High-Selectivity Hydrogen Gas Sensors based on Mesoporous PbOx -ZnO Nanocomposites.

Hydrogen heralded as a promising renewable and environmentally friendly energy carrier, carries inherent risks owing to its highly flammable nature. A mere 4 % concentration of hydrogen in the air can trigger an explosion. To counteract this peril, a composite material comprising PbOX -ZnO (2 : 1) was synthesized, characterized, and subsequently employed to fabricate a hydrogen sensing device. Various analytical tools were used to characterize as-deposited materials, including X-ray diffraction, Scanning electron microscopy /Energy Dispersive X-ray Spectroscopy, Transmission electron microscopy UV-Vis Reflectance Spectroscopy and Fourier-transform infrared spectroscopy. The device exhibited favorable properties, such as good selectivity, stability, and a low detection limit for hydrogen. At ambient room temperature, the device demonstrated a sensing signal reaching 468.7, with a response time (T90) of 155 seconds and a recovery time (Tr90) of 69 seconds when exposed to a hydrogen concentration of 5 ppm. This performance underscores the device's rapid and effective response to hydrogen exposure. Moreover, the PbOX-ZnO (2 : 1) composite-based device exhibited a detection limit of 2.4 ppm, functioning accurately within a linear range spanning from 5 ppm to 50 ppm. This capability confirms its precision in accurately detecting hydrogen concentrations within this designated range.

Conductive Polymer (Graphene/PPy)-BiPO4 Composite Applications in Humidity Sensors.

In this particular experiment, a chain of conductive polymer graphene/polypyrrole (Gr/PPy) and BiPO4-or (Gr/PPy)-BiPO4-materials were prepared and used as moisture-sensitive materials. The structure and morphology of the conductive polymer (Gr/PPy)-BiPO4 materials were analyzed using an X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Moreover, properties such as hysteresis loop, impedance, sensing response, and response and recovery time were calculated and evaluated using an inductance-capacitance-resistance analyzer. The data expressed that PPy/BiPO4, as prepared in this study, exhibited excellent sensing properties, with impedance changing by only a few orders of range. Furthermore, the response time and time of recovery were 340 s and 60 s, respectively, and negligible humidity hysteresis occurred at different relative humidities. Therefore, conductive PPy/BiPO4, as prepared in the present study, is an excellent candidate for application in humidity sensors.

Novel Nanoarchitechtonics Olive-Like Pd/BiVO4 for the Degradation of Gaseous Formaldehyde Under Visible Light Irradiation.

In this research, olive-like Pd/BiVO4 was successfully prepared through a facile hydrothermal coreduction method for the photocatalytic degradation of formaldehyde under visible light irradiation. The structure, composition, and optical properties of the as-prepared Pd/BiVO4 were characterized through X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectrophotometry, X-ray photoelectron spectroscopy, and photoluminescence. In addition, the photocatalytic activities of Pd/BiVO4 were evaluated through the photodegradation of formaldehyde. The experimental results demonstrated that the degradation efficiency of formaldehyde increased with increasing irradiation time. Moreover, 1.0 wt% Pd/BiVO4 exhibited the highest photocatalytic performance for formaldehyde degradation in 180 min, with the formaldehyde degradation rate as high as 87.5%.

Prepared Reticulated Nickel Hydroxide for Sensing Urea by Differential Pulse Voltammetry.

A urea sensor base on reticulated nickel hydroxide is prepared by hydrothermal way and operated by differential pulse voltammetry method. The reticulated nickel hydroxide has been successfully synthesized by a hydrothermal method and has been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The Ni(OH)2 sensor exhibits a higher sensor response (S) of 7.1 than NiO and Au sensing materials to 0.05 M urea concentration at 0.62 V. Various concentration of urea from 0.1 mM to 50 mM are performed on Ni(OH)2, and the sensor response are increased from 1.1 to 7.1 by differential pulse voltammetry (DPV) method. The urea detection limit is measured as 0.1 µM in this system. In addition, the Ni(OH)2 sensor exhibited good reproducibility and short term stability, and the response exhibits no obvious changes after 20 days tests. A possible sensing mechanism of Ni(OH)2 urea sensor is presented.

Fabrication of Pd-Pt/ZnO for High Sensitive Gaseous Formaldehyde Sensor.

In the present work, the successful fabrication of highly sensitive formaldehyde sensor based on ZnO doped Pd and Pt nanoparticles. The Pt-Pt/ZnO has been synthesized through a simple, facile and rapid method and characterized by several techniques. The fabricated Pt-Pt/ZnO exhibited a very high HCHO gas sensor response of 289.2 to 10 ppm, good selectivity and experimental detection limit of 0.5 ppm at room temperature. Response and recovery times for formaldehyde are 96 s and 46 s, respectively, at room temperature. Therefore, Pt-Pt/ZnO is a promising application in the field of detection of formaldehyde.

