Molybdenum Disulfide Quantum Dots Research Articles

Fluorescent Molybdenum Disulfide Quantum Dots for Sensitive Detecting Curcumin in Food Samples through FRET Mechanism.

A selective and sensitive fluorometric assay was developed for specific determination of curcumin (Cur) based on fluorescence resonance energy transfer (FRET) between molybdenum disulfide quantum dots (MoS2 QDs) and Cur. The MoS2 QDs were prepared via a one-step hydrothermal protocol using sodium molybdate dihydrate, L-cysteine (Cys) as precursors, and sodium cholate (SC) as a modification agent. The as-prepared MoS2 QDs possessed maximum fluorescence emission at 460nm with a 20% of fluorescence quantum yield (FQY). It was found that the fluorescence of MoS2 QDs could be quantitatively quenched by Cur through FRET mechanism. Therefore, Cur could be detected in the range of 0.1-20µg mL- 1 with a detection limit of 5 ng mL- 1. Additionally, the developed MoS2 QDs based fluorescent assay has been successfully applied for real food sample analysis with satisfactory results.

Synthesis of a hybrid nanocomposite: Incorporating MoS2 within a ZIF-8 for fluorescence-based detection and adsorption of tetracyclines antibiotics

Molybdenum disulfide quantum dots (MoS2 QDs), a transition-metal disulfide nanomaterial, have aroused an increasing attentions in the last 20 years. Zeolitic imidazolate framework 8 (ZIF-8), a kind of metal-organic frameworks (MOF), have been widely used for pollutant disposal, drug delivery, etc. Due to its well porousness and biocompatibility. We developed a novel course for the synthesis of MoS2 QDs under atmospheric pressure. Ammonium persulfate were introduced into the sodium molybdate and glutathione (GSH) solutions, and blue fluorescent MoS2 QDs can be obtained after heating at 60 °Cfor 2 h. The MoS2 QDs exhibited a redshift of fluorescence emission peak from 440 to 570 nm as excitation wavelength changed from 360 to 460 nm. Furthermore, MoS2 QDs were further encapsulated in ZIF-8, and the prepared nanohybrids (named as MoS2@MOF) were successfully applied into the fluorescence detection antibiotics including tetracycline (TC), oxytetracycline (OTC) and chlorotetracycline (CTC) based on different fluorescent response mode. Moreover, MoS2@MOF exhibited excellent adsorption performance for TC, OTC and CTC. The maximum adsorption capacity for TC, OTC or CTC after 300 min incubation of MoS2@MOF can reach 163, 154 or 197 mg g−1.

Development of biocompatible dualistic probe based on methionine capped MoS2 QDs for selective sensing and annihilation of persistent organic pollutants

Upscaling in the agricultural and pharmaceutical industries has resulted in intractable intrusion of persistent organic pollutants (POPs) into the aquatic domain, raising alarming concerns about human and environment safety. With this concern, novel L-methionine capped molybdenum disulfide quantum dots (MET-MoS2 QDs) have stood out as an efficient fluorescence sensor cum photocatalyst for detection and annihilation of persistent organic pollutants. In this view, in-situ surface functionalization of MoS2 QDs with biocompatible methionine amino acid (MET) was accomplished using facile hydrothermal route and their successful fabrication was corroborated by FT-IR, XRD, XPS, EDX, HRTEM, fluorescence and UV–vis spectroscopy studies. The intrinsic fluorescence response of MET-MoS2 QDs were benefitted for the selective detection of two types of POPs; organochlorine pesticide (dichloroaniline, DCNA) and an anticancer drug (doxorubicin, DOX), with limit of detection of as low as 1.01 µM and 0.09 µM for DCNA and DOX, respectively. Additionally, light harvesting property of MET-MoS2 QDs suggested their efficacy as a photocatalyst for the degradation of DOX, with degradation efficiency of 93 % under UV light irradiation. The present study employs the use of biocompatible and non-toxic MET-MoS2 QDs for the first-time for fluorescence sensing and mineralization of POPs.

Catalyzing Desolvation at Cathode-Electrolyte Interface Enabling High-Performance Magnesium-Ion Batteries.

