Inorganic Quantum Dots Research Articles

Carbon Dot-Mediated Capillary Electrophoresis Separations of Metallated and Demetallated Forms of Transferrin Protein.

Carbon dots (CDs) are fluorescent nanomaterials used extensively in bioimaging, biosensing and biomedicine. This is due in large part to their biocompatibility, photostability, lower toxicity, and lower cost, compared to inorganic quantum dots or organic dyes. However, little is known about the utility of CDs as separation adjuvants in capillary electrophoresis (CE) separations. CDs were synthesized in-house according to a ‘bottom-up’ method from citric acid or other simple carbon precursors. To demonstrate the applicability of CDs as separation adjuvants, mixtures of holo- (metallated) and apo- (demetallated) forms of transferrin (Tf, an iron transport protein) were analyzed. In the absence of CDs, the proteins were not resolved by a simple CE method; however, upon addition of CDs to the separation buffer, multiple forms of Tf were resolved indicating that CDs are valuable tools to facilitate the separation of analytes by CE. CE parameters including sample preparation, buffer identity, ionic strength, pH, capillary inside diameter, and temperature were optimized. The results suggest that dots synthesized from citric acid provide the best resolution of various different forms of Tf and that CDs are versatile and promising tools to improve current electrophoretic separation methods, especially for metalloprotein analysis.

Inorganic Quantum Dot Materials and their Applications in “Organic” Hybrid Solar Cells

AbstractSemiconductor quantum dots (QDs) are promising materials for polymer‐nanocrystal hybrid solar cells (HSCs). The aim of this review article is to present a comprehensive and current overview of inorganic QDs and their applications in HSCs. Fundamental properties of QDs are first illustrated. And then recent studies that have been done to elucidate charge dynamics of QDs and improve hybrid device performance are summarised and discussed in detail. Finally, an outlook is presented considering current existing challenges in HSCs.

Gold Nanoparticle-Induced Photocurrent Quenching and Recovery of Polymer Dots: Toward Signal-On Energy-Transfer-Based Photocathodic Bioanalysis of Telomerase Activity in Cell Extracts.

Energy transfer (ET) in photoelectrochemical (PEC) bioanalysis is usually generated between noble metal nanoparticles (NPs) and traditional inorganic quantum dots (QDs). Using the innovative polymer dot (Pdot)-involved ET, this work reports the first signal-on and cathodic PEC bioanalysis toward telomerase (TE) activity in cell extracts. Specifically, the sequential binding of capture DNA (cDNA), telomerase primer sequence (TS), and Au NP-labeled probe DNA (Au NP-pDNA) on the electrode would place the Au NPs in close proximity of the Pdots, leading to obvious quenching of the cathodic photocurrent. The subsequent extension of the TS by TE in the presence of deoxyribonucleoside triphosphates (dNTPs) would then release the Ag NP-pDNA from the electrode, leading to the recovery of the photocurrent. On the basis of the Au NP-induced photocurrent quenching and the recovery of Pdots, a sensitive biosensor could thus be developed by tracking the photocurrents to probe the TE activity. This strategy allows for signal-on and cathodic PEC bioanalysis of TE, which can be easily extended for numerous other targets of interest. We believe this work could offer a new perspective for the rational implementation of Pdot-involved ET for advanced PEC bioanalysis.

Simultaneous formation of ultra-thin MoSe2 nanosheets, Inorganic Fullerene-Like MoSe2 and MoO3 quantum dots using fast and ecofriendly Pulsed Laser Ablation in Liquid followed by microwave treatment

