School of Science Department of Chemistry 3 Developing New Nanomaterials for Advanced Optical Analysis in Health and Environmental Monitoring Supervisor: HUANG Jinqing / CHEM Student: LAM Man Hei / CHEM Course: UROP 1000, Summer Soil composition is vital for healthy plant growth, as essential elements are often present only in minute amounts. Precise detection of these trace elements is therefore critical for optimizing soil and crop management. While conventional spectroscopy offers rapid, non-destructive analysis for detecting elements in complex matrices, its sensitivity is limited for low-concentration elements. To address this, the method of amplifying signals by utilizing nanostructured metallic surfaces is employed to improve the sensitivity and selectivity. In this study, silver nanoporous sheet were utilized as enhancing agents for the direct detection of trace nutritional elements in Nutrient A. Spectra were systematically collected from the nutrient sample by the spectral pencil, with particular attention to low-concentration components, and the impact of nanoporous Ag sheet on signal enhancement was evaluated. The results highlight the capability of spectral measurement for sensitive, direct detection of soil components, demonstrating its promise as a rapid, nondestructive tool for elemental identification in environmental and agricultural monitoring. Developing New Nanomaterials for Advanced Optical Analysis in Health and Environmental Monitoring Supervisor: HUANG Jinqing / CHEM Student: ZHU Siya / CHEM Course: UROP 1100, Summer This study aimed to optimize the synthesis of silver nanocolloids for enhanced Surface-Enhanced Raman Scattering (SERS) performance by producing small-sized nanoparticles (10-20 nm) and introducing positive surface charges. Silver nanocolloids were synthesized via hydroxylamine hydrochloride (1.67×10⁻³ M) and sodium hydroxide (3.33×10⁻³ M) reduction of silver nitrate, followed by modification with dodecyltrimethylammonium chloride (DDTC). Particle size and zeta potential were characterized using a ZETAview nanoparticle tracking analyzer. Results showed conventional nanocolloids with an average particle size of 60.1 ± 7.5 nm and an anomalous positive zeta potential of +10.3 ± 0.7 mV, while DDTC-modified nanocolloids exhibited a size of 70.3 ± 8.4 nm and a zeta potential of +15.2 ± 1.2 mV, both indicating low stability. The larger particle sizes and low stability likely limit SERS enhancement. ZETAview measurements were affected by high sample concentrations (10⁹ particles/mL), necessitating dilution that introduced aggregation and data variability. These findings highlight challenges in particle size control and charge stability, suggesting future optimization of reagent ratios, alternative modifiers like CTAB, and complementary characterization methods such as DLS and TEM to improve SERS substrate performance.
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