Magnesium ion batteries (MIBs) are expected to be the promising candidates in the post-lithium-ion era with high safety, low cost and almost dendrite-free nature. However, the sluggish diffusion kinetics and strong solvation capability of the strongly polarized Mg2+ are seriously limiting the specific capacity and lifespan of MIBs. In this work, catalytic desolvation is introduced into MIBs for the first time by modifying vanadium pentoxide (V2 O5 ) with molybdenum disulfide quantum dots (MQDs), and it is demonstrated via density function theory (DFT) calculations that MQDs can effectively lower the desolvation energy barrier of Mg2+ , and therefore catalyze the dissociation of Mg2+ -1,2-Dimethoxyethane (Mg2+ -DME)bonds and release free electrolyte cations, finally contributing to a fast diffusion kinetics within the cathode. Meanwhile, the local interlayer expansion can also increase the layer spacing of V2 O5 and speed up the magnesiation/demagnesiation kinetics. Benefiting from the structural configuration, MIBs exhibit superb reversible capacity (≈300mAhg-1 at 50mAg-1 ) and unparalleled cycling stability (15 000 cycles at 2Ag-1 with a capacity of ≈70mAhg-1 ). This approach based on catalytic reactions to regulate the desolvation behavior of the whole interface provides a new idea and reference for the development of high-performance MIBs.

Copper nanoclusters modified molybdenum disulfide quantum dots probe for sensitive detection of tetracycline

By combining molybdenum disulfide quantum dots (MoS2 QDs) synthesized using a facile hydrothermal method with copper nanoclusters (Cu NCs), copper-ion-modified molybdenum disulfide probes (Cu-MoS2 QDs) were obtained, enabling sensitive detection and specific recognition of tetracycline (TET). The synthesized probes were characterized using techniques such as fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The fluorescence values of the probes and TET after their reaction at different concentrations were used to calculate a detection limit of 30 nM for the synthesized probes. The recovery rate of actual samples reached a high value of 95.70%, with a relative standard deviation below 2.00%, demonstrating excellent accuracy and precision. The probe exhibited high selectivity towards TET. The accuracy is maximized when the concentration of the probe is 4.50 × 10−5 mol/L, indicating enhanced performance of the molybdenum disulfide probe after copper ion modification and obtaining favorable detection outcomes. This probe holds great potential in enhancing the safety of animal-derived food, ensuring public health, and preserving water resources.

A ratiometric fluorescence probe based on dual quantum dots for methyl parathion detection in agricultural products

Methyl parathion (MP) is an organic phosphorus pesticide widely used for pest control of various crops, however, the residual MP can enter the human body and damage the nervous system. Therefore, it is necessary to effectively monitor MP residues. Based on dual-fluorescent quantum dots, this study establishes a ratio fluorescence sensing platform for MP detection, wherein the probe is β-cyclodextrin (β-CD) modified molybdenum disulfide quantum dots (MoS2 QDs) called β-CD-MoS2 QDs. Under alkaline conditions, MP is hydrolyzed into p-nitrophenol (p-NP) and enters the hydrophobic cavity of β-CD, quenching the blue fluorescence of MoS2 QDs whose quenching degree of fluorescence intensity (I400) correlates with the concentration of MP, while the fluorescence intensity (I540) of gQDs remains unchanged and is selected as reference signal. The quantitative detection of MP is conducted by calculating the ratio of fluorescence intensities (I540/I400). The probe detected MP in the range of 0.05–25 ppm with a detection limit of 0.032 ppm which is proved to meet the requirements for biological sample detection according to the methodological validation results. The probe has been successfully applied for the detection of MP in apples and vegetables, confirming its applicability for MP detection in crops.

Exotic femtosecond nonlinear optical properties of laser ablated MoS2 quantum dots

Molybdenum disulfide (MoS2) quantum dots (QDs) of sizes 2.05–4.40 nm were synthesized using the femtosecond pulse laser ablation in liquid (PLAL) method. The optical and ultrafast nonlinear optical (NLO) properties of MoS2 QDs were comprehensively studied using photoluminescence and femtosecond Z-scan method. We synthesized these QDs in ethanol (Et) and DI water (DW) with varying ablation times of 20 min and 10 min; the sample names are Et20 and Et10, DW20, and DW10, respectively. The nonlinear absorption (NLA) coefficients [three-photon absorption (3PA)], nonlinear refractive index, etc., of these QDs, were studied using the fs Z-scan method. Interestingly, Et20 possessed saturable absorption (SA) followed by reverse saturable absorption (RSA) due to the free carrier absorption (FCA) with FCA cross-section values of – (0.61–0.89) × 10−18 cm2. While for Et10, DW20, and DW10, we found 3PA, a rare finding for MoS2 QDs. The estimated values of the second hyperpolarizability of these samples were found to be ∼10−30 esu. Due to the strong NLA phenomena, these samples have the optical limiting (OL) onset values in the range of ∼ (5.11–8.43) mJ/cm2, proving the optical limiting application potential of these QDs. The obtained optical, NLO parameters, and Kane energy values of laser-ablated MoS2 QDs suggest that these can be suitable material systems for optoelectronic, NLO switching, logic gates, and other photonic applications.

