Hybrid carbon dots platform enabling opportunities for desired optical properties and redox characteristics by-design (original) (raw)
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Carbon Dots: Zero-Dimensional Carbon Allotrope with Unique Photoinduced Redox Characteristics
ACS Omega
Carbon dots (CDots) exploit and enhance the intrinsic properties of small carbon nanoparticles. Their optical absorptions and photoinduced redox characteristics are competitive with those of conventional semiconductor quantum dots at one end and fullerenes and other carbon nanomaterials at the other. Highlighted in this mini review are the effective photon harvesting over a broad spectral range by CDots and their subsequent excited-state charge transfer processes and interactions, which have enabled their use as sensors, for photodynamic effects, and in various energy conversion technologies.
Carbon, 2019
Carbon dots (CDots), generally small carbon nanoparticles with surface passivation by a soft corona-like layer of mostly organic species, have been actively pursued for potential applications in optoelectronics, including various functions that have been served by some popular fullerene derivatives. For the preparation of CDots, chemical functionalization of pre-processed and selected small carbon nanoparticles by organic molecules, so far mostly molecules with primary and secondary amine groups, has been an effective method. In this study, carbon nanoparticles were functionalized by N-ethylcarbazole (NEC) under microwave-assisted reaction conditions for NEC-CDots, analogous but with advantages to the CDots of surface functionalization by poly(N-vinylcarbazole) (PVK, which holds a special place in optoelectronics). NEC molecules can apparently be activated under the reaction conditions for reactive functionalities such as radicals to bind to surface carbons of the nanoparticles, consistent with the observed high stability of NEC-CDots. These dots, likely with a unique surface passivation scheme, exhibited optical properties and photoinduced redox characteristics similar to those found in other high-performance CDots. The potentially broad applicability of the new functionalization approach is discussed, so are implications of the unique surface passivation of carbon nanoparticles by the carbazole moieties. 1. Introduction Carbon dots (CDots), 1,2 generally characterized by a nanoscale structural configuration of small carbon nanoparticles with various surface passivation schemes (Figure 1), have attracted much attention, as reflected by the large and ever increasing number of publications in the literature. 3-11 Among the known characteristic properties of CDots are their bright and colorful fluorescence emissions in the visible spectrum, extending into the near-IR. A mechanistic framework for the fluorescence properties, 7,8,12 as supported by results from experimental investigations in various aspects, 12-16 is such that upon the photoexcitation of the core carbon nanoparticles in CDots (with the surface passivation layer illustrated in Figure 1 optically transparent at the excitation wavelengths), there must be rapid charge separations in the nanoparticles. The resulting electrons and holes from the charge separations must be trapped at
Carbon dots for energy conversion applications
Journal of Applied Physics
Quantum dots (QDs), generally referring to semiconductor nanocrystals that display the quantum confinement effect, have been widely pursued for many energy conversion applications. More recently, carbon dots (CDots), which are small carbon nanoparticles with various surface passivation schemes, have been found to possess optical properties and photoinduced redox characteristics resembling those of conventional semiconductor QDs and thus are amenable to some of the same uses in energy conversions. Among the various carbon nanomaterials, fullerenes have been extensively investigated for their use as critical components in optoelectronic devices and systems. Carbon nanoparticles, representing a largely ignored nanoscale carbon allotrope, are in fact more effective in some of the same functions, which are materialized and much enhanced upon the surface passivation of the nanoparticles in CDots. In this perspective article on CDots for energy conversion applications, the optical properties and redox characteristics of CDots, including the related mechanistic framework and its relationship to the use of CDots as potent photocatalysts for the conversion of CO 2 into small organic molecules, are highlighted. Also highlighted are results from representative studies using CDots in light-emitting diodes and various solar cells to demonstrate their excellent potential for a wide range of roles in optoelectronic devices and systems. Issues and opportunities in the further development of the CDots platform and related technologies are discussed.
Redox Modifications of Carbon Dots Shape Their Optoelectronics
The Journal of Physical Chemistry C, 2019
Carbon dots (CDs) are 1-10 nm scaled complex nanostructures with a wide range of applications and show unconventional photophysical behavior upon excitation. In this article, we have unveiled some of the underlying mechanisms and excited state dynamics of CDs by perturbing their interface with oxidizing and reducing agents. With no substantial alteration in size of surface treated oxidized (O CDs), reduced (R CDs) and untreated CDs (U CDs), we observe marked changes in their charge transport properties and diverse spectral signatures in singlet and triplet excited states. Fine tuning of the spectral behavior of nanomaterials is often treated as an outcome of quantum confinement of the excitons. Herein with different spectroscopic techniques along with conducting atomic force microscopy and triplet-triplet absorption, we elucidate that, not just confinement, the structural modification at the surface also dictates optoelectronic behavior by altering some properties like energy bandgap, quantum tunneling across metal-CD-metal junction and yield of triplet excitons.
