Unveiling the noxious effect of polystyrene microplastics in aquatic ecosystems and their toxicological behavior on fishes and microalgae

Microplastic (MP) particles are considered noxious pollutants due to their presence in aquatic habitats at almost every level of the food chain. Thus, the entry of MP particles into marine waterbodies has triggered a common research interest. Until recently, the toxicity of polystyrene towards aquatic creatures in comparison to other polymers has not been widely investigated. This article provides an extensive overview of the occurrence of microplastic particles, the route of polystyrene (PS) in the aquatic ecosystem, the PS properties characterization, and its noxious effects on the aquatic biota, particularly fishes and microalgae. Alarming high levels of polystyrene were found in urban, coastal, and rural surface waters and sediments. The fast-screening technique began with a stereoscope to determine the polystyrene particles’ shape, size, and color on the organism. SEM and complemented by micro FTIR or Raman spectroscopy were used to evaluate MP’s polymer structures. The findings present evidence suggesting that polystyrene buildup in fish can have long-term and unknown consequences. Meanwhile, the presence of polystyrene on microalgae causes a decrease in chlorophyll concentration and photosynthetic activity, which may disrupt photosynthesis by interfering with the electron characters and leading to the production of reactive oxygen species (ROS)

Growth-controlled synthesis of polymer-coated colloidal-gold nanoparticles using electrospray-based chemical reduction

In this study, the controlled nucleation and growth of gold nanoparticles (GNPs) were investigated using a self-repelled mist in a liquid chemical reaction environment. An electrospray-based chemical reduction method was conducted in the aqueous region and at room temperature to synthesize the polymeric-stabilized gold nanoparticles. The electrospray technique was used to atomize a hydrogen tetrachloraurate (III) (HAuCl4) precursor solution into electrostatically charged droplets. The atomized droplets were dispersed in an aqueous reaction bath containing L-ascorbic acid as a reducing agent and polyvinylpyrrolidone (PVP) as a stabilizer. The effect of the electrospray parameters, specifically the flow rate and electrospray droplet size, as well as the reaction conditions such as the concentration of reactants, pH, and stabilizer (PVP), were investigated. The mean diameter of the GNPs increased from around 4 to 9 nm with an increase in the electrospray flow rate, droplet size, and current passing through the electrospray jet. Spherical and monodispersed GNPs were synthesized at a relatively high flow rate of 2 mL/h and a moderate concentration of 2 mM of precursor solution. The smallest-sized GNP with a high monodispersity was obtained in the reaction bath at a high pH of 10.5 and in the presence of PVP. It is expected that continuous and mass production of the engineered GNPs and other noble metal nanoparticles could be established for scaling up nanoparticle production via the proposed electrospray-based chemical reduction method

Growth-controlled synthesis of polymer-coated colloidal-gold nanoparticles using electrospray-based chemical reduction

In this study, the controlled nucleation and growth of gold nanoparticles (GNPs) were investigated using a self-repelled mist in a liquid chemical reaction environment. An electrospray-based chemical reduction method was conducted in the aqueous region and at room temperature to synthesize the polymeric-stabilized gold nanoparticles. The electrospray technique was used to atomize a hydrogen tetrachloraurate (III) (HAuCl4) precursor solution into electrostatically charged droplets. The atomized droplets were dispersed in an aqueous reaction bath containing L-ascorbic acid as a reducing agent and polyvinylpyrrolidone (PVP) as a stabilizer. The effect of the electrospray parameters, specifically the flow rate and electrospray droplet size, as well as the reaction conditions such as the concentration of reactants, pH, and stabilizer (PVP), were investigated. The mean diameter of the GNPs increased from around 4 to 9 nm with an increase in the electrospray flow rate, droplet size, and current passing through the electrospray jet. Spherical and monodispersed GNPs were synthesized at a relatively high flow rate of 2 mL/h and a moderate concentration of 2 mM of precursor solution. The smallest-sized GNP with a high monodispersity was obtained in the reaction bath at a high pH of 10.5 and in the presence of PVP. It is expected that continuous and mass production of the engineered GNPs and other noble metal nanoparticles could be established for scaling up nanoparticle production via the proposed electrospray-based chemical reduction method