Macrophage Membrane-Modified MoS2 Quantum Dots as a Nanodrug for Combined Multi-Targeting of Alzheimer's Disease.

The complex pathological mechanism of Alzheimer's disease (AD) limits the efficacy of simple drug therapy, and drugs are difficult to penetrate the blood-brain barrier (BBB). Therefore, it is a breakthrough to enhance the therapeutic effect of AD by rationally using multiple therapeutic strategies to inhibit multiple pathological targets. In this study, macrophage membrane (MM) with active targeting inflammation function is used to functionalize molybdenum disulfide quantum dots (MoS2 QDs) with the properties of elimination of reactive oxygen species (ROS) and anti-Aβ1-42 deposition to form the nano drug (MoS2 QDs/MM), and play the role of multi-target combined therapy with NIR. The results show that MoS2 QDs/MM has a targeted therapeutic effect on ROS elimination and anti-deposition of Aβ1-42 . In addition, the combined therapy group effectively reduced Aβ1-42 mediated cytotoxicity. The modification of MM could effectively target the brain, and NIR irradiation could actively increase the cross of BBB of materials. In vivo behavioral study also show that APP/PS1 mice in the combined treatment group showed the similar exploration desire and learning ability to mice in the group of WT. MoS2 QDs/MM is an excellent nano drug with multiple effects, which has advantages in the field of neurological diseases with crisscross pathogenesis.

Near-infrared electrochemiluminescence of defect-rich molybdenum disulfide quantum dots for sensitive bioanalysis

Developing high-efficiency near-infrared (NIR) electrochemiluminescence (ECL) active transition metal dichalcogenides quantum dots (TMDs QDs) for spectroscopic multiplex analysis and biological imaging poses a significant challenge in versatile bioanalysis. In this work, we report a facile one-step hydrothermal method for the synthesis of defect-rich molybdenum disulfide quantum dots (MoS2 QDs). Because of the defect effect on the nanocrystalline surface, the MoS2 QDs exhibit enhanced fluorescence (quantum yield is 7.7%) in comparison with those from top-down physical approaches. Moreover, the defect-rich MoS2 QDs exhibit remarkable ECL performance using K2S2O8 as a coreactant, with a maximum emission at ∼810 nm. The ECL mechanisms of potential-dependent emission from MoS2 QDs were elucidated based on electrochemistry, photoluminescence, and spooling ECL spectroscopy. Leveraging the good biocompatibility and defect-induced ECL enhancement of MoS2 QDs, a sandwich ECL immunosensor was developed for carcinoembryonic antigen (CEA) detection. Without any signal amplification techniques, the proposed biosensor demonstrated a detection limit of 0.005 ng/mL CEA with a linear range from 0.005 ng/mL to 400 ng/mL, and a good selectivity and potential for real human serum analysis. The defect engineering of MoS2 QDs in this study provides guidance for regulating their optical properties and exploring new bioanalysis applications.

Dependence of reaction time in hydrothermal synthesis of MoS2 quantum dots: An investigation using optical tools and fractal analysis

The article discusses the novel fractal nature of hydrothermally synthesized Molybdenum Disulfide (MoS2) Quantum Dots (QDs), where the key parameter controlling the process is the 'reaction time’. This parameter is adjusted from 7 to 30 h, including five intermediate values, while keeping all other synthesis conditions constant. The study employs various structural, morphological, and optical techniques, including X-ray diffraction (XRD), X-ray photoelectron Spectroscopy (XPS), High-Resolution Transmission Electron Microscopy (HRTEM) equipped with Selected Area Electron Diffraction (SAED), Scanning Transmission Electron Microscopy (STEM), UV–Vis, and photoluminescence (PL) spectroscopy to track the evolution of MoS2 samples with changing reaction times. The average size of the QDs exhibits a trend of increase followed by a decrease with longer reaction times. This trend is also compared with band gap calculations. STEM images indicate that shorter reaction times lead to the formation of MoS2 sheets, while extended reaction times cause these sheets to fragment into MoS2 QDs. The concept of “compactness” in the system is explored and analyzed using fractal analysis, a statistical tool. The observations from PL, absorption, and STEM align with the time-evolved fractal dimensional analysis, demonstrating the synthesis dynamics.