This research reports a rapid and scalable synthesis of MoSe2 Nanosheets (NSs), Inorganic Fullerene-Like (IF) MoSe2 and MoO3 quantum dots (QDs) with varying morphologies and crystal structures using Pulsed Laser Ablation in Liquid (PLAL) technique followed by microwave treatment of Bulk-MoSe2 powders. We show that using water as a solvent result in the formation of MoO3 QDs, single and few layered MoSe2 NSs and IF-MoSe2 structures from both Laser Modified (LM) and Laser Microwave Modified (LMM) MoSe2 samples. The presence of the predominant A1g mode in the Raman spectra of LM-MoSe2 and LMM-MoSe2 samples further showed the formation of single layer MoSe2 NS. Moreover, formation of small-sized MoSe2 heterolayers with an expanded interlayer spacing along the (002) planes for LMM samples which were subjected to microwave treatment for 30 min was demonstrated. Comparatively, for the samples subjected to microwave treatment for 60 min, most of the crystal orientations were vertical. The current study showed the controllable crystal orientation in MoSe2 samples by combined PLAL and microwave treatment. The two successive microwave steps led to change in the MoSe2 crystal orientation from horizontal to vertical. Selective oxygen incorporation induced by both PLAL and microwave treatment was also shown along the (100) and (002) planes for LM-MoSe2 and LMM-MoSe2, respectively. Understanding the selective oxygen incorporation in MoSe2 planes can shed light on the precise control of oxygenation in the crystal structures of 2D nanomaterials, synthesized heterostructures and nanocomposites.

Highly Oxidized Graphene Quantum Dots from Coal as Efficient Antioxidants.

Graphene quantum dots (GQDs) have recently been employed in various fields including medicine as antioxidants, primarily because of favorable biocompatibility in comparison to common inorganic quantum dots, although the structural features that lead to the biological activities of GQDs are poorly understood. Here, we report that coal-derived GQDs and their poly(ethylene glycol)-functionalized derivatives serve as efficient antioxidants, and we evaluate their electrochemical, chemical, and in vitro biological activities.

Hybrid Heterostructured LEDs Based on Superstrate Architecture of ZnO and ZnS Quantum Dots

Hybrid white light-emitting devices consisting of inorganic semiconducting quantum dots of ZnO and ZnS and conducting polymers in a superstrate configuration are reported. Low-temperature wet chemical route was followed to synthesize quantum dots. Spin coating technique was used for the fabrication of devices where multilayers of self-organized nanoparticles were vertically aligned on conducting polymers and a transparent indium titanium oxide substrate. Optical, electroluminescence, and IV characterization of the devices revealed that they exhibit broad emission spectra covering the entire visible range at low turn-on voltage. Moreover, these Cd free devices present cheaper, cleaner, and greener solutions for futuristic display and lighting applications.

Enhanced UV‐C Detection of Perovskite Photodetector Arrays via Inorganic CsPbBr3 Quantum Dot Down‐Conversion Layer

AbstractOrganometal halide perovskites have been considered as promising candidates for high‐performance low‐cost photodetectors. Nonetheless, as perovskite photodetectors are usually built on glass or polymer substrates, their UV‐C (200–280 nm) photodetection ability is quite limited due to the high absorption of glass or polymer substrates. Here, a uniform UV photodetector array which integrates perovskite photodiodes with inorganic CsPbBr3 quantum dot (QD) fluorophor is reported. CsPbBr3 quantum dot fluorophor not only acts as an efficient down‐conversion layer to convert UV light into 510 nm light, but also functions as a protective layer to prevent degradation of hybrid organic–inorganic perovskite by UV light. Compared to direct UV‐C (279 nm) detection with perovskite photodiode, the QD integrated photodetector shows a higher responsibility and detectivity to UV‐C, with values enhanced by 1 order in magnitude. This work provides a low‐cost and effective approach for all perovskite‐based UV‐C photodetectors and imagers.

Facile Room‐Temperature Anion Exchange Reactions of Inorganic Perovskite Quantum Dots Enabled by a Modular Microfluidic Platform

AbstractIn an effort to produce the materials of next‐generation photoelectronic devices, postsynthesis halide exchange reactions of perovskite quantum dots are explored to achieve enhanced bandgap tunability. However, comprehensive understanding of the multifaceted halide exchange reactions is inhibited by their vast relevant parameter space and complex reaction network. In this work, a facile room‐temperature strategy is presented for rapid halide exchange of inorganic perovskite quantum dots. A comprehensive understanding of the halide exchange reactions is provided by isolating reaction kinetics from precursor mixing rates utilizing a modular microfluidic platform, Quantum Dot Exchanger (QDExer). The effects of ligand composition and halide salt source on the rate and extent of the halide exchange reactions are illustrated. This fluidic platform offers a unique time‐ and material‐efficient approach for studies of solution phase‐processed colloidal nanocrystals beyond those studied here and may accelerate the discovery and optimization of next‐generation materials for energy technologies.