Applications of Carbon Dots in Optoelectronics
Nanomaterials, 2021
Carbon dots (CDs) are an attractive class of nanomaterials due to the ease of their synthesis, biocompatibility, and superior optical properties. The electronic structure of CDs and hence their optical transitions can be controlled and tuned over a wide spectral range via the choice of precursors, adjustment of the synthetic conditions, and post-synthetic treatment. We summarize recent progress in the synthesis of CDs emitting in different colors in terms of morphology and optical properties of the resulting nanoparticles, with a focus on the synthetic approaches allowing to shift their emission to longer wavelengths. We further consider formation of CD-based composite materials, and review approaches used to prevent aggregation and self-quenching of their emission. We then provide examples of applications of CDs in optoelectronic devices, such as solar cells and light-emitting diodes (LEDs) with a focus on white LEDs.
Fluorescent carbon dots (CDs) were synthesized by following a hydrothermal route in which butane-1,4-diamine and maleic acid were employed in a Teflon autoclave reactor. The structure and morphology of the so-formed spherically shaped CDs were confirmed by a combination of spectroscopic and imaging techniques, such as NMR, ATR-IR, DLS, XRD, and HR-TEM. Additionally, it was found that raw CDs possess numerous −NH 2 functionalities located in their external periphery, responsible for their enhanced aqueous solubility as well as the excellent dissolution CDs showed in polar protic solvents. Moreover, these −NH 2 units were utilized for covalently associating CDs with oxidized multi-walled carbon nanotubes (MWCNTs) yielding robust CDs−MWCNTs hybrids. Based on photoluminescence spectroscopy, electronic communications between the individual components of CDs−MWCNTs were evidenced by the quantitative quenching of the emission of CDs in the presence of MWCNTs as well as the shortening of the photoluminescence lifetime of CDs from 7.3 ns for raw CDs to 300 ps for CDs−MWCNTs. Finally, the redox properties of CDs−MWCNTs were evaluated by electrochemistry measurements, allowing to determine the electrochemical band gap of the hybrid material to be 1.2 eV.
Carbon Dots: The Newest Member of the Carbon Nanomaterials Family
Carbon nanomaterials have been extensively researched in the past few years owing to their interesting properties. The massive research efforts resulted in the emergence of carbon dots, which belong to the carbon nanomaterials family. Carbon dots (C-dots) have garnered the attention of researchers mainly due to their convenient availability from organic as well as inorganic materials and also due to the novel properties they exhibit. C-Dots have been said to overcome the era of quantum dots, referring to their levels of toxicity and biocompatibility. In this review, we focus on the discovery of C-dots, their structure and composition, surface passivation to enhance their optical properties, the various synthetic methods used, their applications in different areas, and future perspectives. Emphasis has been given to greener approaches for the synthesis of C-dots in order to make them cost effective as well as to improve their biocompatibility.
Carbon Quantum Dots : Synthesis and Optronics Applications
ICSESD-2017
The emerging carbon quantum dots (CQDs) have gained tremendous attention for their enormous potentials for optronics, for biomedical applications and as an optical sensing probe, owing to their small size, unique and tunable photoluminescence properties, exceptional physicochemical properties, high photo stability and biocompatibility. This paper reviews simple and novel synthesis methods of preparation of carbon quantum dots and its applications in solar cell and superconductor in the field of optronics.
The Transformation of 0-D Carbon Dots into 1-, 2- and 3-D Carbon Allotropes: A Minireview
Nanomaterials
Carbon dots (CDs) represent a relatively new type of carbon allotrope with a 0-D structure and with nanoparticle sizes < 10 nm. A large number of research articles have been published on the synthesis, characteristics, mechanisms and applications of this carbon allotrope. Many of these articles have also shown that CDs can be synthesized from “bottom-up” and “top-down” methods. The “top-down” methods are dominated by the breaking down of large carbon structures such as fullerene, graphene, carbon black and carbon nanotubes into the CDs. What is less known is that CDs also have the potential to be used as carbon substrates for the synthesis of larger carbon structures such as 1-D carbon nanotubes, 2-D or 3-D graphene-based nanosheets and 3-D porous carbon frameworks. Herein, we present a review of the synthesis strategies used to convert the 0-D carbons into these higher-dimensional carbons. The methods involve the use of catalysts or thermal procedures to generate the larger stru...
A Brief Review of Applications on Carbon Quantum Dots
Eurasian Journal of Science and Technology, 2025
Carbon quantum dots are rapidly advancing as a promising approach to address challenges in renewable energy conversion and storage. Their low cost and environmental friendliness as well as versatile properties make them suitable for a range of applications, including biomedical sciences, solar cells, photocatalysis, super-capacitors, batteries, and fuel cells. As research and development in this field continue, it is expected to play a significant role in the transition to more sustainable and efficient energy systems.