Quantum Dot Nanocomposites Research Articles

Facile synthesis and preparation of graphite/chitosan/graphene quantum dots nanocomposite cathode for electrochemical removal of tetracycline from aqueous solution

In this research, graphene quantum dots (GQDs) was synthesized via the facile pyrolysis method. The properties of the prepared GQDs were examined by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), dynamic light scattering (DLS), photoluminescence (PL), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet–visible (UV–Vis) methods. Afterward, the graphite/chitosan/graphene quantum dots (Gr/CS/GQDs) nanocomposite was prepared and used as a cathode electrode in electro-Fenton (EF) process to study the tetracycline (TCL) removal from the aqueous solution. The effect of operational parameters in EF, including current density (mA/cm2), initial pH, initial TCL concentration (mg/L), and process time (min) on the TCL removal efficiency, was investigated via response surface methodology (RSM). The results showed that the optimal values for current density, pH, initial TCL concentration, and process time were 60 mA/cm2, 5, 30 mg/L, and 150 min, respectively. Maximum TCL removal efficiency was 92.98%. FT-IR, XRD, Raman spectroscopy, atomic force microscopy(AFM), SEM, mapping, energy dispersive X-Ray (EDX), Brunauer Emmett Teller (BET), and cyclic voltammetry (CV) analyses were performed to investigate the Gr/CS/GQDs cathode. Finally, gas chromatography–mass spectrometry (GC-MS), total organic carbon(TOC), and atomic absorption spectroscopy (AAS) analyses were performed and the reusability of the Gr/CS/GQDs cathode was investigated.

Preparation, Crystallization Behavior, Simultaneous Spectroscopic and Rheological Characterization of Polyphenylene Sulfide/Graphene Quantum Dots Nanocomposites

AbstractGraphene quantum dots are prepared conveniently and quickly with brown‐black humic acid as raw material by green oxidation process. The average size of GQDs is about 12 nm with a lattice spacing of 0.26 nm and GQDs have hydroxyl and carboxyl functional groups on their surface. Moreover, photoluminescence testing shows that GQDs have excellent photoluminescence properties with maximum excitation/emission wavelength at 347/478 nm. Next, polyphenylene sulfide (PPS)/GQDs nanocomposites are prepared by melt blending with GQDs and PPS. Mechanical tests show that the tensile strength and the impact strength of PPS can be greatly improved when the amount of GQDs is 0.5 wt% and tensile strength and the impact strength are increased by 53.38% and 375%, respectively. The nonisothermal crystallization of PPS/GQDs nanocomposites is investigated by differential scanning calorimetry, which shows that GQDs effectively increase the crystallization rate of PPS. The crystallization of PPS/GQDs nanocomposites during cooling are studied by Rheonaut technology analysis. The rheological results show that the storage modulus of PPS/GQDs (0.5 wt%) nanocomposites is increased by about 1.04 times than that of pure PPS, and 2D IR spectrum confirms that GQDs accelerate crystallization of PPS. Rheological studies present that GQDs have good compatibility with PPS.

Na2MnPO4F/Ti3C2-CQDs composite cathode material with enhanced electrochemical properties for lithium/sodium hybrid ion battery

Na2MnPO4F and Ti3C2‑carbon quantum dots (CQDs) nanocomposites were prepared by wet mixing method combined with spray drying method, and the two materials were further compounded by heat treatment to get different ratios of Na2MnPO4F/Ti3C2-CQDs cathode material (NTC), the effects of Ti3C2-CQDs on the structure and electrochemical performance of the composite of Na2MnPO4F as a lithium-ion battery cathode material were investigated. The results showed that Na2MnPO4F was uniformly attached to the surface and between layers of Ti3C2-CQDs. The initial specific discharge capacity of NTC-2 at 0.1C was 67.8 mAh·g−1, and the reversible capacity after 100 cycles was 60.7 mAh·g−1, the capacity retention rate was as high as 90%, which all showed that Ti3C2-CQDs can enhance the cycle performance, rate performance and capacity retention rate of Na2MnPO4F. It also showed good rate performance under high current density. After the high current test, the current returned to 0.1C, and the capacity can be restored to the original value, which showed that the material has good structural stability. Therefore, Ti3C2-CQDs doped Na2MnPO4F is an important way to improve the electrochemical performance of polyanionic compounds.

