Production Of Quantum Dots Research Articles

Valorization of nopal wastes to produce quantum dots: optimizing synthesis and exploring in smart textile applications

Quantum carbon dots (QCDs) were efficiently synthesized from post-extraction residues generated during nopal fabric production using a hydrothermal treatment. These QCDs were applied to nopal fabrics, enhancing their UV solar radiation absorption. The synthesized QCDs exhibited fluorescence emissions in the 200–300 nm range. An eco-friendly dispersion was created by incorporating QCDs into TiO2 for use in smart textiles, which underlines our commitment to maintaining a sustainable process. Bright and fluorescent patterns were successfully applied to commercial and nopal fabrics using a spray printing technique. Additionally, the QCDs demonstrated pH-sensitive color changes, paving the way for practical applications. This work represents an initial step towards a circular economy by utilizing residues from nopal fabric production to synthesize quantum dots, which may be employed in smart textiles applications with UV absorption capabilities.

Highly fluorescent nitrogen-doped carbon quantum dots prepared using sucrose and urea: Green synthesis, characterization, and use for determination of torsemide in its tablets and plasma samples.

A simple and facile microwave-assisted method was developed for the synthesis of highly fluorescent nitrogen-doped carbon quantum dots (N-CQDs) using sucrose and urea. The produced quantum dots exhibited a strong emission band at 376 nm after excitation at 216 nm with quantum yield of 0.57. The as-prepared N-CQDs were characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) images, and ultraviolet-visible (UV-visible) spectra. The average particle size was 7.7nm. It was found that torsemide (TRS) caused an obvious quenching of the fluorescent N-CQDs; so, they were used for its spectrofluorometric estimation. An excellent linear correlation was found between the fluorescence quenching of N-CQDs and the concentration of the drug in the range of 0.10 to 1.0μg/mL with limit of quantitation (LOQ) of 0.08 μg/mL and limit of detection (LOD) of 0.027 μg/mL. The method was successfully applied for the assay of the drug in its commercial tablets and spiked human plasma samples, and the results obtained were satisfactory. Complex GAPI was used for greenness assessment of the analytical procedures and the pre-analysis steps. Interference likely to be introduced from co-administered drugs was also studied.

Colloidal Aziridinium Lead Bromide Quantum Dots.

The compositional engineering of lead-halide perovskite nanocrystals (NCs) via the A-site cation represents a lever to fine-tune their structural and electronic properties. However, the presently available chemical space remains minimal since, thus far, only three A-site cations have been reported to favor the formation of stable lead-halide perovskite NCs, i.e., Cs+, formamidinium (FA), and methylammonium (MA). Inspired by recent reports on bulk single crystals with aziridinium (AZ) as the A-site cation, we present a facile colloidal synthesis of AZPbBr3 NCs with a narrow size distribution and size tunability down to 4 nm, producing quantum dots (QDs) in the regime of strong quantum confinement. NMR and Raman spectroscopies confirm the stabilization of the AZ cations in the locally distorted cubic structure. AZPbBr3 QDs exhibit bright photoluminescence with quantum efficiencies of up to 80%. Stabilized with cationic and zwitterionic capping ligands, single AZPbBr3 QDs exhibit stable single-photon emission, which is another essential attribute of QDs. In particular, didodecyldimethylammonium bromide and 2-octyldodecyl-phosphoethanolamine ligands afford AZPbBr3 QDs with high spectral stability at both room and cryogenic temperatures, reduced blinking with a characteristic ON fraction larger than 85%, and high single-photon purity (g(2)(0) = 0.1), all comparable to the best-reported values for MAPbBr3 and FAPbBr3 QDs of the same size.

Living Materials Based Dynamic Information Encryption via Light-Inducible Bacterial Biosynthesis of Quantum Dots.

Microbial biosynthesis, as an alternative method for producing quantum dots (QDs), has gained attention because it can be conducted under mild and environmentally friendly conditions, distinguishing it from conventional chemical and physical synthesis approaches. However, there is currently no method to selectively control this biosynthesis process in a subset of microbes within a population using external stimuli. In this study, we have attained precise and selective control over the microbial biosynthesis of QDs through the utilization of an optogenetically engineered Escherichia coli (E. coli). The recombinant E. coli is designed to express smCSE enzyme, under the regulation of eLightOn system, which can be activated by blue light. The smCSE enzymes use L-cysteine and Cd2+ as substrates to form CdS QDs. This system enables light-inducible bacterial biosynthesis of QDs in precise patterns within a hydrogel for information encryption. As the biosynthesis progresses, the optical characteristics of the QDs change, allowing living materials containing the recombinant E. coli to display time-dependent patterns that self-destruct after reading. Compared to static encryption using fluorescent QD inks, dynamic information encryption based on living materials offers enhanced security.

