Zhen Yuan

The Investigation of Reduced Graphene Oxide/P3HT Composite Films for Ammonia Detection

In this paper, single reduced graphene oxide (rGO) and rGO/Poly (3-hexylthiophene) (P3HT) composite films were prepared by the spray process, which were deposited on the interdigitated transducers for preparing the resistive ammonia (NH3) sensor. The morphology of sensitive films was characterized by scanning electron microscopy (SEM). The gas-sensing properties of GO/P3HT film sensor were tested and analyzed. The results showed that rGO/P3HT composite film sensor exhibited better sensing properties and restorability than that rGO film sensor, which maybe was ascribed to π-π interaction between rGO and P3HT and the superior surface morphology of composite films.

Reduced graphene oxide–polyethylene oxide hybrid films for toluene sensing at room temperature

A reduced graphene oxide (RGO)–polyethylene oxide (PEO) hybrid film was constructed with composite and bilayer film structures for effective ambient toluene detection. The morphology and chemical properties of the fabricated RGO–PEO hybrid materials were characterized by SEM, and Raman and FTIR spectroscopies, respectively. Sensitive properties of real-time response, sensitivity, repeatability and selectivity to toluene vapor were studied as well at room temperature. The experimental data show that the gas sensors based on composite film have a higher sensitivity than the ones based on bilayer film and pure RGO film at toluene concentrations from 80 ppm to 140 ppm. In addition, the effect of PEO volume fraction and humidity on the sensing performance was also studied. The sensor with a PEO volume fraction of 50% has a better sensitivity and faster response/recovery than others. With respect to selectivity, the gas response of the prepared sensors to toluene was at least 2-fold higher than those to other vapor species, including acetone, ethanol, hydrogen, water and formaldehyde. Furthermore, the sensing mechanism of the fabricated sensors was investigated by comparing the device performance in the presence of dry air or nitrogen as carrier gas.

A wearable and highly sensitive strain sensor based on a polyethylenimine–rGO layered nanocomposite thin film

In recent years, graphene has attracted enormous attention and has been utilized in the investigation of flexible strain sensors due to its prominent mechanical and electrical properties. In this paper, the naturally viscous material polyethylenimine (PEI) and reduced graphene oxide (rGO) were used to fabricate flexible strain sensors by facile chemical layer-by-layer self-assembly (CLS) and thermal reduction methods. The morphology, spectroscopy and thermal properties of the as-prepared sensing films were measured by SEM, AFM, FTIR and TGA. The influences of GO solution concentration and PEI–GO bilayer number on the sensing performance were studied. The optimal sensor obtained a remarkable performance with a high gauge factor (754 under 5% stretch deformation) and an ultralow limit of detection (0.1% strain). A linear relationship between the normalized response of the sensors and the stretch deformation was observed in the low strain range. The proposed sensor achieved durable properties after 500 stretching–relaxing cycles and could work and withstand a strain up to 50%. Moreover, the proposed sensor was able to detect the subtle motion of a knuckle. This research proposed a facile strategy for the large-scale fabrication of a flexible strain sensor with high sensitivity and excellent repeatability.

The investigation of reduced graphene oxide/titanium dioxide-based sensor for formaldehyde detection at room temperature

Reduced graphene oxide/titanium dioxide (rGO/TiO2) layered film was firstly utilized through simple spray method for trace detection of formaldehyde (HCHO) at room temperature. A remarkable sensitivity of layered film (0.8 ppm-1) was identified in the concentration range of 0.1 ppm to 0.5 ppm, which was higher than that of rGO-based sensor (0.5 ppm-1). It was worth noting that an interesting abruption behavior of rGO sheets during the thermal reduction process was observed. However, the collapse of rGO honeycomb network during temperature-rise period could be prevented due to the introduction of TiO2 nanoparticles. Furthermore, a novel mechanism based on àie combination of catalytic reactions and supporting function of TiO2 nanoparticles was introduced to explain the enhanced sensing performance of rGO/TiO2 layered film in contrast to bare rGO film.

Enhancement humidity sensing properties of graphene oxide/Poly(ethyleneimine) film QCM sensors

In this work, a novel graphene oxide (GO)/Poly(ethyleneimine) (PEI) layered film was prepared on the quartz crystal microbalance (QCM) by feasible spray process for the humidity detection. The morphology of sensitive film was analyzed by field emission scanning electron microscopy (FESEM). it was worth mentioning that a chemical bonding could be formed at the interface between PEI and GO sheets due to the acylation reaction, which was proved by the Fourier transform infrared (FTIR) transmission spectrum characterization. The humidity-sensing results showed that the frequency shift of sensors exhibited the excellent response and reproducibility, which might be partly ascribed to the effective interaction between PEI and GO. Meanwhile, an instant recovery time (5s) and negligible humidity hysteresis (less than 1%RH) were achieved. Furthermore, the mechanism of performance enhancement of layered film sensors was analyzed.