Insight into the Excitation-Dependent Fluorescence of Carbon Dots.

High quantum yield, photoluminescence tunability, and sensitivity to the environment are a few distinct trademarks that make carbon nanodots (CDs) interesting for fundamental research, with potential to replace the prevalent inorganic semiconductor quantum dots. Currently, application and fundamental understanding of CDs are constrained because it is difficult to make a quantitative comparison among different types of CDs simply because their photoluminescence properties are directly linked to their size distribution, the surface functionalization, the carbon core structures (graphitic or amorphous) and the number of defects. Herein, we report a facile one-step synthesis of mono-dispersed and highly fluorescent nanometre size CDs from a 'family' of glucose-based sugars. These CDs are stable in aqueous solutions with photoluminescence in the visible range. Our results show several common features in the family of CDs synthesized in that the fluorescence, in the visible region, is due to a weak absorption in the 300-400 nm from a heterogeneous population of fluorophores. Fluorescence quenching experiments suggest the existence of not only surface-exposed fluorophores but more importantly solvent inaccessible fluorophores present within the core of CDs. Interestingly, time-resolved fluorescence anisotropy experiments directly suggest that a fast exchange of excitation energy occurs that results in a homo-FRET based depolarization within 150 ps of excitation.

Spectral behavior of plasmon enhanced fluorescence in organic–inorganic perovskite quantum dot solutions

In this work, the fluorescence emission of hybrid lead bromide perovskite quantum dots is enhanced with the assistance of surface plasmon resonance of gold nanoparticles. Due to the high sensitivity of these quantum dots to an aqueous environment, a water-free synthesis method is chosen for the synthesis of gold nanoparticles. Spherical gold nanoparticles, with a diameter of 13 nm and a surface plasmon resonance peak at 527 nm, are synthesized using oleylamine. CH3NH3PbBr3 perovskite quantum dots, with two different sizes, are also synthesized that show fluorescence emission peaks at 507 and 534 nm. Different concentrations of gold nanoparticles are added to the quantum dots solutions. For quantum dots with a fluorescence peak at a higher energy than localized surface plasmon resonance (LSPR) energy, quenching of fluorescence is observed. However, for quantum dots with a fluorescence peak slightly red-shifted, compared to LSPR, the fluorescence is enhanced by the factor of 2. This fluorescence enhancement is resulted by adding nanoparticles with concentration of 140 μl. By further addition of nanoparticles, quenching of the emission is observed due to the reduction of the distances between the nanoparticles and the perovskite quantum dots.

Spectrally Matched Quantum Dot Photoluminescence in GaAs-Si Tandem Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) can capture both direct and diffuse irradiance via isotropic absorption of waveguide-embedded luminophores. Additionally, LSCs have the potential to reduce the overall cost of a photovoltaic (PV) module by concentrating incident irradiance onto an array of smaller cells. Historically, LSC efficiencies have suffered in part from incomplete light absorption and non-unity quantum yield (QY) of the luminophores. Inorganic quantum dot (QD) luminophores allow the spectral tuning of the absorption and photoluminescence bands, and have near-unity QYs. In a four-terminal tandem LSC module scheme, visible light is trapped within the LSC waveguide and is converted by GaAs cells, and near infrared light is optically coupled to a Si subcell. Here, we investigate the efficiency of a GaAs/Si tandem LSC as a function of luminophore absorption edge and emission wavelength for QD luminophores dispersed in an LSC waveguide with embedded, coplanar GaAs cells. We find that positioning the luminophore absorption edge at 660 nm yields a maximum module power efficiency of approximately 26%, compared with 21% for the non-optimized luminophore and 19% for the bare Si cases.