PLGA-graphene quantum dot nanocomposites targeted against αvβ3 integrin receptor for sorafenib delivery in angiogenesis.

Angiogenesis is a vital step in many severe diseases such as cancer, diabetic retinopathy, and rheumatoid arthritis. Sorafenib (SFB), a multi-tyrosine kinase inhibitor, has recently been shown to inhibit tumor progression and suppress angiogenesis. Its narrow therapeutic window, however, has limited its clinical application and therapeutic efficacy. Accordingly, in this study, a nanocomposite formulation comprising of graphene quantum dots (GQDs) and poly (D, l-lactide-co-glycolide) (PLGA) nanoparticles was functionalized with an integrin-targeting ligand (RGD peptide) to improve SFB delivery for the treatment of angiogenesis. Physicochemical and biological properties of the targeted nanocomposite were evaluated in terms of chemical structure, morphology, particle size, zeta potential, photoluminescence, and cell toxicity. The loading capacity of the nanocomposite was optimized at different drug-to-PLGA ratios. Drug release behavior was also investigated at 37°C in pH=7.4. The SFB-to-PLGA ratio of 1:3 was selected as the optimum condition which resulted in the encapsulation efficiency and encapsulation capacity of 68.93±1.39 and 18.77±0.46, respectively. Photoluminescence properties of GQD in nanocomposite were used to track the delivery system. The results indicated that conjugating targeting ligand could enhance cellular uptake of nanocomposite in cells overexpressing integrin receptors. In vivo anti-angiogenesis activity of targeted nanocomposite was investigated in chick chorioallantoic membrane (CAM). The findings showed that SFB loaded in the targeted nanocomposite reduced VEGF secretion in vitro and its anti-angiogenic effect surpass free SFB. Thanks to its unique therapeutic and bioimaging properties, the developed nanocomposite could be an effective drug delivery system for poorly water-soluble therapeutic agents.

Highly stable and recoverable humidity sensor using fluorescent quantum dot film.

Fluorescent sensors are resistant to electromagnetic interference and are electrically insulated, allowing for highly accurate measurements. Quantum dots (QDs) serve as outstanding sensing materials owing to the unique optical properties such as tunable photoluminescence (PL), excellent visible light activity, and high chemical and physical stability. In this paper, we develop an optical humidity sensor based on a QDs nanocomposite film. The film is made of polyvinyl alcohol (PVA), SiO2 microsphere (SM), and QDs through the layer-by-layer self-assembly method. The mechanism of humidity detection is moisture-induced quenching of the QDs fluorescence intensity. The results reveal that our sensor shows a good linear response to relative humidity in the range of 5% to 97%, a fast response-recovery time of 25 s and 20 s, and good repeatability for more than 50 cycles as well as high stability for over 180 days. Possessing the remarkable property, optical humidity sensors are envisaged for great potential applications in environmental monitoring.

