Gold nanorods (GNRs) have emerged as the most efficient photothermal agent in cancer therapy and photocatalysis. Understanding the influence of the surrounding medium, particle size, and excitation wavelength is critical to optimising the photothermal conversion rate. Here, three pairs of large and small gold nanorods of different aspect ratios and their heat generation under laser radiation at on and off surface plasmon resonance wavelengths in aqueous solution and gel-like media are investigated. In the aqueous solution, the temperature rise of the large gold nanorods is more than with small gold nanorods at resonance excitation. In contrast to the large gold nanorods (LGNRs), the small gold nanorods (SGNRs) were less sensitive to excitation wavelength. At off-resonance excitation, the temperature rise of the SGNRs is larger than that of the LGNRs. In the agarose gel, the photothermal effect of the SGNRs is greater than LGNRs excited at the wavelength near their solution phase longitudinal surface plasmon resonance wavelength. The temperature increase of LGNRs in gel is significantly less than in aqueous solution. These findings suggest that SGNRs could be more beneficial than the LGNRs for photothermal applications in biological systems and provides further insight when selecting GNRs.

中文翻译：

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金纳米棒在水溶液和凝胶介质中的光热效应：粒径和激发波长的影响。

金纳米棒 (GNR) 已成为癌症治疗和光催化中最有效的光热剂。了解周围介质、粒径和激发波长的影响对于优化光热转化率至关重要。在这里，研究了三对不同纵横比的大金纳米棒和小金纳米棒及其在水溶液和凝胶状介质中在表面和表面等离激元共振波长的激光辐射下的热生成。在水溶液中，在共振激发下，大金纳米棒的温升大于小金纳米棒。与大金纳米棒 (LGNR) 相比，小金纳米棒 (SGNR) 对激发波长不太敏感。在偏共振激发下，SGNRs 的温升大于 LGNRs。在琼脂糖凝胶中，SGNRs 的光热效应大于在其溶液相纵向表面等离子体共振波长附近激发的 LGNRs。凝胶中 LGNR 的温度升高明显低于水溶液。这些发现表明，对于生物系统中的光热应用，SGNR 可能比 LGNR 更有益，并在选择 GNR 时提供进一步的见解。