Dot Nanohybrid Research Articles

Microplasma-Enabled Graphene Quantum Dot-Wrapped Gold Nanoparticles with Synergistic Enhancement for Broad Band Photodetection.

Plasmonic nanostructure/semiconductor nanohybrids offer many opportunities for emerging electronic and optoelectronic device applications because of their unique geometries in the nanometer scale and material properties. However, the development of a simple and scalable synthesis of plasmonic nanostructure/semiconductor nanohybrids is still lacking. Here, we report a direct synthesis of colloidal gold nanoparticle/graphene quantum dot (Au@GQD) nanohybrids under ambient conditions using microplasmas and their application as photoabsorbers for broad band photodetectors (PDs). Due to the unique AuNP core and graphene shell nanostructures in the synthesized Au@GQD nanohybrids, the plasmonic absorption of the AuNP core extends the usable spectral range of the photodetectors. It is demonstrated that the Au@GQD-based visible light photodetector simultaneously possesses an extraordinary photoresponsivity of ∼103 A/W, ultrahigh detectivity of 1013 Jones, and fast response time in the millisecond scale (65 ms rise time and 53 ms fall time). We suggest that the synergistic effect can be attributed to the strong fluorescence quenching in Au@GQD coupled with the two-dimensional graphene layer in the device. This work provides knowledge of tailoring the optical absorption in GQDs with plasmonic AuNPs and the corresponding photophysics for broad band response in PD-related devices.

A sensitive and stable visible-light-driven photoelectrochemical aptasensor for determination of oxytetracycline in tomato samples

Sensitive detection of oxytetracycline (OTC) has attracted increasing attention worldwide due to the relationship between food safety and human health problems. In this work, a visible-light-driven photoelectrochemical (PEC) OTC aptasensor was constructed using Bi4VO8Cl/nitrogen-doped graphene quantum dots (Bi4VO8Cl/N-GQDs) nanohybrids as photoactive material and OTC aptamer as identification element. Owing to the well matched heterojunction of Bi4VO8Cl and nitrogen-doped graphene quantum dots (N-GQDs), the photogenerated electron-hole pairs could be separated effectively, so that the photocurrent intensity of as-prepared Bi4VO8Cl/N-GQDs nanohybrids was about 7 times higher than pure Bi4VO8Cl and had higher stability. The constructed “signal-off” PEC aptasensor realized OTC detection in tomato samples with excellent sensitivity, specificity and repeatability. The photocurrent decreased with the increase of OTC concentration in a range from 0.1 nM to 150 nM, and the detection limit was 0.03 nM (S/N = 3). The national standard method was used to compare with our method and the results were consistent.

Hybrid of quantum dots for interfacial tension reduction and reservoir alteration wettability for enhanced oil recovery (EOR)

Nanoparticle stabilized emulsions in enhanced oil recovery are more attractive and practical than conventional emulsions which stabilized by colloidal particles and different surfactants due to their advantages and special characteristics such as high stability in harsh condition, move long distance in reservoirs without high retention due to small size of nanoparticles. Only one third of original oil in place (OIP) is usually produced and two third of oil in place will be trapped to reservoir rockthus suitable chemical enhanced oil recovery (C-EOR) methods should be used. In this research, we have suggested a novel, economical and commercial method for synthesis N-doped graphene quantum dots (N-GQDs)/MoS2 quantum dots (MQDs) nanohybrids for preparing different percentage of Nanoemulsions which can reduce alterfacial tension significantly so it can used for Enhanced Oil Recovery (EOR) application. MoO3 material was used as a base of MQDs. MQDs was synthesized via exfoliation of MoS2 nanoparticles by Butyl lithium under N2 atmosphere condition. N-GQDs were synthesized by citric acid and urea materials via hydrothermal method. GQDs/MQDs were prepared via a simple sol-gel method for 5 h string. Synthetic materials were characterized with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV–visible absorption, Scanning Microscopic Electron (SEM), EDX profile and mapping, Transmission electron microscopy (TEM), High Resolution Transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). Then, emulsions were prepared with two different cationic and anionic surfactants and the stability and morphology of emulsion droplets were investigated in condition close to reservoir environment. Our results show that 10% GQDs/MQDs in cationic surfactant and 50% GQDs/MQDs in anionic surfactant have good stability and very small and fine emulsion droplets in simulated reservoir conditions in laboratory. The Interfacial Tension (IFT) measurement shows >70% improvement which indicates the high ability of these nanohybrids in reducing the surface tension than previous nanohybrids. Contact angle values show that these nanohybrids can alter the wettability of reservoir rock from oil-wet to water-wet so the trapped oil in the porous region of rock can be easily extracted in the presence of a layer of these nanohybrids. Furthermore, according to the results of altering the density and viscosity of nanohybrids, these are not as limiting parameters and only about 1% increasing observed for density and viscosity, respectively. Coreflooding test revealed the high oil recovery efficiency (22%) at very low nanofluid concentration (0.01 wt%).

