Sulfide Quantum Dots Research Articles

Boron functionalized and phosphorous doped molybdenum di-sulfide quantum dots for the photoluminescence based detection of HbA1c

Highly fluorescent transition metal dichalcogenides (TMDs) based quantum dots (QDs) have been the focus of immense research owing to their bio-compatibility, non-toxicity, easy chemical synthesis and broad spectrum of applications which includes biosensing, optoelectronics, energy storage devices, etc. Herein, we present a one-step hydrothermal growth of in-situ blue fluorescent phosphorous doped-molybdenum di sulfide QDs (P-MoS2 QDs) in aqueous media. A range of functional groups over the surface of chemically synthesized P-MoS2 QDs helps in conserving its fluorescence along with high aqueous stability and solubility. Besides, remarkable photoluminescence (PL) properties of P-MoS2 QDs were then explored to concoct an optical sensor with excellent selectivity and sensitivity for glycated hemoglobin (HbA1c) followed by functionalization with boronic acid. The response of the sensor was found to be linear in the range of 2–15 %, which is under the typical physiological aliquot range (0.75–22.93 mM with limit of detection to be 77.5 μM, under optimized conditions. Moreover, PL quenching processes and TRPL data of P-MoS2 QDs were explored to elucidate the plausible quenching mechanism which suggests mixed kind of quenching processes. In conclusion, we envisaged that the present methodology can provide an effective and potent tool for HbA1c sensing in real biological (hemolysate/whole blood-lysate) samples.

Microbial Fabrication of Quantum Dots: Mechanism and Applications.

More recently, the application of semiconductor nanomaterials called quantum dots (QDs), has gained considerable attention as they possess tunable optoelectronic and physicochemical properties. There are several routes of QDs synthesis some of which include lithography, molecular beam epitaxy, and chemical reduction. However, most of these methods are expensive, labour intensive, and produce toxic by-products. Hence, the biosynthesis of QDs has been extensively researched for addressing the issues. This review elaborates on the biogenic synthesis of cadmium selenide, cadmium telluride, cadmium sulfide, lead sulfide, and zinc sulfide QDs using bacteria, and fungi. Further, we attempt to identify the underlying mechanism and critical parameters that can control the synthesis of QDs. Eventually, their application in detectors, photovoltaics, biodiesel, photocatalysis, infection-control, and bioimaging are discussed. Thus, biogenic QDs have a tremendous scope in future to emerge as next generation nanotheranostics although thorough pharmacokinetic, and pharmacodynamic studies are required.

Ultrabright NIR-IIb Fluorescence Quantum Dots for Targeted Imaging-Guided Surgery.

Pioneering approaches for precise tumor removal involve fluorescence-guided surgery, while challenges persist, including the low fluorescence contrast observed at tumor boundaries and the potential for excessive damage to normal tissue at the edges. Lead/cadmium sulfide quantum dots (PbS@CdS QDs), boasting high quantum yields (QYs) and vivid fluorescence, have facilitated advancements in the second near-infrared window (NIR-II, 900-1700 nm). However, during fluorescent surgical navigation operations, hydrophilic coatings of these inorganic nanoparticles (NPs) guarantee biosafety; it also comes at the expense of losing a significant portion of QY and NIR-II fluorescence, causing heightened damage to normal tissues caused by cutting edges. Herein, we present hydrophilic core-shell PbS@CdS@PEG NPs with an exceptionally small diameter (∼8 nm) and a brilliant NIR-IIb (1500-1700 nm) emission at approximately 1600 nm. The mPEG-SH (MW: 2000) addresses the hydrophobicity and enhances the biosafety of PbS@CdS QDs. In vivo fluorescence-guided cervical tumor resection becomes achievable immediately upon injection of an aqueous solution of PbS@CdS@PEG NPs. Notably, this approach results in a significantly reduced thickness (100-500 μm) of damage to normal tissues at the margins of the resected tumors. With a high QY (∼30.2%) and robust resistance to photobleaching, NIR-IIb imaging is sustained throughout the imaging process.

