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Direct localized surface plasmon resonance (LSPR) sensor using anisotropic gold nanoparticles with bipyramidal structure namely as gold nanobipyramids (GNBPs) has been proposed. The high curvature at the tips of GNBPs enhanced LSPR effect owing to electron-rich sites thus improved sensor performance. In this study, we demonstrated that GNBPs-based LSPR sensor is sensitive and can detect the presence of glyphosate as low as 0.1 % (w/w). Our experimental studies show that the GNBPs-based LSPR sensor exhibits improved sensitivity compared to the gold bone nanorods (GBNRs) and gold nanorods (GNRs)-based LSPR sensor. For t-SPR band, the GNBPs provided sensitivity factor as high as 4.76 and 5.17 times larger than the sensitivity factor of GBNRs and GNRs, while for l-SPR band, the sensitivity factor of GNBPs are 2.87 times larger than GBNRs and 1.57 times larger than GNRs. The selectivity of GNBPs-based LSPR sensor was evaluated by comparing its response to four different analytes and the response of LSPR sensor towards glyphosate is much higher than the responses towards chlorpyrifos, acetic acid and acetone. Hence, it is confirmed that GNBPs-based LSPR sensor has a good selectivity towards glyphosate. In addition, the proposed sensor system shows a good stability and repeatability for a period of 600 seconds and during five cycling tests, respectively.

We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the solid substrate. Controlling the growth solution ageing time using the modifiable GNRs is an approach to overcome the limitations of rods formation due to inhomogeneous and uncontrollable size and aspect ratio. In this study, the suitable ageing time of GNRs was determined to produce optimum GNRs in terms of surface density and aspect ratio. As the ageing time was increased from 30 min to 24 h, the colour of the growth solution was changed from light to dark purple. The change is associated with the density of the nanorods formation. The optical spectral peaks of GNRs occur in a range between 500 nm and 800 nm in the visible and near-infrared region spectrum for transverse surface resonance (t-SPR) and longitudinal surface resonance (l-SPR), respectively. From the morphological analysis, it was found that 20 h ageing time resulting in high density and homogeneous GNRs with 74.81% surface density with 4.23 ± 0.04 aspect ratio. Hence, the growth ageing time of GNRs can be manipulated to control their shape evolution and dimension in terms of size and aspect ratio. The controllable aspect ratio and size GNRs can be potentially used as sensing material in plasmonic applications.

An anisotropic structure, gold (Au) nanoplates was synthesized using a two-step wet chemical seed mediated growth method (SMGM) directly on the substrate surface. Prior to the synthesis process, poly-l-lysine (PLL) as a cation polymer was used to enhance the yield of grown Au nanoplates. The electrostatic interaction of positive charged by PLL with negative charges from citrate-capped gold nanoseeds contributes to the yield increment. The percentage of PLL was varied from 0% to 10% to study the morphology of Au nanoplates in term of shape, size and surface density. 5% PLL with single layer treatment produce a variety of plate shapes such as hexagonal, flat rod and triangular obtained over the whole substrate surface with the estimated maximum yield up to ca. 48%. The high yield of Au nanoplates exhibit dual plasmonic peaks response that are associated with transverse and longitudinal localized surface plasmon resonance (TSPR and LSPR). Then, the PLL treatment process was repeated twice resulting the increment of Au nanoplates products to ca. 60%. The thin film Au nanoplates was further used as sensing materials in plasmonic sensor for detection of boric acid. The anisotropic Au nanoplates have four sensing parameters being monitored when the medium changes, which are peak position (wavelength shift), intensity of TSPR and LSPR, and the changes on sensing responses. The sensor responses are based on the interaction of light with dielectric properties from surrounding medium. The resonance effect produces by a collection of electron vibration on the Au nanoparticles surface after hit by light are captured as the responses. As a conclusion, it was found that the PLL treatment is capable to promote high yield of Au nanoplates. Moreover, the high yield of the Au nanoplates is an indication as excellent candidate for sensing material in plasmonic sensor.

This study aims to observe laser technology applications in two critical sectors which are military and medical. These two crucial sectors required a technology that is compatible with the nature of the field; safe, precise and fast (time –saving). A laser is defined as a device that emits a focused beam of light by stimulating the emission of electromagnetic radiation. The characteristics of lasers; coherence, directionality, monochromatic and high intensity are very suitable to be used in the critical sectors. In the military sector, the implementation of laser is commonly used in various types of weapons manufacturing. In this paper, three different military weapon systems namely weapon simulator, laser anti-missile system and navy ship laser weapon system were studied. Meanwhile, in the medical sector, the laser is widely implemented in medical equipment especially in dentistry, surgery and skin treatment. The capability of laser technology to be adapted in the critical sectors can be further investigated and enhanced for future discovery.

