One-Dimensional HKUST-1-Decorated Glassy Carbon Electrode for the Sensitive Electrochemical Immunosensor of NS1 Dengue Virus Serotype-3.

In this work, simple and sensitive detection of dengue virus serotype-3 (DENV-3) antigen was accomplished by a one-dimensional (1D) HKUST-1-functionalized electrochemical sensor. 1D HKUST-1 was synthesized via a coprecipitation method using triethanolamine (TEOA) as pH modulator and structure-directing agent. The structure, morphology, and sensing performance of the HKUST-1-decorated carbon electrode were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). We found that 40 wt% TEOA transforms the octahedron HKUST-1 to the nanorods while maintaining its crystal structure and providing chemical stability. The 1D HKUST-1-decorated carbon electrode successfully detects the antigen in the range of 0.001-10 ng/mL with a detection limit of 0.932 pg/mL. The immunosensor also exhibits remarkable performance in analyzing the antigen in human serum and showed recovery as high as ∼98% with excellent selectivity and reproducibility.

Synthesis of Titanium Ion Sieves and Its Application for Lithium Recovery from Artificial Indonesian Geothermal Brine.

Indonesia is one of the countries in the world that has been utilizing geothermal as a renewable energy source to generate electricity. Depending on the geological setting, geothermal brine possesses critical elements worthwhile to extract. One of the critical elements is lithium which is interesting in being processed as raw material for the battery industries. This study thoroughly presented titanium oxide material for lithium recovery from artificial geothermal brine and the effect of Li/Ti mole ratio, temperature, and solution pH. The precursors were synthesized using TiO2 and Li2CO3 with several variations of the Li/Ti mole ratio mixed at room temperature for 10 min. The mixture of 20 g of raw materials was put into a 50 mL crucible and then calcined in a muffle furnace. The calcination temperature in the furnace was varied to 600, 750, and 900 °C for 4 h with a heating rate. of 7.55 °C/min. After the synthesis process, the precursor is reacted with acid (delithiation). Delithiation aims to release lithium ions from the host Li2TiO3 (LTO) precursor and replace it with hydrogen ions through an ion exchange mechanism. The adsorption process lasted for 90 min, and the stirring speed was 350 rpm on a magnetic stirrer with temperature variations of 30, 40, and 60 °C and pH values of 4, 8, and 12. This study has shown that synthetic precursors synthesized based on titanium oxide can absorb lithium from brine sources. The maximum recovery obtained at pH 12 and a temperature of 30 °C was 72%, with the maximum adsorption capacity obtained was 3.55 mg Li/gr adsorbent. Shrinking Core Model (SCM) kinetics model provided the most fitted model to represent the kinetics model (R2 = 0.9968), with the constants kf, Ds, and k, are 2.2360 × 10-9 cm/s; 1.2211 × 10-13 cm2/s; and 1.0467 × 10-8 cm/s.

Lithium Separation from Geothermal Brine to Develop Critical Energy Resources Using High-Pressure Nanofiltration Technology: Characterization and Optimization.

There is a shift from internal combustion engines to electric vehicles (EVs), with the primary goal of reducing CO2 emissions from road transport. Battery technology is at the heart of this transition as it is vital to hybrid and fully electric vehicles' performance, affordability, and reliability. However, it is not abundant in nature. Lithium has many uses, one of which is heat transfer applications; synthesized as an alloying agent for batteries, glass, and ceramics, it therefore has a high demand on the global market. Lithium can be attained by extraction from other natural resources in igneous rocks, in the waters of mineral springs, and geothermal brine. During the research, geothermal brine was used because, from the technological point of view, geothermal brine contains higher lithium content than other resources such as seawater. The nanofiltration separation process was operated using various solutions of pH 5, 7, and 10 at high pressures. The varying pressures are 11, 13, and 15 bar. The nanofiltration method was used as the separation process. High pressure of inert nitrogen gas was used to supply the driving force to separate lithium from other ions and elements in the sample. The research results supported the selected parameters where higher pressure and pH provided more significant lithium recovery but were limited by concentration polarization. The optimal operating conditions for lithium recovery in this research were obtained at a pH of 10 under a pressure of 15 bar, with the highest lithium recovery reaching more than 75%.

Circular Economy of Coal Fly Ash and Silica Geothermal for Green Geopolymer: Characteristic and Kinetic Study.

The study of geopolymers has become an interesting concern for many scientists, especially in the infrastructure sector, due to having inherently environmentally friendly properties and fewer energy requirements in production processes. Geopolymer attracts many scientists to develop practical synthesis methods, useful in industrial-scale applications as supplementary material for concrete. This study investigates the geopolymerization of fly ash and geothermal silica-based dry activator. The dry activator was synthesized between NaOH and silica geothermal sludge through the calcination process. Then, the geopolymer mortar was produced by mixing the fly ash and dry activator with a 4:1 (wt./wt.) ratio. After mixing homogeneously and forming a paste, the casted paste moved on to the drying process, with temperature variations of 30, 60, and 90 °C and curing times of 1, 3, 5, 7, 14, 21, 28 days. The compressive strength test was carried out at each curing time to determine the geopolymer's strength evolution and simulate the reaction's kinetics. In addition, ATR-FTIR spectroscopy was also used to observe aluminosilicate bonds' formation. The higher the temperature, the higher the compressive strength value, reaching 22.7 MPa at 90 °C. A Third-order model was found to have the highest R2 value of 0.92, with the collision frequency and activation energy values of 1.1171 day-1 and 3.8336 kJ/mol, respectively. The utilization of coal fly ash and silica geothermal sludge as a dry activator is, indeed, an approach to realize the circular economy in electrical power generations.

Silver Nanoparticles Coupled with Graphene Nanoplatelets Modified Screen-Printed Carbon Electrodes for Rhodamine B Detection in Food Products.

A rapid, simple, and sensitive voltammetric sensor has been fabricated to determine Rhodamine B (RhB), a textile coloring agent. Silver nanoparticles (AgNPs) were synthesized by the chemical reduction method of silver nitrate and sodium citrate. Graphene nanoplatelets (GPLs) and AgNPs were drop-casted on the surface of a working electrode of a screen-printed carbon electrode (SPCE), forming the SPCE-GPLs/AgNPs samples. Scanning electron microscopy-energy dispersive X-ray and cyclic voltammetry confirmed the altered surface of the SPCE. The square wave voltammetry was used for the electrochemical determination of RhB. The SPCE-GPLs/AgNPs demonstrated electrochemical responses to detect RhB with a linear range of 2-100 µM, and the limit of detection was 1.94 µM. The SPCE-GPLs/AgNPs demonstrated a selective detection of RhB in the presence of common interfering compounds present in the food samples, including sucrose and monosodium glutamate. Furthermore, the sensor presented good reproducibility as well as repeatability in the detection of RhB. When the sensor was used to determine RhB in an actual food sample, similar results were shown as suggested by UV-vis spectroscopy analysis. Hence, the fabricated sensor can be applied for the detection of RhB in food samples.