Transport Properties of a Molybdenum Disulfide and Carbon Dot Nanohybrid Transistor and Its Applications as a Hg2+ Aptasensor

Unique electronic, optical, and mechanical properties of molybdenum disulfide (MoS2) hold great potential and can be harnessed as a key component in novel applications in electronics, optoelectroni...

Controllable and robust dual-emissive quantum dot nanohybrids as inner filter-based ratiometric probes for visualizable melamine detection.

The ratiometric fluorescence technique is of great interest due to its visualization characteristics. The construction of a reliable fluorescent ratiometric nanoprobe for high-sensitivity visual quantification is highly sought after but it is limited by poor stability and controllability. Herein, we report a robust dual-emissive quantum dot nanohybrid with precise color tunability and demonstrate its potential as a two-signal-change ratiometric probe for visual detection. A novel assembly strategy was developed for spatially implanting hydrophobic green and red quantum dots (QDs) into a silica scaffold to form a dual-emissive hierarchical fluorescent silica nanohybrid. The fluorescence intensity ratio and color of the nanohybrid were precisely tailored by altering the amounts of green and red QDs. Particularly, after the alkylsilane-mediated phase transfer and exterior silica shell growth, the nanohybrid exhibited the well-preserved fluorescence features of the original QDs and robust optical/colloid stability. An inner filter-based ratiometric nanoprobe for the visual determination of melamine was ultimately devised by combining the spectra-overlapped two-colored fluorescent nanohybrid with analyte-specific gold nanoparticles. Furthermore, based on the reversible fluorescence signal changes in two-colored QDs induced by melamine, a logic gate strategy for melamine monitoring was constructed. The newly developed fluorescent ratiometric nanoprobe shows great prospects for the visual and quantitative determination of analytes in a complex biological matrix.

Environmentally Benign Hydrophobic Hyperbranched Waterborne Polyester/SiO2–Carbon Dot Nanocomposite as an Efficient Photocatalyst and White-Light Emitter

In this study, a SiO2@carbon dot (CD) nanohybrid was prepared by a hydrothermal method and incorporated into waterborne polyester matrix through an in situ process to develop the polyester nanocomp...

Cellulose nanofiber-polyaniline nanofiber-carbon dot nanohybrid and its nanocomposite with sorbitol based hyperbranched epoxy: Physical, thermal, biological and sensing properties

The increase of blood sugar level in the human body causes severe health issues. Several electrochemical and optical sensing methods were developed in this regard. However, the use of low cost, efficient chemosensors are mostly preferred for practical applications. In this context, a fluorescent nanohybrid of cellulose nanofiber (CNF) modified carbon dot (CD)-polyaniline nanofiber using a facile in-situ polymerization method was reported herein. The nanohybrid exhibited good sensing ability of glucose with concentration as low as 8 μM in 0.1 M phosphate buffer solution. Further, this nanohybrid was incorporated in different weight percentages in the bio-based hyperbranched epoxy consisting of sorbitol and monoglyceride of castor oil as bio-based components, in addition to the conventional reactants. The formation of the nanocomposites was verified using spectroscopic, microscopic and diffraction techniques. The thermosetting nanocomposites showed good mechanical properties, such as tensile strength (39 MPa), elongation at break (82%), scratch resistance (>10 kg) and impact resistance (16.5 kJ/m) and good thermal stability. The nanocomposites displayed good hematocompatibility with mammalian blood in accordance with anti-hemolytic studies. The nanocomposites exhibited better biodegradability compared to the pristine epoxy due to the presence of CNF and CD which accelerated the degradation process.