High Photoluminescence Polyindole/CuInS Quantum Dots for Pb Ions Sensor

Polyindole is considered an excellent conducting polymer with interested properties for different applications. A novel polyindole (PIn)/CuInS (CIS)/ZnS quantum dots (QDs) nanocomposite was synthesized via in situ polymerization of PIn in presence of CIS/ZnS QDs. By investigating the effect of CIS/ZnS QDs on optical properties of PIn, it was found that the optical band gaps of PIn, CIS/ZnS QDs, and PIn/CIS/ZnS QDs nanocomposite were 3.24 eV, 4.68 eV and 3.44 eV, respectively. From the luminance spectra, it was observed that emission peaks of PIn at 442 and 468 nm are independent of the excitation wavelength with the highest intensity at excitation wavelength of 380 nm. However, the luminance spectrum of PIn/CIS/ZnS QDs nanocomposite exhibited a quenching peak for CIS/ZnS QDs while the intensity of PIn peak was enhanced. High resolution of transmission electron microscope image of CIS/ZnS QDs revealed nanocrystals with a size of 3–4.5 nm and lattice space of 0.2 nm. PIn/CIS/ZnS QDs nanocomposite as the fluorescent probe was employed for sensing different concentrations of Pb2+ from 5 to 50 ppb. The reaction between PIn/CIS/ZnS QDs and Pb2+ was slightly quenched and fixed after 90 min. The emission peak was reduced gradually with increasing concentration of lead via photo-induced electron transfer or ion exchange mechanism. The value of correlation coefficient (R2) was 0.99, the sensitivity was 0.0041 ppb−1 and limit of detection value was 4.48 ppb.

High-sensitive humidity sensor based on MoS2/graphene oxide quantum dot nanocomposite

In this work, a high sensitivity humidity sensor based on Molybdenum disulfide/graphene oxide quantum dot (MoS2/GOQD) composite film was proposed. The humidity sensitive thin film of MoS2/GOQD was deposited on Au interdigitated microelectrodes via a facile drop-coating technique. The sensing characteristics of the MoS2/GOQD composite film sensor were investigated against various relative humidity (RH) at room temperature. The experimental results indicated that MoS2/GOQD composite film sensor possessed a high sensitivity of 369 pF/%RH, which is about twenty times larger than that of pure MoS2 based humidity sensor. Moreover, the sensor exhibited a good repeatability, rapid response/recovery speed, low hysteresis, and good long-term stability. Furthermore, the underlying humidity sensitivity enhancement mechanism of the fabricated sensor was analyzed and discussed in detail. This research demonstrates that the MoS2/GOQD composite film is a promising sensitive material for fabricating a high sensitivity humidity sensor.

Bandgap engineering of ZnX (X = O, S, Se, Te) QDs/Graphene nanocomposites: Towards the designing of a highly efficient light-harvesting device

Increasing the power conversion efficiency (PCE) of photovoltaic devices (PVDs) is a topic of fundamental importance not only for academia but also for industry. In this study, we systematically investigated the electronic structure of ZnX (X = O, S, Se, and Te) quantum dots (QDs)/Graphene (G) nanohybrid systems by employing the density functional method. To understand the key issues, associated with photoinduced charge generation, generated charge separation, charge transfer process, recombination probability, and variations of PCE, we have considered different combinations of hybrid nanostructures composed with ZnX QD and G. The tuning of the electronic properties of hybrid systems has been done as a function of the size of ZnX QD's, chalcogenides, and hydrogen coverage percentage on G to design a highly efficient hybrid solar cell. We have also explored the photovoltaic efficiency of ZnX/ZnX’ (X/X' = O, S, Se, and Te) core/shell QDs/G to investigate the effect of core/shell QDs in composite nanomaterials. Bandgaps of ZnX QDs/G nanocomposites are very low (0.028eV–0.158 eV) which implies the probability of recombination of photo-induced separated charges at the heterojunction region is very high. After passivation with hydrogen atoms partially on the G, this unsavory circumstance is overcome. We have performed the bandgap and band alignment engineering of ZnX QDs/G hybrid nanostructures by varying the size of QD's and H-coverage percentage on G to form a type-II material which is very important to reduce the recombination rate and ultimately increase the PCE of the hybrid solar cells. Considering hydrogenated graphene (HG)-ZnX QDs nanocomposites we were achieving high PCE values (up to 30.25%), which implies our explored materials efficiency is exceptionally good and competitive with recently explored tandem/hybrid/latest perovskite solar cells.

Magnetic Fluorescent Quantum Dots Nanocomposites in Food Contaminants Analysis: Current Challenges and Opportunities.

