We present a method for measuring the optical absorption cross section ( $$\sigma_{abs}$$σ abs ) of gold nanoparticles (GNPs) based on optically heating the solution of GNPs with an 808 nm near-infrared (NIR) laser and measuring the temperature increase of the solution. We rely on the theoretical calculations based on the heat diffusion equations and experimental measurements based on the energy balance equations to measure the $$\sigma_{abs}$$σ abs and the temperature distribution of single GNPs. Several morphologies, including gold nanospheres (GNSs), spherical gold nanoparticle conjugate (AuNPC), which are 20 nm GNSs surface-functionalized with an IR 808 dye, gold nanorods (GNRs), and gold nanourchins (GNUs), were studied. The study found that a single 20 nm GNS has the lowest $$\sigma_{abs}$$σ abs and temperature distribution as compared to 100 nm GNUs. By increasing the size of GNSs from 20 to 30 nm, the magnitude of $$\sigma_{abs}$$σ abs as well as temperature distribution increases by a factor of 5. The $$\sigma_{abs}$$σ abs values of 20 and 30 nm GNSs calculated by Mie theory and the experimentally measured are in a good agreement. GNRs with equivalent radius ( $$R_{eq}$$R eq ) 9.16 nm show the second lowest $$\sigma_{abs}$$σ abs . By increasing the $$R_{eq}$$R eq by a factor of 2 to 19.2 nm, the measured $$\sigma_{abs}$$σ abs and temperature distribution also increased by a factor of 2. We also estimated $$\sigma_{abs}$$σ abs for GNUs with diameters at 80 and 100 nm, which also have higher $$\sigma_{abs}$$σ abs values. This work confirms that we can use temperature to accurately measure the $$\sigma_{abs}$$σ abs of a variety of GNPs in solution.

The S-scheme In–CeO ₂ /g-C ₃ N ₄ heterojunction achieves enhanced photocatalytic degradation of levofloxacin by preserving strong redox carriers and promoting the efficient generation of ˙OH and ˙O ₂ ⁻ radicals under visible light.

Electrocatalytic hydrogen generation in alkaline medium has become widely used in a variety of sectors. However, the possibility for additional performance improvement is hampered by slow kinetics. Because of this restriction, careful control over processes such as water dissociation, hydroxyl desorption and hydrogen recombination is required. Covalent organic frameworks (COFs) based on porphyrin and polyoxometalates (POMs) show encouraging electrocatalytic performance, offering a viable route for effective and sustainable hydrogen generation. Their specific architectures lead to increased electrocatalytic activity, which makes them excellent choices for developing water electrolysis as a clean energy conversion method in the alkaline medium. In this regard, TTris@ZnPor and Lindqvist POM were coordinated to create a new eco-friendly and highly active covalent organic framework (TP@VL-COF). In order to describe TP@VL-COF, extensive structural and morphological investigations were carried out through FTIR, ¹H NMR, elemental analysis, SEM, fluorescence, UV-visible, PXRD, CV, N₂-adsorption isotherm, TGA and DSC analyses. In an alkaline medium, the electrocatalytic capability of 20%C/Pt, TTris@ZnPor, Lindqvist POM and TP@VL-COF was explored and compared for the hydrogen evolution reaction (HER). The TP@VL-COF showed the best catalytic efficiency for HER in an alkaline electrolyte, requiring just a 75 mV overpotential to drive 10 mA cm⁻² and outperforming 20%C/Pt, TTris@ZnPor, Lindqvist POM and other reported catalysts. The Tafel slope value also indicates faster kinetics for TP@VL-COF (114 mV dec⁻¹) than for 20%C/Pt (182 mV dec⁻¹) TTris@ZnPor (116 mV dec⁻¹) and Lindqvist POM (125 mV dec⁻¹).

In this paper, we analyze the optical properties and sensitivities of spherical silver nanoparticles (AgNPs) with varying diameters (10–60 nm) in different surrounding medium, including water, ethanol, and chloroform. The investigation focuses on analytically assessing scattering efficiencies (\({{Q}_{{{\text{sca}}}}}\)), absorption efficiencies (\({{Q}_{{{\text{abs}}}}}\)), total extinction efficiencies (\({{Q}_{{{\text{ext}}}}}\)), shedding light on how the properties of AgNPs change with the size and surrounding medium of AgNPs. The results show that smaller AgNPs exhibit sharper plasmon resonance peaks at shorter wavelengths, while larger AgNPs display broader peaks in the visible spectrum, showcasing the size-dependent behavior of AgNPs. Additionally, the study calculates the molar attenuation coefficient (ε) and extinction cross section (\({{\sigma }_{{{\text{ext}}}}}\)) for AgNPs, highlighting the differences in absorption properties between small and large particles and their sensitivity to the surrounding medium. The research also discusses the implications of these properties for applications such as plasmonic sensing and sensor design, emphasizing the importance of particle size and surrounding medium in optimizing sensor performance. Moreover, the refractive index sensitivity (S) and the figure of merit (FOM) are introduced as critical parameters for assessing sensor performance, revealing their relationship with particle size, and providing valuable insights into sensor design and optimization.