Luminescent perovskite nanocrystal-epoxy resin composite with high stability against water and air

The preparation of perovskite-polymer composites is one of the most effective ways to improve the stability and expand the application of inorganic perovskite quantum dots (QDs). The current study adopts a convenient and rapid ultraviolet polymerization method to prepare perovskites-polymer (CsPbX3, X = mixed Cl/Br, Br, mixed Br/I, and I) composites using inexpensive commercial epoxy resin (EP). The photoluminescence (PL) spectrum and photoluminescence quantum yield (PLQY) show that the composites can well retain the luminescent colors of the original solutions. The emission spectra of these composites can be tuned in the range of 420 nm-680 nm, which are almost consistent with the emission spectrum of perovskites QDs. Moreover, perovskite-EP composites demonstrate excellent stability in air and water without changing the PLQY for more than 30 days in air and maintaining the PL intensity above 85% for 10 days in water. These new perovskite-EP composites exhibit tensile and flexural properties due to the incorporation of flexible epoxy resin, which can be well applied to the fields of flexible luminescent devices and optical functional materials.

Light-Stimulated Synaptic Transistors Fabricated by a Facile Solution Process Based on Inorganic Perovskite Quantum Dots and Organic Semiconductors.

Implementation of artificial intelligent systems with light-stimulated synaptic emulators may enhance computational speed by providing devices with high bandwidth, low power computation requirements, and low crosstalk. One of the key challenges is to develop light-stimulated devices that can response to light signals in a neuron-/synapse-like fashion. A simple and effective solution process to fabricate light-stimulated synaptic transistors (LSSTs) based on inorganic halide perovskite quantum dots (IHP QDs) and organic semiconductors (OSCs) is reported. Blending IHP QDs and OSCs not only improves the charge separation efficiency of the photoexcited charges, but also induces delayed decay of the photocurrent in the IHP QDs/OSCs hybrid film. The enhanced charge separation efficiency results in high photoresponsivity, while the induced delayed decay of the photocurrent is critical to achieving light-stimulating devices with a memory effect, which are important for achieving high synaptic performance. The LSSTs can respond to light signals in a highly neuron-/synapse-like fashion. Both short-term and long-term synaptic behaviors have been realized, which may lay the foundation for the future implementation of artificial intelligent systems that are enabled by light signals. More significantly, LSSTs are fabricated by a facile solution process which can be easily applied to large-scale samples.

Fluorescent Nano-Assembly of Organic Conjugate Molecules with Benzoxazole Moiety and Its Application in Sensor.

Fluorescence labeling or sensing is a very useful analytical technique for investigating the structure of living cells or for detecting ionic metals. Numerous materials including inorganic quantum dots and organic fluorescent dyes have been used and investigated for further development so far. However, they are inherited natural discrepancies of cyto-toxicity or easy degradation. Thus, developing highly emissive, biocompatible, and chemically readily modifiable luminescent materials is strongly desired. Here, we report the enhanced photoluminescence of an oxazole derivative for possible use in the field of fluorescent sensor.

Organic-inorganic nanoparticles molecularly imprinted photoelectrochemical sensor for α-solanine based on p-type polymer dots and n-CdS heterojunction

