Sri Juari Santosa

Gold nanoparticles (AuNPs) were synthesized using L-histidine as a reducing and capping agent for the detection of environmental contaminant Hg2+ in water. Synthesis was done by combining HAuCl4 solution with L-histidine at pH 11 to produce red AuNPs(his) solution. The zeta potential measurement showed AuNPs(his) had a negative surface charge of −22.4 mV. Characterization using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) showed the formation of AuNPs(his). Morphology analysis of AuNPs(his) shows a spherical shape. XRD measurement showed that the addition of Hg2+ caused an increase in the crystal size of Au0 in the (111) plane from 13.96 to 34.34 nm, which was calculated using the Scherrer equation. Characterization using a particle size analyzer (PSA) showed the formation of peaks at wavelengths around 525 nm, with an average particle size of 17.9 nm. The addition of Hg2+ ions affects the aggregation of nanoparticles, causing a color change from red to purple that can be seen visually. The decrease in stability is characterized by a redshift to 560 nm. Therefore, AuNPs(his) can be developed as Hg sensors with the advantages of fast response, ease of use, and the ability to detect color changes with the naked eye.

Gold nanoparticles functionalized with ethylenediaminetetraacetic acid (EDTA-AuNPs) were successfully synthesized using a sonochemical approach. The synthesis results show a characteristic red color with a SPR peak at 524 nm. The addition of Al³⁺ ions induces a color change in EDTA-AuNPs to blue with a new absorption peak at 700 nm, indicating nanoparticle aggregation. Transmission electron microscopy data confirmed that EDTA-AuNPs particles were dispersed and aggregated after reacting with Al³⁺. Particle size analysis (PSA) confirmed an increase in particle diameter from 27 nm to 161 nm after the addition of Al³⁺. The colorimetric sensor exhibited high selectivity toward Al³⁺ ions. The quantitative analysis was conducted using both UV-Visible spectrophotometry and colorimeter methods. The UV-Visible spectrophotometer method has a detection limit of 0.15 mM, while the colorimeter shows a sensitivity of 0.07 mM. The integration of digital image-based colorimeter methods enables the development of a portable, sensitive, low-cost, and simple platform for on-site detection of Al³⁺ ions.

A B S T R A C TThin film nanocomposite (TFN) membranes incorporating nanofillers are emerging as high-performance alternatives for nanofiltration (NF) desalination. Here, we introduce exfoliated glycine-functionalized hydrotalcite (eHT–gly) as a novel filler to enhance the transport and fouling resistance properties of polyamide TFN membranes. Hydrotalcite was functionalized with glycine and then delaminated; the disappearance of the basal reflection in X-ray diffraction confirmed the success of the exfoliation. TFN membranes were prepared with eHT–gly loadings ranging from 0.005 to 0.25 wt%. The membrane containing 0.125 wt% eHT–gly achieved the best overall performance, delivering a NaCl rejection of 95% at a water flux of 89.8 LMH—substantially higher than membranes loaded with unmodified eHT (80.7% rejection, 97.7 LMH at 0.1% loading). This improvement is attributed to enhanced surface hydrophilicity (water contact angle of 43.6°) and reduced protein fouling (BSA adsorption test), indicating improved surface properties and filler-matrix compatibility. The anionic layers of the exfoliated hydrotalcite create a chemically active interface that facilitates water permeation pathways while hindering salt passage. These findings demonstrate that eHT–gly is an effective nanofiller for constructing surface-engineered TFN membranes with superior desalination efficiency and antifouling behaviour.

