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| Carbon quantum dot | |
|---|---|
| Name | Carbon quantum dot |
| Type | Nanomaterial |
Carbon quantum dot is a class of zero-dimensional nanomaterial characterized by carbonaceous nanoparticles with sizes below ~10 nm that exhibit size-dependent optical and electronic properties. Developed from research in University of Cambridge, Massachusetts Institute of Technology, Tsinghua University, Columbia University and industrial laboratories such as Samsung and IBM, these materials bridge concepts from graphene, fullerene and single-walled carbon nanotube research. Investigations by groups associated with Max Planck Society, Chinese Academy of Sciences, Lawrence Berkeley National Laboratory and Rensselaer Polytechnic Institute have accelerated applications spanning imaging, sensing and optoelectronics.
Carbon quantum dots emerged from parallel efforts in University of California, Berkeley, Peking University, Harvard University, Stanford University and University of Tokyo to produce fluorescent nanocarbons akin to semiconductor quantum dot systems developed at Bell Labs and studied by researchers connected to Nobel Prize in Physics laureates. Their discovery was influenced by earlier work on carbon nanotube photophysics at Rice University and Institut Pasteur collaborations. Compared with cadmium-based quantum dot systems commercialized by companies like Qdot partners, carbon quantum dots have prompted cross-disciplinary projects at institutions including ETH Zurich, University of Oxford and The Weizmann Institute of Science.
Synthesis routes derive from techniques pioneered at MIT Lincoln Laboratory and adopted by groups at Seoul National University, National University of Singapore, Indian Institute of Science and University of Sydney. Common bottom-up methods include hydrothermal and solvothermal treatments used by teams at Zhejiang University and Fudan University, microwave-assisted protocols developed at Oak Ridge National Laboratory and Argonne National Laboratory, and combustion/arc-discharge approaches traced to Los Alamos National Laboratory. Top-down methods such as laser ablation explored at Lawrence Livermore National Laboratory and chemical oxidation refined at University of Cambridge produce precursor-dependent populations. Precursors range from citric acid studied at University of California, Los Angeles and Monash University to biomass feedstocks examined by researchers at University of São Paulo and University of Kerala, and polymeric precursors used in work at Imperial College London. Scale-up efforts involve partnerships with industrial research centers like Dow Chemical and BASF.
Structural models combine concepts from graphene oxide sheets characterized at Brookhaven National Laboratory and nanocrystalline domains observed in studies at National Institute of Standards and Technology. The core–shell depiction adopted by teams at Riken and Korea Institute of Science and Technology integrates sp2/sp3 hybridized carbon, residual fullerene-like cages and surface functional groups. Optical properties such as excitation-dependent emission were elucidated in spectroscopic investigations at Max Planck Institute for Polymer Research and correlated with size distributions measured at Centre National de la Recherche Scientifique. Absorption features resembling π–π* transitions were reported in collaborative studies involving University of California, Santa Barbara and University of Illinois Urbana-Champaign, while two-photon fluorescence performance has been optimized in projects with Fudan University and University of British Columbia.
Surface chemistry strategies trace back to methodologies from Dow Chemical research and academic work at University of Chicago, Delft University of Technology and University of Alberta. Functionalization with amines, carboxylates and polyethylene glycol was developed in labs at Johns Hopkins University and Karolinska Institutet to improve colloidal stability and targeting. Heteroatom doping—nitrogen, sulfur, phosphorus—was advanced in studies at University of Pennsylvania, University of Michigan and Nanyang Technological University to tune electronic structure. Conjugation to biomolecules used techniques from Salk Institute and Institut Curie for applications requiring specific interactions with receptors investigated at Mayo Clinic and Cleveland Clinic.
Applications span diagnostics and therapeutics pursued at National Institutes of Health, Centers for Disease Control and Prevention collaborations, and industrial implementations evaluated by Siemens and Philips. In bioimaging, carbon quantum dots have been employed in preclinical studies at Johns Hopkins Hospital and Massachusetts General Hospital for fluorescent labeling. Sensors leveraging fluorescence quenching/enhancement were developed in partnerships with Honeywell and research groups at University of Waterloo and University of Göttingen to detect metal ions and organic pollutants. Optoelectronic devices, including light-emitting diodes and solar cells, were prototyped by teams at Samsung Electronics and Sony alongside academic groups at University of Cambridge and École Polytechnique Fédérale de Lausanne. Environmental remediation and catalysis applications were investigated at Argonne National Laboratory and Lawrence Berkeley National Laboratory, while drug delivery and photothermal therapy studies occurred at Memorial Sloan Kettering Cancer Center and Dana-Farber Cancer Institute.
Multiple emission mechanisms were proposed in theoretical and experimental work spanning University of Oxford, University of Chicago, California Institute of Technology and Princeton University. Models include quantum confinement of sp2 domains inspired by Kavli Institute for Theoretical Physics discussions, surface state emission correlated in experiments at University of California, Irvine and radiative recombination at defect centers studied at National Institute for Materials Science. Time-resolved spectroscopy performed at Lawrence Berkeley National Laboratory and Brookhaven National Laboratory distinguished between core-related and surface-related lifetimes. Computational studies employing methods from Argonne National Laboratory and Oak Ridge National Laboratory complemented experimental assignments of emissive traps identified by groups at University of Texas at Austin.
Toxicological evaluations were conducted in collaborations involving World Health Organization frameworks and regulatory science groups at European Medicines Agency and U.S. Food and Drug Administration centers. In vitro cytotoxicity assays were carried out in laboratories at University of Toronto and University of Melbourne, while in vivo biodistribution and clearance studies were performed at Scripps Research and Yale University. Biocompatibility outcomes depended on surface chemistry and synthesis residues, with safety assessments informed by testing protocols from National Toxicology Program and Organisation for Economic Co-operation and Development. Clinical translation efforts liaise with hospitals such as Brigham and Women's Hospital and research consortia including Coalition for Epidemic Preparedness Innovations to establish standardized evaluation pipelines.