Doping in carbon nanomaterial with various hetero atoms draws attention due to their tunable properties. Herein, we have synthesized nitrogen containing carbon dots [C-dots (N)], phosphorus co-doped nitrogen containing carbon dots [C-dots (N, P)], and boron co-doped nitrogen containing carbon dots [C-dots (N, B)]; and detailed elemental analysis has been unveiled by X-ray photoelectron spectroscopy (XPS) measurements. Our emphasis is given to understand the effect of doping on the photophysical behavior of carbon dots by using steady-state and time-resolved spectroscopy. Nitrogen containing carbon dots have quantum yield (QY) of 64.0% with an average decay time of 12.8 ns. Photophysical properties (radiative decay rate and average decay time) are found to be increased for phosphorus co-doping carbon dots due to extra electron incorporation for n-type doping (phosphorus dopant) to carbon dots which favors the radiative relaxation pathways. On the contrary, boron (p-type dopant) co-doping with nitrogen containing carbon dots favors the nonradiative electron–hole recombination pathways due to incorporation of excess hole; as a result QY, radiative rate, and average decay time are decreased. To understand the effect of doping on charge transfer phenomena, we have attached nickel (II) phthalocyanine on the surface of C-dots. It is seen that phosphorus co-doping carbon dots accelerates the electron transfer process from carbon dots to phthalocyanine. In contrast, after boron co-doping in carbon dots, the electron transfer process slows down and a simultaneous hole transfer process occurs.

Luminescent copper nanoclusters (Cu NCs) have emerged as fascinating nanomaterials for potential applications in optoelectronics, catalysis, and sensing. Here, we demonstrate the synthesis of L-cysteinecapped Cu NCs in aqueous medium having a bright cyan emission (489 nm) with a quantum yield of 6.2%. The structure of the Cu NCs (Cu 7 L 3 ) is investigated by using density functional theory (DFT) calculation and mass spectrometric study. Further, time-dependent density functional theory (TD-DFT) calculations provide the insights of electronic transitions, and it is correlated with experimental data. With near-HOMO−LUMO gap excitation, Cu NCs are excited to the S 4 state and subsequently relaxed to the S 1 state through an internal conversion process with a time scale in the ultrafast region (326.8 ± 6.5 fs). Furthermore, the structural relaxation in S 1 takes place at a picosecond time scale, and the radiative relaxation occurs from S 1 to S 0 . Finally, Cu NCs are attached with imidazole-functionalized partially reduced graphene oxide (ImRGO) via electrostatic attraction. A dramatic photoluminescence (PL) quenching and shortening of the decay time of the Cu cluster in the presence of ImRGO indicate the photoinduced electron transfer process, which is confirmed from ultrafast spectroscopic study. The photoinduced electron transfer in a Cu NC−ImRGO nanocomposite should pave the way for potential applications in light harvesting.

Shape dependent carrier relaxation dynamics of lead halide perovskite nanocrystal (NCs) is an important issue for efficient light harvesting system.

Metal-semiconductor nanostructures have been the subject of great interest, mainly due to their interesting optical properties and their potential applications in light harvesting, photocatalysis and photovoltaic devices. Here, we have designed raspberry type organic-inorganic hybrid nanostructures of the poly-3-hexylthiophene (P3HT)-Au nanoparticle (NP) composite by a simple solution based synthetic method. The electronic interaction of semiconducting P3HT polymer nanoparticles with Au nanoparticles exhibits a bathochromic shift of absorption bands and significant photoluminescence quenching of P3HT nanoparticles in this organic-inorganic hybrid system. The photocatalytic activity of this raspberry type hybrid nanostructure is demonstrated under the visible light irradiation and the degradation efficiency is found to be 90.6%. Such organic-inorganic hybrid nanostructures made of a semiconducting polymer and plasmonic nanoparticles could pave the way for designing new optical based materials for applications in photocatalytic and light harvesting systems.

Carbon nanodots (CNDs) were photochemically altered to produce dihydrogen under light irradiation. Within the complex structure of CNDs, photo-oxidation takes place at citrazinic acid molecular fluorophore sites. Important is the fact that the resulting CND materials have a dual function. On one hand, they absorb light, and on the other hand, they photo-and electrocatalytically produce dihydrogen from water and seawater, without any external photosensitizer or cocatalyst. Record HER activities of 15.15 and 19.70 mmol(H 2 ) g(catalyst) −1 h −1 were obtained after 1 h of 75 mW/cm 2 Xe lamp illumination, from water and seawater, respectively. This impressive performance outweighs the remaining structural uncertainties. A fullfledged physicochemical investigation based on an arsenal of steady-state and time-resolved spectroscopic characterizations together with microscopy enabled a comprehensive look into the reaction mechanism. For an efficient dihydrogen formation, a precatalytic activation by means of reduction with a sacrificial electron donor is imperative.