Disulfide Quantum Dots Research Articles

Selective and Sensitive Electrochemical Sensor for Aflatoxin M1 with a Molybdenum Disulfide Quantum Dot/Metal-Organic Framework Nanocomposite.

Aflatoxins are the hepatotoxic secondary metabolites which are highly carcinogenic and known to cause several adverse effects on human health. The present study reports a simple, sensitive, and novel electrochemical sensor for aflatoxin M1 (AFM1). The sensor has been fabricated by modifying the screen-printed carbon electrodes with a functional nanocomposite of molybdenum disulfide (MoS2) quantum dots (QDs) and a zirconium-based metal–organic framework (MOF), that is, UiO-66-NH2. The MoS2/UiO-66-modified electrodes were decorated with the AFM1-specific monoclonal antibodies and then investigated for the electrochemical detection of AFM1. Based on the electrochemical impedance spectroscopy analysis, it was possible to detect AFM1 in the concentration range of 0.2–10 ng mL–1 with a limit of detection of 0.06 ng mL–1. The realization of an excellent sensing performance can be attributed to the electroactivity of MoS2 QDs and the large surface to volume area achieved by the addition of the MOF. The presence of UiO-66-NH2 is also useful to attain readily available amine functionality for the robust interfacing of antibodies. The performance of the developed sensor has also been validated by detecting AFM1 in the spiked milk samples.

A MoS2QDs/chitin nanofiber composite for improved antibacterial and food packaging

Chitin nanofiber has potential application as antibacterial nanocomposite material because of its inherent biocompatibility, biological activity, amino containing macromolecular structure and nano-size effect. Molybdenum disulfide quantum dots (MoS2QDs) were uniformly bonded on partially deacetylated chitin nanofibers (DEChNs) by hydrothermal reactions. The antibacterial properties of MoS2QDs/DEChN against Escherichia coli were detected under different conditions. When the antibacterial agent was fixed at 200 μg/mL, the survival rates of bacteria were 2.77% (pH = 4), 5.58% (pH = 5) and 7.83% (pH = 6), which were lower than those in the DEChN groups. Unlike DEChN, which only had excellent antibacterial activity under acidic conditions (pH < 5), the combination of DEChN and MoS2QDs had antibacterial activity close to neutral conditions, with a bacteriostatic rate > 90%. When TEMPO-oxidized cellulose nanofibers (TOCN) were applied for the preparation of MoS2QDs/TOCN, they did not show obvious antibacterial ability, which proved the positive role of DEChN and its amino groups. The MoS2QDs/DEChN assembled film could be applied to preserve meat by delaying spoilage. The current study might inspire new ideas for designing food packaging based on the prepared MoS2QDs/DEChN films.

MoS2 QDs-nanoparticle-engineered based hydrophobic filter for high performance water-oil separation

• A novel hydrophobic AC/MoS2 QDs/SSM filter for separation oil–water emulsion. • Preparation by economical materials, simple and one step hydrothermal method. • High selectivity, high flux and high recyclability. The demand for the development of inexpensive and effective approaches for the oil–water separation is increasing due to the global concern in oil industries. In this study, we synthesized nano porous activated carbon (AC)/ Molybdenum disulfide (MoS2) quantum dots (QDs) stainless still mesh (SSM) as a hydrophobic and oleophilic nano filter by hydrothermal method in one step in 200 °C for 12 h, which was characterized by various XRD, FTIR, SEM/Map, TEM, BET-BJH, CV, AFM, DLS and PL techniques. The results showed that the solvent type was also effective in the amount of its separation from oil. Further, the effect of water-to-solvent ratio and pH was investigated. Based on the results of petrol with a water-to-solvent ratio of 20/20 at pH = 7 and at a time of 10 s, 99.99% was separated by AC/MoS2 QDs/SSM. The results showed that repeatability cycle of the AC/MoS2 QDs/SSM was 23 times and its duration to 30 s. The results of kinetic studies revealed that the Pseudo second order kinetic model was in good agreement with the experimental data. This novel filter demonstrated an excellent separation with high selectivity, good flux > 6000 L/m 2 h and high repeatability with great durability from low cost materials and simple method that was appropriate for treating stratified water–oil and water in oil emulsion without using demulsifier.