Efficient visible light performance of MoS2QDs/TiO2 hollow sphere photocatalysts for the degradation of dyes and antibiotics

In this paper, molybdenum disulfide quantum dots (MoS2QDs) and TiO2 nanoparticles were used as visible light-responsive photocatalysts. The intensity of the bandgap photoluminescence of quantum dots was reduced after combining MoS2QDs with TiO2. This indicates that the photoexcited electrons in MoS2QDs are easily transferred to TiO2. The combination of MoS2QDs and TiO2 inhibits the recombination of charges and the complexation of photogenerated carriers, thus improving the degradation efficiency of dyes and antibiotics in the photocatalytic process. The cycling results showed that the MoS2QDs/TiO2 composites had good cycling stability. After five cycles of experiments, the composites still maintained similar degradation activity. Finally, a possible mechanism of the photocatalytic reaction of MoS2QDs/TiO2 is proposed. The charge generation and electron-hole separation capability of MoS2QDs/TiO2 in a wide spectral range can effectively separate photogenerated electron-hole pairs and maintain its high redox capability. It provides a broad prospect for composite materials to improve photocatalytic activity in different fields and offers many new possibilities for solar energy collection systems.

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.

Dual-mode detection of KRAS gene by target recycling amplification based on molybdenum disulfide quantum dots and the catalytic reduction of rhodamine B

In this work, a novel dual-mode ratiometric fluorometric and colorimetric system was proposed based on molybdenum disulfide quantum dots (MoS2 QDs) and rhodamine B (RhB) by combining the Exo III-assisted target recycling approach with the magnetic separation method. KRAS (Kirsten rat sarcoma viral oncogene homolog) gene as the target DNA could hybridize with the hairpin DNA to generate the output DNA through exonuclease III-assisted recycling amplification. The output DNA served as a bridge to link magnetic beads labeled with ssDNA1 (MBs-ssDNA1) to gold nanoparticles modified with ssDNA2 (AuNPs-ssDNA2). After magnetic separation, the remaining AuNPs could catalyze the reduction of RhB with the aid of sodium borohydride (NaBH4). When the KRAS gene concentration increased, the AuNPs in the solution decreased and thus less RhB was reduced. In this process, the fluorescence of RhB at 582 nm enhanced while the fluorescence of MoS2 QDs at 420 nm as a reference signal kept unchanged. Meanwhile, the absorbance of the MoS2 QDs/RhB sensing platform at 554 nm gradually increased. The dual-mode fluorometric and colorimetric sensing methods displayed excellent selectivity for KRAS gene determination with limits of detection (LOD) of 0.22 and 0.41 pM, respectively. By combining signal amplification and magnetic separation technology, this method effectively eliminated background interference and improved the sensitivity of the results. The two detection modes were successfully applied to detect the KRAS gene in real samples.

Hydrothermal Synthesis of Molybdenum Disulfide Quantum Dots for Highly Sensitive Detection of Iron Ions in Protein Succinate Oral Solution.

In this paper, a molybdenum disulfide fluorescent probe with an Fe3+ fluorescent system was first synthesized by the hydrothermal method for the detection of iron ion concentration in oral solution of protein succinate. It was characterized by infrared, fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The probes were found to have good stability, photobleaching, and storage stability. The effects of dilution, pH, reaction time, and iron ion concentration on the fluorescent system were also investigated. The relative fluorescence intensity [(I0 - I)/I0] showed a good linear relationship with the iron ion concentration in the range of 0-50 μM, with the linear equation [(I0 - I)/I0] = 0.0148[Fe3+] + 0.0833 (r2 = 0.9943, n = 11) and the detection limit of 2.43 μM. The reaction mechanism was also explored, as well as its ion selectivity, reversibility, accuracy, precision, and concentration of Fe ions in the actual sample. It was found that the probe can selectively detect Fe ions with a certain degree of reversibility, accuracy, precision, and ideal recovery, and it can be used for the determination of Fe3+ in proteosuccinic acid oral solution.

