We report the conducting nature of carbon dots (Cdots) synthesized from citric acid and ethylene diamine. Chemically synthesized conducting nanocomposite consisting of Cdots and polypyrrole (PPy) is further reported, which showed higher electrical conductiviy in comparison to the components i.e., Cdots or PPy. The conductive film of the composite material was used for highly sensitive and selective detection of picric acid in water as well as in soil. To the best of our knowledge, this is the first report on the conductivity based sensing application of Cdot nanocomposite contrary to the traditional fluorescence based sensing approaches.

The present review article focuses on novel findings corresponding to the structural and photophysical properties of carbon dots. The article also highlights unique characteristics of crystalline dots that offer new chemistry and thus new application potential.

A highly ordered crystalline structure in carbon dots (Cdots) can substantially enhance the gamut of their applications in conversion, transfer and transport of energy; however, achievement of such crystallinity in a controlled manner has been elusive.

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Aggregation-induced emission (AIE) has unlocked a completely new research area corresponding to application potentials of luminescent materials. Notably, carbon dots (Cdots) are emerging as well-recognized alternative to organic dyes because of their fascinating fluorescence properties. They exhibit improved emission when aggregated due to the changes in solvent polarity, higher concentration, externally added chemical species. Herein, a review on the AIE property is demonstrated with a substantial emphasis on Cdot optical property. Mechanistic overview along with application potentials of the same in sensing, optoelectronic devices, fingerprints recognition and solar concentrators are highlighted. Finally, a summary corresponding to recent developments and future prospects have been discussed.

Herein we report that boron doping in carbon dots results in increased photoluminescence (PL) quantum yield, which could be used for ratiometric intracellular pH sensing in cancer cell lines. Using a mixture of citric acid monohydrate, thiourea, and boric acid, microwave‐assisted synthesis of boron doped blue emitting carbon dots (B‐Cdots) with an average size of 3.5±1.0 nm was achieved. For B‐Cdots, the maximum quantum yield (QY) was observed to be 25.8 % (11.1 % (w/w) H3BO3 input concentration), whereas, the same was calculated to be 16.9 % and 11.4 % for Cdots (synthesized from citric acid monohydrate and thiourea only) and P‐Cdots (phosphorus doped carbon dots; synthesized using citric acid monohydrate, thiourea and phosphoric acid) (11.1 % (w/w) H3PO4 input concentration), respectively. The observed luminescence efficiencies as obtained from steady state and time‐resolved photoluminescence measurements suggest an alternative emission mechanism due to boron/phosphorus doping in carbon dots. We furthermore demonstrated facile composite formation using B‐Cdots and another carbon dots with orange emission in presence of polyvinyl alcohol (PVA), resulting in white light emission (0.31, 0.32; λex 380 nm). The white light emitting composite enabled ratiometric pH sensing in the aqueous medium and showed favorable uptake properties by cancerous cells for intracellular pH sensing as well.

We have demonstrated a rapid and facile synthetic method to prepare N-doped Cdots that has excitation independent-emission in yellow-orange region. The Cdots showed solvatochromic behavior in different solvents due to change in solvent polarity illustrating n → π* transition (edge band).

Single-particle level white-light-emitting carbon dots via a one-step microwave synthesis.