Living Materials Based Dynamic Information Encryption via Light‐Inducible Bacterial Biosynthesis of Quantum Dots

AbstractMicrobial biosynthesis, as an alternative method for producing quantum dots (QDs), has gained attention because it can be conducted under mild and environmentally friendly conditions, distinguishing it from conventional chemical and physical synthesis approaches. However, there is currently no method to selectively control this biosynthesis process in a subset of microbes within a population using external stimuli. In this study, we have attained precise and selective control over the microbial biosynthesis of QDs through the utilization of an optogenetically engineered Escherichia coli (E. coli). The recombinant E. coli is designed to express smCSE enzyme, under the regulation of eLightOn system, which can be activated by blue light. The smCSE enzymes use L‐cysteine and Cd2+ as substrates to form CdS QDs. This system enables light‐inducible bacterial biosynthesis of QDs in precise patterns within a hydrogel for information encryption. As the biosynthesis progresses, the optical characteristics of the QDs change, allowing living materials containing the recombinant E. coli to display time‐dependent patterns that self‐destruct after reading. Compared to static encryption using fluorescent QD inks, dynamic information encryption based on living materials offers enhanced security.

Full Factorial Design Analysis of the Facile Synthesis of Organo-Conjugated Carbon Quantum Dots from Glycerol

Recent findings on the production of quantum dots from various carbon sources shed light on their advantages such as sustainability, low toxicity and cost, and one-step synthesis over their heavy-metal counterpart. This paper focused on developing and analyzing the production of carbon quantum dots from glycerol via hydrothermal carbonization and conjugated with Tetraethylenepentamine (TEPA). A 23 full factorial experimental design was applied considering factors: the compositional ratio of TEPA (A), time of exposure (B), and temperature of reaction (C). Statistical analyses revealed experimental factors A and B; and interactions of AB and AC had statistically significant effects on the response variable, quantum yield (QY). Factor C as the main effect was not significant but was included in the statistical model to maintain hierarchy and integrity. Coded and actual statistical models were presented here.

Microbial biosynthesis of quantum dots: regulation and application

The production of quantum dots by microorganisms is regulated by both intracellular and extracellular factors. Gaining a better understanding of the regulatory mechanism will facilitate the precise modulation of their properties.

Applications of novel quantum dots derived from layered materials in cancer cell imaging

Quantum dots (QDs) is one of the very important zero dimensional nanostructure which are known as the semiconductor nanocrystals. These nanostructures are of great interest due to their unique optical properties such as high absorption amplitude, strong fluorescence and high resistance to photobleaching. Therefore, quantum dots are widely used as a fluorescence indicator in vitro and in vivo in the field of bioimaging. In addition, quantum dots are widely used in the preparation of multifunctional thranostic nanomaterials. Although organic dye and quantum dots synthesized with heavy metals has been used for cell imaging in recent years, but the production of quantum dots from two-dimensional nanostructures due to having unique properties such as more stable fluorescence, less toxicity and more eco-friendly has recently received more attention. Graphene oxide, molybdenum disulfide, and black phosphorus are the most popular two-dimensional layered nanostructures used to synthesize quantum dots. These quantum dots are used to imaging different types of cancers. Recently, they have also been used in techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) for normal cell imaging. In this review the synthesis methods as well as surface modifications of QDs derived from two dimensional nanostructures are discussed. Furthermore the newest applications of these QDs in the field of cancer cellular imaging are reviewed.

Ultralow duty cycle chopper instigated low power continuous wave laser assisted synthesis of silver nanoparticles: A novel approach

This paper is the first report of advancement in the drastic reduction of the laser power density from 105 to 7.5 W/cm2 for the synthesis of silver nanoparticles (SNPs) using a low power (60 mW) continuous-wave (cw) laser and a specially designed ultralow duty cycle (3%) optical chopper wheel for modulating the laser beam at low frequencies (2 Hz). The target is irradiated by keeping it in a liquid medium at 40–60 °C to produce quantum dots to SNPs of size less than 40 nm. The UV-visible spectroscopic and electron microscopic analyses confirm the formation of quantum dots and SNPs of size-dependent bandgap energy varying from 1.92 to 2.37 eV. The photoluminescence studies not only support the above observations but also reveal the blue emission upon UV excitation through the chromaticity diagram. The proposed greener approach using the low power cw laser is cost-effective when compared with the high-power laser-assisted synthesis of SNPs reported until now.

