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

Thermo-electrical and mechanical studies on polymer-organically modified montmorillonite composites / Norhana Abdul Halim

The field of polymer-nanoclay composite has attracted a lot of attention in materials studies due to the dramatic improvement on polymers characteristics. For example mechanical and thermal properties, chemical resistance as well as the reduced gas permeability. However, structural changes and the mechanisms that may contribute to these improvements are not fully understood. In this work, the study on polymer nanoclay composite concentrates on the effects of OMON inclusion within different polymer matrix systems. The matrixes are a series of natural rubbers (Standard Malaysia Rubber – Latex grade (SMRL); Deproteinized Natural Rubber (DPNR) and Epoxidized Natural Rubber (ENR-50)), plasticized Polyvinyl chloride (pPVC) and Polyethylene (PE). OMON is a renewed Montmorillonite (Mon) clay mineral, where chemical modifications carried out had changed the organophobic property of this mineral into organophylic. XRD analyses demonstrate the intercalation of polymeric chains, showing the increase in OMON basal spacing d001 from 1.840 nm to 3.864 nm. From the FTIR spectra of polymer-OMON composites, matrix-OMON silicates interaction is shown with the appearance of (Si-O-R) band and the changes in SiH (SiH and SiH) vibrations. Investigation on the improved matrix-OMON interactions within polymer-OMON composites concentrates on their thermo-electrical and mechanical responses. TSC measurement is chosen to carry out the thermo-electrical studies, which involves instrumentation of TSC system. The high sensitivity of TSC technique is capable to detect various dipoles and space charges relaxations, as shown with the emergence of , and peaks. Observations and analyses on and OMON peaks reveal the effects of matrix-alkyl and matrix-silicate interactions on methylene groups (CH2) and alkyl chains (CH2)n within OMON gallery in the composites. Decomposition on TSC peaks confirm the involvement of various distributed relaxation processes. It also reveals the existence of molecular-ion deep traps with high activation energy E (> 4eV). Analyses on pre-exponential factor n from N-fitting method distinguish a range of dipole relaxations. It gives characteristic relaxation time n that suggest the occurances of dipole (10-10 s to 10-13 s), dipole-segmental (10-14 s to 10-17 s) and segmental (10-18 s to 10-28 s) relaxation modes. Several n (10+1 s to 10-4 s) from experimental TSC peaks also confirm the cooperative relaxation around the glass transition temperature Tg. Abstract Analyses and observations on some basic mechanical properties generated from tensile test demonstrate structural effects on the entire composite system. Various matrix-alkyl chains and matrix-silicate interactions induce interfacial adhesion, interparticle bridging flocculated and stacking layer structure, which influence the elasticity modulus Young Y, Tensile strength max and Maximum elongation max. Polar matrix-silicate interactions within CENR-50 (30%) composite had improved the interfacial adhesion, which contributed to the significant increase in modulus Y (15420 %) compares to that of pristine ENR-50. Similarly, CpPVC (30%) that is a pPVC composite with the improved OMON stacked structure (N 21 layers) also demonstrates the increased modulus Y (2323 %). Polymers intercalation into OMON gallery can promote certain chemical reactions, which affect the inner structure of a composite. For example, chains crosslinking within OMON gallery that creates the interparticle bridging flocculated structure also promotes more slippage on the matrix chain during stress loading. As a result, it improves the Maximum elongation max with the increase of OMON content as shown by the CSMRL (30%) (max 70 %) and CDPNR (30%) (max 125 %) composites

Students’ perceptions on ethnic tolerance in Malaysia: A study in three public universities

This study is an attempt to develop an index on ethnic tolerance among the Malay, Chinese and Indian undergraduate students of three Malaysian public universities. It focuses on three main domains: religious practices, ethnic‒cross relationship and governance. The data of 378 respondents were analyzed using the Statistical Package for the Social Science (SPSS) software version 22. The calculation and the measurement of the index are based on the method and equations used in calculating the index among Malaysian youths in 2015 that were capable of incorporating many domains. All the domains are significant in contributing to ethnic tolerance the composite index value of 4.13 out of 5 was obtained which shows the students are at the level of highly tolerant. </jats:p

