Nurhidayatullaili Muhd Julkapli

Titanium dioxide as a catalyst support in heterogeneous catalysis.

The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications.

Recent Advances in Heterogeneous Photocatalytic Decolorization of Synthetic Dyes

During the process and operation of the dyes, the wastes produced were commonly found to contain organic and inorganic impurities leading to risks in the ecosystem and biodiversity with the resultant impact on the environment. Improper effluent disposal in aqueous ecosystems leads to reduction of sunlight penetration which in turn diminishes photosynthetic activity, resulting in acute toxic effects on the aquatic flora/fauna and dissolved oxygen concentration. Recently, photodegradation of various synthetic dyes has been studied in terms of their absorbance and the reduction of oxygen content by changes in the concentration of the dye. The advantages that make photocatalytic techniques superior to traditional methods are the ability to remove contaminates in the range of ppb, no generation of polycyclic compounds, higher speed, and lower cost. Semiconductor metal oxides, typically TiO2, ZnO, SnO, NiO, Cu2O, Fe3O4, and also CdS have been utilized as photocatalyst for their nontoxic nature, high photosensitivity, wide band gap and high stability. Various process parameters like photocatalyst dose, pH and initial dye concentrations have been varied and highlighted. Research focused on surface modification of semiconductors and mixed oxide semiconductors by doping them with noble metals (Pt, Pd, Au, and Ag) and organic matter (C, N, Cl, and F) showed enhanced dye degradation compared to corresponding native semiconductors. This paper reviews recent advances in heterogeneous photocatalytic decolorization for the removal of synthetic dyes from water and wastewater. Thus, the main core highlighted in this paper is the critical selection of semiconductors for photocatalysis based on the chemical, physical, and selective nature of the poisoning dyes.

Effects of Engineered Nanomaterials on Plants Growth: An Overview

Rapid development and wide applications of nanotechnology brought about a significant increment on the number of engineered nanomaterials (ENs) inevitably entering our living system. Plants comprise of a very important living component of the terrestrial ecosystem. Studies on the influence of engineered nanomaterials (carbon and metal/metal oxides based) on plant growth indicated that in the excess content, engineered nanomaterials influences seed germination. It assessed the shoot-to-root ratio and the growth of the seedlings. From the toxicological studies to date, certain types of engineered nanomaterials can be toxic once they are not bound to a substrate or if they are freely circulating in living systems. It is assumed that the different types of engineered nanomaterials affect the different routes, behavior, and the capability of the plants. Furthermore, different, or even opposing conclusions, have been drawn from most studies on the interactions between engineered nanomaterials with plants. Therefore, this paper comprehensively reviews the studies on the different types of engineered nanomaterials and their interactions with different plant species, including the phytotoxicity, uptakes, and translocation of engineered nanomaterials by the plant at the whole plant and cellular level.

Graphene–Gold Nanoparticles Hybrid—Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene–AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene–Au nanocomposites. The paper highlights the graphene–gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer.

Thermal Properties of Kenaf-Filled Chitosan Biocomposites

Kenaf filled chitosan biocomposites have been prepared via solution blending method. 0.1 M acetic acid was used as diluent. Five types of biocomposites with different compositions of kenaf fiber by weight designated as (CH, CH7, CH14, CH21, and CH28) were prepared. Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to study various thermal properties of the biocomposites. It was found that the biocomposites have undergone several decomposition stages over a range of temperatures as revealed by TGA thermograms, with CH exhibited highest mass loss as compared to other composites. From the DSC thermogram, incorporation of kenaf dust into chitosan has reduced the thermal stability of the chitosan film. The reduction is proportionate to the amount of kenaf dust added and was attributed to the formation of inter- and intrahydrogen bonding between amine groups of chitosan matrix and hydroxyl methyl groups of kenaf fiber.

