Dot Nanocomposites Research Articles

A label-free RTP sensor based on aptamer/quantum dot nanocomposites for cytochrome c detection.

Given the outstanding room-temperature phosphorescence (RTP) of Mn–ZnS quantum dots (QDs) and the specific recognition performance of the aptamer, we built phosphorescent composites from aptamers conjugated with polyethyleneimine quantum dots (PEI-QDs) and applied them to cytochrome c (Cyt c) detection. Specifically, QDs/CBA composites were generated from the electrostatic interaction between the positively-charged PEI-QDs and the negatively-charged Cyt c binding aptamer (CBA). With the presence of Cyt c, the Cyt c can specifically bind with the QDs/CBA composites, and quench the RTP of QDs through photoinduced electron-transfer (PIET). Thereby, an optical biosensor for Cyt c detection was built, which had a detection range of 0.166–9.96 μM and a detection limit of 0.084 μM. This aptamer-mediated phosphorescent sensor with high specificity and operational simplicity can effectively avoid the interference of scattering light from complex substrates. Our findings offer a new clue for building biosensors based on QDs and aptamers.

Direct laser writing of flexible planar supercapacitors based on GO and black phosphorus quantum dot nanocomposites.

The research interest in wearable electronics has continuously stimulated the development of flexible energy storage systems with high performance and robustness. However, open problems with respect to energy storage efficiency and device integration are still challenging. Here, we demonstrate the laser fabrication of flexible planar supercapacitors based on graphene oxide (GO) and black phosphorus quantum dot (BPQD) nanocomposites. By combining graphene and BPQDs, the resultant supercapacitors feature high conductivity and activity, demonstrating enhanced specific capacity and superior rate performance, compared to those based on reduced GO (RGO) alone. Furthermore, the as-obtained devices present outstanding flexibility. Their performance shows unobvious degradation after repeated cycles of bending and straightening. Additionally, with the help of direct laser writing (DLW) technology, integration of the supercapacitors has been achieved without the need for any metal interconnection. The integrated devices delivered reasonable performance uniformity with a voltage extension of 3 V, which could easily power a LED. The supercapacitor-based RGO and BPQD nanocomposites demonstrate great potential for practical applications in flexible and wearable electronics.

A ratiometric fluorometric epinephrine and norepinephrine assay based on carbon dot and CdTe quantum dots nanocomposites

A ratiometric fluorescence nanoprobe, consisted of water-soluble fluorescent carbon dots (CDs) and 3‑mercapropionic acid-coated cadmium telluride quantum dots (CdTe QDs), was constructed for the detection of epinephrine (EP) and norepinephrine (NE). Under single-wavelength excitation (370 nm), the hybrid nanoprobe possessed dual emission peaks at 460 and 610 nm belongs to CDs and CdTe QDs, respectively. CdTe QDs fluorescence was quenched by EP or NE via electron transfer from QDs to the oxidation products of catecholamines, while the fluorescence intensity of CDs remained almost constant, which provided a ratiometric fluorescence assay for the catecholamines detection. The relative fluorescence intensity ratios were directly proportional to the concentration of catecholamines. Meanwhile, some structural analogues of the target molecules, including dopamine hydrochloride and isoprenaline hydrochloride, had no significant interference for the detection mode. The novel fluorescence detection platform was rapid and convenient, and applied to the detection of EP and NE in human serum samples with satisfactory results.

Rheological behavior of polypropylene/carbon quantum dot nanocomposites: the effects of particles size, particles/matrix interface adhesion, and particles loading

The effects of nanoparticles size, nanoparticles/matrix interface adhesion, and nanoparticles loading on the rheological properties of polypropylene (PP)/carbon quantum dot (CQD) nanocomposites were investigated. The storage modulus of the samples was found to be raised with an increase in the volume fraction of CQDs up to 1 wt%. The addition of the compatibilizer had no significant effect on the storage and loss modulus of the samples; however, it resulted in the reduction in the viscosity at the lower frequencies. With increasing the CQDs size, the rise in the loss modulus was found to be greater than that of the storage modulus. The damping factor of the samples was lower for the smaller size nanoparticles at the lower frequencies. Also, the size of the nanoparticles had no significant effect on the complex viscosity of the samples. The storage modulus obtained from the Cohan model deviated the most from the experimental results for the samples containing various loadings of CQDs.

