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Four different sensor devices were fabricated using the deposition of gold and nickel on top of polyaniline and polyaniline/zinc oxide composite thin films on glass substrates. Prepared samples were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and UV-Visible spectroscopy. FESEM images confirmed the formation of interwoven nanofibers for all samples with the mean diameter of about 90 nm for PANI. The responses of the prepared samples toward various concentrations of ammonia gas were investigated by conductometric measurements at room temperature. The responses of the fabricated sensors toward 100 ppm of NH₃ were obtained to be 112%, 3%, 177% and 148% for PANI/Au, PANI/Ni, PANI/ZnO/Au and PANI/ZnO/Ni samples, respectively. Results show both Ni and Au thin films as a metallic catalyst on top of PANI/ZnO nanocomposite can greatly improve the sensing characteristics toward NH₃ at room temperature. However, PANI/ZnO/Au has the highest response with the lowest response time (4 s). The mechanism for the sensitivity enhancement of the fabricated devices was discussed.

Room-temperature analog-to-digital converters (ADCs) based on nanoscale silicon (Si) quantum dot (QD)-based single-electron transistors (SETs) can be very attractive for high-speed processors embedded in future generation nanosystems. This paper focuses on the design and modeling of advanced single-electron converters suited for operation at room temperature. In contrast to conventional SETs with metallic QD, the use of sub-10-nm Si QD results in stable operation at room temperature, as the observable Coulomb blockade regime covers effectively the higher temperature range. Si QD-based SETs are also fully compatible with advanced CMOS technology and they can be manufactured using routine nanofabrication steps. At first, we present the principles of operation of Si SETs used for room-temperature operation. Possible flash-type ADC architectures are then investigated and the design considerations of possible Coulomb oscillation regimes are addressed. A modified design procedure is then introduced for $n$-bit SET-based ADCs, and validated through simulation of a 3-bit ADC with a sampling frequency of 5 GS/s. The ADC core is comprised from a capacitive signal divider followed by three periodic symmetric functions (PSFs). Simulation results demonstrate the stability of output signals at the room-temperature range.

Cadmium sulfide (CdS) nanocrystals are successfully fabricated on glass and silicon substrates at room temperature with low-frequency (460 kHz) inductively coupled plasma assisted magnetron sputtering technique. Both size and shape can be controlled by changing deposition parameters and substrates. Field-emission scanning electron microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction are adopted to measure the properties of CdS nanorods.

Zinc oxide (ZnO) and aluminum (Al) doped ZnO nanostructures with and without surfactant have been successfully prepared via sol-gel route. The effect of the surfactant glyoxalic acid and various concentration of Al on the structural property of ZnO was analyzed by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). The morphology of the samples was recorded using field emission scanning electron microscopy. The uniform distribution of ZnO nanostructures with hexagonal facets is facilitated by the surfactant and the grain growth is further inhibited by the increase in concentration of Al. The ethanol (0–300ppm) sensing characteristics of the as-prepared samples were systematically investigated at room temperature. Surfactant-assisted ZnO/Al:ZnO nanostructures show higher sensitivity of 94% at room temperature than ZnO/Al:ZnO nanostructures without surfactant. Faster response at 68s and recovery at 50s is also achieved by the samples. The surfactant-assisted ZnO nanostructures exhibit sharp selective detection towards ethanol when compared to the samples without surfactant. The enhanced ethanol sensing property may be ascribed to the larger surface area which is due to uniform and smaller crystallite size of the surfactant-assisted sample.