Lead-free all-inorganic halide perovskite quantum dots: review and outlook

Halide perovskite is attracting significant attention in optoelectronic because of its unique properties. Lead-free halide perovskites, in particular, have been studied intensively for their nontoxicity. In addition to the attention given to lead-free halide perovskites, the manufacture of these materials on a quantum scale has also received considerable attention due to the quantum confinement effect. This review discusses the current status of lead-free, all-inorganic halide perovskite quantum dots (LFAIHP QDs). First, synthetic methods for producing quantum dots are introduced; then materials are discussed with a focus on tin, bismuth, antimony, copper-based and double perovskite quantum dots. The properties of these materials-such as their physical structure, optical properties, electrical properties, and stability-are discussed. The application of these materials for solar cells, light-emitting diodes, photodetectors, photocatalysts, and memory devices are also examined. Finally, the limitations of LFAIHP QDs, possible methods to overcome them and prospects for these materials in the future are provided.

Rapid Induction and Microwave Heat-Up Syntheses of CdSe Quantum Dots.

The production of nanoparticles on an industrial scale requires an approach other than the widely used hot-injection method. In this work, two heat-up methods are applied to nanoparticle synthesis. The induction heating method produces CdSe quantum dots with ultrasmall properties in seconds. Initial flow-through experiments demonstrate that induction heating continuously produces quantum dots. These results are compared with those from microwave synthesis, which produces quantum dots on a longer timescale but provides fast, continuous heating. Both methods can produce quantum dots within seconds because of rapid heating. In addition, different precursors, single source and separate source, give different results, ultimately providing a handle to control quantum dot properties.

Precise Control of Quantum Confinement in Cesium Lead Halide Perovskite Quantum Dots via Thermodynamic Equilibrium.

Cesium lead halide (CsPbX3) nanocrystals have emerged as a new family of materials that can outperform the existing semiconductor nanocrystals due to their superb optical and charge-transport properties. However, the lack of a robust method for producing quantum dots with controlled size and high ensemble uniformity has been one of the major obstacles in exploring the useful properties of excitons in zero-dimensional nanostructures of CsPbX3. Here, we report a new synthesis approach that enables the precise control of the size based on the equilibrium rather than kinetics, producing CsPbX3 quantum dots nearly free of heterogeneous broadening in their exciton luminescence. The high level of size control and ensemble uniformity achieved here will open the door to harnessing the benefits of excitons in CsPbX3 quantum dots for photonic and energy-harvesting applications.

Phosphine-free synthesis and characterization of type-II ZnSe/CdS core-shell quantum dots

A phosphine-free route for synthesis of type-II ZnSe/CdS core-shell quantum dots, using green, low cost and environmentally friendly reagents and phosphine-free solvents such as 1-octadecene (ODE) and liquid paraffin has been reported. Hot-injection technique has been used for the synthesis of ZnSe core quantum dots. The CdS shell quantum dots prepared by reaction of CdO precursor and S powder in 1-octadecene (ODE). The ZnSe/CdS core-shell quantum dots were synthesized via successive ion layer adsorption and reaction (SILAR) technique. The characterization of produced quantum dots were performed by absorption and fluorescence spectroscopy, X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results showed the formation of type-II ZnSe/CdS core-shell quantum dots with FWHM 32 nm and uniform size distribution.

Eco-friendly intracellular biosynthesis of CdS quantum dots without changing Escherichia coli's antibiotic resistance.

In the paper, a green and efficient biosynthetical technique was reported for preparing cadmium sulfide (CdS) quantum dots, in which Escherichia coli (E. coli) was chosen as a biomatrix. Fluorescence emission spectra and fluorescent microscopic photographs revealed that as-produced CdS quantum dots had an optimum fluorescence emission peak located at 470nm and emitted a blue-green fluorescence under ultraviolet excitation. After extracted from bacterial cells and located the nanocrystals' foci in vivo, the CdS quantum dots showed a uniform size distribution by transmission electron microscope. Through the systematical investigation of the biosynthetic conditions, including culture medium replacement, input time point of cadmium source, working concentrations of raw inorganic ions, and co-cultured time spans of bacteria and metal ions in the bio-manufacture, the results revealed that CdS quantum dots with the strongest fluorescence emission were successfully prepared when E. coli cells were in stationary phase, with the replacement of culture medium and following the incubation with 1.0×10-3mol/L cadmium source for 2 days. Results of antimicrobial susceptibility testing indicated that the sensitivities to eight types of antibiotics of E. coli were barely changed before and after CdS quantum dots were prepared in the mild temperature environment, though a slight fall of antibiotic resistance could be observed, suggesting hinted the proposed technique of producing quantum dots is a promising environmentally low-risk protocol.