MWCNTs/Ionic Liquid/Graphene Quantum Dots Nanocomposite Coated with Nickel‐Cobalt Bimetallic Catalyst as a Highly Selective Non‐enzymatic Sensor for Determination of Glucose

AbstractIn this work, a glassy carbon electrode (GCE) was modified with multiwall carbon nanotubes/ionic liquid/graphene quantum dots (MWCNTs/IL/GQDs) nanocomposite. Then, the nanocomposite was decorated with nickel‐cobalt nanoparticles (Ni−Co NPs), and it was used as a non‐enzymatic glucose sensor. Field emission scanning electron microscopy, X‐ray diffraction spectroscopy, and energy dispersive spectroscopy were employed to prove the electrodeposition of the Ni−Co NPs on the surface of MWCNTs/IL/GQDs/GCE. Also, cyclic voltammetric and amperometric methods were utilized for the investigation of the electrochemical behaviour of the Ni−Co NPs/MWCNTs/IL/GQDs/GCE for glucose oxidation. The novel amperometric sensor displayed two linear ranges from 1.0 to 190.0 μmol L−1 and 190.0 to 4910 μmol L−1 with a low detection limit of 0.3 μmol L−1 as well as fast response time (2 s) and high stability. Also, the sensor showed good selectivity for glucose determination in the presence of ascorbic acid, citric acid, dopamine, uric acid, fructose, and sucrose, as potential interference species. Finally, the performance of the proposed sensor was investigated for the glucose determination in real samples. Ni−Co NPs/MWCNTs/IL/GQDs/GCE showed good sensitivity and excellent selectivity.

One-Pot Magnetic Iron Oxide-Carbon Nanodot Composite-Catalyzed Cyclooxidative Aqueous Tandem Synthesis of Quinazolinones in the Presence of tert-Butyl Hydroperoxide.

The development of synthetic protocols for biologically important molecules using biocompatible catalysts in aqueous medium holds the key in green and sustainable chemistry. Herein, a magnetically recoverable iron oxide–carbon dot nanocomposite has been demonstrated as an effective catalyst for cyclooxidative tandem synthesis of quinazolinones in aqueous medium using alcohols as starting materials. Fluorescent carbon dots, the newest entrant in the nanocarbon family, were used as the stabilizing agent for the iron oxide nanoparticles, and a continuous layer of carbon dots decorates the iron oxide nanoparticle surface as observed by transmission electron microscopy. The fluorescence studies demonstrated the effective electron transfer from carbon dots to the iron oxide nanoparticles resulting in complete quenching of emission owing to carbon dots, once it binds with iron oxide nanoparticles. The nanocatalyst showed high activity with significant reusability for the syntheses of quinazolinones in the presence of tert-butyl hydroperoxide (TBHP) in an aqueous medium. Controlled experiments revealed the synergistic effect of carbon dots in enhancing the catalytic activity of iron oxide, as they might influence the decomposition of TBHP into radicals owing to their peroxidase activity. These radicals stabilized over the nanoparticle surface are known to have increased lifetime compared to solution-based radicals. These surface-stabilized radicals then could catalyze the tandem reaction resulting in the formation of the quinazolinone derivatives in high yields.

MiR-122 and hepatocellular carcinoma: from molecular biology to therapeutics.

miR-122 and hepatocellular carcinoma: from molecular biology to therapeutics.

Reduced graphene oxide/polymer dots-based flexible symmetric supercapacitors delivering an output potential of 1.7 V with electrochemical charge injection

Electrochemical charge injection (ECI) is proved a powerful technique to maximize the available widen potential range of aqueous electrolyte. In this report, reduced graphene oxide/polymer dots (rGO/PDs) nanocomposites are prepared and tested as electrode materials for flexible supercapacitors. The weight ratio of GO/PDs plays an important role in the electrochemical performance of rGO/PDs nanocomposites. Through the ECI technique, a 1.7-V output potential can be delivered by rGO/PDs-based flexible supercapacitors operating with 1 mol L−1 Na2SO4 aqueous electrolyte. A specific energy of 7.1 W h kg−1 with corresponding specific power of 85 W kg−1 can be achieved for a typical flexible supercapacitor, which exhibits a capacitance retention of 90.6% after 5000 cycles at 0.5 A g−1.