NATURAL VS. SYNTHETIC REPELLENTS ON TREATED CLOTHING: ADVANTAGES, CHALLENGES AND THEIR EFFICACY

Arthropod-borne viruses have become a major threat to human health worldwide. The implementation of personal protection through clothing is necessary to avoid insect bites, especially for military operations and public health emergencies. Development of synthetic repellents in clothing impregnation has been well-established whilst, numerous studies regarding the application of essential oils on textile substrates have been carried out to develop their use as an alternative to synthetic repellents. The present review attempts to give a general overview and summarize the current technology used in treated clothing, as well as the advantages, challenges, limitations, and factors that may affect the performance of synthetic repellents and essential oils in textiles. Current research trends in developing more effective repellents from essential oils are also summarized.</jats:p

Morphology Studies of SWCNT Dispersed in Conducting Polymer as Potential Sensing Materials

Novel electronic nanomaterial, the carbon nanotube (CNT) has emerged in many sensor applications as such its state dispersion has considerable importance to ensure the sustainability of its electronic properties. In this paper, we reported a state of art conductivity mapping on nanostructure surface of single walled carbon nanotubes (SWCNT) and poly(3-hexylthiophene-2,5-diyl), (P3HT) as potential sensing film. This composite is proposed to give selective analyte anchoring across the film as well as improved carrier mobility. The easy solution processing method was chosen to produce non-covalently wrapped conducting polymer onto the surface of SWCNT. We successfully observed high resolution images of the SWCNT walls that indicated increase of the thickness due to polymer wrapping. The image obtained from conductivity atomic force microscopy (CAFM) show the film’s electrical distribution that correlated with the observed nanostructure of film. Supporting optical characteristics of the nanocomposite obtained from UV-Vis spectroscopy and Raman spectroscopy discussed the morphology of the polymer wrapping and the state of dispersion of the polymer and the nanotubes. It is hypothesized the filament structures made by P3HT/SWCNT can give better sensing performance due to modification of π-π electronic band of SWCNT.</jats:p

Comparative Study of Chemical and Mechanical Treatment Effects on Bacterial Cellulose from Nata de Coco

In this work, bacterial cellulose was obtained from nata de coco. Initially, the samples were subjected to three types of different condition which were raw, chemical treatment and mechanical treatment. Bacterial cellulose was characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffractometer (XRD) and Field Emission Scanning Electron Microscopy (FESEM). Bacterial cellulose met the specifications of pure cellulose either using chemical or mechanical treatments proved by IR spectra reading. XRD results indicated that the crystallinity of chemical treatment bacterial cellulose is higher than the mechanical treatment bacterial cellulose which was 68.6% and 59.5% respectively. The FESEM analysis shows that the size of the bacterial cellulose that obtained from chemical treatment is smaller than mechanical treatments which were 19.42μm and 50.35μm.</jats:p

Dasar dan Perundangan Pengajian Pekerja Asing di Malaysia: Melestari Matlamat Pembangunan Mampan No. 8

Dalam memastikan kelastarian pembagunan ekonomi Malaysia pemintaaan pekerja asing meningkat saban tahun dalam sektor 3 D (Dangerous, Dirty, Difficult ataupun Bahaya, Kotor dan Susah). Pekerjaan Baik dan Kemajuan Ekonomi (SDG 8) merupakankan salah satu daripada 17 Matlamat Pembangunan Mampan yang berkait rapat dengan pekerja asing. Objektif utama kertas kerja ini adalah menganalisa dasar dan peruntukan undang-undang serta agensi berkaitan pekerja asing dalam konteks SDG 8 dengan mengunakan pendekataan kaedah kualitatif. Matlamat Pembangunan Mampan No. 8, merupakan titik kesimbangan sosial dan perkembangan ekonomi negara sangat diperlukan. Hak pekerja asing di Malaysia turut dilindungi dan tertakluk kepada pemakaian dasar dan perundangan sediaada. Namun kegitu kebanjiran migran dari pelbagai benua perlu dikawal supaya Malaysia tidak menjadi tempat ·pusat himpunan' pelbagai kerakyatan serta boleh mengundang pelbagai masalah seperti jenayah dan sosial dikalangan masyarakat setempat