Carbon dots (CDs) have become one of most promising fluorescent materials in recent days, because of their promising photoluminescence and photocatalytic properties. However, the practical applicabilities for emissive and catalytic devices are still debatable, because of the lack of fundamental understanding behind the structure–property correlations. Herein, we have developed different types of nitrogen-doped CDs (N-CDs) by varying different nitrogen-containing precursors through a simple bottom-up based carbonization technique. Depending on the nature of nitrogen atom precursor, we are able to critically control the subpopulations of various intrinsic constituents of N-CDs, i.e., aromatic domains, amorphous domains, and small molecular fluorophores inside N-CDs. Detailed structural and elemental features have been correlated with the underpinning photophysical processes by means of steady-state and time-resolved fluorescence spectroscopy. In addition, the effect of temperature on overall photoluminescence properties has been corroborated with the internal structure of N-CDs. Finally, we have investigated the photocatalytic properties and the detailed photocatalysis mechanisms by scavenging the active species originated upon light irradiation. Results suggest that photocatalytic efficiency is maximum at a larger extent of amorphous domains and in the presence of nitrogen atoms specifically located at the edges, while photoluminescence intensity is higher at larger extent of molecular fluorophores and aromatic domains. Therefore, these fundamental investigations will open up new possibilities considering the optimizations of heteroatom functionalized CDs for their on-demand applicabilities in emitting as well as photocatalytic devices.

Carbon dots (CDs) have become one of the most emerging materials as an alternative solar light-induced photocatalyst in contrast to traditional metal-based systems. However, one of the major challenges is the lack of visible light absorption. Herein, we have fabricated unique N, P-codoped CDs with a self-assembled onion-like layered structure by using a bottom-up facile synthesis technique from chitosan gel and phosphoric acid as molecular precursors. This typical layered structure of N, P-co-doped carbon nano onions (N, P-CNOs), with an average size of 25-50 nm, displays an enhanced visible light absorption. Detailed structural and elemental characterizations confirm the extensive aromatic domain with P-containing surface functionalities, while electrochemical study clarifies the lowering of band gaps as well as the creation of new electronic states in comparison to the pristine N-CDs. Furthermore, the intrinsic structural features are correlated with the underpinning photophysical processes by steady-state and time-resolved fluorescence spectroscopy. In addition, steady-state polarized emission and thermo-responsive PL properties have been carried out to unveil further the structure-property correlation of N, P-CNOs, and their comparative study with pristine N-CDs at the different excitation wavelengths. Finally, N, P-CNOs exhibit efficient visible-light-induced photocatalysis, and the detailed mechanistic study is carried out by trapping the photogenerated species in an aqueous medium. The prepared N, P-CNOs displayed an excellent visible-light photocatalytic performance over MB dye with a degradation efficiency of 75.8% within 120 min along with a degradation rate constant of~0.0109 min À 1 . It is concluded that the easy to synthesize and low-cost N, P-CNOs with a unique morphology hold great potential for application in visiblelight photocatalysis.

Sulfur dots (S-dots) are one of the most recently developed non-metallic luminescent nanomaterials which possess several advantages over traditional inorganic Quantum dots (QDs). Here, we have synthesized highly luminescent ultra-small...

Complete metal‐free P‐functionalized carbon nanomaterials are synthesized from a single molecular precursor, phytic acid, for photocatalytic solar H2 production and simultaneous organic transformation of 4‐methyl benzyl alcohol to 4‐methyl benzaldehyde by managing the complete redox cycle. It is observed that by increasing the carbonization time, P‐functionalized amorphous carbon dots convert to the highly defined 2D sheet‐like nanostructure with optimum P‐functionality, resulting in efficient light absorption, charge separation, and improved active sites for photocatalysis. Finally, the highly defined sheet‐like structure converts to a more defected aggregated form, resulting in the depletion of photocatalytic efficiency. The structural and elemental features are further correlated with the ongoing photophysics by means of steady‐state and time‐resolved fluorescence spectroscopy. Transient photocurrent responses and Mott‐Schottky plots directly support the optimization of P‐functionalized carbon nanostructure for efficient photocatalysis. Finally, the detailed computational studies are carried out to unveil the charge separation mechanism and the crucial role of P‐functionalities as active sites for better charge accumulation as well as H2O adsorption on the surface. Overall, the in‐depth structure–property correlation and critical optimization of the heteroatom functionalized carbon nanomaterials will open up new possibilities for further development of metal‐free photocatalysts for solar‐energy conversion devices.

Herein, we have fabricated self-assembled semiconducting organic nanomaterials with various morphologies (1Dfiber, 2D-flakes, and 2D-nanosheets) made of small conjugated oligomer 2,2′:5′,2″:5″,2‴-quaterthiophene (α-QTH) by a simple solution-based coprecipitation method. By simply varying the good-solvent-to-bad-solvent ratio, we can critically tune the selfassembly process and eventually can control the intermolecular interactions of the constituent molecules in these self-assembled nanostructures. Different types of self-assembled nanostructures have been utilized for photocatalytic solar H 2 production. The H 2 production efficiencies directly depend on the morphology of selfassembledselfassembled nanomaterials as well as intermolecular interactions of QTH molecules. The overall photocatalytic properties are further correlated with the ongoing photophysical properties by means of detailed steady-state and time-resolved fluorescence spectroscopy and dimer-based time dependent-density functional theory (TD-DFT) calculations. Furthermore, femtosecond transient absorption spectroscopy has been utilized to explore the detailed photoinduced exciton dynamics by global analysis of spectrally resolved pump−probe traces. In addition to that, the overall photocatalytic activities are further supported by an in-depth electrochemical study. Finally, a boost in photocatalytic H 2 production has been observed by using 4-methylbenzyl alcohol (4-MBA) as a specific hole scavenger for the completion of the redox cycle. Therefore, the present system can be utilized for simultaneous solar H 2 production and the specific organic transformation through a green and cost-efficient approach.