Early stage evaluation of colon cancer using tungsten disulfide quantum dots and bacteriophage nano-biocomposite as an efficient electrochemical platform

BackgroundRecently, biosensors have become popular analytical tools for small analytes due to their high sensitivity and wide analytical range. In the present work, development of a novel biosensing method based on tungsten disulfide quantum dots (WS2 QDs)-Au for rapidly and selectively detecting c-Met protein is introduced. As a proof of concept, M13 bacteriophage-based biosensors were used for the electrochemical detection of c-Met protein as a colon cancer biomarker.MethodThe M13 bacteriophage (virus), as the biorecognition element, was immobilized on glassy carbon electrodes which were modified by WS2 QDs-functionalized gold nanoparticles. The stepwise presence of the WS2 QDs, gold nanoparticles, and immobilized phage on glassy carbon electrodes were confirmed by scanning electron microscope (SEM) and square wave voltammetry (SWV) technique.ResultsThe designed biosensor was applied to measure the amount of c-Met protein in standard solutions, and consequently the desirable detection limit of 1 pg was obtained. Finally, as a proof of concept, the developed platform was used for the evaluation of c-Met protein in serum samples of colon cancer-suffering patients and the results were compared with the results of the common Elisa kit.ConclusionsAs an interesting part of this study, some concentrations of the c-Met protein in colon cancer serum samples which could not be determined by Elisa, were easily analyzed by the developed bioassay system. The developed bioassay system has great potential to application in biomedical laboratories.Graphical

Targeted enhancement of electrochromic memory in Fe(II) based metallo-supramolecular polymer using molybdenum disulfide quantum dots

Bistable electrochromic (EC) display with long EC memory has been a much-anticipated goal owing to its zero-energy consumption when maintaining the colored or bleached state when used in smart windows. However, it is very challenging to engineer the structure of the materials to accomplish a long EC memory along with high optical contrast, durability, switching fastness, and coloration efficiency which are of significance for fabricating the electrochromic devices with essentially power efficiency. Herein, we have judiciously incorporated the charge trapping MoS2 quantum dots (QDs) to prepare an electrochromic nanocomposite (polyFe-QD-10) of an Fe2+-based metallo-supramolecular EC polymer (polyFe) for the targeted enhancement of EC memory than the pristine polyFe polymer. The polyFe-QD-10 based electrochromic device (ECD) exhibits more cycle durability as it produced no loss in ΔT after the measurement of 100 cycle, while pristine polyFe-based ECD produced 14% loss in similar 100 cycle. The prototype ECD with polyFe-QD-10 film is also demonstrated with fast switching time (3.3 s for bleaching and 0.78 s for coloring), and good coloration efficiency (242.2 cm2 C−1). Remarkably, the ECD based on polyFe-QD-10 composite displays higher EC memory in open circuit condition as it takes 32 min for 90% reappearance of the original purple color after complete bleaching, while the pristine polyFe based ECD regains 90% of the transmittance of the color state only in 15 min. The strategy reported here presents the polyFe-MoS2 QD composite thin film an encouraging candidate for developing power efficient electrochromic information displays and smart windows.

A dual-signal fluorescent sensor based on MoS2 and CdTe quantum dots for tetracycline detection in milk

A dual-signal fluorescent sensor was developed for tetracycline (TET) detection in milk with excellent reproducibility and stability. In this protocol, molybdenum disulfide quantum dots (MoS2 QDs) with blue fluorescence and cadmium telluride quantum dots (CdTe QDs) with yellow fluorescence were synthesized to establish the MoS2/CdTe-based sensor with two fluorescence emission peaks at 433 nm and 573 nm. With the addition of TET, the fluorescence of MoS2/CdTe were quenched by photoinduced electron transfer (PET), and the fluorescence of CdTe QDs were quenched more obvious than MoS2 QDs. With the strategy, a calibration curve was established between the TET concentration in the range of 0.1–1 μM and the ratio of fluorescence intensity at 573 nm and 433 nm (F573/F433). Furthermore, the dual-signal sensor was applied for TET detection in milk samples with the recovery of 95.53–104.22% and the relative standard deviation (RSD) less than 5%, indicating the strong application potential.

False luminescence of molybdenum disulfide quantum dots from carbon dots.

For the first time, a systematical investigation has been carried out to verify luminescent molybdenum disulfide quantum dots (MoS2 QDs). We found that the well-reported blue fluorescence of the so-called "MoS2 QDs" is mainly originated from the co-present carbon based dots rather than MoS2. Furthermore, the band gap of MoS2 is independent of the lateral size, and it is impossible to obtain luminescent MoS2 QDs by reducing the lateral size.

Chiral non-stoichiometric ternary silver indium sulfide quantum dots: investigation on the chirality transfer by cysteine.