Mechanochemical synthesis of molybdenum disulfide quantum dots with enhanced dye adsorption and photocatalytic performance

Wet-mechanochemical exfoliation of molybdenum disulfide (MoS2) flakes into MoS2 quantum dots (QDs) using various exfoliation agents is studied, and the photoluminescence, adsorption and photocatalytic activities of QDs toward the degradation of rhodamine B (RhB) are evaluated. The application of ethanol as the low-boiling point (≈78 °C) exfoliation agent leads to the formation of E-MoS2 QDs (4.6 nm) with 1T-crystalline modification, dominately functionalized with hydroxyl groups. Initial MoS2 provides a weak adsorption capacity (27 mg/g), while no photocatalytic activity is observed under LED-light irradiation. E-MoS2 QDs exhibit a poor photocatalytic performance, but an excellent RhB adsorption with an equilibrium capacity of 180 mg/g under dark condition. In contrast, the application of N-Methyl-2-pyrrolidone (NMP) as the high-boiling point (≈202 °C) exfoliation agent leads to the fabrication of N-MoS2 QDs (4.8 nm) with stable 2H-crystalline modification. N-MoS2 QDs exhibits a limited adsorption capacity (32 mg/g), but an excellent stability and photocatalytic performance. At the photocatalyst dosage of 0.1 g/L, the degradation rate of dye (20 mg/L) is recorded at 100 % after 140 min of LED-light (450 nm) illumination. Reusability of N-MoS2 QDs in photocatalysis process is confirmed. Appropriate energy band gap, together with the surface amino/carboxyl functional groups are discussed to be responsible for enhanced light-induced intramolecular electron transfer, thus photocatalytic performance of the material.

In situ growth MoS2 quantum dots as promising interface materials for silicon solar cells

The carrier selectivity at interface is one key factor to improve the performance of silicon solar cells. Here, Molybdenum disulfide (MoS2) quantum dots were successfully synthesized by one-step in situ plasma enhanced atom layer deposition. A transmission electron microscope was employed to investigate nano-size scaled as well as growth mechanism of the crystalline MoS2 quantum dots. MoS2 quantum dots with additional molybdenum-oxygen (Mo–O) bonding were prepared by co-reactant plasma processing, which exhibited photo-generated carrier selectivity as promising interface materials for silicon heterojunction solar cells. Our results indicated their carrier selectivity of electron-blocking and hole-transporting at interface was attributable to unique quantum effects and tunneling effects. A photovoltaic conversion efficiency 23% was achieved by a sample silicon solar cell combined with MoS2 quantum dots interface materials. Because the interface engineering is well-defined, and the synthesis is low-cost, this bottom-up strategy provides a potential advance in design and construction of innovative and highly efficient photovoltaic devices.

Structural Modification in Au-MoS2 Quantum Dot Composites for Improved Catalytic Efficiency in p-Nitrophenol Reduction

Au-MoS2 quantum dots (QDs) composites are ideal catalysts for a number of reactions, including the reduction of p-nitrophenol (PNP). However, the structural role of Au-MoS2 QDs composites in their catalytic efficiency has never been investigated. In this work, a comparative study is carried out to investigate the catalytic reactivities of a gold nanorod–molybdenum disulfide quantum dots (AuNR-MoS2 QDs) composite and a gold nanosphere–molybdenum disulfide quantum dots (AuNS-MoS2 QDs) composite. In addition, the catalytic reactivities of a gold nanorod (AuNR) and a gold nanosphere (AuNS) are also studied. The catalytic efficiency of the as-prepared composites is then investigated for the reduction of p-nitrophenol, taken as the model reaction. The kinetics of the catalytic reduction of p-nitrophenol reveal that the AuNR-MoS2 QDs composite demonstrates the highest catalytic efficiency, having a rate constant of 0.06 min–1, compared to the AuNS-MoS2 QDs composite, AuNR, and AuNS, having a rate constant of 0.023, 0.021, and 0.008 min–1, respectively. The possible mechanism is also discussed in the paper. Finite difference time domain (FDTD) simulation was carried out to simulate the electric field intensity of the AuNR-MoS2 QDs composite, AuNS-MoS2 QDs composite, AuNR, and AuNS. It is observed that, in general, the electric field intensity increases for the AuNR-MoS2 QDs and AuNS-MoS2 QDs composites when compared with only AuNR and AuNS. Therefore, this study emphasizes understanding the structural role of AuNR-MoS2 QDs and AuNS-MoS2 QDs composites, which is paramount in evaluating the catalytic efficiencies as demonstrated in the reduction of aromatic nitro compounds.