Nanocomposite of waterborne hyperbranched polyester and clay@carbon dot as a robust photocatalyst for environmental remediation

In this study, eco-friendly high performing waterborne hyperbranched polyester nanocomposites with different doses of clay@carbon dot nanohybrid were fabricated for the first time through an in situ polymerization technique in absence of any solvent and compatibilizing agent. X-ray diffractometeric (XRD), Fourier transform infrared spectroscopic (FTIR) and transmission electron microscopic (TEM) analyses support the formation of nanocomposite. XRD confirmed the absence of d001 reflections of bentonite clay while TEM study revealed the partial exfoliation of the layers by the polyester chains. The thermoset of this nanocomposite with hyperbranched epoxy of glycerol and poly(amido amine) showed an appreciable improvement in tensile strength (7.8–35.7 MPa), scratch hardness (4–>10 kg), impact resistance (>8.3–>10 kJ/m), Young's modulus (245–340 MPa), toughness (17.18–49.89 MJ/m3) and thermal stability (by 32 °C) compared to the pristine system. The nanocomposite also exhibited a high adsorption capacity (90.9 mg/g) of Pb(II) ions. Further, the nanocomposite was also used as a visible light active photocatalyst for removal of organic dye like Rodamine B. In addition, the nanocomposite exhibited biodegradability behavior against Pseudomonus aerugionosa bacterial strain. Thus, the nanocomposite is an exceptionally promising candidate as an environmentally friendly, low-cost and effectual adsorbent for the elimination of contaminants from the atmosphere.

PH-Responsive Degradable Dextran-Quantum Dot Nanohybrids for Enhanced Gene Delivery.

It is of great significance to develop biocompatible and degradable gene carriers with stimuli-enhanced gene therapy and imaging function. In this work, low-cytotoxic polycation PGEA (ethanolamine-functionalized poly(glycidyl methacrylate))-functionalized dextran-quantum dot (QD) nanohybrids (DQ-PGEA) were proposed as safe and efficient gene carriers via a facile and feasible method. The highly water-soluble dextran gives the carrier good stability, biocompatibility, and abundant modification sites, while QDs allow fluorescence (FL) imaging. Taking advantage of the pH-responsive self-destruction characteristic introduced by Schiff base linkages, DQ-PGEA nanohybrids could not only result in enhanced gene release but also contribute to the elimination of the carriers. Reduced (nondegradable) DQ-PGEA-R nanohybrids were also synthesized as counterparts to reveal the superiority of the responsive DQ-PGEA carriers. The effectiveness of the as-prepared gene delivery systems was verified adopting the antioncogene p53 in the mouse model of breast cancer. As expected, DQ-PGEA nanohybrids demonstrated a superior gene transfection performance and antitumor inhibition compared with their counterparts. Meanwhile, the gene delivery processes could be tracked in real time to visualize the therapeutic processes and realize FL imaging-guided gene therapy. The current multifunctional stimuli-responsive nanoplatforms with the self-destruction feature are intriguing candidates to achieve enhanced gene therapy for tumor treatment.

Quantum Dot Based Fluorescent Traffic Light Nanoprobe for Specific Imaging of Avidin-Type Biotin Receptor and Differentiation of Cancer Cells.

