http://www.mdpi.com/journal/sensors/special_issues/metal_oxide_based_nanosensors/ Dear Colleagues, Going to the nanoscales changes the characteristic material properties, and characteristic lengths/timescales of dominant interactions. In metal-oxide based nanosensors, these effects have resulted in higher sensing-information-channel-capacity that includes increased sensitivity, higher selectivity, and increased speed. Room temperature applications allow low-power devices. In this special issue, the metal-oxide based sensor structures of interest include: nanoparticles, nanolayers, nanowires, thin films with nanostructures, functionalization, nanoscale coating and phases, nanocomposites, carbon nanotube - oxide systems, catalytic metal - oxide junctions, etc. Among others, the following sub-topics are of interest: Fabrication, design, methodology Characterization, physical, chemical and sensing properties Transduction mechanism: resistance, field-effect, thermoelectric, photoelectric, fluctuation-statistics, etc. Reproducibility, sensitivity, selectivity Recognition principle and sensor signal processing: information-enhancement, linear and nonlinear filtering, pattern recognition, fluctuation-enhanced sensing, etc. Applications: environmental, medical, food, defense, etc. Agent-specific sensors and electronic noses Sensing at room temperatures and other ways of reducing power requirements Prof. Dr. Laszlo B. KishDr. Gabor SchmeraGuest Editors{snippet name="submission_info"} http://www.mdpi.com/1424-8220/10/5/4855/ Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors. http://www.mdpi.com/1424-8220/10/5/4855/ Wed, 12 May 2010 00:00:00 CEST Sensors 2010-05-12 10 5 Review 4855 4886 1424-8220 A Comprehensive Review of Glucose Biosensors Based on Nanostructured Metal-Oxides 2010-05-12 doi: 10.3390/s100504855 Rahman Ahammad Jin Ahn Lee http://www.mdpi.com/1424-8220/10/4/4083/ In this article, we review gas sensor application of one-dimensional (1D) metal-oxide nanostructures with major emphases on the types of device structure and issues for realizing practical sensors. One of the most important steps in fabricating 1D-nanostructure devices is manipulation and making electrical contacts of the nanostructures. Gas sensors based on individual 1D nanostructure, which were usually fabricated using electron-beam lithography, have been a platform technology for fundamental research. Recently, gas sensors with practical applicability were proposed, which were fabricated with an array of 1D nanostructures using scalable micro-fabrication tools. In the second part of the paper, some critical issues are pointed out including long-term stability, gas selectivity, and room-temperature operation of 1D-nanostructure-based metal-oxide gas sensors. http://www.mdpi.com/1424-8220/10/4/4083/ Thu, 22 Apr 2010 00:00:00 CEST Sensors 2010-04-22 10 4 Review 4083 4099 1424-8220 One-Dimensional Oxide Nanostructures as Gas-Sensing Materials: Review and Issues 2010-04-22 doi: 10.3390/s100404083 Choi Jang http://www.mdpi.com/1424-8220/10/4/3882/ Electronic noses (E-noses) use various types of electronic gas sensors that have partial specificity. This review focuses on commercial and experimental E-noses that use metal oxide semi-conductors. The review covers quality control applications to food and beverages, including determination of freshness and identification of contaminants or adulteration. Applications of E-noses to a wide range of foods and beverages are considered, including: meat, fish, grains, alcoholic drinks, non-alcoholic drinks, fruits, milk and dairy products, olive oils, nuts, fresh vegetables and eggs. http://www.mdpi.com/1424-8220/10/4/3882/ Thu, 15 Apr 2010 00:00:00 CEST Sensors 2010-04-15 10 4 Review 3882 3910 1424-8220 Metal Oxide Sensors for Electronic Noses and Their Application to Food Analysis 2010-04-15 doi: 10.3390/s100403882 Berna http://www.mdpi.com/1424-8220/10/3/2088/ Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. http://www.mdpi.com/1424-8220/10/3/2088/ Mon, 15 Mar 2010 00:00:00 CET Sensors 2010-03-15 10 3 Review 2088 2106 1424-8220 Metal Oxide Gas Sensors: Sensitivity and Influencing Factors 2010-03-15 doi: 10.3390/s100302088 Wang Yin Zhang Xiang Gao http://www.mdpi.com/1424-8220/10/3/1753/ The study presents a micro carbon monoxide (CO) sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and carbon nanotube (CoOOH/CNT) film that is prepared by a precipitation-oxidation method. The structure of the CO sensor is composed of a polysilicon resistor and a sensing film. The sensor, which is of a resistive type, changes its resistance when the sensing film adsorbs or desorbs CO gas. The readout circuit is used to convert the sensor resistance into the voltage output. The post-processing of the sensor includes etching the sacrificial layers and coating the sensing film. The advantages of the sensor include room temperature