The presence of food contaminants can cause foodborne illnesses, posing a severe threat to human health. Therefore, a rapid, sensitive, and convenient method for monitoring food contaminants is eagerly needed. The complex matrix interferences of food samples and poor performance of existing sensing probes bring significant challenges to improving detection performances. Nanocomposites with multifunctional features provide a solution to these problems. The combination of the superior characteristics of magnetic nanoparticles (MNPs) and quantum dots (QDs) to fabricate magnetic fluorescent quantum dots (MNPs@QDs) nanocomposites are regarded as an ideal multifunctional probe for food contaminants analysis. The high-efficiency pretreatment and rapid fluorescence detection are concurrently integrated into one sensing platform using MNPs@QDs nanocomposites. In this review, the contemporary synthetic strategies to fabricate MNPs@QDs, including hetero-crystalline growth, template embedding, layer-by-layer assembly, microemulsion technique, and one-pot method, are described in detail, and their advantages and limitations are discussed. The recent advances of MNPs@QDs nanocomposites in detecting metal ions, foodborne pathogens, toxins, pesticides, antibiotics, and illegal additives are comprehensively introduced from the perspectives of modes and detection performances. The review ends with current challenges and opportunities in practical applications and prospects in food contaminants analysis, aiming to promote the enthusiasm for multifunctional sensing platform research.

Novel chitosan - graphene quantum dots composite for therapeutic delivery and tracking through enzymatic stimuli response

The designing of highly efficient and biocompatible nanocomposites with multifunctional delivery and tracking characteristics is noteworthy for clinical and therapeutic applications. Herein, we report the proof-of-concept for the delivery of anti-glaucoma drug, latanoprost (LP) under an enzymatic stimulus, lysozyme (Lyz) with novel chitosan (CS) - graphene quantum dots (GQD) nanocomposite via reverse switching photoluminescence (PL) phenomenon. The LP caged CS-GQDs nanocomposite was well characterized through extensive spectral, morphological, band-gap, particle size, and zeta potential studies along with cytotoxicity assays. The regaining of PL not only confirmed LP delivery, but also facilitated intercellular tracking through in vitro bio-imaging against human corneal epithelial (HCE) cells. The AO/EB staining and biocompatibility assays further proved excellent cell viability of >80%. The successfully delivered LP protected HCE cells from oxidative injury induced by 800 μM hydrogen peroxide (H2O2). These findings justify further utility of novel CS-GQDs caged drug nanocomposite for preclinical investigations.

Photoluminescence properties of silk–carbon quantum dots composites

In this paper, we report silk fibroin (SF) and carbon quantum dots (CQDs) nanocomposites obtained through a facile solution casting approach. The optical properties of the nanocomposites have been characterised by UV–vis absorption and photoluminescence spectroscopy. Crosslinking of SF and chemical interactions with the CQDs have been investigated by FTIR spectroscopy. In addition, water stability and degradability of the prepared composites have been investigated in terms of mass loss, important for applications in a real scenario. We observed that for a concentration of CQDs above 1%wt aggregation of nanoparticles occurs, affecting the photoluminescence of the material. The results show that the best composition in terms of photoluminescence intensity and water stability is 0.5%wt CQDs.Graphical abstract

Thermal and Optical Properties of Cdo-Pbo Quantum Dot Nanocomposites Prepared by a Novel Thermal Decomposition Technique

Thermal and Optical Properties of Cdo-Pbo Quantum Dot Nanocomposites Prepared by a Novel Thermal Decomposition Technique

A novel rapid synthesis of highly stable silver nanoparticle/carbon quantum dot nanocomposites derived from low-grade coal feedstock

Coal-based highly stable carbon quantum dot/silver nanocomposites.