Maximization of cytochrome C oxidase enzyme activity by optimizing color conversion from red organic light-emitting diodes

Photobiomodulation (PBM) therapy using red and near-infrared (NIR) light can effectively activate cytochrome C oxidase (CCO) enzyme to promote wound healing in living organisms. To maximize this therapeutic effect, the use of a light source with a spectrum absorbed by the CCO enzyme is necessary. A red/NIR light source optimized for CCO enzyme was obtained by partially color-converting a red organic light-emitting diode with copper indium sulfide/zinc sulfide quantum dots (QDs). To increase color conversion efficiency, the dispersion of QDs was improved by using a fibrous color conversion layer (FCCL). By optimizing the QD content in the FCCL, a red/NIR light source similar to the absorption spectrum of CCO enzyme was obtained with a spectral matching ratio of 81.7 %. When this light source was used in PBM therapy, it was experimentally verified that it showed a much faster wound closure effect compared to general red light, and it was proven that this was due to increased activity of the CCO enzyme. This study is a method of obtaining a red/NIR light source for PBM suitable for a specific enzyme performing a specific function, and is particularly useful due to its excellent form factor of being large, thin, and flexible.

High Volumetric Energy Density Supercapacitor of Additive-Free Quantum Dot Hierarchical Nanopore Structure.

The high surface-area-to-volume ratio of colloidal quantum dots (QDs) positions them as promising materials for high-performance supercapacitor electrodes. However, the challenge lies in achieving a highly accessible surface area, while maintaining good electrical conductivity. An efficient supercapacitor demands a dense yet highly porous structure that facilitates efficient ion-surface interactions and supports fast charge mobility. Here we demonstrate the successful development of additive-free ultrahigh energy density electric double-layer capacitors based on quantum dot hierarchical nanopore (QDHN) structures. Lead sulfide QDs are assembled into QDHN structures that strike a balance between electrical conductivity and efficient ion diffusion by employing meticulous control over inter-QD distances without any additives. Using ionic liquid as the electrolyte, the high-voltage ultrathin-film microsupercapacitors achieve a remarkable combination of volumetric energy density (95.6 mWh cm-3) and power density (13.5 W cm-3). This achievement is attributed to the intrinsic capability of QDHN structures to accumulate charge carriers efficiently. These findings introduce innovative concepts for leveraging colloidal nanomaterials in the advancement of high-performance energy storage devices.

Metal organic framework-derived CuO/Cu2O polyhedron-CdS quantum dots double Z-scheme heterostructure for cathodic photoelectrochemical detection of Hg2+ in food and environment

This study employed an innovative copper oxide/cuprous oxide (CuO/Cu2O) polyhedron‑cadmium sulphide quantum dots (CdS QDs) double Z-scheme heterostructure as a matrix for the cathodic PEC determination of mercury ions (Hg2+). First, the CuO/Cu2O polyhedral composite was prepared by calcining a copper-based metal organic framework (Cu-MOF). Subsequently, the amino-modified CuO/Cu2O was integrated with mercaptopropionic acid (MPA)-capped CdS QDs to form a CuO/Cu2O polyhedron-CdS QDs double Z-scheme heterostructure, producing a strong cathodic photocurrent. Importantly, this heterostructure exhibited a specifically reduced photocurrent for Hg2+ when using CdS QDs as Hg2+-recognition probe. This was attributed to the extreme destruction of the double Z-scheme heterostructure and the in situ formation of the CuO/Cu2O-CdS/HgS heterostructure. Besides, p-type HgS competed with the matrix for electron acceptors, further decreasing the photocurrent. Consequently, Hg2+ was sensitively assayed, with a low detection limit (0.11 pM). The as-prepared PEC sensor was also used to analyse Hg2+ in food and the environment.