operation, short response/recovery times and easy post-processing. Experimental results show that the sensitivity of the CO sensor is about 0.19 mV/ppm, and the response and recovery times are 23 s and 34 s for 200 ppm CO, respectively. http://www.mdpi.com/1424-8220/10/3/1753/ Wed, 03 Mar 2010 00:00:00 CET Sensors 2010-03-03 10 3 Article 1753 1764 1424-8220 Cobalt Oxide Nanosheet and CNT Micro Carbon Monoxide Sensor Integrated with Readout Circuit on Chip 2010-03-03 doi: 10.3390/s100301753 Ching-Liang Dai Yen-Chi Chen Chyan-Chyi Wu Chin-Fu Kuo http://www.mdpi.com/1424-8220/10/2/1216/ Nanostructured ZnO with its unique properties could provide a suitable microenvironment for immobilization of enzymes while retaining their biological activity, and thus lead to an expanded use of this nanomaterial for the construction of electrochemical biosensors with enhanced analytical performance. ZnO-based enzyme electrochemical biosensors are summarized in several tables for an easy overview according to the target biosensing analyte (glucose, hydrogen peroxide, phenol and cholesterol), respectively. Moreover, recent developments in enzyme electrochemical biosensors based on ZnO nanomaterials are reviewed with an emphasis on the fabrications and features of ZnO, approaches for biosensor construction (e.g., modified electrodes and enzyme immobilization) and biosensor performances. http://www.mdpi.com/1424-8220/10/2/1216/ Mon, 01 Feb 2010 00:00:00 CET Sensors 2010-02-01 10 2 Review 1216 1231 1424-8220 ZnO-Based Amperometric Enzyme Biosensors 2010-02-01 doi: 10.3390/s100201216 Zhiwei Zhao Wei Lei Xiaobing Zhang Baoping Wang Helong Jiang http://www.mdpi.com/1424-8220/10/1/670/ An innovative fabrication method to produce a macroporous Si surface by employing an anodic aluminium oxide (AAO) nanopore array layer as an etching template is presented. Combining AAO with a reactive ion etching (RIE) processes, a homogeneous and macroporous silicon surface can be effectively configured by modulating AAO process parameters and alumina film thickness, thus hopefully replacing conventional photolithography and electrochemical etch methods. The hybrid process integration is considered fully CMOS compatible thanks to the low-temperature AAO and CMOS processes. The gas-sensing characteristics of 50 nm TiO2 nanofilms deposited on the macroporous surface are compared with those of conventional plain (or non-porous) nanofilms to verify reduced response noise and improved sensitivity as a result of their macroporosity. Our experimental results reveal that macroporous geometry of the TiO2 chemoresistive gas sensor demonstrates 2-fold higher (~33%) improved sensitivity than a non-porous sensor at different levels of oxygen exposure. In addition, the macroporous device exhibits excellent discrimination capability and significantly lessened response noise at 500 °C. Experimental results indicate that the hybrid process of such miniature and macroporous devices are compatible as well as applicable to integrated next generation bio-chemical sensors. http://www.mdpi.com/1424-8220/10/1/670/ Tue, 19 Jan 2010 00:00:00 CET Sensors 2010-01-19 10 1 Article 670 683 1424-8220 A Macroporous TiO2 Oxygen Sensor Fabricated Using Anodic Aluminium Oxide as an Etching Mask 2010-01-19 doi: 10.3390/s100100670 Chih-Cheng Lu Yong-Sheng Huang Jun-Wei Huang Chien-Kuo Chang Sheng-Po Wu http://www.mdpi.com/1424-8220/10/1/361/ We have developed a simple way to generate binary patterns based on spectral slopes in different frequency ranges at fluctuation-enhanced sensing. Such patterns can be considered as binary "fingerprints" of odors. The method has experimentally been demonstrated with a commercial semiconducting metal oxide (Taguchi) sensor exposed to bacterial odors (Escherichia coli and Anthrax-surrogate Bacillus subtilis) and processing their stochastic signals. With a single Taguchi sensor, the situations of empty chamber, tryptic soy agar (TSA) medium, or TSA with bacteria could be distinguished with 100% reproducibility. The bacterium numbers were in the range of 2.5 × 104-106. To illustrate the relevance for ultra-low power consumption, we show that this new type of signal processing and pattern recognition task can be implemented by a simple analog circuitry and a few logic gates with total power consumption in the microWatts range. http://www.mdpi.com/1424-8220/10/1/361/ Tue, 05 Jan 2010 00:00:00 CET Sensors 2010-01-05 10 1 Article 361 373 1424-8220 Binary Fingerprints at Fluctuation-Enhanced Sensing 2010-01-05 doi: 10.3390/s100100361 Hung-Chih Chang Laszlo B. Kish Maria D. King Chiman Kwan http://www.mdpi.com/1424-8220/9/12/9903/ This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. http://www.mdpi.com/1424-8220/9/12/9903/ Fri, 04 Dec 2009 00:00:00 CET Sensors 2009-12-04 9 12 Review 9903 9924 1424-8220 Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures 2009-12-04 doi: 