by UV-Vis spectroscopy and confocal florescence microscopy. Solution processed devices were fabricated by using these DNA immobilized nanostructures and I-V characteristics of these devices were taken in dark and under illumination conditions at different wavelengths of light at fixed intensity. Interestingly, Mott-Gurney law was observed in the I-V characteristics of the devices fabricated using DNA immobilized ZnO nanorods. Chapter 5 presents the chemical synthesis of molecular scale ultrathin Au nanowires. These nanostructures were then used for fabricating electronic biosensors. In this study, the devices were fabricated over Au nanowires by e-beam lithography and a methodology to functionalize Au nanowires and then characterize them by florescence microscopy as well as AFM has been established. The fabricated biosensors were employed for the label free, electrical detection of DNA hybridization process. Chapter 6 presents a simple, cost effective and solution processed route to fabricate devices using ultrathin Au nanowires. The devices were then used for sensing ethanol, H2 and NH3. An important property of these devices is that they can sense these gases at room temperature which reduce their operation cost and makes them desirable to use under explosive conditions.