Determination of Melamine by Label-Free Ratiometric Fluorescence Using the Inner-Filter Effect (IFE) between Cadmium Tellurium/Cadmium Sulfide Quantum Dots (QDs) and Gold Nanoparticles (Au NPs)

A simple and sensitive ratiometric fluorescent assay has been developed for the determination of melamine based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and fluorescent quantum dots (QDs). In the IFE-based fluorescent assay, a complementary overlap was established between the absorption spectrum of AuNPs and emission spectrum of cadmium tellurium/cadmium sulfide quantum dots (CdTe/CdS QDs). Consequently, AuNPs in the dispersion state quench the emission of green CdTe/CdS QDs at 520 nm (QDs520), while the aggregated AuNPs quench emission of red CdTe/CdS QDs at 680 nm (QDs680). Along with the addition of melamine, the fluorescence of the QDs at 680 nm was quenched while the fluorescence of at 520 nm was recovered by the aggregation of AuNPs so the ratiometric fluorescent detection of melamine was complete. The system determined melamine from 30 to 1030 nM and was employed to determine melamine in milk products with satisfactory recoveries. The simple proposed sensing approach may improve the selectivity and sensitivity of IFE-based ratiometric fluorescent assays.

Photoluminescence enhancement of aluminum ion intercalated MoS2 quantum dots

Low photoluminescence (PL) quantum yield of molybdenum disulfide (MoS2) quantum dots (QDs) has limited practical application as potential fluorescent materials. Here, we report the intercalation of aluminum ion (Al3+) to enhance the PL of MoS2 QDs and the underlying mechanism. With detailed characterization and exciton dynamics study, we suggest that additional surface states including new emission centers have been effectively introduced to MoS2 QDs by the Al3+ intercalation. The synergy of new radiative pathway for exciton recombination and the passivation of non-radiative surface traps is responsible for the enhanced fluorescence of MoS2 QDs. Our findings demonstrate an efficient strategy to improve the optical properties of MoS2 QDs and are important for understanding the regulation effect of surface states on the emission of two dimensional sulfide QDs.

Assessment of the effective parameters for the enhancement of light-harvesting power in the photoelectrochemical microbial fuel cell

ABSTRACT Photo-assisted microbial fuel cells (PMFCs) are novel bioelectrochemical systems that employ light to harvest bioelectricity and efficient contaminant reduction. In this study, the impact of different operational conditions on the electricity generation outputs in a photoelectrochemical double chamber configuration Microbial fuel cell using a highly useful photocathode are evaluated and their trends are compared with the photoreduction efficiency trends. As a photocathode, a binder-free photo electrode decorated with dispersed polyaniline nanofiber (PANI)−cadmium sulphide Quantum Dots (QDs) is prepared here to catalyse the chromium (VI) reduction reaction in a cathode chamber with an improvement in power generation performance. Bioelectricity generation is examined in various process conditions like photocathode materials, pH, initial concentration of catholyte, illumination intensity and time of illumination. Results show that, despite the harmful effect of the initial contaminant concentration on the reduction efficiency of the contaminant, this parameter exhibits a superior ability for improving the power generation efficiency in a Photo-MFC. Furthermore, the calculated power density under higher light irradiation intensity has experienced a significant increase, which is due to an increment in the number of photons produced and an increase in their chance of reaching the electrodes surface. On the other hand, additional results indicate that the power generation decreases with the rise of pH and has witnessed the same trend as the photoreduction efficiency.

A study on the mechanism of Indium phosphide/zinc sulfide core/shell quantum dots influencing embryo incubation of rare minnow (Gobiocypris rarus)

Quantum dots (QDs) inhibit fish hatching, but the mechanism is still unclear. In this study, the effect of Indium phosphide/zinc sulfide quantum dots (InP/ZnS QDs) on the embryo incubation of rare minnow was investigated. Five experimental concentration groups were set up according to the preliminary experimental results, which were 0, 50, 100, 200 and 400 nM. A direct exposure method was adopted to expose embryos to InP/ZnS QDs solution. The results showed that InP/ZnS QDs significantly inhibited the embryo hatching rate, delayed embryo emergence, affected the expression of genes associated with hatching gland cells and hatching enzymes. InP/ZnS QDs also destroy the structure of the embryo chorion. In addition, QDs can cause oxidative stress in embryos. Transcriptional sequencing analysis showed that InP/ZnS QDs InP/ZnS QDs may have induced the production of a hypoxic environment and triggered induce abnormal cardiac muscle contraction, inflammatory response and apoptosis process in embryos. In conclusion, QDs influences embryo hatchability largely through egg chorion mediation.