Informasi Covid-19 sebagai barang awam : analisis Nvivo

Maklumat Covid-19 yang disalurkan melalui pelbagai media bukan sahaja merupakan satu keperluan bagi masyarakat untuk sentiasa melindungi diri, tetapi juga ia menjadi penentu kepada pergerakan individu atau aktiviti yang ingin dilakukan setiap hari. Justeru, objektif kajian ini adalah untuk mengenalpasti bagaimana maklumat Covid-19 yang disalurkan oleh agensi kerajaan mampu bertindak sebagai barang awam untuk digunakan oleh semua masyarakat tanpa persaingan dan tanpa pengecualian. Menerusi analisis Nvivo terhadap temubual dengan penduduk di Lembah Klang, dua dapatan utama diperolehi. Pertama, dapatan temubual menunjukkan media sosial dan televisyen lebih kerap digunakan informan untuk mendapatkan maklumat Covid-19 daripada agensi kerajaan berkaitan. Kedua, maklumat harian Covid-19 yang disebarkan oleh agensi kerajaan berkaitan berjaya menggalakkan masyarakat untuk mematuhi SOP serta cenderung membuat pembelian dan pembayaran secara dalam talian

Synthesis of various size gold nanoparticles by chemical reduction method with different solvent polarity

Complicated and strict protocols are followed to tune the size of gold nanoparticles (GNPs) in chemical synthesis methods. In this study, we address the polarity of solvents as a tool for tailoring the size of GNPs in the chemical reduction method. The effects of varying polarity index of the reaction medium on synthesizing gold nanoparticles by chemical reduction method have been investigated. Ethanol as a polar solvent, ethanol–water mixture as reaction medium, L-ascorbic acid as reducing agent, and polyvinylpyrrolidone as stabilizer were used to synthesize GNPs. The polarity index of the reaction medium was adjusted by changing the volume ratio of ethanol to water. UV–Vis, dynamic light scattering (DLS), and transmission electron microscopy (TEM) characterizations reveal that the growth of nanoparticles was gradually increased (~ 22 to 219 nm hydrodynamic diameter) with decreasing value of polarity index of the reaction medium (~ 8.2 to 5.2). Furthermore, the high polarity index of the reaction medium produced smaller and spherical nanoparticles, whereas lower polarity index of reaction medium results in bigger size of GNPs with different shapes. These results imply that the mechanistic of the growth, assembly, and aggregation phenomena of ligand or stabilizer-capped GNPs strongly rely on the polarity of solvent molecules. Using the proposed methodology, wide size range of GNPs with different morphology sizes can be synthesized by simply modulating the volume percentage of organic solvent in the reaction medium

Electrospun polyetherimide-graphene oxide nanofiber electrodes for enhanced conductivity

Polyetherimide (PEI) is recognized as a potential candidate for electrochemical sensor matrix which can be used for heavy metal ion and reactive chemical substance sensing applications. However, the relatively low conductivity of PEI material limits its usage of electrochemical sensor applications. Modifying PEI membrane considerably improve the electron conductivity and electrochemical property of polymer. Conductive polyetherimide-graphene oxide (PEI-GO) composite nanofiber membrane was synthesized via electrospinning technique in order to modify electrochemical sensor electrodes. In order to optimize the electrospinning process protocol such as viscosity, surface tension and conductivity and obtained smooth electrospun fiber, PEI were electrospun from two different solvents namely n-methyl-2-pyrrolidone (NMP) and combination of NMP/ dimethylformamide (DMF). Physical and electrical properties of the nanofiber were analysed in terms of its hydrophobicity, porosity and conductivity by manipulating the concentration of PEI from 20 wt% to 30 wt% and GO loading from 0.1 wt% to 0.5 wt%. Electrospun of 25 wt% PEI in NMP/DMF produced the highest porosity and liquid uptake of 97.81% and 2846.23% respectively. The addition of GO at 0.5 wt% into 25 wt% of PEI (NMP/DMF) improved the porosity and liquid uptake up to 98.83% and 5400%,respectively, while the conductivity increases to 32.71 µS/cm which is 10 folds higher than GO free PEI fiber. When the conductivity of drop-casted PEI-GO modified electrodes was compared to the electrospun PEI-GO fiber modified electrodes, the latter showed 2-3 folds higher. Proposed PEI-GO electrospun fiber with the enhanced conductivity, porosity and hydrophobicity along with high chemical stability can be used as an efficient conductive matrix for electrochemical electrode applications such as heavy metal ion sensing and reactive chemical sensing application