Construction of crosslinked chitosan/nitrogen-doped graphene quantum dot nanocomposite for hydroxyapatite biomimetic mineralization

Crosslinked Chitosan/nitrogen doped-graphene quantum dot nanocomposites (CCS/NGQD NC) with 10 wt% of glutaraldehyd as crosslinker were fabricated under ultrasonic cavitation. Structure and physicochemical properties of the prepared nanocomposites (NC) were systematically characterized by a number of techniques. The swelling capacity of the crosslinked films in the simulated intestinal (pH 7.4) media was evaluated. However, rate of water ingress of specimens was nearly same, but, the CCS/NGQD NC 8 wt% showed the more water absorption ability than the CCS. Bioactivity of the CCS and CCS/NGQD NCs were evaluated by studying their ability to form of apatite on their surface after soaking in a simulated body fluid (SBF) for 30 days. In images of field emission scan electron microscopy, small island-like agglomerated apatite deposited on the sample surface. Also, the pH fluctuation displayed that the hydroxyapatite was formed on the surface of the samples after one month of immersion in SBF. The finding showed that the CCS/NGQD NCs immersed into SBF had a better apatite-forming bioactivity compared with the CCS, which may be due to the high surface area, adequate function groups and appropriate swelling of the NCs. Such improved behaviors of CCS/NGQD NCs may have potential use in the bone tissue engineering.

Highly-stable write-once-read-many-times switching behaviors of 1D\u20131R memristive devices based on graphene quantum dot nanocomposites

One diode and one resistor (1D–1R) memristive devices based on inorganic Schottky diodes and poly(methylsilsesquioxane) (PMSSQ):graphene quantum dot (GQD) hybrid nanocomposites were fabricated to achieve stable memory characteristics. Current-voltage (I-V) curves for the Al/PMSSQ:GQDs/Al/p-Si/Al devices at room temperature exhibited write-once, read-many-times memory (WORM) characteristics with an ON/OFF ratio of as large as 104 resulting from the formation of a 1D–1R structure. I-V characteristics of the WORM 1D–1R device demonstrated that the memory and the diode behaviors of the 1D–1R device functioned simultaneously. The retention time of the WORM 1D–1R devices could be maintained at a value larger than 104 s under ambient conditions. The operating mechanisms of the devices were analyzed on the basis of the I–V results and with the aid of the energy band diagram.

Effect of porous modification on the synthesis and photocatalytic activity of graphitic carbon nitride/carbon quantum dot nanocomposite

Metal-free graphitic carbon nitride (g-C3N4) and carbon quantum dots (CQDs) have a promising attention as to their superior photocatalytic activities and physicochemical properties. In the article, g-C3N4 and CQDs were connected effectively through porous modification of g-C3N4 by directly heating melamine hydrochlorid, which benefits to the enhancement of the composites’ photocatalytic activity. The structures and morphologies of the photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectrum and photoluminescence spectroscopy. Meanwhile, the porous g-C3N4 and CQDs composite (pg-C3N4/CQDs) exhibited the improved photocatalytic activity for the degradation of RhB under visible light irradiation, which may be contributed three reasons: (1) pg-C3N4 has much higher surface area (~ 20 times) and more stronger photocatalytic oxidation capacity than that of g-C3N4; (2) as the electron-sinks, CQDs can improve the photogenerated electron–hole pair’s separation; (3) CQDs can upconvert the light with wavelengths longer than 650 nm into the shorter wavelengths to increase light harvesting, while pg-C3N4 utilizes the light to degrade pollutants. In addition, the possible photocatalytic degraded mechanism was investigated in detail. This work will be useful for designing other CQDs-based photocatalysts and providing a promising approach to environmental purification.

The acetone sensing properties of ZnFe2O4-graphene quantum dots (GQDs) nanocomposites at room temperature

ZnFe2O4/graphene quantum dots (GQDs) nanocomposites were prepared via hydrothermal method. The as-prepared nanocomposites were characterized by XRD, SEM, TEM, HRTEM, TG, FTIR, Raman, XPS and N2 adsorption-desorption, respectively. The effect of GQDs content on the gas-sensing responses and the gas-sensing selectivity of the ZnFe2O4/GQDs nanocomposites was investigated. It was found that the sensor based on ZnFe2O4/GQDs nanocomposite (S-15) exhibited good response and good selectivity to acetone vapor at room temperature, the responses of the sensor based on ZnFe2O4/GQDs nanocomposite (S-15) to 1000 ppm acetone and 5 ppm acetone reached 13.3 and 1.2, respectively; the response times and the recovery times for 1000-5 ppm acetone were all shorter than 12 s. The ZnFe2O4/GQDs nanocomposite (S-15) will be a potential acetone sensing materials if its long-term gas sensing stability is improved.