Promotion effect of Pd on TiO2 for visible light photocatalytic degradation of gaseous formaldehyde.

TiO2 and Pd doped TiO2 (Pd/TiO2) nanoparticles were prepared by sol gel method. Pd/TiO2 material was characterized by XRD, TEM, TPR, XPS and BET. From XRD data, the crystalline type of TiO2 is known to as Anatase type. TiO2 and Pd/TiO2 were in the order of 9-10 nm and 10-13 nm respectively. The photocatalytic activities of the TiO2 and Pd/TiO2 nanomaterials were evaluated and compared for the photodegradation of formaldehyde (HCHO). HCHO degradation on Pd/TiO2 catalyst, at 60 min, the degradation rate of gaseous HCHO is 95%. Using Pd/TiO2, the rate was faster than TiO2 or doped with other metals (Au/TiO2; Ag/TiO2; Pt/TiO2).

Fast detection of local anesthetic levobupivacaine by impedance method on PPy/SWCNT.

Fast response electrochemical impedance (EI) method was developed to detect concentrations of local anesthetic Levobupivacaine. It revealed the EI method possessed fast response and recovery times and the lowest detected concentration was 1 ppm. Pyrrole was electrochemically polymerized to polypyrrole and made a composite with single walled carbon nanotubes coated over gold electrodes for sensing studies. Ppy and Ppy/SWCNT composite materials were coated upon Au electrodes and characterized by UV/Vis, Fourier Transform Infrared (FTIR), Cyclic Voltammetry (CV) and Transmission Electron Microscope (TEM). Various concentrations of levobupivacaine in the range, 1 to 500 ppm were prepared in medically significant saline solution of 0.9% NaCI as test samples. A 10-kHz frequency was used for the calibration curve, and the short response and recovery time were tested as 5 s and 3 s, respectively. The Ppy/SWCNT material with R2 as 0.9971 showed better linearity than Ppy material. Using molecular dynamic simulation studies exothermic adsorption energies and bond lengths have been calculated and explained the fast response time and lower impedance of Ppy/SWCNT than Ppy.

Bis(2-chloroethoxy)methane degradation by TiO2 photocatalysis: parameter and reaction pathway investigations.

Haloethers are widely used in industry, and the release of these species into the environment is of great concern because of their toxicity and carcinogenicity. The present study deals with the photocatalytic degradation of the haloether, bis(2-chloroethoxy)methane (BCEXM), in the presence of TiO(2) particles and UV-A (lambda=365 nm) radiation. About 99.5% of BCEXM was degraded after UV irradiation for 16h. Factors such as solution pH, TiO(2) dosage, and the presence of anions were found to influence the degradation rate. To obtain a better understanding of the mechanistic details of this TiO(2)-assisted photodegradation of BCEXM with UV irradiation, the intermediates of the processes were separated, identified, and characterized by the solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) technique. To the best of our knowledge, this is the first report on the degradation pathways of BCEXM. The first step in the destruction of BCEXM is thought to be abstraction of a hydrogen by ()OH to form a carbon-centered radical which then reacts with O(2) to form a peroxyl radical. Peroxyl radicals react with one another and produce an alkoxy radical. The beta-bond fragmentation of the alkoxy radical produces different intermediates.

In situ prepared polypyrrole for low humidity QCM sensor and related theoretical calculation.

In situ preparation of polypyrrole (Ppy) by photo-polymerization coated on a quartz crystal microbalance (QCM) as a low humidity sensor was reported. Different concentrations of Ppy films say 0wt.% (as blank), 0.1, 1, and 10wt.% were investigated to measure humidity concentrations between 14.7 and 5412.5ppm(v). The adsorption/desorption behavior was also examined at humidity concentration 510.2ppm(v). The sensitivities of 0, 0.1 and 1wt.% Ppy films at 51.5ppm(v) were 0.143, 0.219 and 0.427, respectively. For 1wt.% Ppy, the highest sensitivity was obtained. The slope and correlation coefficients (R(2)) for 1wt.% Ppy at the ranges of 14.7-898.6ppm(v) were 0.0646 and 0.9909, respectively. A series of molecular simulations have been carried out to calculate bond energy for the water molecule interaction with Ppy, which was found to be approximately 3kcal/mol indicating the existence of hydrogen bonding during the sorption process. Based on Langmuir isotherm adsorption assumption, for 0.1 and 1wt.% Ppy films, the association constants were 2606.30 and 5792.98, respectively. This larger association constant for 1wt.% Ppy film explains higher sensitivity.