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Highlights • A new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized via a facile hydrothermal method. • Numerous SnO 2 vertical-standing nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length formed a porous microstructure. • NiO nanoplates with the size of 20 nm in diameter decorated on the inside or outside surface of SnO 2 nanotubes formed a heterojunction structure. • The NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited excellent response characteristics to ethanol at 250 ℃. Abstract In this work, a new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized successfully via a facile hydrothermal method. The microstructure, physico-chemical surface state and morphology of the composite thin film were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The results showed that the NiO decorated SnO 2 vertical-standing nanotubes composite thin film with a coral-like microstructure was built of numerous 1D SnO 2 nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length; while NiO nanoplates with the size of 20 nm in diameter decorated on the surface of SnO 2 nanotubes. Due to the enhanced adsorption of oxygen molecules, formation of p -NiO/ n -SnO 2 heterojunction and porous structure, the NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited high response value, good selectivity and quick response characteristics to ethanol at the optimum working temperature of 250 ℃. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu 2 O) nanocrystalline thin films were prepared on two types of substrates known as crystalline silicon and amorphous glass, by radio frequency reactive magnetron sputtering method. Scanning electron microscopy images confirmed that Cu 2 O particles covered the entire surface of both substrates with smoothing distribution. The root mean square surface roughness for the prepared Cu 2 O thin films on glass and Si (111) substrates is 4.16, and 3.36 nm, respectively. Meanwhile, X-ray diffraction results demonstrated that the two phases of Cu 2 O and CuO were produced on Si (111) and glass substrates. The optical bandgap of Cu 2 O thin films synthesised on glass substrate is 2.42 eV. Furthermore, the prepared Cu 2 O nanocrystalline thin films have showed low reflectance value in the visible spectrum. Metal-Semiconductor-Metal photodetector based Cu 2 O nanocrystalline thin films deposited onto Si (111) was fabricated using aluminium and platinum, with the current-voltage and photoresponse characteristic investigated under various applied bias voltages. The fabricated Metal-Semiconductor-Metal (M-S-M) photodetector had shown 126% sensitivity in the presence of 10 mW/cm 2 of 490 nm light with 1.0 V bias, displaying 90 and 100 ms response and recovery times, respectively. These findings have demonstrated the suitability of M-S-M Cu 2 O photodetector as an affordable photosensor in the future. [ABSTRACT FROM AUTHOR]

This paper presents the experimental work on the sensitivity enhancement of porous aluminium oxide based capacitive humidity sensor for trace moisture measurement. The pore morphology of nanostructured Al 2 O 3 sensing film has been tuned by adding the different amount of polyethylene glycol (PEG) in the sol solution. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Bruner–Emmet–Teller (BET) were performed for pore morphology analysis of thin films prepared by sol–gel technique. Three parallel plate capacitive sensors with identical geometries but different pore morphologies have been fabricated on Fluorine doped Tin Oxide (FTO) substrate and experimented to analyze the effects of PEG addition. The electrical characterization of the sensors has been performed to determine sensitivity, hysteresis, response and recovery time using Agilent 4294A impedance analyzer with frequency range of 1–1000 kHz. It has been observed that the addition of suitable amount of PEG improves the electrical characteristics of the sensor significantly in the range of 10–210 ppm moisture. Response characteristics of the sensors are highly linear ( R 2 = 0.995) and the sensitivity is almost twice in comparison to a sensor without PEG addition. [ABSTRACT FROM AUTHOR]