Chiral semiconductor quantum dots have recently received broad attention due to their promising application in several fields such as sensing and photonics. The extensive work in the last few years was focused on the observation of the chiroptical properties in binary Cd based systems. Herein, we report on the first evidence of ligand-induced chirality in silver indium sulfide semiconductor quantum dots. Ternary disulfide quantum dots are of great interest due to their remarkable optical properties and low toxicity. Non-stoichiometric silver indium sulfide quantum dots were produced via a room temperature coprecipitation in water, in the presence of cysteine as a capping agent. The obtained nanocrystals show a notable photoluminescence quantum yield of 0.24 in water dispersions. Several critical aspects of the nanocrystal growth and chemico-physical characterization, and the optimisation of the surface passivation by the chiral ligand in order to optimize the nanoparticle chirality are thoroughly investigated. Optical spectroscopy methods such as circular dichroism and luminescence as well as nuclear magnetic resonance techniques are exploited to analyze the coordination processes leading to the formation of the ligand-nanocrystal chiral interface. This study highlights the dynamic nature of the interaction between the nanocrystal surface and the chiral ligand and clarifies some fundamental aspects for the transfer and optimization of the chiroptical properties.

Tungsten disulfide (WS2)/fluorescein ratiometric fluorescent probe for detection of cefixime residues in milk

In this research work, it has been reported a ratiometric fluorescent sensor based on tungsten disulfide quantum dots (WS2 QDs) and fluorescein for the determination of Cefixime (CEF). When excited by radiation of 400 nm wavelength the probe illustrates dual emissions centered at 460 nm and 510 nm. CEF quenches the fluorescence (FL) intensity of fluorescein (510 nm), while it doesn't affect the FL emission of WS2 QDs at 460 nm. The change in the ratio of the two peaks (F460/F510) of the prepared sensor (WS2 QDs/fluorescein) is linearly proportional to the CEF concentration in the range of 200–2.500 ng/mL with a limit of detection (LOD) of 45 ng/mL. Hence, the proposed probe can be successfully used for CEF quantification in the milk samples.

Ascorbic acid detector based on fluorescent molybdenum disulfide quantum dots.

A rapid and facile method is reported for the detection of ascorbic acid using molybdenum disulfide quantum dots (MoS2 QDs) as a fluorescence sensor. Water-soluble and biocompatible MoS2 QDs with the maximum fluorescence emission at 506nm have been successfully synthesized by hydrothermal method and specific detection for ascorbic acid (AA) was constructed to utilize the modulation of metal ion on the fluorescence of MoS2 QDs and the affinity and specificity between the ligand and the metal ion. The fluorescence of MoS2 QDs was quenched by the irreversible static quenching of Fe3+ through the formation of a MoS2 QDs/Fe3+ complex, while the pre-existence of AA can retain the fluorescence of MoS2 QDs through the redox reaction between AA and Fe3+. Based on this principle, a good linear relationship was obtained in the AA concentration range 1 to 150μM with a detection limit of 50nM. The proposed fluorescent sensing strategy was proven to be highly selective, quite simple, and rapid with a requirement of only 5min at room temperature (RT), which is particularly useful for rapid and easy analysis. Satisfactory results were obtained when applied to AA determination in fruits, beverages, and serum samples as well as AA imaging in living cells, suggesting its great potential in constructing other fluorescence detection and imaging platforms.

Plasmonic Gold Nanorod Size-Controlled: Optical, Morphological, and Electrical Properties of Efficiency Improved Tin Disulfide Vacuum-Free Hybrid Solar Cells

The different size of plasmonic gold nanorods (NRs) were synthesized by the overgrown seeds method and applied to vacuum-free hybrid solar cells (VFHSCs). Tin disulfide (SnS2) quantum dots were synthesized and used as an n-type material of the device. The synthesized materials were characterized by different techniques such as transmission electron microscopy (TEM), UV-Vis spectroscopy, and atomic force microscopy (AFM). The Au (NRs) had a different of size of NR1 (Width: 4 nm; Length: 12 nm), NR2 (Width: 5 nm; Length: 16 nm), NR3 (Width: 6 nm; Length: 22 nm) which were measured using a TEM technique. The Au NR particles were incorporated into the PEDOT:PSS as a hole transport layer (HTL) of solar cells device. The effects of Au NRs size on the device performance were investigated. A thin film of Zin oxide (ZnO) was used as a buffer layer of the device. The influence of buffer layer thickness on the device’s active layer surface morphology was also studied. At the optimized condition, the highest power conversion efficiency was obtained at about ~3.7%.

