Cadmium pollution from industrial effluent can cause major health concerns, so it must be removed from wastewater prior to disposal. The objective of this study was to remove cadmium (Cd2+) from aquatic environments using red macroalgae Digenia simplex pretreated with calcium chloride (CaCl2) (DSC).
Batch adsorption studies were carried out to evaluate the individual impacts of adsorbent-metal contact time, cadmium concentration, and temperature on the cadmium removal efficiency and biosorption capacity. The Box-Benhken experimental design of response surface methodology was also used to investigate the relationship between different factors (pH, Cd2+ concentration and algal dose) and the cadmium removal efficiency of pretreated D. simplex.
The highest removal efficiency of 97.27% was achieved by combining different optimal parameters, including pH 5.78, initial Cd2+ concentration of 24.79 mg/L, and adsorbent dosage of 6.13 g/L. Moreover, cadmium removal from agricultural wastewater samples by pretreated D. simplex was evaluated under the optimal conditions, and the removal rate excessed 97%. Kinetic and isotherm investigations showed that the pseudo-second-order, Freundlich, Langmuir, and Dubinin–Radushkevich models of cadmium biosorption on pretreated algal biomass correlated well with the experimental biosorption data, implying that the biosorption of Cd2+ is a homogeneous monolayer and multilayer chemisorption process. The equilibrium isotherm data indicated that the biosorption capacity of the biosorbent was 11.16 mg/g as determined by the Langmuir model. Furthermore, the biosorption process was evaluated as an endothermic process with entropy and enthalpy values of 0.134 kJ/mol K and 38.01 kJ/mol, respectively. The functional groups, surface morphology, and elemental composition of the algal biomass were investigated, revealing the porous nature of the cell surface and the abundance of functional groups responsible for the Cd2+ biosorption process. These results suggest that DSC biomass can be used as a biosorbent for the effective removal of Cd2+ ions from effluent due to its availability and strong biosorption capability.
In close proximity to quantum emitters (QEs), plasmonic nanoparticles (NPs) facilitate energy exchange with the QEs, which is known as plasmon–exciton coupling. The strong coupling regime, associated with Rabi splitting, is crucial for advanced nanophotonic devices, including solar cells, single-photon nonlinear optics, and nanolasers. Recently, high refractive index semiconductor NPs (typically Si NPs) have emerged for designing strongly coupled systems. However, their large mode volumes of magnetic Mie resonances have limited their success in achieving strong coupling. This study investigates the plasmon–exciton coupling between an Ag–Si core–shell and a monolayer QE of WS2 (Ag–Si–WS2 system) in air and water environments. Here, we compare the coupling dynamics of the hybrid Ag–Si–WS2 system to
that of the Si–WS2 system as a benchmarking system. Employing Mie’s theory of core–shell scattering, in conjunction with Maxwell–Garnett effective medium theory, we analyze the optical responses of both configurations. Then, we calculate the Rabi splitting frequency for each system to identify the coupling regime. Our results suggest that the Ag–Si–WS2 system can achieve a deep-strong coupling regime when the Ag core radius is less than 30 nm, with enhanced coupling strength in water compared to air. Conversely, the Si–WS2 system does not achieve strong coupling in either medium. The hybrid modes in Ag–Si–WS2 demonstrate remarkable symmetrical spectral characteristics compared
to the asymmetric spectral line shape observed in the Si–WS2 system. The findings suggest avenues for utilizing the plasmon–exciton strong coupling in the Ag–Si–WS2 system to enhance optoelectronic and quantum electronic devices.
Titanium dioxide (TiO2) shows excellent pseudocapacitive properties. However, the low internal conductivity of TiO2 limits its use in supercapacitor applications. Therefore, an efficient surface engineering process was developed to enhance the overall pseudocapacitive performance of rutile TiO2 nanorods. Specifically, surface-engineered TiO2 nanorod arrays coordinated on carbon cloth were established through the Kapton tape-assisted hydrothermal route. X-ray diffraction analysis confirmed the formation of a tetragonal TiO2 rutile phase. Morphological analysis revealed the formation of uniform nanorods with an apparent high surface-to-volume aspect ratio. X-ray photoelectron spectroscopy analysis showed that the TiO2 synthesized in the presence of Kapton tape and annealed under air had high content of hydroxyl groups and Ti3+, which is favorable for supercapacitor performance. Surface treatment of the samples led to significantly enhanced conductivity and electrochemical behavior of TiO2. The surface-engineered TiO2 nanorod arrays show specific capacitance of about 57.62 mF/cm2 at 10 mV/s in 2 M KOH, with excellent rate capability of about 83% at 200 mV/s, and also exhibit long cycle life, retaining 91% of their original capacitance after 10,000 charge/discharge cycles, which is among the highest values reported for TiO2-based supercapacitors.
Advanced functional materials with fascinating properties and extended structural design have greatly broadened their applications. Metamaterials, exhibiting unprecedented physical properties (mechanical, electromagnetic, acoustic, etc.), are considered frontiers of physics, material science, and engineering. With the emerging 3D printing technology, the manufacturing of metamaterials becomes much more convenient. Graphene, due to its superior properties such as large surface area, superior electrical/thermal conductivity, and outstanding mechanical properties, shows promising applications to add multi-functionality into existing metamaterials for various applications. In this review, the aim is to outline the latest developments and applications of 3D printed graphene-based metamaterials. The structure design of different types of metamaterials and the fabrication strategies for 3D printed graphene-based materials are first reviewed. Then the representative explorations of 3D printed graphene-based metamaterials and multi-functionality that can be introduced with such a combination are further discussed. Subsequently, challenges and opportunities are provided, seeking to point out future directions of 3D printed graphene-based metamaterials.
