Study of electronic and optical properties of quantum dots

Rani, Priya; Dalal, Ranjeet; Srivastava, Sunita

doi:10.1007/s13204-022-02485-8

Cited by 5 publications

(3 citation statements)

References 40 publications

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“…The quantum confinement effects of QDs come into play when their sizes get comparable to their Bohr excitonic radius, and their properties become size-dependent. Semiconductor QDs have been studied extensively for their optical properties [1][2][3], which leads to their fruitful usage in solar cells, lasers, bioimaging, and bio-sensing. The usage of semiconductor QDS has highlighted concerns regarding their environmental contamination and renewability [4,5] due to the heavy metals used in their manufacturing and their toxicity.…”

Section: Introductionmentioning

confidence: 99%

Enhanced NIR fluorescence quantum yield of graphene quantum dots using dopants

2023

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In the present work, several efforts have been made theoretically to achieve an excellent non-toxic fluorescent graphene quantum dot (GQD) in the near-infrared region for the application of bio-imaging and sensing. Although the QY of GQDs is a maximum of 98.5% in the visible region, it is still very low, and it is as low as 7% in NIR. Sulfur and its group elements have been used for doping because they are pretty cheap and nontoxic and hence suitable for this application. The surface-doped position is considered for studying their effect on the energy band gap, absorption and fluorescence properties. The HOMO and LUMO isosurfaces have been analyzed in order to comprehend the nature of the dominant transition taking place in absorption spectra. Additionally, the quantitative indices, transition density matrix contour maps, and charge difference density have all been examined in order to determine whether this particular transition is locally excited or involves charge transfer. Following this, the QY of each GQD has been determined by considering the fluorescence spectra. The wavelength of fluorescence of doped GQDs is found to be in the region of 800-1400 nm, i.e. in NIR, which is strongly desirable for bio-imaging and bio-sensing applications. With a fluorescence of ~ 850 nm, sulfur-doped GQDs (S-GQD: C52S2H18) have the greatest QY, 26%, which is larger than the 7% achieved earlier in NIR and such a high QY in NIR is being reported for the first time.

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Section: Introductionmentioning

confidence: 99%

Enhanced NIR fluorescence quantum yield of graphene quantum dots using dopants

2023

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“…This is because biological organisms have a background of scattered light in a short-wavelength region, therefore, don't provide good image contrast. There are many strategies to tune the band gap of quantum dots, which includes the change in size, and shape [13,14], the introduction of heteroatoms [15,16], modifying their surfaces [17,18], etc.…”

Section: Introductionmentioning

confidence: 99%

Systematic Engineering of Properties of Graphene Quantum Dots by Aryl Amines

Rani,

Srivast

2023

Preprint

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Graphene quantum dots (GQDs) are becoming an efficient nanomaterial to control their optoelectronic properties by molecular engineering due to the advantages of tunability by size, shape, doping, and comparatively low degree of toxicity and a great extent of spatial confinement. Their bandgap can be tuned effectively by functionalization of their surface or edges with some specific groups. In the present study, systematic efforts have been made to tune the band gap and corresponding optical properties of the GQDs by functionalizing them with different aryl amine groups because of their potential for extremely strong and wide-ranging light absorption; these GQDs have also been demonstrated to be advantageous for photocatalysis. The absorption and fluorescence spectra have been investigated by employing density functional theory with Becke three parameters hybrid functional with Lee-Yang-Perdew (B3LYP) correlation functional as implemented in Gaussian 09 package. Functionalization with such aryl amine groups accounts for the decrement in band gap and shift of absorption spectra towards longer wavelength. Such narrow band gap GQDs are highly required for the applications such as photocatalysis and bio-imaging etc. The outcomes achieved in this way are highly consistent with other experimental findings.

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“…13 Recently, the GQD has fascinated the research community worldwide due to its remarkable characteristics such as quantum confinement, 14 quantum tunneling, and surface effects. 15,16 GQDs with high fluorescence, in particular, are expected to emerge as next-generation nanoparticles and a potential replacement for hazardous and expensive luminous semiconductor QDs. 17,18 GQDs are gaining popularity because of their resistance to chemicals and high biocompatibility, making them a potential solution for bioimaging, 19,20 energy storage devices, 21 optoelectronic applications, 22,23 photocatalysis, light-emitting diodes, 24,25 and biosensors.…”

Section: Introductionmentioning

confidence: 99%