Bis(stearoyl) Sulfide: A Stable, Odor‐Free Sulfur Precursor for High‐Efficiency Metal Sulfide Quantum Dot Photovoltaics

AbstractThe synthesis of metal sulfide nanocrystals is a crucial step in the fabrication of quantum dot (QD) photovoltaics. Control over the QD size during synthesis allows for precise tuning of their optical and electronic properties, making them an appealing choice for electronic applications. This flexibility has led to the implementation of QDs in both highly‐efficient single junction solar cells and other optoelectronic devices including photodetectors and transistors. Most commonly, metal sulfide QDs are synthesized using the hot‐injection method utilizing a toxic, and air‐ and moisture‐sensitive sulfur source: bis(trimethylsilyl) sulfide ((TMS)2S). Here, bis(stearoyl) sulfide (St2S) is presented as a new type of air‐stable sulfur precursor for the synthesis of sulfide‐based QDs, which yields uniform, pure, and stable nanocrystals. Photovoltaic devices based on these QDs are equally efficient as those fabricated by (TMS)2S but exhibit enhanced operational stability. These results highlight that St2S can be widely adopted for the synthesis of metal sulfide QDs for a range of optoelectronic applications.

Intracellularly-photosensitized bio-hybrid with biogenic quantum dots for enhanced wastewater denitrification

Synergizing photocatalytic and biological processes in bio-hybrids offers opportunities to address the carbon deficiency challenge of wastewater denitrification, but is currently limited by the sluggish reaction kinetics due to inefficient transmembrane electron transfer. Herein, we report a self-assembled, intracellularly-photosensitized bio-hybrid, consisting of heterotrophic denitrifiers Pseudomonas aeruginosa and biogenic selenide/ sulfide quantum dots (CdSexS1-x QDs), to allow significantly improved photo-electrons utilization. It achieved 97.1 % nitrate removal within 36 h for treating low-carbon wastewater, which is 3.5-fold and 3-fold faster than those of the bare cells and the physically-mixed cells and bio-QDs. The selectivity for nitrogen gas production reached 72.1 %, against only 59.9 % in the bare cells control. Accordingly, the expression of several key denitrifying enzymes was stimulated by the photo-excited electrons. The bio-hybrid exhibited good denitrification performance during 5 cyclic operations. Its good performance for treating several real wastewaters was also demonstrated. This work broadens the application niches of photocatalytic bio-hybrid and may inspire the development of more sustainable biotechnologies for low-carbon wastewater denitrification application.

Three-dimensional reconstruction of subsurface defects in fused silica optical components using cadmium selenide/zinc sulphide quantum dots

Three-dimensional reconstruction of subsurface defects in fused silica optical components using cadmium selenide/zinc sulphide quantum dots

Protein Analysis of A. halleri and N. caerulescens Hyperaccumulators When Exposed to Nano and Ionic Forms of Cd and Zn

Hyperaccumulator plant species growing on metal-rich soils can accumulate high quantity of metals and metalloids in aerial tissues, and several proteomic studies on the molecular mechanisms at the basis of metals resistance and hyperaccumulation have been published. Hyperaccumulator are also at the basis of the phytoremediation strategy to remove metals more efficiently from polluted soils or water. Arabidopsis halleri and Noccea caerulescens are both hyperaccumulators of metals and nano-metals. In this study, the change in some proteins in A. halleri and N. caerulescens was assessed after the growth in soil with cadmium and zinc, provided as sulphate salts (CdSO4 and ZnSO4) or sulfide quantum dots (CdS QDs and ZnS QDs). The protein extracts obtained from plants after 30 days of growth were analyzed by 2D-gel electrophoresis (2D SDS-PAGE) and identified by MALDI-TOF/TOF mass spectrometry. A bioinformatics analysis was carried out on quantitative protein differences between control and treated plants. In total, 43 proteins resulted in being significatively modulated in A. halleri, while 61 resulted in being modulated in N. caerulescens. Although these two plants are hyperaccumulator of both metals and nano-metals, at protein levels the mechanisms involved do not proceed in the same way, but at the end bring a similar physiological result.

