Heterojunctions of rGO/metal oxide nanocomposites as promising gas-sensing materials—A review

Monitoring environmental hazards and pollution control is vital for the detection of harmful toxic gases from industrial activities and natural processes in the environment, such as nitrogen dioxide (NO2), ammonia (NH3), hydrogen (H2), hydrogen sulfide (H2S), carbon dioxide (CO2), and sulfur dioxide (SO2). This is to ensure the preservation of public health and promote workplace safety. Graphene and its derivatives, especially reduced graphene oxide (rGO), have been designated as ideal materials in gas-sensing devices as their electronic properties highly influence the potential to adsorb specified toxic gas molecules. Despite its exceptional sensitivity at low gas concentrations, the sensor selectivity of pristine graphene is relatively weak, which limits its utility in many practical gas sensor applications. In view of this, the hybridization technique through heterojunction configurations of rGO with metal oxides has been explored, which showed promising improvement and a synergistic effect on the gas-sensing capacity, particularly at room temperature sensitivity and selectivity, even at low concentrations of the target gas. The unique features of graphene as a preferential gas sensor material are first highlighted, followed by a brief discussion on the basic working mechanism, fabrication, and performance of hybridized rGO/metal oxide-based gas sensors for various toxic gases, including NO2, NH3, H2, H2S, CO2, and SO2. The challenges and prospects of the graphene/metal oxide-based based gas sensors are presented at the end of the review

Effect of reaction time on the structure and optical properties of P3HT/MWCNT-OH nanocomposites

In the present study, regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) coated hydroxylated multi-walled carbon nanotubes (MWCNT-OH) nanocomposites were prepared over different reaction times of non-covalent functionalization. The reaction time was set as 24, 48, 72, 96, and 120 hours. The structure and optical characteristics of nanocomposites were analyzed using Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, respectively. Reaction time affected prepared nanocomposites by decreasing the intensity of the P3HT/MWCNT-OH peaks gradually with increasing of the reaction time. Comparing with the pure P3HT and MWCNT-OH, the calculated energy band gap and the Urbach energy of the nanocomposites were reduced proportionally as the reaction time reached 120 hours and achieved 2.60 and 0.329 eV, respectively

Research progress on polythiophene and its application as chemical sensor

The π-conjugated polymers and their derivatives have attracted significant attention in recent decades for research and development as chemical sensor. This is because of their wide range of potential applications especially as an active layer in various electronic devices. The organic structure of these polymers had confer the electronic and material properties and facilitate their processibility. This includes several promising of conjugated polymers such as polyacetylene, polyaniline, polypyrole, polythiophene (PTh) and etc. Above all, the conjugated polythiophene and its derivatives stand out as one of the promising members of the conjugated polymer family. Due to their unique in electrical characteristics, excellent environmental and thermal stability, low-cost synthesis, and mechanical strength, various procedures have been invoked in order to increase the usability of polythiophene. This includes side chain functionalization of the different derivatives and copolymers, functionalised with carbonaceous materials, and combination of both of these strategies. In this review, focus is on the present conductive polymers, the characteristics and the synthesization of polythiophene and its derivatives, and their applications in chemical sensor are highlighted at the last part

Carbon Nanotubes: Functionalisation And Their Application In Chemical Sensors

Carbon nanotubes (CNTs) have been recognised as a promising material in a wide range of applications, from safety to energy-related devices. However, poor solubility in aqueous and organic solvents has hindered the utilisation and applications of carbon nanotubes. As studies progressed, the methodology for CNTs dispersion was established. The current state of research in CNTs either single wall or multiwall/polymer nanocomposites has been reviewed in context with the various types of functionalisation presently employed. Functionalised CNTs have been playing an increasingly central role in the research, development, and application of carbon nanotube-based nanomaterials and systems. The extremely high surface-to-volume ratio, geometry, and hollow structure of nanomaterials are ideal for the adsorption of gas molecules. This offers great potential applications, such as in gas sensor devices working at room temperature. Particularly, the advent of CNTs has fuelled the invention of CNTbased gas sensors which are very sensitive to the surrounding environment. The presence of O2, NH3, NO2 gases and many other chemicals and molecules can either donate or accept electrons, resulting in an alteration of the overall conductivity. Such properties make CNTs ideal for nano-scale gas-sensing materials. Conductive-based devices have already been demonstrated as gas sensors. However, CNTs still have certain limitations for gas sensor application, such as a long recovery time, limited gas detection, and weakness to humidity and other gases. Therefore, the nanocomposites of interest consisting of polymer and CNTs have received a great deal of attention for gas-sensing application due to higher sensitivity over a wide range of gas concentrations at room temperature compared to only using CNTs and the polymer of interest separatel

インジウムスズ酸化物と有機半導体界面の光学的第二高調波の研究

Supervisor:水谷　五郎マテリアルサイエンス研究科博

Vibrational Spectroscopy Analysis of Oligothiophene Blend Film

One of the challenges in fabricating organic semiconductor thin film is to produce bettermolecular ordering that compromise its electronic properties. Molecular ordering of amorphous thin film can be improved in many ways. Here, high molecular weight polylactic acid (PLA) is introduced as binding matrix to promote 3'''-didodecyl-2,2':5',2'':5'',2'''-quaterthiophene (4T) film’s homogeinity across indium tin oxide (ITO) surface. Molecular ordering of the spin coated biodegradable PLA and 4T blend film processed at ambient atmosphere was studied using two vibrational spectroscopy methods. The complementary analysis of infrared absorption spectrum and Raman spectrum had identified several vibrational modes contributed by thiophene rings and alkyl functional groups. The Raman analysis implied there is a slight change of thiophene ringsʼ molecular orientation due to compressive stress after introduction of polymer. Microscopic characteristics of oligothiophenes especially at the π-π conjugated backbones contained crucial information in order to exploit the oligothiophene as flexible electronics devices.</jats:p

High voltage switch mode power supply for laser system

This paper describes a high voltage design using switch mode power supply (SMPS) technique. The intention is to have low risk and high efficient to deal with laser system. At primary stage an input signal of 12 V was provided into a comparator which acts as a switching drive control unit. MOSFET was employed as a switching unit. It drives the given signal into an isolation transformer to step-up into 230 AC voltages. Network comprises of diodes and capacitors used to rectify the output voltage into a smooth DC signal. The performance of the high voltage SMPS circuit is found to be dependent on the input supply current, the input frequency, the negative feedback resistance and the number stages of voltage multipliers