This study investigated the potential of Casuarina equisetifolia needle (CEN) on the removal of two important dyes, methylene blue (MB) and malachite green (MG), by batch adsorption experiments. Characterisation of CEN’s functional groups was done using Fourier Transform infrared spectroscopy while elemental analysis was carried out using CHNS analysis and X-ray fluorescence. The experiments were carried out by varying the adsorbent dosage, pH, ionic strength, contact time and initial dye concentration. The pseudo-second-order kinetics model best represented the experimental data for both CEN-MB and CEN-MG systems. The Weber–Morris intraparticle diffusion model showed that intraparticle diffusion is not the rate-limited step for both adsorbates, while the Boyd model suggested both systems could be controlled by film diffusion. The Langmuir, Freundlich and Dubinin–Radushkevich isotherm models were used for describing the adsorption process. Of these, the Langmuir model best represented both adsorbents systems (CEN-MB and CEN-MG) giving maximum adsorption capacity (qm) of 110.8 and 77.6mgg−1, respectively, at 25°C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic

Casuarina equisetifolia needle (CEN), a lignocellulosic-rich and sustainable material, was used in order to investigate its ability as an adsorbent to remove rhodamine B (RB) dye from aqueous solution. Fourier Transform Infrared spectrometer was used to characterise CEN functional groups and scanning electron microscope was used to study its surface morphology. Batch experiments were done in order to determine the effect of some parameters such as adsorbent dosage, initial pH, contact time, ionic strength, temperature and initial dye concentration. Kinetics, isotherm modelling and thermodynamics studies were also performed in order to explore an insight into the mechanism of the adsorption process. The study showed that the adsorption of RB by CEN is endothermic in nature and follows the pseudo-second-order kinetics model. The Langmuir isotherm model fitted the experimental data best with a maximum adsorption capacity of 82.34 mg g⁻¹.

Multiple resonance modes in an optical absorber are necessary for nanophotonic devices and encounter a challenge in the visible range. This article designs a multiple-channel plasmonic metamaterial absorber (PMA) that comprises a hexagonal arrangement of metal-shell nanorods in a unit cell over a continuous thin metal layer, operating in the visible range of the sensitive refractive index (RI) and temperature applications. Finite element method simulations are utilized to investigate the physical natures, such as the absorptance spectrum, magnetic flux and surface charge densities, electric field intensity, and electromagnetic power loss density. The advantage of the proposed PMA is that it can tune either three or five absorptance channels with a narrowband in the visible range. The recorded sensitivity and figure of merit (S, FOM) for modes 1–5 can be obtained (600.00 nm/RIU, 120.00), (600.00 nm/RIU, 120.00 RIU⁻¹), (600.00 nm/RIU, 120.00 RIU⁻¹), (400.00 nm/RIU, 50.00 RIU⁻¹), and (350.00 nm/RIU, 25.00 RIU⁻¹), respectively. Additionally, the temperature sensitivity can simultaneously reach 0.22 nm/°C for modes 1–3. The designed PMA can be suitable for RI and temperature sensing in the visible range.

In this study, locally grown bamboo ( Gigantochloa spp.) was used as feedstock for pyrolysis production of biochar under various pyrolysis temperatures (400–800°C). The resultant biochars were tested for their performance in adsorptive removal of the methylene blue (MB) dye. The scope of the adsorption experiment includes the effects of adsorbent dosage, solution pH, initial adsorbate concentration, and contact time. The adsorption data confirmed that pyrolysis temperature has a significant effect on adsorptive performance, whereas biochar pyrolysed at 500°C (BC500) has the highest adsorptive performance with the maximum adsorption capacity (derived from the Langmuir model) being 86.6 mg g^-1. Basic characterisations (SEM, EDX, XRD, FTIR, and BET) were carried out for BC500 where FTIR and SEM confirmed the adsorption of MB onto the biochar, while the BET data showed the reduction of the BET surface area, total pore volume, and pore diameter after the adsorption process.

We numerically and theoretically investigate a highly sensitive and tunable plasmonic refractive index sensor that is composed of a metal-insulator-metal waveguide with a side-coupled nanoring, containing silver nanorods using the finite element method. Results reveal that the presence of silver nanorods in the nanoring has a significant impact on sensitivity and tunability performance. It gives a flexible way to tune the system response in the proposed structure. Our designed sensor has a sensitivity of 2080 nm/RIU (RIU is the refractive index unit) along with a figure of merit and a quality factor of 29.92 and 29.67, respectively. The adequate refractive index sensitivity can increase by adding the silver nanorods in a nanoring, which can induce new surface plasmon polaritons (SPPs) modes that cannot be found by a regular nanoring. For a practical application, a valid introduction of silver nanorods in the nanoring can dramatically reduce the dimension of the proposed structure without sacrificing performance.