Zno/Boron Nitride Quantum Dots Nanocomposites for the Enhanced Photocatalytic Degradation of Methylene Blue and Methyl Orange

Zno/Boron Nitride Quantum Dots Nanocomposites for the Enhanced Photocatalytic Degradation of Methylene Blue and Methyl Orange

Flexible Memristive Devices Based on Graphene Quantum-Dot Nanocomposites

Artificial neural networks (ANNs) are attracting attention for their high performance in various fields, because increasing the network size improves its functioning. Since large-scale neural networks are difficult to implement on custom hardware, a two-dimensional (2D) structure is applied to an ANN in the form of a crossbar. We demonstrate a synapse crossbar device from recent research by applying a memristive system to neuromorphic chips. The system is designed using two-dimensional structures, graphene quantum dots (GQDs) and graphene oxide (GO). Raman spectrum analysis results indicate a D-band of 1421 cm−1 that occurs in the disorder; band is expressed as an atomic characteristic of carbon in the sp2 hybridized structure. There is also a G-band of 1518 cm−1 that corresponds to the graphite structure. The G bands measured for RGO-GQDs present significant GQD edge-dependent shifts with position. To avoid an abruptly-formed conduction path, effect of barrier layer on graphene/ITO interface was investigated. We confirmed the variation in the nanostructure in the RGO-GQD layers by analyzing them using HR-TEM. After applying a negative bias to the electrode, a crystalline RGO-GQD region formed, which a conductive path. Especially, a synaptic array for a neuromorphic chip with GQDs applied was demonstrated using a crossbar array.

BNNT-ZnO QDs nanocomposites for improving piezoelectric nanogenerator and piezoelectric properties of boron nitride nanotube

Boron nitride nanotubes (BNNTs) are eco-friendly and lightweight materials with various physical, chemical, piezoelectric and mechanical properties. In particular, their exceptional properties can be exploited for piezoelectric applications. However, it remains a great challenge to improve the efficiency of the piezoelectric properties in the radial direction rather than the longitudinal direction. Thus, design with BNNT-inorganic composite materials is required including the outstanding inorganic piezoelectric materials to induce the improved performance of the piezoelectric properties. Here, we suggest the high-performance piezoelectric device as a nanogenerator based on BNNT-ZnO quantum dots (QDs) nanocomposites. The ZnO QDs were chemically synthesized on the surface of BNNTs by hydrothermal synthesis. As to the critical piezoelectric properties, we have investigated piezoelectric constants of BNNT-ZnO QDs nanocomposites and the difference in piezoelectric properties between out-of-plane and in-plane through conventional piezoelectric force microscopy (PFM) analysis. In addition, we confirmed the piezoelectric effect generated by applying a specific force to the single wire of BNNT-ZnO QDs nanocomposites in the radial direction using in-situ hybrid SEM-PFM technique. The effective piezoelectric coefficient (d33) of the single wire of BNNT-ZnO QDs in the radial direction and the piezoelectric charge coefficient of BNNT-ZnO QDs films were increased by 42.8% (0.340 pm/V) and 41.9% (−60.3 pC/N), respectively, compared to that of the single wire of BNNT and BNNT films. BNNT-ZnO QDs nanocomposites based transparent and flexible piezoelectric device showed excellent piezoelectric properties with a small amount of 0.18 wt%. The piezoelectric performance of nanogenerator with electrically poled BNNT-ZnO QDs nanocomposites was improved by more than 140% and 45%, respectively, compared to those of intrinsic BNNT-ZnO QDs nanocomposites and BNNT. Therefore, this study will pave a new path to the development of innovative materials and devices to generate recycled energy.