Paper-based scaffolds are an attractive material for generating 3D tissue-like cultures because paper is readily available and does not require specialized equipment to pattern, cut, or use. By controlling the exchange of fresh culture medium with the paper-based scaffolds, we can engineer diffusion-dominated environments similar to those found in spheroids or solid tumors. Oxygen tension directly regulates cellular phenotype and invasiveness through hypoxia-inducible transcription factors and also has chemotactic properties. To date, gradients of oxygen generated in the paper-based cultures have relied on cellular response-based readouts. In this work, we prepared a luminescent thin film capable of quantifying oxygen tensions in apposed cell-containing paper-based scaffolds. The oxygen sensors, which are polystyrene films containing a Pd(II) tetrakis(pentafluorophenyl)porphyrin dye, are photostable, stable in culture conditions, and not cytotoxic. They have a linear response for oxygen tensions ranging from 0 to 160 mmHg O, and a Stern-Volmer constant ( K) of 0.239 ± 0.003 mmHg O. We used these oxygen-sensing films to measure the spatial and temporal changes in oxygen tension for paper-based cultures containing a breast cancer line that was engineered to constitutively express a fluorescent protein. By acquiring images of the oxygen-sensing film and the fluorescently labeled cells, we were able to approximate the oxygen consumption rates of the cells in our cultures. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The antimony-doped tin oxide thin films for gas sensors were prepared via a sol–gel route on alumina substrates. The influence of the antimony addition amount on the electrical resistance of thin films was concluded. The relationship between them was plotted in the coordinates of logarithmic resistance against doping amount. On the basis of the Schottky barrier model, a novel method was used to evaluate the width of depletion layer of semiconductive gas sensors by using the first-order derivative of logarithmic resistance with respect to doping amount. The values of the depletion layer width were calculated for the antimony-doped thin films. The H 2 S gas was used to examine the sensor properties, which positively correlated to the depletion layer width. The oxygen species of O 2− and O − were determined to be the adsorbates on SnO 2 grains with the same proportion at the operating temperature of 300 °C. The location of the Fermi level was found to be a crucial factor that dominated the calculation results. [ABSTRACT FROM AUTHOR]

Thin films of indium tin oxide were grown by the direct evaporation technique. The sensors fabricated under the optimized deposition conditions were exposed at room temperature (303 K) to different concentrations of formaldehyde vapours and the relative change in resistance was measured. The effect of the film thickness on the response to test vapours was studied. In order to enhance the sensitivity, sensors with thin promoting layers of different metals and oxide like Cu, Ag and MgO deposited on the top of the film were fabricated and tested. The sensors with improved sensitivity were studied for the elaborate response to formaldehyde vapours at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: A contactless smart card with integral wireless power and data link and on-board chemical sensor is described. The chemical sensor part of the smart card comprises a planar conductometric interface onto which a chemically or biologically sensitive thin film may be cast using microfabrication techniques. The thin film sensor and conductometric interface form an integral part of a radio-frequency smart card that has been designed for use in distributed chemical and biological detection systems, and which is based upon the International Standards Organisation high-frequency (HF) ISO 15693 radio-frequency identification (RFID) protocol. Conductometric measurements are controlled, sampled and stored by the smart card electronics. Measurement results achieved with an organic semiconductor, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), PEDOT-PSS, as a model thin film conductometric sensor material cast on planar gold electrodes are reported. The standardisation of short-range wireless radio protocols such as Bluetooth, RuBee, ZigBee, WiFi and RFID is opening new markets for distributed sensors and sensor networks, and the fusion of chemical and biosensor technologies with short-range, low-cost, wireless technologies will create new opportunities for chemical and biological sensor systems in healthcare, environmental monitoring, process and quality control, and chemical and biological threat detection. The chemical sensor smart card described here could in future be suitable for use in various distributed short range wireless data applications and sensor networks as part of the emerging sensor Internet of Things. [Copyright &y& Elsevier]

A surface plasmon resonance (SPR) sensor based on exposed‐core microstructured optical fibres (EC‐MOFs) is presented and numerically characterised. The exposed section (analyte channel) of the EC‐MOF is coated with a SPR supporting thin film of gold. The asymmetrically coated fibre can support two separate resonance peaks, with orthogonal polarisations (x‐ and y‐polarised peaks). Although the sensitivity of both the polarised peaks is very similar, the narrower linewidth of the y‐polarised peak provides a much enhanced signal‐to‐noise ratio. The SPR sensing performance for a large refractive index (RI) range from 1.33 to 1.42 is evaluated. The sensor has higher sensitivity for detecting the high analyte RI. The feasibility of using EC‐MOFs to develop a fast‐response, real‐time and distributed SPR sensor is determined. [ABSTRACT FROM AUTHOR]