Ozone sensing properties of mixed oxides of In₂O₃, ZnO, and SnO₂ in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In₂O₃, ZnO, and snO₂ were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

A novel composite of Au-functionalized porous silicon (PS)/V₂O₅ nanorods (PS/V₂O₅:Au) was prepared to detect NO₂ gas. PS/V₂O₅ nanorods were synthesized by a heating process of pure vanadium film on PS, and then the obtained PS/V₂O₅ nanorods were functionalized with dispersed Au nanoparticles. Various analytical techniques, such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), have been employed to investigate the properties of PS/V₂O₅:Au. Herein, the PS/V₂O₅:Au sample exhibited improved NO₂-sensing performances in response, stability and selectivity at room temperature (25${}^{\circ }$C), compared with the pure PS/V₂O₅ nanorods. These phenomena were closely related to not only the dispersed Au nanoparticles acting as a catalyst but also the p-n heterojunctions between PS and V₂O₅ nanorods. Whereas, more Au nanoparticles suppressed the improvement of response to NO₂ gas.

Cu/Cu₂O nanoparticles-reduced graphene oxide composites (CuGCs) have been successfully prepared by a facile solvothermal method. The combined characterizations indicate the successful formation of CuGCs. The $\sim$ 3 nm Cu/Cu₂O nanoparticles homogeneously in situ grow on reduced graphene oxide sheets. CuGCs-based gas sensors were investigated for detection of NO₂ at room temperature. The CuGCs exhibited fast response behavior, relatively high response and could achieve a detection limit as low as 5ppm. Furthermore, sensing mechanism and the reason for enhancing sensing performance have also been discussed.

Highly ordered TiO₂ nanotube arrays were fabricated by anodization in an ethylene glycol solution containing NH₄F. A pair of platinum electrodes was deposited on the surface of the nanotube layer to fabricate a Pt/TiO₂ nanotube arrays hydrogen sensor. The subject sensors exhibited a seven order of magnitude change in resistance with a response time of 13 s at room temperature upon exposure to 2000 ppm (parts per million) hydrogen. We investigated the hydrogen response of the Pt/TiO₂ sensors as a function of the length of the nanotubes and compared their activity with that of a reference film.

It is interesting to obtain catalysts to degrade organic dye pollutants at room temperature for simultaneous purposes of environment-treating and energy-saving. In this work, a novel ZrHIO${}_6\cdot 4$H₂O catalyst was synthesized by reacting ZrO(NO${}_3{)}_2$ with H₅IO₆ in aqueous nitric acid. The catalyst was found effective in degradation of rhodamine B (RhB) or methylene blue (MB) dyes at room temperature without light illumination. We used the ultraviolet–visible (UV–Vis) absorption spectra of dye solution as well as X-ray photoelectron spectroscopy (XPS) of ZrHIO${}_6\cdot 4$H₂O to confirm that the dye degradation was due to its catalytic role. Importantly, the ZrHIO${}_6\cdot 4$H₂O catalyst can be recycled five times without obvious activity loss and it achieved higher mineralization efficiency than the previously reported analogue in the degradation experiments.

The performance of a portable propane air conditioner system, in which the temperatures of the air passing over the condenser and evaporator are equal, has been experimentally investigated under different room temperatures and refrigerant charge levels. The research has been carried out in a range of room temperatures from 20°C to 35°C and in undercharge, standard charge and overcharge conditions. The results show that, at higher room temperatures, the refrigerant temperature in all parts of the system, the density of the refrigerant at the inlet and outlet of the condenser, mass of the refrigerant in the compressor, the mass flow rate of the refrigerant and the cooling capacity of the system in either the undercharge or full charge condition, the specific cooling capacity of the undercharge system, the useful work of the compressor, and the maximum pressure of the refrigerant increase. The increase in room temperature decreases the density of the refrigerant at the inlet and outlet of the capillary tube, the mass of the refrigerant in the capillary tube, the refrigerant subcooling at the inlet of the capillary tube, the maximum velocity of the refrigerant and the coefficient of performance. In addition, the increase in room temperature at overcharge condition causes an increase in the mass flow rate, cooling capacity and specific cooling capacity to a maximum value followed by their decrease. The most important difference between a portable air conditioner and a nonportable system is the increase in cooling capacity with an increase in room temperature in full charge condition.