Sensitive and specific visualization of cell surface biotin receptors (BRs) a class of clinically important biomarkers, remains a challenge. In this work, a dual-emission ratiometric fluorescent nanoprobe is developed for specific imaging of cell surface avidin, a subtype of BRs. The nanoprobe comprises a dual-emission quantum dot nanohybrid, wherein a silica-encapsulated red-emitting QD (rQD@SiO2) is used as the "core" and green-emitting QDs (gQDs) are used as "satellites", which are further decorated with a new "love-hate"-type BR ligand, a phenanthroline-biotin conjugate with an amino linker. The nanoprobe shows intense rQD emission but quenched gQD emission by the BR ligand. Upon imaging, the rQD emission stays constant and the gQD emission is restored as cell surface avidin accrues. Accordingly, the overlaid fluorescence color collected from red and green emission changes from red to yellow and then to green. We refer to such a color change as a traffic light pattern and the nanoprobe as a fluorescent traffic light nanoprobe. We demonstrate the application of our fluorescent traffic light nanoprobe to characterize cancer cells. By the traffic light pattern, cervical carcinoma and normal cells, as well as different-type cancer cells including BR-negative colon cancer cells, BR-positive hepatoma carcinoma cells, breast cancer cells, and their subtypes, have been visually differentiated. We further demonstrate a use of our nanoprobe to distinguish the G2 phase from other stages in a cell cycle. These applications provide new insights into visualizing cell surface biomarkers with remarkable imaging resolution and accuracy.

Ratiometric fluorescent sensing of Pb2+ and Hg2+ with two types of carbon dot nanohybrids synthesized from the same biomass

This work initially describes two ratiometric fluorescent nanosensors that use dual- and three-emission carbon dot (CD) nanohybrids for highly sensitive detection of sub-nanomolar Pb2+ and Hg2+, respectively. The two new types of CD hybrids are prepared via solvothermal treatment of the same extracts of bamboo leaves. This strategy is facile, cost-effective, environmentally-friendly and useful, as it avoids the post-modification of CDs or their mixing with other fluorescent probes which are typically adopted in most of CD-based ratiometric nanosensors previously reported. More importantly, the utilities of the two new nanosensors that enable built-in correction of external effects are well demonstrated by achieving detection limits as low as ˜0.14 and 0.22 nM (3σ) for Pb2+ and Hg2+, respectively. This makes them be among the most sensitive systems currently available for sensing the two analyte ions. The satisfactory recovery results of analyzing a series of real river water examples additionally validate their feasibilities for practical applications. To the best of our knowledge, this may be the first report of applying the same natural biomass as raw material to synthesize two types of multi-emission CD hybrids for ratiometric sensing. Considering their simplicity, low cost, good sensitivity and specificity, and accuracy, the developed ratiometric fluorescent nanosensors hold great potential to find wide applications in environmental monitoring, water safety, and waste management.

Förster Resonance Energy Transfer Regulated Multicolor Photopatterning from Single Quantum Dot Nanohybrid Films

Precise patterning and localization of functional nanomaterials is the key step for miniaturization and building of optoelectronic devices. Present study utilizes a robust methodology for the multicolor patterning of luminescent Indium Phosphide/Zinc Sulfide Quantum Dot (InP/ZnS QD) film, by taking the advantage of QD’s enhanced photostability over organic dyes. The photoirradiation regulates the composition of donor–acceptor pair, and thereby, the efficiency of Förster Resonance Energy Transfer (EFRET) in QD–dye nanohybrid film. The photopatterned films are reusable over multiple cycles without any compromise of the color clarity, owing to the reversible switching between FRET ON and OFF states. The highlight of the present work is the use of a single QD nanohybrid system to create multicolor luminescent patterns; as opposed to the common practice of using different-colored QDs. FRET assisted photopatterning of luminescent InP/ZnS QD films provides a fundamentally unique and cost-effective approach for the manufacturing of luminescent optoelectronic devices.

Nanostructured molybdenum/heteroatom-doped carbon dots nanohybrids for lubrication by direct carbonization route

Inorganic-organic hybrid ternary molybdenum-doped carbon dots-metal nanohybrids(CDs-Mo) have been prepared by in situ carbonization of tri-functional glutamic acid, bis-functional dicationic liquid([BHDABCO][Ntf]) and ammonium molybdate, which were explored as lubricant additive in PEG base oil that reduced the friction coefficient of 62.90% and wear volume of 80.21%. The positively charged steel surface attracted CDs-Mo during friction thus leading to the fluorescence decrease of PEG with 1 wt% CDs-Mo, which aggregated and transformed into uneven carbon-based oil film that avoided the direct contact of frictional pairs.

