研究目的
To investigate the kinetics of formation of silver nanoparticles and derive equations to calculate the concentration and mean size of nanoparticles using the Finke-Watzky mechanism, and to estimate the number of atoms in the catalytically effective nucleus.
研究成果
The study successfully derived equations linking Finke-Watzky rate constants to nanoparticle concentration and size, estimating the catalytically effective nucleus to be around 13 atoms for silver nanoparticles. This provides a method to analyze nucleation kinetics, but further investigations are needed to confirm assumptions and explore other systems.
研究不足
The approach assumes complete separation of nucleation and growth in time, which may not hold in all cases. It is limited to monomolecular transformations and does not account for aggregation effects at higher concentrations. The use of ethylene glycol as a weak stabilizer may not prevent aggregation, leading to polydispersity.
1：Experimental Design and Method Selection:
The study uses the Finke-Watzky two-step mechanism for kinetic analysis, with a stepwise mechanism assumption and quasi steady-state approximation for theoretical derivations.
2：Sample Selection and Data Sources:
Silver nanoparticles were synthesized by reducing Ag+ ions from AgNO3 with hydrazine in ethylene glycol at 25°C. Initial concentrations were [AgNO3]0 = 0.1–0.3 mmol/L and [N2H4]0 = 0.3 mmol/L. Kinetic data were obtained from absorbance measurements.
3：1–3 mmol/L and [N2H4]0 = 3 mmol/L. Kinetic data were obtained from absorbance measurements.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a photoelectric colorimeter 'type KF–77' (Zalimp, Poland) with an analog-to-digital converter (MTech ADC-24-3; Ukraine), and an FEI Tecnai F30 transmission electron microscope (TEM). Materials include AgNO3 (99%; ALSI, distributor of Sigma-Aldrich), hydrazine (N2H4 × H2O, 98%; Systema Optimum), and ethylene glycol (98%; Systema Optimum).
4：Experimental Procedures and Operational Workflow:
The reaction was monitored by measuring absorbance at 400 nm over time. Kinetic curves were fitted using a linear form of the Finke-Watzky equation to obtain rate constants. TEM was used to determine nanoparticle sizes.
5：Data Analysis Methods:
Rate constants k1,obs and kg were calculated from absorbance data. The quasi steady-state approximation was applied to derive equations for nanoparticle concentration and size. Statistical analysis included averaging and uncertainties from replicate experiments.
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