Here, we study the human serum albumin (HSA) protein–Au nanoparticle interaction to identify the specific binding site of protein with nanoparticles by using the surface energy transfer (SET) method among tryptophan (Trp) of HSA, ANS-dye-labeled HSA protein, and Au nanoparticles. Here, ANS dye is used as a probe located at domain IIIA of HSA. In particular, absorbance, fluorescence quenching, decay time, circular dichroism, dynamic light scattering, and TEM measurements are performed to understand the physical properties of protein-conjugated Au nanoparticles. Using the SET method, the measured distances between the Trp residue of HSA and the binding site of HSA interacting with Au nanoparticles are 42.5, 41.9, and 48.1 Å for 1.5, 2.0, and 2.9 nm HSA-conjugated Au nanoparticles, respectively. The measured distances between the binding site of ANS dye (located at domain IIIA) in HSA to the binding site of HSA interacting with Au nanoparticles are 51, 51.5, and 54.7 Å for 1.5, 2.0, and 2.9 nm HSA-conjugated Au nanoparticles, respectively. From the protein structural data (using PyMol software), the distances from the center of domain IIIA to Cys53–Cys62 disulfide bond and Trp to Cys53–Cys62 disulfide bond are obtained to be 51.5 and 39.1 Å, respectively. Thus, the distances calculated by using SET equation (Trp to Au binding site distance and ANS to Au binding site distance) nicely match with the distances obtained from protein structural data by using PyMol software. Analysis suggests that the Au nanoparticle is attached to HSA by linkage through Cys53–Cys62 disulfide bond which is located at subdomain IA of HSA.

In this report, we have demonstrated the synthesis of surfactant-assisted different morphologies of meso-tetra(4-carboxyphenyl)porphyrin assemblies (spherical to flower shaped). These nano/micro assemblies are well characterized by scanning electron microscopy and X-ray diffraction. The formation of assemblies is driven by noncovalent interactions such as hydrophobic-hydrophobic and aromatic π-π stacking between the molecules. The steady state and time-resolved spectroscopic investigation reveal that different assemblies are formed by virtue of special supramolecular organizations. The photocatalytic activities of different assemblies have been demonstrated with an organic pollutant Rhodamine B dye under the visible light irradiation. Such porphyrin based assemblies could pave the way for designing new optical based materials for the applications in photocatalytic, photovoltaic, and light harvesting system.

An advantage of colloidal quantum dots, particularly perovskite quantum dots (PQDs), as photoactive components is that they easily form complexes with functional organic molecules, which results in hybrids with enriched photophysical properties.

This paper focuses on the spectroscopic studies and self-assembly behavior of zinc octaethylporphyrin (ZnOEP) doped semiconducting [poly(N-vinylcarbazole) (PVK)] polymer nanoparticles (NP) using steady state and time-resolved spectroscopy. The bathochromic shift of both Soret (by 12 nm) and Q bands (by 6−8 nm) in the absorption spectra and shortening of the porphyrin lifetime indicate the J-aggregation of porphyrin molecules in the ZnOEP doped PVK NP system. The significant quenching of fluorescence spectrum and the shortening of decay time of the PVK host unambiguously confirm an effective energy transfer (above 90%) from PVK to ZnOEP in the nanoparticles.

Well-defined organic nanostructures of porphyrin are promising candidates toward photocatalysis, photovoltaics, and electronics applications where a photoinduced electron transfer process occurs. On the other hand, reduced graphene oxides (RGO) have attracted much attention in light energy conversion owing to their efficient charge separation property. In this respect, we have demonstrated a composite of a one-dimensional (1D) nanostructure of 5, 10, 15, and 20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) and RGO for enhancing photoinduced charge separation. The composite was characterized by scanning electron microscopy (SEM), UV−visible spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC), and femtosecond fluorescence upconversion spectroscopy. It is noted that a very fast decay of TCPP NR was observed in the TCPP NR−RGO composite due to the electron transfer process, and the electron transfer rate is found to be 10.0 × 10 −4 ps −1 for the TCPP NR−RGO system. An increment (1.9 fold) of photocurrent of this composite system under visible light illumination is obtained due to electron transfer from TCPP NR to RGO. This new class of porphyrin-based composite structures opens up new possibilities in solar energy conversion and photocatalytic, photovoltaic, and other new emerging applications.