Use of a smartphone for visual detection of melamine in milk based on Au@Carbon quantum dots nanocomposites

Gold nanoparticles@Carbon quantum dots nanocomposites (Au@CQDs) were designed for analyzing melamine in milk visually. Fluorescent emission of Au@CQDs enhanced with the increase of melamine concentration. A calibration curve (R2 = 0.9856) and fluorescence standard array were established for detection of melamine in the range of 1 μM–10 μM. Limit of quantification and limit of detection were 12 nM and 3.6 nM, respectively. The approximate concentration of melamine adulterated in milk samples were detected visually by the fluorescence standard array and smartphone. The accurate concentration was obtained by the calibration curve and portable fluorescence spectrometer with recoveries of 105.64%–102.75% and less than 2% of coefficient of variation (CV) (n = 18). This performance was consistent with that of the high-performance liquid chromatography (HPLC) method (recoveries of 105.56%–107.95% with 2.24%–3.56% of CVs). The Au@CQDs-based fluorescent method for visual and accurate detection of melamine in milk was presented and showed strong application potential.

CNT–CdSe QDs nanocomposites: synthesis and photoluminescence studies

In this study, synthesis of carbon nanotube (CNT)–CdSe Quantum dots (QDs) nanocomposites has been investigated. CdSe QDs were synthesized via hydrothermal process. The chemical tendency of CNT and QDS was increased by precipitation after surface functionalization of CNTs (by carboxylated groups) and CdSe QDs (by silane groups), separately. The structure of nanocomposites was amorphous with a little amount of nanocrystalline cubic CdSe. The Fourier-transform infrared (FTIR) spectra and Raman spectrum revealed the strong chemical tendency of linkage between CNTs and QDs after functionalization on the surface of them. The morphology of nanocomposites depended on the QDs concentration and changed from aggregates of CNTs to the marvelous decoration of quantum dots on the ropes of CNTs. Transmission electron microscope (TEM) and atomic force microscope (AFM) images confirmed the adorable coatings of CNTs with CdSe QDs. The nanocomposites emitted in blue–green region with a maximum peak at 490 nm under the exposure of Ultraviolet (UV) light. Below 50 wt% QDs, the emission was quenched completely.

Screening and identification of ligand-protein interactions using functionalized heat shock protein 90-fluorescent mesoporous silica-indium phosphide/zinc sulfide quantum dot nanocomposites

Currently, nanosphere-based ligand fishing cannot be accomplished with imaging processing, although this step is important for real-time identification. Herein, a ligand fishing technique combined with real-time imaging is presented for the identification of ligands for heat shock protein 90α (Hsp 90α) from a complex matrix, Alisma plantago-aquatica Linn. crude extract, using Hsp 90α-functionalized mesoporous silica nanoparticle (MSN)-InP/ZnS quantum dot (QD) nanocomposites as a support material. Twenty ligands for Hsp 90α were screened, and their structures were identified by mass spectrometry. The activities of the ligands were verified by real-time imaging of cells apoptotic morphological changes. Quantitative analysis showed that Alisma plantago-aquatica Linn contained 8.19μg/g Alisol F, which regarded as one typical component of Alisma plantago-aquatica Linn, and the extraction ratio of Alisol F was 76.2%. The precision for five replicate measurements was 7.0% (RSD). The prepared nanocomposites were also used to screen proteins from a mixture of cellular extracts, and five proteins from HeLa cells were identified as potential client proteins of Hsp 90α.

One-Step Synthesis of Size-Tunable Gold@Sulfur-Doped Graphene Quantum Dot Nanocomposites for Highly Selective and Sensitive Detection of Nanomolar 4-Nitrophenol in Aqueous Solutions with Complex Matrix

In this study, a simple one-step synthesis procedure for the fabrication of a gold nanoparticle (Au NP)@sulfur-doped graphene quantum dot (Au@S-GQD) with tunable size was developed for the sensitive and selective detection of 4-nitrophenol in water and wastewater with a complex matrix. The particle size of two to six layered S-GQD is in the range of 1–7 nm with a mean diameter of 4.0 ± 0.5 nm. The S-GQD serves as a reducing agent for both Au ions and 4-nitrophenol reduction to generate Au@S-GQD nanocomposites as well as to produce the absorption signal of 4-aminophenol at 307 nm. The particle size of Au@S-GQD is tunable by simply adjusting the Au precursor concentration, and the mean diameter increases from 5 to 25 nm when the Au precursor concentration increases from 50 to 200 μM. Moreover, the Au@S-GQD nanocomposite exhibits good UV–visible absorption properties, and the change of wavelength ratio between 307 and the SPR peak of Au at 530 nm (A307/A530) is used to detect nanomolar levels of 4-nitropheno...