In situ-Synthesized cadmium sulfide quantum dots in pore-forming protein and polysaccharide matrices for optical biosensing applications

The main limitation for practical implementation of quantum dots-based sensors and biosensors is the possible contamination of sensing media with quantum dots (QDs) moved out from the sensor structure, being critical for living systems measurements. Numerous efforts have addressed the challenge of pre-synthesized QDs incorporation into porous matrix provide, on the one hand, proper fixation of quantum dots in its volume and preserving a free analyte transfer from the sensing media to them - on the other hand. Here, we propose an alternative insight into this problem. Instead of using preliminary synthesized particles for doping a matrix, we have in situ synthesized cadmium sulfide QDs in porous biopolymeric matrices, both in an aqueous solution and on a mica substrate. The proposed technique allows obtaining QDs in a matrix acting simultaneously as a ligand passivating surface defects and preventing QDs aggregation. The conjugates were used as a photoluminescence sensor for the metal ions and glutathione detection in an aqueous media. Different kinds of sensor responses have been found depending on the analyte nature. Zinc ions' presence initiates the intraband QDs emission increases due to the reduction of non-radiative processes. The presence of copper ions, in contrast, leads to a gradual photoluminescence decrease due to the formation of the non-luminescent copper-based alloy in the QDs structure. Finally, the presence of glutathione initiates a ligand exchange process followed by some QDs surface treatment enhancing defect-related photoluminescence. As a result, three different kinds of sensor responses for three analytes allow claiming development of a new selective QD-based sensor suitable for biomedical applications.

Synthesis of SiO2-coated CdSe/ZnS quantum dots using various dispersants in the photoresist for color-conversion micro-LED displays

Quantum dots (QDs) are a promising technology for next-generation display screens owing to their well-defined and tunable emission wavelengths. However, QDs can chemically react with external environment, decreasing their photoluminescence efficiency and reliability. In addition, further work is needed on lithography techniques to make QDs compatible with semiconductor manufacturing processes. In this study, silicon dioxide (SiO2)-coated cadmium selenide/zinc sulfide QDs are synthesized using tetraethoxysilane. The ratio of cadmium oxide to zinc acetate was tuned before coating the SiO2 passivation layer to adjust the emission wavelength of the QDs between 520 and 625 nm. The SiO2 passivation layer not only enhanced the photoluminescence intensity (PLI) by 69% but also effectively decelerated the fluorescence decay rate (<1% PLI decay after 100 h). In addition, the hydrophilicity of the SiO2-coated QDs enabled them to integrate with appropriate dispersants and photoresist for creating a 50-μm × 50-μm pixel on the color-conversion layer of a blue microlight emitting diode (micro-LED) display. Finally, a structure of a distributed Bragg reflector (DBR) was designed using TFCalc software. Subsequently, a DBR layer was deposited on the red–green QDs’ color-conversion layer to fabricate a full-color micro-LED display.

Highly thermal stable RNase A@PbS/ZnS quantum dots as NIR-IIb image contrast for visualizing temporal changes of microvasculature remodeling in flap

Surgeons face great challenges in acquiring high-performance imaging because fluorescence probes with desired thermal stability remains rare. Here, hybrid lead sulfide/zinc sulfide quantum dots (PbS/ZnS QDs) nanostructures emitting in the long-wavelength end of the second near-infrared (NIR-IIb) window were synthesized and conjugated with Ribonuclease-A (RNase A). Such formed RNase A@PbS/ZnS QDs exhibited strong NIR IIb fluorescence and thermal stability, as supported by the photoluminescent emission assessment at different temperatures. This will allow the RNase A@PbS/ZnS QDs to provide stable fluorescence signals for long-time intraoperative imaging navigation, despite often happened, undesirable thermal accumulation in vivo. Compared to NIR-IIa fluorescence imaging, NIR-IIb vascular fluorescence imaging achieved larger penetration depth, higher signal/background ratios and nearly zero endogenous tissue autofluorescence. Moreover, these QDs illustrate the reliability during the real-time and long-time precise assessment of flap perfusion by clearly visualizing microvasculature map. These findings contribute to intraoperative imaging navigation with higher precision and lower risk.Graphical

