Capacitive-Resistive Measurements of Cobalt-Phthalocyanine Organic Humidity Sensors

In this study, the fabrication and characterization of capacitive humidity sensors using cobalt-phthalocyanine （CoPc） as the active material were presented. Thin films of CoPc were deposited by drop casting on glass substrates with pre-deposited aluminum electrodes to form A1/CoPc/A1 surface-type humidity sensors. The effect of humidity on the electrical properties of the CoPc film was investigated by measuring capacitance and resistance of the samples at four different frequencies of the applied voltage. It was observed that the capacitance of the sensor increased while the resistance decreased with raising the relative humidity. It was also found that the values of capacitance and resistance decreased with increasing frequency. The optical absorption spectra and optical band gap energy of CoPc films were measured. The structure of CoPc powder and thin films has been studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and atomic force microscopy （AFM）. Results of XRD studies show that the film structure is polycrystalline with the monoclinic structure while thin films have a peak for annealing temperatures with （100） orientation. Also, the surface morphology （grain size and roughness） for CoPc films have been studied by AFM.

Zeolite Thin Film-Coated Fiber Sensors Based on Fabry-Perot Interferometer for Detection of Chemical Vapors

A novel zeolite-coated fiber sensors for detection of volatile organic compounds （VOCs） based on the Fabry-Perot interferometer was proposed and demonstrated. The sensor comprised a polycrystalline silicalite thin film grown up on the cleaved end face of a standard single-mode fiber. The inline Fabry-Perot cavity was composed by the end face of the single-mode fiber and the thin film. The sensor device operated by measuring the interference signal, which was a function of the amount of chemical vapor adsorption in its crystalline micro porous structure. Experimental results showed that the proposed VOC sensor worked well and the sensitivities were 2.78×10^-3dB/ppm when the concentration ranged from 350ppm to 2100ppm and 1.23×10^-3 dB/ppm when the concentration ranged from 2100ppm to 5250 ppm.

Highly stretchable,soft and sticky PDMS elastomer by solvothermal polymerization process

Siloxane rubber shows attractive properties of high stability,elasticity and transparency.Besides,the regulation of its properties renders it widely used in many application fields.However,most of the reported performance improvement methods of siloxane rubber focus on the change of chemical composition of siloxane rubber,including the design of molecular chain and the introduction of other compounds,etc.Such a strategy is still faced with many limitations in practical application.In this work,on the premise of not changing the chemical composition of siloxane rubber,we propose a facile solvothermal polymerization process to change the structure of cross-linking networks,so as to obtain the siloxane rubber with controllable mechanical properties.Compared to the normal curing method,we realized polydimethylsiloxane elastomer(PDMS)with maximum elongation of more than 3,000%(>10 times of normally cured one)and tensile modulus lower than 0.15 MPa(<1/10 of normally cured one).In addition to superior stretchability,it gains extra high softness,stickiness and sensitive response to organic solvents.Based on our solvothermal cured PDMS,its applications in oil collection and organic solvent sensor have been demonstrated.It is expected that this method can be readily utilized widely and shows great application potentials.

Synthesis and Characterization of ZnO Nanowires and ZnO–CuO Nanoflakes from Sputter-Deposited Brass(Cu_(0.65)–Zn_(0.35)) Film and Their Application in Gas Sensing

A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass （Cu0.65-Zn0.35） films were deposited on oxidized Si substrate by radio frequency （RF） diode sputtering. Subsequently, these films having thickness in the range of 100-200 nm were oxidized in different oxidizing ambient in the temperature range of 300-550 ℃. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and photoluminescence （PL） techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy （XPS）. The synthesized nanowires had diameter in the range of 60-100 nm and length up to 50 μm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be -150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance Of the sensor was investigated for different nanostructured materials for various volatile organic compounds （VOCs）, It was observed that ZnO- CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.

Electrocatalytic reduction of ortho nitrobenzaldehyde using modified aluminum electrode and its determination

A simple, cost effective and rapid electrochemical method has been developed for the determination of micro level ortho nitrobenzaldehyde（ONB） based on outstanding properties of modified aluminum electrode tin nanorods/anodic aluminum oxide/aluminum（SnNR/AAO/Al） for the first time. The SnNR/AAO/Al electrode was fabricated by a second step anodization, followed by electrodeposition and its electrochemical behavior was investigated in detail. The cyclic voltammetry results indicated that the SnNR/AAO/Al electrode exhibited efficient electrocatalytic activity toward reduction of ONB in the acidic solution. It provides an appreciable improvement of reduction peak for ONB at-0.721 V.Furthermore, various kinetic parameters such as transfer electron number, transfer proton number and standard heterogeneous rate constant were calculated from the scan rates.The electrocatalytic behavior was further exploited as a sensitive detection scheme for the ONB determination by differential pulse voltammetry. Under the optimized conditions, the concentration range and detection limit are 0.1-100 μmol/L and 0.05 μmol/L, respectively,for ONB. The analytical performance of this modified sensor has been evaluated for detection of real sample such as river water and recovery of ONB was achieved all-out up to102.3% under standard addition method.