MoS2 quantum dots based on lipid drug delivery system for combined therapy against Alzheimer's disease

Pathological pathways of Alzheimer's disease (AD) are criss-crossed, various pathological factors are dynamically correlated and relatively independent, which makes the single-target drug therapy less effective. Therefore, rational use of multiple therapeutic strategies for accurate inhibition of multiple pathological targets are effective to enhance the efficacy of AD therapy. The combination of drug loading and the excellent photothermal conversion property of nanocomposites is highly innovative to combat the two prominent pathological factors of Alzheimer's disease, oxidative stress and amyloid-β-(1–42) (Aβ1-42) deposition caused by reactive oxygen species (ROS) imbalance. Molybdenum disulfide quantum dots (MoS2 QDs) were selected as carriers and functionalized with lipids (MoS2 QDs/lipid) to improve their dispersibility in water, while effectively escaping immune clearance, improving the efficiency of multi-target applications and targeting advantages. The loading of curcumin (MoS2 QDs/lipid-Cur) not only overcomes the disadvantages of poor water solubility and low bioavailability of the drug, but also achieves the function of sustained release and long-term effect. MoS2 QDs/lipid-Cur showed excellent performance in the two therapeutic targets of anti-Aβ1-42 deposition and elimination of ROS in the early stage, and also obtained consistent excellent results in cell experiments. The drug-loaded combined with NIR treatment group significantly reduced Aβ1-42 mediated neurotoxicity. The in vivo photothermal experiment showed that NIR irradiation in the mouse brain can effectively open the blood-brain barrier (BBB) and increase the permeability of the material to the BBB. At the same time, NIR irradiation enriched drug-loaded material in the mouse brain, resulting in a significant increase in the temperature difference between the mice brains. MoS2 QDs/lipid-Cur is an excellent nanocomposite that integrates multiple functions and can be used for multi-target therapy.

Rapid and ratiometric fluorescent detection of hypochlorite by glutathione functionalized molybdenum disulfide quantum dots

We proposed a rapid and ratiometric fluorescent detection method for hypochlorite by glutathione functionalized molybdenum disulfide quantum dots (G-MoS2 QDs). The G-MoS2 QDs were obtained through a hydrothermal method and the maximum fluorescence intensity was obtained at 430 nm under excitation of 360 nm. The fluorescence of G-MoS2 QDs at 430 nm can be weakened by curcumin through the inner filter effect, meanwhile the fluorescence of curcumin at 540 nm appeared. Hypochlorite can fast oxidize curcumin and weaken the inner filter effect, thus the fluorescence of curcumin at 540 nm decreased and the fluorescence of G-MoS2 QDs at 430 nm increased. This process takes only 30 s at room temperature. This is the rationale behind our rapid ratiometric fluorescent detection model for hypochlorite. Two linear detection ranges for hypochlorite are obtained with concentration from 1 to 20 μM and 20 to 30 μM, the limit of detection (LOD) was 11.5 nM. The standard spike recovery tests on milk and tap water samples showed satisfactory results, which extended the application of G-MoS2 QDs in the field of ratiometric fluorescence detection assays.

Peptide functionalized actively targeted MoS2 nanospheres for fluorescence imaging-guided controllable pH-responsive drug delivery and collaborative chemo/photodynamic therapy

The combination of imaging and different therapeutic strategies into one single nanoplatform often demonstrates improved efficacy over monotherapy in cancer treatments. Herein, a multifunctional nanoplatform (labelled as MPRD) based on molybdenum disulfide quantum dots (MoS2 QDs) is developed to achieve enhanced antitumor efficiency by integrating fluorescence imaging, tumor-targeting and synergistic chemo/photodynamic therapy (PDT) into one system. First, polyethylene glycol (PEG)ylated MoS2 QDs (MP) with desirable stability are synthesized via a hydrothermal process using MoS2 QDs and carboxyamino-terminated oligomeric PEG as raw materials. Then, MP were conjugated with arginine-glycine-aspartic acid (RGD) peptide via amidation to form a novel nanocarrier (MPR), which possesses strong blue fluorescence, good biocompatibility and ανβ3 receptor-mediated targeting ability. More importantly, MPR generated reactive oxygen species under 808 nm laser activation to realize targeted antitumor PDT. Further doxorubicin (DOX) was loaded onto MPR, which endows MPRD with localized chemotherapy and pH-responsive drug release. The MPRD exhibits improved chemotherapy performance on HepG2 cells (overexpressing integrin ανβ3) owing to enhanced cellular uptake mediated by ανβ3 receptor and effective drug release triggered by intracellular pH. Notably, MPRD with efficient tumor targeting ability and high chemo/PDT efficacy under NIR laser irradiation is capable of inhibiting HepG2 tumor cell growth both in vitro and in vivo, which is significantly superior to each individual therapy. These findings demonstrate that MPRD holds great potential in effective cancer therapy.