Bio‐based epoxy/polyaniline nanofiber‐carbon dot nanocomposites as advanced anticorrosive materials

ABSTRACTApplication of anticorrosive coating on metal surface enhances the durability of the metal. Anticorrosion can be achieved by the incorporation of conducting nanomaterials like polyaniline or its nanohybrid to a coating material. Thus, bio‐based epoxy nanocomposites were fabricated by the in situ method using polyaniline nanofiber‐carbon dot nanohybrid (0.50 and 1 wt % with respect to epoxy), as the anticorrosive material. The epoxy resin was obtained by polycondensation of bisphenol‐A, sorbitol, and monoglyceride of castor oil (mole ratio of 16:3:1), as hydroxyl compounds with epichlorohydrin (1:3 equivalent, hydroxyl:epichlorohydrin). The morphological analyses of the nanocomposites revealed the uniform dispersion and good compatibility of the nanohybrid in the epoxy matrix. The thermosets demonstrated good tensile strength (30 MPa), elongation at break (45%), scratch resistance (>10 kg) and impact resistance (14.75 kJ/m), good thermal stability (above 250°C), and chemical resistance. The anticorrosion study of the nanocomposites showed excellent corrosion protection efficiency (corrosion rate: 5.68 × 10−3 mils per year) in 3.5 wt % NaCl compared to the pristine epoxy system. Therefore, this bio‐based thermosetting epoxy nanocomposite was demonstrated as efficient anticorrosive material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47744.

Eco-friendly AgInS2/ZnS quantum dot nanohybrids with tunable luminescent properties modulated by pH-sensitive biopolymer for potential solar energy harvesting applications

Semiconductor quantum dots (QDs) are very interesting candidates for the development of green-energy based nanomaterials and devices. However, currently they present serious concerns because the large majority of efficient QDs have been synthesized using organometallic routes with toxic heavy metals. Herein, we designed and produced novel fluorescent ternary and quaternary QD nanostructures based on AgInS2 (AIS) core and ZnS (ZAIS) shell stabilized with carboxymethyl cellulose (CMC) polymer ligand for potential applications in green solar energy harvesting. Colloidal AgInS2 QDs were prepared by co-precipitation process using a one-pot aqueous green route directly stabilized by CMC at room temperature and varying pH conditions. Then, an outlayer of ZnS was grown and thermally annealed to improve and tune their optical properties and split the emission range, leading to core–shell alloyed nanostructures. Their physicochemical and optical properties were extensively characterized, demonstrating that photoluminescent monodispersed AIS and ZAIS QDs were produced with size typically ranging from 8.5 ± 2.4 nm and 3.2 ± 1.1 nm under acidic or alkaline media, respectively. Therefore, by adjusting the parameters of synthesis, the QD nanohybrids showed tunable optical properties ranging from UV to NIR, with maxima absorption/emission in the visible-range of the light spectrum (from λ = 650 to 750 nm). More importantly, the optical properties demonstrated remarkable enhancement of quantum yield of over one order of magnitude due to the combination of processing parameters and engineered core–shell nano-architecture of AgInS2–ZnS. Thus, these luminescent nanomaterials offer great perspectives for developing innovative broad spectral converters for a wide range of applications in solar energy harvesting.

Fabrication of renewable resource based hyperbranched epoxy nanocomposites with MWCNT-polyaniline nanofiber-carbon dot nanohybrid as tough anticorrosive materials

Fabrication of renewable resource based hyperbranched epoxy nanocomposites with MWCNT-polyaniline nanofiber-carbon dot nanohybrid as tough anticorrosive materials

Ratiometric fluorescence response of a dual light emitting reduced carbon dot/graphene quantum dot nanohybrid towards As(iii)

A dual light emitting fully carbon-based nanohybrid system comprising of glutathione-functionalized reduced carbon dots and graphene quantum dots is fabricated as ratiometric fluorescence probe for As(iii).