10.3390/s91209903 Jin Huang Qing Wan http://www.mdpi.com/1424-8220/9/11/8911/ ZnO nanotubes and nanorods grown on gold thin film were used to create pH sensor devices. The developed ZnO nanotube and nanorod pH sensors display good reproducibility, repeatability and long-term stability and exhibit a pH-dependent electrochemical potential difference versus an Ag/AgCl reference electrode over a large dynamic pH range. We found the ZnO nanotubes provide sensitivity as high as twice that of the ZnO nanorods, which can be ascribed to the fact that small dimensional ZnO nanotubes have a higher level of surface and subsurface oxygen vacancies and provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods, thus affording the ZnO nanotube pH sensor a higher sensitivity. Experimental results indicate ZnO nanotubes can be used in pH sensor applications with improved performance. Moreover, the ZnO nanotube arrays may find potential application as a novel material for measurements of intracellular biochemical species within single living cells. http://www.mdpi.com/1424-8220/9/11/8911/ Mon, 09 Nov 2009 00:00:00 CET Sensors 2009-11-09 9 11 Communication 8911 8923 1424-8220 Miniaturized pH Sensors Based on Zinc Oxide Nanotubes/Nanorods 2009-11-09 doi: 10.3390/s91108911 Alimujiang Fulati Syed M. Usman Ali Muhammad Riaz Gul Amin Omer Nur Magnus Willander http://www.mdpi.com/1424-8220/9/10/8158/ A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. http://www.mdpi.com/1424-8220/9/10/8158/ Fri, 16 Oct 2009 00:00:00 CEST Sensors 2009-10-16 9 10 Review 8158 8196 1424-8220 Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection 2009-10-16 doi: 10.3390/s91008158 Sofian M. Kanan Oussama M. El-Kadri Imad A. Abu-Yousef Marsha C. Kanan http://www.mdpi.com/1424-8220/9/9/7445/ Ever since the discovery of the pH-sensing properties of ZnO crystals, researchers have been exploring their potential in electrochemical applications. The recent expansion and availability of chemical modification methods has made it possible to generate a new class of electrochemically active ZnO nanorods. This reduction in size of ZnO (to a nanocrystalline form) using new growth techniques is essentially an example of the nanotechnology fabrication principle. The availability of these ZnO nanorods opens up an entire new and exciting research direction in the field of electrochemical sensing. This review covers the latest advances and mechanism of pH-sensing using ZnO nanorods, with an emphasis on the nano-interface mechanism. We discuss methods for calculating the effect of surface states on pH-sensing at a ZnO/electrolyte interface. All of these current research topics aim to explain the mechanism of pH-sensing using a ZnO bulk- or nano-scale single crystal. An important goal of these investigations is the translation of these nanotechnology-modified nanorods into potential novel applications. http://www.mdpi.com/1424-8220/9/9/7445/ Wed, 16 Sep 2009 00:00:00 CEST Sensors 2009-09-16 9 9 Review 7445 7480 1424-8220 The pH Response and Sensing Mechanism of n-Type ZnO/Electrolyte Interfaces 2009-09-16 doi: 10.3390/s90907445 Safaa Al-Hilli Magnus Willander http://www.mdpi.com/1424-8220/9/8/6504/ One-dimensional (1D) metal-oxide nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating size and dimensionality dependence of nanostructure properties for potential applications. The construction and integration of photodetectors or optical switches based on such nanostructures with tailored geometries have rapidly advanced in recent years. Active 1D nanostructure photodetector elements can be configured either as resistors whose conductions are altered by a charge-transfer process or as field-effect transistors (FET) whose properties can be controlled by applying appropriate potentials onto the gates. Functionalizing the structure surfaces offers another avenue for expanding the sensor capabilities. This article provides a comprehensive review on the state-of-the-art research activities in the photodetector field. It mainly focuses on the metal oxide 1D nanostructures such as ZnO, SnO2, Cu2O, Ga2O3, Fe2O3, In2O3, CdO, CeO2, and their photoresponses. The review begins with a survey of quasi 1D metal-oxide semiconductor nanostructures and the photodetector principle, then shows the recent progresses on several kinds of important metal-oxide nanostructures and their photoresponses and briefly presents some additional prospective metal-oxide 1D nanomaterials. Finally, the review is concluded with some perspectives and outlook on the future developments in this area. http://www.mdpi.com/1424-8220/9/8/6504/ Thu, 20 Aug 2009 00:00:00 CEST Sensors 2009-08-20 9 8 Review 6504 6529 1424-8220 A Comprehensive Review of One-Dimensional Metal-Oxide Nanostructure Photodetectors 2009-08-20 doi: 10.3390/s90806504 Tianyou Zhai Xiaosheng Fang Meiyong Liao Xijin Xu Haibo Zeng Bando Yoshio Dmitri Golberg