研究目的
Investigating the unusual changes in plasmonic properties of Au nanorods after polydopamine coating, specifically the decrease in longitudinal plasmon resonance and increase in transversal plasmon resonance, through experimental and simulation approaches.
研究成果
The research demonstrates that PDA coating on Au nanorods leads to a decrease in longitudinal plasmon resonance and an increase in transversal resonance, contrary to typical dielectric coatings. Simulations confirm this behavior, which is influenced by the aspect ratio of nanorods and the imaginary part of PDA's refractive index. This provides new insights into the optical properties of composite plasmonic particles, with implications for theranostic applications.
研究不足
The study is limited to specific sizes and shapes of Au nanoparticles and PDA shell thicknesses; the refractive index of PDA is approximated from melanin data, which may not be fully accurate. Simulations assume spheroidal models, which may not perfectly match the actual cigar-like shapes of nanorods. The effects of aggregation or environmental factors are not extensively explored.
1：Experimental Design and Method Selection:
The study involved synthesizing Au nanospheres and nanorods, coating them with silica or polydopamine shells of varying thicknesses, and characterizing their optical properties using extinction spectroscopy and TEM. Theoretical simulations were performed using Mie theory, separation of variables method (SVM), electrostatic approximation (EA), and commercial software (COMSOL, FDTD) to model the optical responses.
2：Sample Selection and Data Sources:
Samples included 40-nm Au nanospheres, short Au nanorods (44 nm length, 11 nm width), and long Au nanorods (80 nm length, 16 nm width). Data were obtained from extinction spectra measurements and TEM imaging.
3：List of Experimental Equipment and Materials:
Equipment included a Specord 250 spectrophotometer (Analytik Jena), Libra-120 transmission electron microscope (Carl Zeiss), and reagents such as dopamine hydrochloride, CTAB, HAuCl4, etc., from Sigma-Aldrich and Alfa Aesar.
4：Experimental Procedures and Operational Workflow:
Nanoparticles were synthesized via seed-mediated growth, coated with silica or PDA by controlled polymerization, purified by centrifugation, and characterized. Simulations involved calculating cross-sections using various models and software.
5：Data Analysis Methods:
Data were analyzed by comparing experimental extinction spectra with simulated spectra, using models for refractive indices and electromagnetic simulations to interpret changes in plasmonic peaks.
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