45-nm CdS QDs photoluminescent filter for photovoltaic conversionefficiency recovery

Different energy loss mechanisms have restricted the breakthroughs in concentrated photovoltaic/thermal (CPVT) hybrid solar systems that use photoluminescent filters. Re?ected and transmitted light, emission spectrum, nonideal absorption, Stokes shift (proportional to $f_1 f_2$), overlapping absorption, and scattering of light are mechanisms in photoluminescent filters that restrict optical efficiency to below theoretical limits. In addition, increases in temperature by light concentration affect the operation of photovoltaic cells and photoluminescent filters because of an increase in molecular motion and collisions that consequently lead to energy loss. Meanwhile, nanocrystals or quantum dots (QDs) from groups II VI hold electrical, optical, chemical, and physical properties that can be used to mitigate the aforementioned limitations. In this study, cadmium sulfide QDs with a diameter of 45 nm and absorption and photoluminescent spectra centered at 480 and 600 nm, respectively, were deposited in a soda-lima glass to obtain a 200-nm-thick film photoluminescent filter. The photoluminescent filter was matched to a silicon solar cell and used as an electrical power efficiency recovery filter in a hybrid CPVT solar system. A recovery of electrical power conversion efficiency higher than 3.1\% at temperatures greater than 100$^{\circ}$C was theoretically predicted and practically confirmed. A predicted trend of increases in recovered electrical power parameters as temperature increases was also verified.

Synthesis of Water-Soluble Cadmium Selenide/Zinc Sulfide Quantum Dots on Functionalized Multiwalled Carbon Nanotubes for Efficient Covalent Synergism in Determining Environmental Hazardous Phenolic Compounds

Increasing pollution and ecological imbalance have accentuated the need to develop sensors through an efficient technique. Typically, the core–shell nanocrystals of cadmium selenide/zinc sulfide (CdSe/ZnS) with functionalized multiwalled carbon nanotubes (f-MWCNTs) are used for developing an efficient electrochemical sensor that simultaneously detects 4-aminophenol (4-AP) and 4-nitrophenol (4-NP). The composite network formed by CdSe/ZnS quantum dots with the f-MWCNTs (CdSe/ZnS QDs @ f-MWCNT) behaves as an excellent electrocatalyst and provides a transportation pathway by engendering the electron–hole pair. The sensor exhibits low detection limit values of 34.8 and 17.7 nM for detection of 4-AP and 4-NP, respectively. The sensor also showed excellent sensitivity at a linear working range of 0.149–510 μM concentration for both the analytes. Additionally, the study also shows the potential for commercial feasibility of the as-prepared sensor by acquiring a satisfactory recovery percentage of the analytes in real-time biological and environmental sample analyses.

Synthesis of colloidal ZnS quantum dots

Nanomaterials are important class of materials due to their size and shape-dependent properties as compared to bulk materials. As a result, nanomaterials are increasingly interested in the technological applications of fundamental research. Among these semiconductor quantum dots (QDs) are a significant class of nanomaterials. Zinc Sulfide (ZnS) is an important semiconductor belongs to II–VI group in periodic table, a wide bandgap semiconductor, bulk energy gap 3.6 eV, with exciton binding energy of 39 meV, which is easily synthesizable material and chemically stable as compared to other chalcogenides and hence many research pronounced on zinc sulfide. Herein, we report the synthesized of Zinc Sulfide QDs by the chemical precipitation method using thioglycolic acid (TGA) as a capping agent and hydrazine hydrate-sulphur complex plays avital role in the growth ZnS QDs. The synthesized ZnS QDs were characterized using UV–visible absorption spectroscopy, photoluminescence spectroscopy (PL) , XRD, FTIR, SEM and TEM. To support the formation of ZnS QDs, XRD spectrum results the arrangement of ZnS in the cubic crystal system. The estimated particle size is 2.62 nm. The ZnS QDs are stable, fluorescent and spherical in shape as noted by the results of the PL spectral analysis and TEM images. The produced ZnS QDs are amorphous in nature and can be used in the applications like sensors, Field Emitting Diodes (FET), electroluminescence, flat panel displays and photocatalysis.