Photoluminescence studies of GaSbBi quantum dots grown on GaAs by liquid phase epitaxy

Liquid phase epitaxial growth from a saturated GaSb solution in Ga with 1.3 at.% Bi, on GaAs substrates is shown to produce quantum dots with a Bi content of 0.5 at.%. The height and dimensions of the QDs are investigated by field effect scanning electron microscopy and atomic force microscopy. The density of the small QDs is approximately 4.3 × 109cm−2, with dimensions in the range of 20–100 nm and height of ∼10 nm. Theoretical calculations reveal that the QDs have band alignment structure of type-II as predicted from GaSbBi bulk band structure. The 12 K photoluminescence (PL) of the QDs shows broad emission band in the range 1.25–1.37 eV. Gaussian deconvolution is used to resolve the broad peak into three individual PL emission peaks which are thoroughly explored by their dependence on temperature and excitation power.

High density quantum dots by direct laser fabrication

ABSTRACTWe report a study of direct laser fabrication that produces quantum dots with their density higher than the critical density without appearance of large clumps. Atomic force microscopy is used to image GaAs(001) surfaces that are irradiated by high power laser pulses interferentially. The analysis suggests that high density quantum dots be fabricated directly on semiconductor surfaces during epitaxial growth processes.

Highly stable and efficient solid-state solar cells based on methylammonium lead bromide (CH3NH3PbBr3) perovskite quantum dots

Highly stable and efficient solid-state solar cells have been made based on perovskite quantum dots of methylammonium lead bromide (MAPbBr3). Sawanta Mali, Chang Su Shim and Chang Kook Hong of Chonnam National University in South Korea fabricated highly crystalline MAPbBr3 quantum dots by an ex situ process using dimethyl sulphoxide as a solvent and then examined their performance in perovskite solar cells having two different hole-transporting materials. They also produced quantum dots of different sizes by varying the solution processing conditions and found that the solar-cell performance depended significantly on the quantum dot size. The team obtained a maximum conversion efficiency of 11.46% when poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was used as the hole-transporting material and MAPbBr3 quantum dots with diameters smaller than three nanometres were used. They found that the solar cells were stable over a four-month period.

One-pot synthesis of graphene oxide sheets and graphene oxide quantum dots from graphite nanofibers

A one-pot synthesis of graphene oxide (GO) sheets and GO quantum dots using graphite nanofibers (GNF) as starting material is reported. Two types of GNF starting materials, namely herringbone and platelet structures, were used. HRTEM revealed that platelet GNF produces quantum dots typically less than 10 nm in size while herringbone GNF produces relatively larger GO sheets. SAED patterns indicate that the produced GO sheets have a hexagonal crystal structure. UV–Vis, PL, XPS, and Raman show salient differences between the produced GO nanostructures which correlate well with the morphological analysis. Unlike the GO sheets, the GO quantum dots are photoluminescent. The difference in PL properties was attributed to the higher oxygen content in GO quantum dots which were shown by XPS. The results offer a new insight to the importance of starting material in the synthesis of graphene nanostructures.

Biosynthesis of luminescent CdS quantum dots using plant hairy root culture.

CdS nanoparticles have a great potential for application in chemical research, bioscience and medicine. The aim of this study was to develop an efficient and environmentally-friendly method of plant-based biosynthesis of CdS quantum dots using hairy root culture of Linaria maroccana L. By incubating Linaria root extract with inorganic cadmium sulfate and sodium sulfide we synthesized stable luminescent CdS nanocrystals with absorption peaks for UV-visible spectrometry at 362 nm, 398 nm and 464 nm, and luminescent peaks at 425, 462, 500 nm. Transmission electron microscopy of produced quantum dots revealed their spherical shape with a size predominantly from 5 to 7 nm. Electron diffraction pattern confirmed the wurtzite crystalline structure of synthesized cadmium sulfide quantum dots. These results describe the first successful attempt of quantum dots synthesis using plant extract.PACS81.07.Ta; 81.16.-c; 81.16.Rf

Coal as an abundant source of graphene quantum dots

Coal is the most abundant and readily combustible energy resource being used worldwide. However, its structural characteristic creates a perception that coal is only useful for producing energy via burning. Here we report a facile approach to synthesize tunable graphene quantum dots from various types of coal, and establish that the unique coal structure has an advantage over pure sp2-carbon allotropes for producing quantum dots. The crystalline carbon within the coal structure is easier to oxidatively displace than when pure sp2-carbon structures are used, resulting in nanometre-sized graphene quantum dots with amorphous carbon addends on the edges. The synthesized graphene quantum dots, produced in up to 20% isolated yield from coal, are soluble and fluorescent in aqueous solution, providing promise for applications in areas such as bioimaging, biomedicine, photovoltaics and optoelectronics, in addition to being inexpensive additives for structural composites.