Multifunctional chitosan-magnetic graphene quantum dot nanocomposites for the release of therapeutics from detachable and non-detachable biodegradable microneedle arrays.

Biodegradable chitosan-magnetic graphene quantum dot (MGQD) nanocomposites were prepared and investigated for the release of small and large molecular weight (MWt) therapeutics from detachable and non-detachable biodegradable microneedle arrays. The presence of MGQDs in chitosan increased the electrical conductivity and biodegradation rate of chitosan while maintaining its mechanical properties. The detachable microneedle arrays were created by including a water-soluble ring of poly(ethylene glycol) (PEG) at the base of the microneedle, which enabled the rapid detachment of the microneedle shaft from the base. The PEG ring did not impede the microneedle array performance, with mechanical properties and a drug release profile of low MWt lidocaine hydrochloride similar to microneedle arrays without the ring. Without the PEG ring, the chitosan-MGQD microneedles were electrically conductive and allowed for electrically stimulated release of large MWt therapeutics which was challenging without the stimulation. These results demonstrate that chitosan nanocomposites containing MGQDs with intrinsic photoluminescent and supermagnetic properties are promising materials for developing multifunctional microneedles for targeted and tracked transdermal drug delivery.

Smart self-tightening surgical suture from a tough bio-based hyperbranched polyurethane/reduced carbon dot nanocomposite

Design and fabrication of a smart bio-based polymeric material with potent biocompatibility and high performance still remain a challenge in the biomedical realm. In this context, a potential smart suture was fabricated from starch modified hyperbranched polyurethane (HPU) nanocomposites with different weight percentages of reduced carbon dots for the first time. The desired mechanical (tensile strength: 32.14 MPa, elongation at break: 1576% and toughness 439.28 MJ m−3) and thermal (286 °C) attributes of the suture were achieved with 2 wt% of reduced carbon dots in an HPU matrix. The non-contact self-tightening behavior was observed just within 15 s at body temperature of 37 °C ± 1 °C with notable shape fixity (99.6%) and shape recovery (99.7%) effects. The nanocomposites displayed in vitro biodegradability and hemocompatibility. Low lactate dehydrogenase activity and minimal red blood cell lysis indicated the anti-thrombogenicity and anti-hemolytic properties of the nanocomposites. The suitability of the fabricated nanocomposites as a smart biomaterial was supported by the inherent biocompatibility as observed by the growth and proliferation of smooth muscle cells and endothelial cells. Furthermore, they exhibited minimal immunogenic response (TNF α release). Thus, the study paves the way to biodegradable HPU nanocomposites as advanced non-contact triggered rapid self-tightening surgical sutures for biomedical applications.

A novel electrochemiluminescence resonance energy transfer system of luminol-graphene quantum dot composite and its application in H2O2 detection

Luminol-nitrogen doped graphene quantum dot (luminol-NGQDs) nanocomposite was synthesized and a novel electrochemiluminescence resonance energy transfer (ECL-RET) process occurred between luminol as the donor and NGQDs as the acceptor in the composite. This ECL-RET effect helped luminol-NGQDs composite produced an anodic ECL signal without coreactants. The ECL-RET mechanism was also studied based on the fluorescence spectra, the ultraviolet–visible absorption spectra and the electrochemiluminescence (ECL) spectra. Based on the significant sensitization effect of hydrogen peroxide on luminol-NGQDs ECL signal, an ECL method for the sensitive determination of hydrogen peroxide was established and then applied to the detection of hydrogen peroxide in water samples.

Polymer solar cells with reduced graphene oxide–germanium quantum dots nanocomposite in the hole transport layer

Reduced graphene oxide–germanium quantum dots (rGO–Ge QDs) nanocomposite has been successfully employed in modifying poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL) in the preparation of a P3HT:PCBM-based polymer solar cell (PSC). The effect of the surface morphology and the optical transmittance of the PEDOT:PSS/rGO–Ge QDs HTL on the devices’ photovoltaic performance is examined. A significant improvement of up to 50% in the power conversion efficiency is achieved by the incorporation of the composite in the HTL. The modified HTL devices exhibited higher short-circuit current density values which resulted from better transportation and collection of photo-generated charge carriers. The synergistic effect of the high electrical conductivity of the composites and the formation of good ohmic contact at the interface between the anode and the active layer not only facilitates charge carrier transport but also impairs their recombination to yield better photovoltaic performance.