In this study, a molecularly imprinted polymer photoelectrochemcal (MIP-PEC) sensor based on semiconducting organic polymer dots (Pdots) and inorganic CdS quantum dots (QDs) has been established for the determination of α-Solanine. Specifically, p-type Pdots (p-Pdots) and n-type CdS QDs (n-CdS) were utilized to form organic-inorganic nanoparticles p-n heterojunction to enhance signal response, and their specific energy levels (VB/CB or HOMO/LUMO) were calculated for photoelectrochemical (PEC) bioanalysis application. At the same time, the combination of molecular imprinting technology and photoelectrochemistry overcomes the defeats of photoelectrochemistry which is the absence of selectivity, offers a new MIP-PEC sensor with high sensitivity and excellent selectivity based heterojunction enhanced strategy. In short, this study proposes the semiconducting organic-inorganic nanoparticles p-n heterojunction for molecularly imprinted polymer photoelectrochemcal bioanalysis application, and the MIP-PEC sensor was successfully fabricated based on these materials and methods. In the phosphate buffer solution (PBS), it was clearly observed that the photocurrent has a significant change between elution in acetic acid-ethanol mixture and incubation in template molecular solution because of the faster electron transfer speed, this phenomenon fully showed that the MIP-PEC sensor can specifically detect the target. Thus, the work typically offers a linear range from 0.01 to 1000 ng mL−1 with a detection limit of 6.5 pg mL−1 for α-Solanine. Furthermore, the fabricated MIP-PEC sensor will confirm the actual application.

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications.

A method for synthesizing photoactive inorganicperovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are demonstrated. The ink synthesis is based on a simple wet chemical reaction and the inkjet printing protocol is a facile step by step method. The inkjet printed thin films have been characterized by X-ray diffraction, optical absorption spectroscopy, photoluminescent spectroscopy, and electronic transport measurements. X-ray diffraction of the printed quantum dot films indicates a crystal structure consistent with an orthorhombic room temperature phase with (001) orientation. In conjunction with other characterization methods, the X-ray diffractionmeasurements show high quality films can be obtained through the inkjet printing method.

无机钙钛矿量子点改善ZnO基紫外探测器光响应时间的研究

无机钙钛矿量子点改善ZnO基紫外探测器光响应时间的研究

Improvement of Optical and Thermal Properties for Quantum Dots WLEDs by Controlling Layer Location

The inorganic halide perovskite quantum dots (QDs) have been considered as a promising substitute for white light-emitting diodes (WLEDs). In this paper, the green CsPbBr 3 QDs and red K 2 SiF 6 :Mn 4+ (KSF) phosphor were used to fabricate the conversion layers. Because the location of the layers is fundamental to the absorption priority of blue light, the location of KSF and QDs were controlled and the QDs-up type and QDs-down type WLEDs were made. The optical power, luminous efficiency, CCE, and luminous intensity in the middle of QDs-up type are 13.83 mW, 13.54 lm/W, 11.94%, and 2.65 cd, meaning 24.26%, 25.72%, 2.63%, and 23.83% higher than those of QDs-down type, respectively. In addition, the QDs-up type has a lower correlated color temperature (CCT) shift of 734 K and a decreased highest temperature of 56.8° (51.5% and 14.9% lower). These key property differences indicate that the QDs-up type is more suitable for the application in display and backlight. In order to explore the reasons for these differences, the emission spectra, CCE, reflection rate, absorption rate, and temperature curves of QDs or KSF films were also analyzed, which provided a better understanding of designing package structures.

合成及薄膜制备条件对CsPbBr3全无机钙钛矿量子点特性的影响

合成及薄膜制备条件对CsPbBr₃全无机钙钛矿量子点特性的影响

Water-stable and ion exchange-free inorganic perovskite quantum dots encapsulated in solid paraffin and their application in light emitting diodes.

Perovskite quantum dots (PQDs) with high quantum efficiency and broad spectral tunability are promising luminescent materials and show potential applications in light-emitting diodes (LEDs). However, PQDs degrade rapidly in atmosphere moisture due to their easy hydrolysis and undergo undesirable spectral changes associated with ion exchanges. Herein, we encapsulated blue, green and red fluorescence-emitting all-inorganic PQDs respectively with hydrophobic solid paraffin to obtain multi-color luminescent paraffin-PQD composites (P-PQDs). The P-PQD composites not only preserve the bright luminescence, but also greatly improve the water resistance of PQDs. Moreover, the anion exchange phenomenon is effectively inhibited for the isolation of PQD nanoparticles by a solid paraffin layer. Finally, blue, green and red luminescent P-PQD microparticles have been synthesized and show promising applications in LEDs.