Preparation, Properties and Applications of Chitosan-Based Biocomposites/Blend Materials: A Review

Taking inspiration from many published chitosan (Cs)-based biocomposites, this article is written to highlight the significant effect of reinforcing and/or blending Cs polymer with the different constituents to increase various properties (mechanical, hydrophilic, thermal, adsorption ability and stability) of Cs without sacrificing any of its positive properties. It is concluded that the properties of Cs biocomposites with a synthetic constituent have contributed to its rigidity since only mechanical interaction occurred at the interfacial region. Instead of physical interactions, the addition of an organic constituent also promoted the chemical interactions at the interfacial region of the Cs biocomposites. This consequently produced Cs biocomposites with synthetic constituents with relatively low strength and stiffness but high resistance to fracture, whereas the ones with an organic constituent have high strength and stiffness but are very brittle. This review also screens the current applications of Cs-based biocomposites in the field of drug delivery, tissue engineering, antibacterial, food packaging, biomedical, metal adsorption and dye removal.

Functionalized Activated Carbon Derived from Biomass for Photocatalysis Applications Perspective

This review highlighted the developments of safe, effective, economic, and environmental friendly catalytic technologies to transform lignocellulosic biomass into the activated carbon (AC). In the photocatalysis applications, this AC can further be used as a support material. The limits of AC productions raised by energy assumption and product selectivity have been uplifted to develop sustainable carbon of the synthesis process, where catalytic conversion is accounted. The catalytic treatment corresponding to mild condition provided a bulk, mesoporous, and nanostructure AC materials. These characteristics of AC materials are necessary for the low energy and efficient photocatalytic system. Due to the excellent oxidizing characteristics, cheapness, and long-term stability, semiconductor materials have been used immensely in photocatalytic reactors. However, in practical, such conductors lead to problems with the separation steps and loss of photocatalytic activity. Therefore, proper attention has been given to develop supported semiconductor catalysts and certain matrixes of carbon materials such as carbon nanotubes, carbon microspheres, carbon nanofibers, carbon black, and activated carbons have been recently considered and reported. AC has been reported as a potential support in photocatalytic systems because it improves the transfer rate of the interface charge and lowers the recombination rate of holes and electrons.

Influence of a plasticizer on the mechanical properties of kenaf filled chitosan bio-composites

Glycerol (Gy) and di-hydroxyl stearic acid (DHSA) were selected for potential plasticizers of kenaf filled chitosan bio-composites (KCB). Plasticized KCB at various concentrations of plasticizers (0.2%, 0.4% and 0.6%) were obtained by mixing using high speed homogenizer (10,000 to 29,000 rpm) followed by simple casting. Soft and flexible film was obtained with Gy plasticizing system (GyPS) and hard and brittle film was produced with DHSA plasticizing system (DPS). GyPS films exhibit good elongation at break (EB). Films with DPS show good tensile strength (TS) and Youngs modulus (YM) properties.

Review on ZnO hybrid photocatalyst: impact on photocatalytic activities of water pollutant degradation

Abstract Zinc oxide (ZnO) is one of the most widely used benchmark standard photocatalysts in the field of environmental applications. However, the large band gap of ZnO and the massive recombination of photogenerated charge carriers, especially in its nanosize, limit the overall photocatalytic efficiency. This can be further overcome by modifying the electronic band structure of ZnO by hybridization with a narrow band gap material, including metal, metal oxide, carbon based, and polymeric based. Indeed, ZnO hybridization with the respective materials contributed to its sensitizer by shifting the absorption wavelength to the visible region of the spectrum. This review encompasses several advancements made in the mentioned aspects, and also some of the new physical insights related to the charge transfer events, such as charge carrier generation, trapping, detrapping, and their transfer to surface, are discussed for each strategy of the hybrid ZnO. The synergistic effects in the mixed polymorphs of ZnO and also the theories proposed for their enhanced activity are reported. The review also highlights the potential application of ZnO hybrid for different kinds of pollutants from different wastewater sources.

Evaluation of Cross-Linked Chitosan as Filler on Mechanical Properties of Chitosan-Based Bio-Composites

The cross-linked chitosan (XCs) was applied as a filler for chitosan (Cs) matrix. The composites film was prepared by solution casting at 0 to 12 wt/v% content of XCs filler and characterized under tensile analysis. The tensile strength (TS) and Young Modulus (YM) increased lineraly with the content of XCs filler (2 to 8 wt/v%). Contrarily, tensile strain (EB) and toughness (K) reduced corresponding to similar content of filler. The Fourier Transform Infra-Red (FTIR) and Field Emission Scanning Electron Microscope (FESEM) analysis proved, such results were influenced by the inter hydrogen bonds and electrostatic interactions between Cs and XCs.