No abstract

Gold nanorods deserve special attention as they exhibit tunable longitudinal localized surface plasmon resonances (LSPRs). In our study, gold nanorods of the aspect ratio of 2.25 (maximum of LSPR band at 660 nm) and of controllable SiO 2 thickness in the range of 6−14 nm were mixed with pheophorbide (chlorophyll derivative) in order to create a hybrid system. Energy transfer and singlet oxygen generation were studied for different SiO 2 thicknesses of the nanorod shell. The spectral properties of the hybrid mixture were characterized, and the overlapping of the pheophorbide fluorescence and the longitudinal LSPR band of nanorods on the fluorescence emission, energy transfer, and generation of singlet oxygen were studied. Two independent approaches were used to determine the quantum yield and enhanced factor of singlet oxygen generation. For a certain thickness of the SiO 2 shell and for certain concentrations of gold nanorods, the effect of the plasmon-enhanced singlet oxygen production was observed. Moreover, the enhanced of singlet oxygen yield enhancement was correlated with the far-field optical properties of the gold nanorods. The results obtained indicate the significance of further studies of dye-photosensitizers in hybrid mixtures, taking into account the spectral overlap between dye emission and longitudinal LSPR bands as well as the character of coatings (type and thickness) and scattering yields of gold nanorods.

Robust and versatile strategies for the development of functional nanostructured materials often focus on assemblies of metallic nanoparticles. Research interest in such assemblies arises due to their potential applications in the fields of photonics and sensing. Metallic nanoparticles have received considerable recent attention due to their connection to the widely studied phenomenon of localized surface plasmon resonance. For instance, plasmonic hot spots can be observed within their assemblies. A useful form of spectroscopy is based on surface-enhanced Raman scattering (SERS). This phenomenon is a commonly used in sensing techniques, and it works using the principle that scattered inelastic light can be greatly enhanced at a surface. However, further research is required to enable improvements to the SERS techniques. For example, one question that remains open is how to design uniform, highly reproducible, and efficiently enhancing substrates of metallic nanoparticles with high structural precision. In this review, a general overview on nanoparticle functionalization and the impact on nanoparticle assembly is provided, alongside an examination of their applications in surface-enhanced Raman spectroscopy.

Background: The understanding of the action mechanism of the nanoparticles systems consisting of metallic nanoparticles and dyes or cytostatic molecule is crucial for searching and designing the ideal, novel drugs. In this review, we have considered moleculefunctionalized metallic nanoparticle systems for phototherapy. Methods: We performed a thorough search of the high-quality peer-reviewed literature on metallic nanoparticles systems in phototherapy, focusing on their biological importance and the action mechanism. Results: 138 papers were included in the mini-review. The majority of them discussed the way of metallic nanoparticles functionalization and its impact on the biological activity of a hybrid system. Conclusion: In this work, we show numerous medically and chemically important development strategies of hybrid types of drugs which can be used in phototherapy. These systems have a high affinity to the tumor cells surface proteins which transport the nanoparticles directly into a cell. The application of functionalized metallic nanoparticles in phototherapy improved photophysical properties lowered cytotoxicity of commonly used photosensitizers and facilitated the development of the third generation photosensitizers. Furthermore, this type of nanoparticles could also be used as a cytostatic drug carrier in the chemo or combined anticancer therapies.

Plasmonic nanoparticles can be used in photothermal therapy thanks to their ability to generate local heat. The light-to-heat conversion efficiency is crucial for therapeutic and diagnostic applications. The photothermal properties of gold nanorods functionalized with silica layers of controllable thickness were characterized using both theoretical and experimental approaches. The time-resolved laser-induced optoacoustic spectroscopy (LIOAS) was used to determine the amount of absorbed energy that changed promptly into heat. The heat generation efficiencies were simulated by the means of finite integration technique. The obtained parameters were correlated with silica thickness. Experimental results are consistent with theoretical predictions; thus, LIOAS is a unique reliable method for studying photothermal effect in gold nanoparticles.

No abstract

Localized surface plasmon resonance (LSPRs) shown by gold nanorods (AuNRs) has several applications in photocatalysis, sensing, and biomedicine. The combination of AuNRs with Polydopamine (PDA) shells results in a strong photo‐thermal effect, making them appealing nanomaterials for biomedical applications. However, the precise roles and relative contributions of plasmonic effects in gold, and light‐to‐heat conversion in PDA are still debated. Herein, a hybrid nanoplatform made by an AuNR core surrounded by a polydopamine (PDA) shell is synthesized, and its photocatalytic behavior is studied. Synthesis is based on a seed‐mediated growth followed by the further self‐polymerization of dopamine hydrochloride (DA) on the surface of the AuNRs, and the effect of the thickness of the PDA shell on the plasmon response of the composite is the main examined parameter. Photocatalytic performance is tested toward Rhodamine 6G (Rh6G), with the nanocomposites achieving better performance than bare AuNRs and bare PDA nanoparticles. The degradation of 54% of Rh6G initial concentration is achieved within 60 min of irradiation with a catalyst concentration of 7.4 µg mL−1. Photodegradation kinetics, time‐resolved spectroscopy, and finite‐element‐method simulations of plasmons show that AuNRs plasmons, coupled with the low thermal conductivity of PDA, provide slow thermalization, while enhancing the charge carrier transfer.

No abstract