MoS2 QDs/8-Armed Poly(Ethylene Glycol) Fluorescence Sensor for Three Nitrotoluenes (TNT) Detection.

In this work, ammonia cross-linked 8-armed polyethylene glycol hydrogel material was successfully synthesized and used as a template for synthesizing nanoparticles with fluorescent properties. The 8-armed polyethylene glycol hydrogel template was used to prepare molybdenum disulfide quantum dots (MoS2 QDs). The ammonium tetrathiomolybdate functioned as a molybdenum source and hydrazine hydrate functioned as a reducing agent. The fluorescence properties of the as-prepared MoS2 QDs were investigated. The bursting of fluorescence caused by adding different concentrations of explosive TNT was studied. The study indicated that the synthesized MoS2 QDs can be used for trace TNT detection with a detection limit of 6 nmol/L and a detection range of 16–700 nmol/L. Furthermore, it indicated that the fluorescence-bursting mechanism is static bursting.

Polarization-Resolved Electrochemiluminescence Sensor Based on the Surface Plasmon Coupling Effect of a Au Nanotriangle-Patterned Structure

This work focused on the construction of a nanomaterial-patterned structure for high-resolved ECL signal modulation. Due to the surface coupling effect, the different shapes and distribution states of surface plasmonic nanomaterials not only affect the luminescence intensity enhancement but also decide the electrochemiluminescence (ECL) polarization characteristics. Herein, tin disulfide quantum dots were synthesized via a solvothermal method as ECL emitters. Compared with other nanostructures, Au nanotriangle (Au NT) displayed both the localized surface plasmon resonance electromagnetic enhancement effect and the tip amplification effect, which had significant hot spot regions at three sharp tips. Therefore, self-assembled Au NT-based patterned structures with high density and uniform hot spots were constructed as ideal surface plasmonic materials. More importantly, the distribution states of the hot spots affect the polarization characteristics of ECL, resulting in directional ECL emission at different angles. As a result, a polarization-resolved ECL biosensor was designed to detect miRNA 221. Moreover, this polarization-resolved biosensor achieved good quantitative detection in the linear range of 1 fM to 1 nM and showed satisfactory results in the analysis of the triple-negative breast cancer patients' serum.

Tungsten disulfide quantum dots (WS2 QDs) as a fluorescence probe for detection of dopamine (DA)

Tungsten disulfide quantum dots (WS2 QDs) as a fluorescence probe for detection of dopamine (DA)

Tribological properties of bismaleimide-based self-lubricating composite enhanced by MoS2 quantum dots/graphene hybrid

In order to promote the formation of high-quality graphene-based self-lubricating transfer film. The reduced graphene oxide (RGO) deposited with molybdenum disulfide quantum dots (MoS2QDs) were successfully prepared. The as-prepared MoS2QDs/RGO hybrid was used for the first time to improve the tribological properties of polymer composites. Compared with the neat bismaleimide (BMI) and RGO filled composites, the MoS2QDs/RGO/BMI showed the best tribological properties, and the frictional coefficient and volume wear rate could be decreased to 0.15 and 8.9 × 10−6 mm3/(N·m), respectively. This is mainly due to the MoS2QDs loaded on the graphene surface are beneficial to prevent the graphene nanosheet stacking, and the introduction of MoS2QDs can make the self-lubricating transfer film formed more uniform, smooth and robust during the friction process.

Investigation on conformational variation and fibrillation of human serum albumin affected by molybdenum disulfide quantum dots

In this work, binding interaction between molybdenum disulfide quantum dots (MoS2 QDs) and human serum albumin (HSA) was researched deeply to dissect the conformational variation and fibrillation of HSA affected by MoS2 QDs. The results revealed that MoS2 QDs bound strongly with HSA with molar ratio of 1:1 under the joint actions of hydrogen bond and van der Waals force, leading to the static fluorescence quenching of HSA. MoS2 QDs caused the secondary structure transition of HSA from α-helix stepwise to β-turn, β-sheet, and random coil gradually. MoS2 QDs reduced both the molar enthalpy change and the melting temperature of HSA, reducing the thermal stability of HSA significantly. It is worth noting that MoS2 QDs inhibited the fibrillation process of HSA according to the reduced hydrophobic environment and the disturbance of disulfide bonds in HSA network structure. These results reveal the precise binding mechanism of MoS2 QDs with HSA at molecular level, providing indispensable information for the potential application of MoS2 QDs in biological fields.