This review intends to discuss on greywater treatment technologies, which are the physiochemical, biological and advanced oxidation process (AOP) treatment technologies that are used to remove organic, nutrient and surfactant pollutants in greywater. The focus of this study is to compare the treatment technologies to remove greywater pollutant in coastal area. Each technology will be compared in terms of its advantages and disadvantages including its potential in greywater treatment technologies development. Measurement parameters of water quality from other studies includes physicochemical, organic content, nutrient and surfactant that are developed from each greywater treatment mode. AOP has a huge potential in greywater treatment since the technology has low cost of development, easy to install and able to be deployed in small scale. The AOP could be combined with other treatment techniques to produce an improved output..

The presence of sharp tips and edges of gold nanobipyramids (GNBPs) lead to strong local electromagnetic field enhancement. Herein for the first time we present a study on efficacy of additive acid on the formation of GNBPs. The effect of additive acid type and its concentration in growth solution were investigated to obtain various yield and aspect ratio of GNBPs. Morphological characterization shows the nanoseeds that were grown in growth solution prepared using HCl, H2SO4, and HF at concentration from 0 to 1 mL produced GNBPs with yield ranges from 5.21 ± 0.44 to 91.46 ± 3.32% and aspect ratio from 2.00 ± 0.02 to 2.76 ± 0.05. The optical response of GNBPs exhibit dual plasmon band at wavelength around 550 nm–570 nm, corresponding to transverse surface plasmon resonance (t-SPR) and at wavelength around 700 nm–800 nm, corresponding to longitudinal surface plasmon resonance (l-SPR). The presented approach may be used to produce tunable morphological GNBPs nanostructures which potentially used in sensors, SERS, catalysis, and photonics.

A simple technique of seed-mediated growth has been successfully performed to grow anisotropy gold nanoparticles on solid substrates. The growth of the gold nanoparticles has been carried out in the presence of a binary surfactant mixture of hexadecyltrimethylammonium bromide with two different molecular weights of a capping agent, namely polyvinylpyrrolidone: 40,000 and 55,000. In this study, the effect of process parameters, growth time and molecular weight of capping agent was investigated. The growth time shows a significant impact on the shape and size of nanoparticles. The shorter growth time produced small spherical to square-like shape particles, whereas bigger particles including nanorods, nanosquares and nanotriangles were formed with longer growth time. The shape controlling agent, polyvinylpyrrolidone, was used to synthesis gold nanoparticles. It was found that monodisperse gold nanoparticles with uniform shape and size are hardly obtained when polyvinylpyrrolidone 40,000 was used as capping agent. Polyvinylpyrrolidone 55,000 produced more uniform shape and size of gold nanoparticles. Thus, these process parameters were found affected to the size, shape, surface density and uniformity of gold nanoparticles. This sample was further applied as a sensing material in the detection of toxic fungicide, namely chlorothalonil. The sensitivity of the sensor system was determined by the changes in peak positions and intensities of the transverse and longitudinal surface plasmon resonance peaks on different medium, that is, air, deionized water and chlorothalonil solution. The sensor response of gold nanoparticles thin film in 30 mM chlorothalonil showed two resonance peaks in comparison to the control experiment without gold nanoparticle thin film. The gold nanoparticles thin film sensor was successfully synthesized and potentially useful as a sensing material for fungicide detection.

This paper reports the synthesis of ZnO nanorods via seed-mediated growth hydrothermal technique and their application in dye-sensitized solar cells (DSSCs). The growth process was carried out at various temperatures, namely 60, 70, 80, and 90 °C for 8 h at 0.1 M zinc acetate dehydrate (ZAD) to investigate the effect of growth temperature on the property of ZnO sample and on the performance of the DSSC-containing ZnO sample. The growth process was also carried out at various growth times, namely 2, 4, 6, and 8 h at 90 °C at 0.1 M ZAD to investigate the effect of growth time on the property of ZnO sample and on the performance of the DSSC. It was found that the morphology of ZnO nanorods in terms of grain size and length increases with the growth temperature. The peak intensity of XRD patterns, crystallite size, optical absorption, and photocurrent also increase with the growth temperature. The optical absorption and power conversion efficiency (η) increase as the growth time increases. The DSSC utilizing the ZnO nanorods synthesized at 90 °C for 8 h demonstrates the J SC, V OC, FF and η of 1.860 mA cm−2, 0.52 V, 0.287, and 0.277 %, respectively.