Mesoporous silica Mobil Composition of Matter No. 41 (MCM-41) has gained considerable attention as a carrier matrix because of its large surface area, adjustable pore size, and biocompatibility. This study aimed to prepare and thoroughly characterize MCM-41 using a sonochemical approach and to evaluate its potential for adsorbing solasodine, a steroidal alkaloid with anticancer properties. MCM-41 was prepared under different sonication times (30 - 150 min) and characterized using Fourier Transform Infrared Spectroscopy (FTIR, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX), and Brunauer-Emmett-Teller (BET) techniques. XRD results confirmed the formation of a well-defined hexagonal mesostructure, with crystallinity increasing with increasing sonication time. Loading solasodine onto MCM-41 reduced diffraction intensity but preserved the structural framework. BET analysis revealed decreases in surface area (from 1129.39 to 849.31 m2/g), pore volume (from 0.87 to 0.59 cc/g), and pore diameter (from 3.41 to 2.17 nm), indicating successful solasodine incorporation. Adsorption of solasodine was optimum at pH 4, followed well a kinetic model of second order reaching equilibrium and an isotherm model of Langmuir with an adsorption capacity of 1.69×10−2 mmol/g, indicating strong carrier affinity and monolayer adsorption. HIGHLIGHTS Structurally stable and well-ordered MCM-41 was prepared using a sonochemical method. The structural matrix of MCM-41 was not affected after loading solasodine. BET analysis confirmed reduced surface area and pore diameter after loading the drug. Adsorption followed pseudo-second-order kinetics that attained equilibrium. The Langmuir isotherm exhibited high affinity and monolayer adsorption of solasodine. GRAPHICAL ABSTRACT

This research studied the preparation of SiO2-TiO2/Cu(II) by utilizing rice husk ash as the SiO2 precursor, and evaluated its efficiency as a heterogeneous catalyst in biphenyl synthesis through Kumada cross-coupling reaction, which is widely known as an important intermediate in pharmacology and agriculture manufacturing. In this study, the catalyst preparation was conducted by extracting SiO2 from rice husk ash, combining it with TiO2, and introducing Cu(II) onto its surface with CuCl2·2H2O as the precursor with various concentration of Cu(II). Comprehensive characterization using techniques such as IR, XRD, XRF, DLS, N2 isotherm adsorption-desorption, ICP-AES, STEM-EDS, TEM, UV-vis spectrometry, and TGA was conducted to examine the catalyst properties. Catalyst activity was evaluated in the Kumada cross-coupling reaction, using phenylmagnesium bromide and bromobenzene as reactants under stirring-heating condition, and the products were analyzed using GC-FID method. The characterization results indicated that the preparation of SiO2-TiO2/Cu(II) materials was successfully conducted and Cu(II) was formed as Cu(OH)2. The catalyst considerably promoted the Kumada cross-coupling reaction with a biphenyl yield of 78.85% at 50 °C for 6 h under stirring-heating method. Furthermore, catalyst reusability test demonstrated that the catalyst sustained performance over three cycles without losing its activity significantly. Interestingly, SiO2-TiO2 was observed to function primarily as support material and adsorbent, immobilizing Cu(II) and enhancing reactant reduction but not directly influencing biphenyl formation. Overall, this study contributes to the understanding of SiO2-TiO2/Cu(II) catalyst preparation and its application in biphenyl synthesis, offering insights into catalyst design and performance optimization for future applications in organic synthesis.

Optimization of chitosan-based gel electrolytes modified with conducting polymers and ionic liquids for dye-sensitized solar cells (DSSC) has been done to improve its electrochemical activity. The effects of iodide salts, 1-propyl-3-methylimidazolium iodide (PMII), and polyaniline incorporation on the electrochemical properties of chitosan-based electrolyte, as well as its performance as a quasi-solid electrolyte in DSSC, were systematically investigated. A study on the effect of different iodide salts on the electrochemical properties of the electrolyte was conducted by employing various iodide salts (lithium iodide, sodium iodide, potassium iodide, or cesium iodide). Electrolytes with various amounts of PMII and polyaniline were also prepared. X-ray diffraction (XRD) and Fourier transform-infrared (FTIR) analysis were conducted to study the effect of iodide salts, PMII, and polyaniline on the change in intermolecular interaction of the chitosan matrix. The ionic conductivity and the redox activity of the chitosan-based electrolyte were respectively evaluated using conductometry and cyclic voltammetry analysis. It is found that the larger cation size of the iodide salts and a higher amount of PMII resulted in both higher intensity of the redox peak current and conductivity of the electrolyte. Those two characteristics increase with the presence of polyaniline, but the low transparency of this polyaniline-based electrolyte lowers the solar cell’s efficiency. The highest performance DSSC utilizing a chitosan/KI-PMII based electrolyte resulted in a Voc of 0.402 V, Jsc of 0.335 mA/cm², fill factor (FF) of 0.432, and an overall power conversion efficiency (PCE) of 0.058%. This efficiency is approximately one-third that of the conventional liquid electrolyte-based DSSC. The optimized chitosan-based electrolyte offers promising performance in replacing the low-stability liquid electrolyte-based DSSC.