Amino-functionalized nitrogen-doped graphene quantum dots and silver-graphene based nanocomposites: Ultrafast charge transfer and a proof-of-concept study for bioimaging applications

Recent advances in nanotechnology have led to the use of graphene quantum dots (GQDs) for functional imaging and cancer therapy. Thanks to the physicochemical properties of graphene, GQDs have been functionalized and modified to improve their biological properties. In this study, polyethyleneimine functionalized nitrogen-doped graphene quantum dots (PEI N-doped GQDs) and silver nanoparticles/nitrogen-doped graphene quantum dots (AgNPs/PEI N-doped GQDs) nanocomposites have been developed. The PEI N-doped GQDs show a strong emission spectrum at maximum 446 nm with 356 nm excitation wavelength while AgNPs/PEI N-doped GQDs nanocomposites indicate weak fluorescence intensity at maximum 446 nm with 344 nm excitation wavelength. Based on the femtosecond transient absorption spectroscopy measurements, this emission quenching can be attributed that the excited state lifetime of PEI N-doped GQDs decreasing in the presence of AgNPs due to ultrafast electron transfer from PEI N-doped GQDs to AgNPs. It is also supported by theoretical results sensing ability of AgNPs/PEI N-doped GQDs nanocomposite is better than that of PEI N-doped GQDs. When lung adenocarcinoma cells (A549) were treated with GQDs, material-specific fluorescent signals were obtained from the cytoplasm of cells only treated with Ag/PEI N-doped GQDs, as compared with N-doped GQDs. Overall, this study shows that Ag/PEI N-doped GQDs are promising nanosystems for bioimaging applications.

Synthesis of Quinoline-3-carbonitriles on a Cobalt Ferrate–Graphene Quantum Dot Nanocomposite

Synthesis of Quinoline-3-carbonitriles on a Cobalt Ferrate–Graphene Quantum Dot Nanocomposite

Nanocomposite of SnO2 quantum dots and Au nanoparticles as a battery-like supercapacitor electrode material

Quantum dot-based nanocomposite materials have gained huge attention in electrochemical energy storage devices due to their extremely high surface-to-volume ratio and enhanced conductivity. In this work, nanocomposites of SnO2 quantum dots and Au nanoparticles (SQD-Au) has been prepared by an in-situ soft-chemical approach. The structural and charge storage properties of the prepared material were investigated. The prepared composite material coated on the nickel foam and used as working electrode for supercapacitor applications. Results show that the SQD-Au electrode material exhibits an excellent specific capacity of 87 mAh g−1 at the current density of 1A g−1. The columbic efficiency of the electrode was found be 98 % after 5000 GCD cycles. Some of the factors responsible for the observed superior charge storage properties of SQD-Au composite compared pristine SQDs are enhanced conductivity and fast electron transport.

Development of an Efficient Immunosensing Platform by Exploring Single-Walled Carbon Nanohorns (SWCNHs) and Nitrogen Doped Graphene Quantum Dot (N-GQD) Nanocomposite for Early Detection of Cancer Biomarker.

In this work, a novel electrochemical immunosensor based on nitrogen doped graphene quantum dot (N-GQD) and single-walled carbon nanohorns (SWCNHs) was developed for the detection of α-fetoprotein (AFP), a cancer biomarker. Thus, to fabricate the platform of the immunosensor, nanocomposite architecture was developed by decorating N-GQD on the surface of the SWCNHs. The resulting hybrid architecture (N-GQD@SWCNHs) functioned as an exceptional base for the immobilization of antibody (Anti-AFP) through carbodiimide reaction with good stability and bioactivity. The immunosensor was prepared by evenly distributing the bioconjugates (N-GQD@SWCNHs/Anti-AFP) dispersion on the surface of the glassy carbon electrode, and subsequently blocking the remaining active sites by bovine serum albumin to prevent the nonspecific adsorption. Cyclic voltammetry and electrochemical impedance spectroscopy technique was employed to investigate the assembly process of the immunosensor. Under optimal conditions, the immunosensor exhibited a broad dynamic range in between 0.001 ng/mL to 200 ng/mL and a low detection limit of 0.25 pg/mL. Furthermore, the sensor showed high selectivity, desirable stability, and reproducibility. Measurements of AFP in human serum gave outstanding recovery within 99.2% and 102.1%. Thus, this investigation and the amplification strategy exhibited a potential role of the developed nanocomposite based sensor for early clinical screening of cancer biomarkers.