Aggregation-Induced Modulation of the Optoelectronic Properties of Carbon Dots and Removal of Cd²⁺ Ions with Sustainable Use in Photocurrent Generation

Abstract

Herein, we report the room-temperature fabrication of carbon dots (C-dots) using UV light irradiation within 15 min. The formation pathway has been investigated by time-dependent mass spectroscopic and transmission electron microscopic (TEM) studies. The inherent insolubility of carbon dots in organic solvents has been overcome by employing the phase-transfer strategy, and the C-dots have been found to remain in aggregated state in organic solvents. Interestingly, aggregation leads to the generation of a considerable amount of current conductivity in carbon dots, as is evident by current–voltage (I–V) measurements. This is not attainable by carbon dots in aqueous solution. However, the aggregates of C-dots do not show any photocurrent response. The phase transfer of C-dots has also been utilized to remove the toxic Cd2+ ions from contaminated water by dragging them into the organic solvents with carbon dots. The C-dots–metal hybrid obtained by the removal of Cd2+ with carbon dots in organic medium shows a very good photoresponsive nature with significant photogain. This suggests proper utilization of the removed (from polluted water) cadmium ions in a sustainable manner for photocurrent generation.

Dual Fluorescence in Glutathione-Derived Carbon Dots Revisited

“…This mechanism has been attributed to embedded molecular fluorophores in the CDs, aggregation of CDs, and the presence of different types of CDs. 25 , 30 − 32 It was found that the red emission is excitation independent, which indicates that it is related to a specific molecular fluorophore. This fluorophore is not removed during dialysis with a 3.5 kDa membrane ( Figure S1a ).…”

“…Excitation-dependent emission is typical for CDs, which shows that the blue-emitting compounds are CDs. The origin of excitation-dependent emission is a matter of conflict in literature, but it is generally accepted that the behavior can be explained by a heterogeneous composition of fluorescent centers or complex energy levels. ,− Here, only the subpopulation of excited states that are efficiently populated at the excitation wavelength contribute to the PL emission, which results in a shift of the emission with excitation wavelength. This mechanism has been attributed to embedded molecular fluorophores in the CDs, aggregation of CDs, and the presence of different types of CDs. ,− It was found that the red emission is excitation independent, which indicates that it is related to a specific molecular fluorophore.…”

Tunning of Optoelectronic Properties in Nanohybrids of Peptide-Appended Perylenebisimides and Carbon Nanodots

“…It is interesting to note that C-dots themselves could not produce any photocurrent, but after introducing an electron acceptor (P1) in the system, the generation of stable photocurrent is achieved with a significant improvement (Figure ) in the photocurrent gain ( I on / I off ) compared to P1 (Table ). This synergistic effect of the photocurrent gain can be explained in two ways: first, a high amount of photogenerated charge influx into the hybrid systems due to the adhered donor C-dots on the surface of acceptor P1 fibers . The second factor is the separation of charges (electron and hole), which usually plays a crucial role in the photocurrent generation .…”

“…This synergistic effect of the photocurrent gain can be explained in two ways: first, a high amount of photogenerated charge influx into the hybrid systems due to the adhered donor C-dots on the surface of acceptor P1 fibers. 65 The second factor is the separation of charges (electron and hole), which usually plays a crucial role in the photocurrent generation. 21 Charge separation efficiency depends on the degree of π−π stacking as it helps in the long-range delocalization of electrons.…”

Broadened optical absorption, enhanced photoelectric conversion and ultrafast carrier dynamics of N, P co-doped carbon dots

“…The resulting CDs from different methods demonstrate a variety of ambiguous electronic structures and properties. [14][15][16][17][18][19][20] In the past decade, many efforts have been made to improve the optical and physicochemical properties of CDs using surface functionalization and atomic doping strategies. 8 In comparison, the photoelectric properties of CD-based devices are less studied, and the photocurrent density is still very low (<1 μA cm −2 ), far from the satisfactory value needed for practical application.…”