Design of dual drug-loaded dendrimer/carbon dot nanohybrids for fluorescence imaging and enhanced chemotherapy of cancer cells

Design of powerful nanosystems to overcome multidrug resistance (MDR) for effective chemotherapy of cancer currently remains a great challenge. Herein, we report the development of a poly(amidoamine) (PAMAM) dendrimer/carbon dot nanohybrid for dual drug loading to overcome MDR and simultaneously monitor cancer cells via fluorescence imaging. First, blue-emitting carbon dots (CDs) were synthesized using sodium citrate as a carbon source via the hydrothermal method and used as a carrier to load the anticancer drug doxorubicin (DOX) through non-covalent interactions, thus forming CDs/DOX complexes. In parallel, PAMAM dendrimers of generation 5 (G5) were covalently modified by the targeting ligand cyclic arginine-glycine-aspartic (RGD) peptide and the drug efflux inhibitor d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). Then, through electrostatic interaction, functional dendrimers (G5-RGD-TPGS) were complexed with CDs/DOX complexes to form a dual drug-loaded nanohybrid system. The dual drug-loaded dendrimer/CD nanohybrids were well characterized. We showed that the nanohybrids possessed good colloidal stability and enabled significant inhibition of cancer cells due to the presence of TPGS, which can inhibit P-glycoprotein (P-gp) by decreasing ATP levels and increasing ROS levels; simultaneously, fluorescence imaging of cancer cells could be achieved in vitro due to the luminescence of CDs. In addition, the attached RGD ligands rendered the nanohybrid with targeting specificity to cancer cells expressing αvβ3 integrin receptors. The developed dual drug-loaded dendrimer/CD nanohybrid may be used as a promising theranostic platform to overcome MDR for enhanced chemotherapy as well as for fluorescence imaging of cancer cells.

Determination of Hg2+ and Cu2+ ions by dual-emissive Ag/Au nanocluster/carbon dots nanohybrids: Switching the selectivity by pH adjustment

An innovative dual-emissive ratiometric nanohybrid probe comprised of red-emitting a (Ag/Au)@insulin nanoclusters (NCs) and blue-emitting carbon dots (CDs) was designed for sensitive and selective ratiometric determination of Hg2+ and Cu2+ ions.The fluorescence intensity of CDs (λex = 340 nm; λem = 420 nm) was unaffected in the presence of the metal ions tested, whereas the red emitting NCs (λex = 340 nm; λem = 640 nm) was strongly quenched by both Cu2+ and Hg2+ ions. Interestingly, the selectivity of the probe toward these two ions was simply switched by controlling the pH of probe solution without using any chelating agent. The probe selectively responded to Hg2+ ions at acidic condition (pH = 4.0), Cu2+ ions at basic condition (pH = 10.0), and Hg2+-Cu2+ mixtures at pHs within this range. The respective detection limitsfor determination of Cu2+ and Hg2+ ions at their specific pH conditions were estimated as 5 nM and 7 nM, over linear ranges of 20-600 nM and 20-2000 nM, respectively. The fabricated ratiometric probe also showed distinguished fluorescence color changes to visual detection of these ions. Finally, the probe was successfully applied to determination of Hg2+ and Cu2+ ions in tap and mineral water samples.

A facile synthesis of graphene nanoribbon-quantum dot hybrids and their application for composite electrolyte membrane in direct methanol fuel cells

In this work, we report the concept of synthesizing graphene nanoribbon-graphene quantum dot (GNR-GQD) hybrids with even grafting of GQD on GNR sheet in a facile single step process under ultrasonication in chlorosulfonic acid. Further, diazotization route is followed for the preparation of 4-benzenediazonium sulfonate precursor to sulfonate both GNR and GQD to form sulfonated graphene nanoribbons-sulfonated graphene quantum dots (sGNR-sGQD) nanohybrids. Synergistic and structure dependent effect of nanohybrids is seen via its dispersion in sulfonated poly(ether ether ketone) (sPEEK) to form nanocomposite membrane. sPEEK/sGNR-sGQD (1.5 wt %) nanocomposite membrane shows remarkable direct methanol fuel cell (DMFC) performance compared to pristine sPEEK and Nafion 117 with 40% increment in peak power density along with higher durability up to 100 h due to better physicochemical properties like water uptake, ion exchange capacity, proton conductivity, and reduced methanol crossover to suggest its potential which includes diverse membrane applications.