One-step synthesis of high-quality vanadium disulfide quantum dots for long-term lysosome-targetable imaging

Transition metal dichalcogenides, especially vanadium disulfide (VS2), are greatly emphasized in recent years. However, little literature has reported the properties of photoluminescent VS2 quantum dots (QDs) until now. In this study, water-soluble VS2 QDs are prepared by a bottom-up strategy via a hydrothermal method. The obtained VS2 QDs have favorable properties including uniform distribution, relatively small size (average diameter of ∼ 3.1 nm), high quantum yield (∼ 15 %) and robust stability. Furthermore, favorable photostability, low toxicity and desirable lysosome-targeting ability endow VS2 QDs with great potential for cellular lysosome imaging. This strategy paves the way for the facile synthesis of VS2 QDs for biomedical imaging.

Nitrogen-doped MoS2 QDs as fluorescent probes for sequential dual-target detection and their microfluidic logic gate operations

Fluorescence sensors show great potential as molecular logic gates to sensitively detect different analytes in trace level. For achieving multi-target analysis, it is desirable for developing complex molecular logic gates by using multi-target fluorescence sensing system. Herein, novel nitrogen-doped molybdenum disulfide quantum dots (MoS2 QDs) have been synthesized and designed as the fluorescent probes for dual-target detection and microfluidic logic gate operations. Nitrogen-doped MoS2 QDs exhibit fluorescence “on–off-on” characteristics by sequential addition of Fe3+ ions and ascorbic acid (AA). The controllably modulating dispersion or aggregation state of nitrogen-doped MoS2 QDs is successfully obtained by addition of Fe3+ or/and AA. The static quenching mechanism of between nitrogen-doped MoS2 QDs and Fe3+ ions is illustrated in detail. This dual-target fluorescence sensor exhibited good sensitivity and selectivity to Fe3+ and AA, and the limit of detection values were 11 μM and 960 nM, respectively. Inspired by these results, nitrogen-doped MoS2 QDs-based “IMPLY” logic gate is fabricated for intelligent fluorescent sensing of Fe3+ and AA. More importantly, using blue fluorescence of nitrogen-doped MoS2 QDs, fluorescent “IMPLY” logic gate integrating with microfluidic chip is constructed for visually discriminating Fe3+ or/and AA with the naked eyes, which has the advantages of microliter reagent consumption, automated operation and visible readout. This “visible-invisible-visible” photoluminescence property of nitrogen-doped MoS2 QDs and their microfluidic logic gate operations provide a novel strategy for dual-target sensing.

Converting electronic nose into opto-electronic nose by mixing MoS2 quantum dots with organic reagents: Application to recognition of aldehydes and ketones and determination of formaldehyde in milk

A new colorimetric sensor array based on mixing of Molybdenum disulfide quantum dots (MoS2 QDs) and organic reagents is introduced in this study. MoS2 QDs shows a specific and higher affinity to oxygen functionalized volatile compounds like aldehydes and ketones. Therefore, this designed sensor array is used for classification of eight different aldehydes and ketones based on Linear Discriminate Analysis (LDA) at first. The classification accuracy of 96% and 83% was obtained for training and prediction phases, respectively. Then the introduced colorimetric sensor array is used for the semi-quantitative and quantitative analysis of formaldehyde in milk samples. Formaldehyde is an adulteration that is added to the milk for increasing the storage time. Cow milk samples were provided directly from dairy farmer and from supermarkets and were spiked by formaldehyde in the concentration range of 1–25 ppm. The response of sensor array to these samples were analyzed by partial least squares regression (PLS-R) method and were calibrated for concentration of formaldehyde. The PLSR results (R2 = 0.94 and RMSEC = 2.36) shows that proposed sensor is useable in direct analysis of formaldehyde in milk as a complex matrix.

Molybdenum Disulfide Quantum Dots: Properties, Synthesis, and Applications

Molybdenum disulfide quantum dots (MoS2 QDs) are a unique class of zero-dimensional (0D) van der Waals nanostructures. MoS2 QDs have attracted significant attention due to their unique optical, electronic, chemical, and biological properties due to the presence of edge states of these van der Waals QDs for various chemical functionalization. Their novel properties have enabled applications in many fields, including advanced electronics, electrocatalysis, and biomedicine. In this review, the various synthesis techniques, the novel properties, and the wide applications of MoS2 quantum dots are discussed in detail.