High-quality gold nanorods (AuNRs) with a uniform aspect ratio and sizes are crucial for applications in biomedical or sensor industry. AuNRs is implementing Localized Surface Plasmon Resonance (LSPR) as sensing method which is highly dependent on the size, separation of nanoparticles, aspect ratio and the shape of the nanoparticles. Thus, in this process, the shape, surface density and aspect ratio of AuNRs were investigated to be used further as LSPR sensing material. The AuNRs was prepared using Seed Mediated Growth Method (SMGM) and the growth solution of the AuNRs was centrifuged with the speed ranging from 2500 rpm to 5000 rpm to separate the particles shaper prior to deposition as thin film. The XRD result shows the peak at 2θ = 38º which shows the (111) crystal orientation of the AuNRs. There are also two distinct peaks formed at the absorption spectra graph obtained from the UV-Vis result which associated with transverse plasmon peak (t-LSPR) and longitudinal plasmon peak (l-LSPR). The t-LSPR peak is significantly smaller than the l-LSPR and located in the wavelength ranges from 500 nm to 560 nm whereas the l-LSPR of the AuNRs shows a stronger and a higher peak which is located in the wavelength ranges from 700 nm to 780 nm. The morphological analysis using FESEM shows that the higher centrifugation speed separates the AuNRs with higher aspect ratio and higher surface density.

Plasmonic sensor implementing an optical phenomenon called Localized Surface Plasmon Resonance (LSPR) resulting from the interaction of free electron with electromagnetic field of light at the metal nanoparticles surface. In this study, the plasmonic sensor has been developed for toxic detection in solution form. This system consists of five components which are the light source, duplex fiber optic, sensor chamber, spectrometer and computer. The sensor chamber has been specially designed using SolidWork software and printed using 3D printer with polylactic acid (PLA) material. The sensing activity was done in the sensor chamber with a sliding drawer which is used to place the sensing material or sample. OceanView software was used to analyze the recorded spectrum from the spectrometer. For this project, the experiment of the plasmonic sensor was carried out using targeted analyte namely chlorpyrifos with deionized (DI) water was set as a reference medium. Gold nanoparticles with nanospheres shape used as sensing materials. The sensing parameters are based on changing its intensity and resonance peak position. This plasmonic sensor was compared with UV-VIS spectrometer data to make sure it standardize and function correctly. Besides, the sensing process toward different concentrations of chlorpyrifos from 7.15 mM to 28.60 mM have been done. As a conclusion, the plasmonic sensor was successfully developed for toxic detection in solution form.

Seed-mediated growth method (SMGM) in preparation of gold nanoparticles becomes one of the most popular methods due to the simplicity of the experimental procedures and flexibility in structural modifications. In this paper, we report a new method for synthesizing gold nanoparticles using silver seeds. The effect of seed concentration and growth time are investigated in this work. By increasing the silver seed concentration, it is found that the color of the colloidal gold nanorods obtained are changed from light pink to reddish purple, the surface plasmon resonance band is shifted to the blue region whereas absorption spectra becomes narrower. The additional peak is also spotted when increasing silver seed concentration to 5 µl. Meanwhile, increasing the growth time from 5 to 240 minutes tends to increase the color concentration of the solution. Besides that, the absorbance of colloidal gold nanorods is also increased with an increase in the growth time whereas optimum growth time is found to be 45 minutes. FESEM characterization shows that gold nanoparticles shapes are dominated by nanorods with average length, width, and aspect ratio are 129.8 nm, 42.9 nm, and 3.4, respectively. The energy-dispersive x-ray spectroscopy (EDX) shows the chemical composition of the synthesized sample is Gold (Au) with weight % and atomic % are 32.23 and 5.98, respectively. Besides that, signals from Carbon (C), Oxygen (O), and Indium (In) atoms were also recorded from EDS spectra. The present approach thus provides new method for synthesis gold nanoparticles with additional plasmon resonance peak thus it has very potential for application in plasmonic sensing.