Graphene and chemically modified graphene can be fabricated via numerous routes each with its own merits concerning ease of processability, cost-effectiveness for large-scale production, and also health and safety. One of the promising applications of graphene-based composites is gas sensing, which is mainly useful for environmental monitoring. We review some of the significant findings on graphene-based sensing materials for the detection of organic vapors, toxic gases, and chemical warfare agent simulants using an electrochemical method. Electrochemical sensing can be performed by inducing interactions between gas molecules and a graphene layer, such as charge transfer that gives a change in an electrical signal. The intrinsic properties of graphene and its role in some gas sensing applications will be discussed. Graphene and graphene oxide (GO) work as continuous conductive networks with a large number of surface adsorption sites for many gas molecules. Hybrid graphene devices incorporate semiconductors, metals, and molecular binders to enhance the capabilities of solidstate gas sensors. This article also addresses current approaches to the commercialization of graphene-based gas sensors.
Graphene is a single-atom-thick sheet of sp2 hybridized carbon atoms that are packed in a hexagonal honeycomb crystalline structure. This promising structure has endowed graphene with advantages in electrical, thermal, and mechanical properties such as room-temperature quantum Hall effect, long-range ballistic transport with around 10 times higher electron mobility than in Si and thermal conductivity in the order of 5,000 W/mK, and high electron mobility at room temperature (250,000 cm2/V s). Another promising characteristic of graphene is large surface area (2,630 m2/g) which has emerged so far with its utilization as novel electronic devices especially for ultrasensitive chemical sensor and reinforcement for the structural component applications. The application of graphene is challenged by concerns of synthesis techniques, and the modifications involved to improve the usability of graphene have attracted extensive attention. Therefore, in this review, the research progress conducted in the previous decades with graphene and its derivatives for chemical detection and the novelty in performance enhancement of the chemical sensor towards the specific gases and their mechanism have been reviewed. The challenges faced by the current graphene-based sensors along with some of the probable solutions and their future improvements are also being included.
Exposure and misuse of organophosphate (OP) compounds originated from insecticides, drugs and chemical warfare agents are potential hazard to health and environment. OP detection is one of the four strategies (deter, detect, delay, and defend) to protect vulnerable from this chemical threat. Among many methods to detect OP, electrical-based detection and graphene nanomaterials deliver higher sensitivity performance, technological compatibility, and versatility. The magic of graphene originates from its large surface area and excellent electrical conductivity, while electrical methods offer low cost, rapid, and easy handling. This article provides an overview of selected electrical and electrochemical methods employing graphene, reduced graphene oxide, graphene oxide, and other graphene forms reported for OP detection in the recent years. Strategies in using graphene, experimental challenges and fundamental material interactions including advantages using biomaterials as receptors in achieving better detection limit, specificity, and selectivity of OP compounds are the highlights of the paper. Every transformation of graphene has its merits in term of ease of processing, device functionality and sustainability. Since contemporary graphene had successfully reached low detection limit possible in OP sensing, graphene sensor device should be focused on developing rapid and in-situ OP monitoring in water and food resources to alert authorities on possible contamination in the community.
This paper presents a structural analysis of various methods to produce bacterial cellulose (BC) from Nata de Coco (Acetobacter xyllinum). BC sheet, BC chem and BC mech powder were successfully prepared using oven drying, chemical and mechanical treatment. The X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and field emission scanning electron microscopy (FESEM) were used to analyze the structure of prepared BC. The structure of bacterial cellulose was compared with the structure of commercial microcrystalline cellulose (MCC) and cotton fabric. The XRD results showed that the BC sheet sample had the highest degree of crystallinity (81.76%) compared to cotton cellulose (75.73%). The crystallite size of cotton was larger than the BC sheet, with the value of 6.83 ηm and 4.55 ηm, respectively. The peaks in the FTIR spectra of all BC were comparable to the commercial MCC and cotton fabrics. FESEM images showed that the prepared BC sheet, BC mech, and BC chem had an almost similar structure like commercial MCC and cotton fabric. It was concluded that simple preparation of BC could be implemented and used for further BC preparation as reinforcement in polymer composites, especially in food packaging.
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