Low-frequency lattice vibrations are sensitive to intermolecular interactions and crystal packing, but reliable interpretation requires more than matching Raman and terahertz (THz) peak positions. Here, low-wavenumber Raman spectroscopy, THz absorption spectroscopy, and periodic density functional theory calculations were combined to investigate L-alanine, L-glutamic acid, and L-glutamine, which share a common α-amino-acid backbone but differ in side-chain chemistry and crystal packing. The three crystals exhibited distinct low-frequency spectral profiles. Periodic PBE-D3 calculations indicated that the lower-frequency modes are dominated by collective rigid-molecule librations, whereas higher-frequency modes increasingly involve coupling between lattice motion and internal or side-chain coordinates. A selection-rule-aware comparison based on frequency proximity, calculated Raman activities and infrared intensities, and atomic displacement patterns distinguished Raman-selective, IR-selective, cross-technique-compatible, and near-coincident but vibrationally non-equivalent features. These findings demonstrate that frequency coincidence alone is insufficient for establishing Raman–THz mode correspondence. The study provides a mode-resolved approach for interpreting complementary low-frequency Raman and THz spectra of molecular crystals.
A robust and sensitive RP-HPLC method was developed for the simultaneous determination of Glimepiride and Linagliptin in synthetic mixtures by Design of Experiments approach using Central Composite Design to systematically optimize critical chromatographic variables and evaluate their interaction effects on method performance. This study describes the development and validation of an AQbD-based RP-HPLC method for the simultaneous estimation of Glimepiride (GLM) and Linagliptin (LNG) in synthetic mixtures. Critical chromatographic conditions were optimized using a three-factor, three-level Central Composite Design (CCD) to achieve a robust analytical method. Chromatographic separation was achieved on a Shim-pack C18 column (250 mm × 4.6 mm, 5 μm) using a mobile phase of acetonitrile and water (70:30,
Rainwater harvesting is widely practiced in sub-Saharan African communities as an alternative water supply; however, atmospheric deposition, roofing materials, and storage conditions may influence its chemical quality and potential health implications. This study investigated seasonal variation, storage effects, and health risks of metals in rooftop-harvested rainwater from Chokocho and Diobu, Rivers State, Nigeria. Rainwater was collected from five catchment surfaces (asbestos sheet roof, aluminium roof, zinc roof, stone-coated roof, and ambient collection), during early, mid, and late rainfall periods. Fresh samples were analyzed after collection, while a second portion was stored under mesophilic conditions for six months prior to re-analysis to depict the condition of usage by the locals. Metal concentrations were determined and chemometric techniques were applied for source identification. Non-carcinogenic risks via ingestion and dermal exposure were assessed. Results revealed strong first-flush effects in Chokocho with early rain samples showing elevated Na (5.64 mg L⁻¹) and Zn (1.10 mg L⁻¹), but declined to < 0.2 mg L⁻¹ during mid- and late-rain periods. Stored samples of Chokocho showed lower concentrations of Fe, K, Na, Zn, and Cu, than their corresponding fresh samples, especially during early and mid-rain periods. Fresh and stored pH ranged from 5.1 to 7.9 (Chokocho) and 6.0 -7.8 (Diobu). PCA explained 86.1
Biomass-derived carbon materials have attracted considerable attention as sustainable and low-cost electrode materials for electrical double-layer capacitors (EDLCs). This study investigated coconut shell and kluwak shell wastes as the precursors for activated carbon (AC) and partially reduced graphene oxide (p-rGO) electrodes. AC derived from both biomasses was oxidized to graphite oxide (GO) using a modified Hummer’s method, followed by microwave-assisted solvothermal reduction in ethylene glycol to produce p-rGO. The novelty has lied in utilizing kluwak shell as an alternative carbon precursor and systematically comparing its electrochemical performance with coconut shell-derived materials under controlled microwave conditions. For coconut shell-derived p-rGO, microwave power was varied at 100, 180, and 300 W, whereas irradiation times of 15, 30, and 45 min had applied to kluwak shell-derived p-rGO. Structural characterization has shown the reduced interlayer spacing and enhanced pore development with increasing microwave intensity, indicating an improved reduction and structural ordering. The electrochemical characterization by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) demonstrated superior performance of coconut shell-derived materials. The highest specific capacitances of coconut shell AC and p-rGO reached 130.83 and 103.58 F g−1, respectively, with electrical conductivities of 0.78 and 0.30 S m−1 at 300 W. In comparison, kluwak shell-derived AC and p-rGO exhibited specific capacitances of 1.39 and 3.73 F g−1 and conductivities of 0.063 and 0.157 S m−1, respectively, after 45 min irradiation. The results have demonstrated a strong correlation between electrical conductivity and electrochemical performance. Overall, coconut shell was a more favorable precursor, while kluwak shell remained as a promising sustainable alternative for biomass-derived carbon electrodes.
Piperazine is one of the most commonly employed nitrogen-containing heterocycles in the development of pharmacologically active molecules. The adaptable structure of piperazine has made it preferable in the synthesis of novel bioactive molecules for the last several years. However, there is a lack of comprehensive information about the current status of the synthesis and medicinal application of piperazine derivatives. Therefore, this systematic review aims to compile research articles reported in the past six years (between 2020 and 2025) dealing with the various synthetic methodologies and biological activities of piperazine derivatives. The papers compiled in this review were collected from major databases and search engines. Among the various reported piperazine derivatives, compounds 41b, 41d, 42f, and 43e with an MIC of 0.391 μg/mL against S. aureus; compound 98a with an MIC of 0.65 μg/mL against M. tuberculosis; compound 207f with an IC50 value of 1.86 ± 0.03 μM against breast cancer cell line (MCF-7); and compound 218i against Zika virus (ZIKV) with an EC50 of 0.82 ± 0.33 μM were mentioned as promising compounds for various medicinal applications. This review could be beneficial to researchers as a source of compiled and up-to-date preliminary information by highlighting the synthetic methodologies and various medicinal applications of the piperazine derivatives.
