Dot Nanocomposites Research Articles

Nonlinear Interactions of Zinc Phthalocyanine-Graphene Quantum Dots Nanocomposites: Investigation of Effects of Surface Functionalization with Heteroatoms.

This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.

Facile synthesis of gold/gadolinium-doped carbon quantum dot nanocomposites for magnetic resonance imaging and photothermal ablation therapy.

Composites of gold nanomaterials and imaging agents show promise in cancer therapy. Here we have demonstrated a rapid, facile, environmentally friendly, and organic solvent-free method for the synthesis of a gold/gadolinium-doped carbon quantum dot (Au/GdC) nanocomposite for magnetic resonance imaging (MRI) and photothermal ablation (PTA) therapy. The gadolinium-doped carbon quantum dots (Gd@CQDs) were synthesized using a one-pot, microwave-assisted method, and used as reducing and stabilizing agents to both form the Au/GdC nanocomposite and prevent its agglomeration. Formation of the Au/GdC nanocomposite is achieved by simple mixing of Gd@CQDs and a gold precursor, without the addition of any other reducing agents, surface passivating agents, surfactants, or organic solvents. The Au/GdC nanocomposite shows paramagnetism, surface plasma resonance in the near infrared region (NIR), and excellent photostability. Furthermore, it provides high longitudinal relaxivity (r1 = 13.95 mM-1 s-1), indicating its potential for use as a T1 contrast agent in MRI. Furthermore, in vitro and in vivo studies using HeLa cells and zebrafish embryos as cancer and animal cell models, respectively, confirmed the low toxicity and excellent biocompatibility of the Au/GdC nanocomposite. Notably, our results demonstrate the ability of the Au/GdC nanocomposite to efficiently destroy cancer cells using PTA. Therefore, this work reveals a simple and powerful strategy to fabricate an Au/GdC nanocomposite for MRI and photothermal ablation of cancer cells.

Fe3O4/hydroxyapatite/graphene quantum dots as a novel nano-sorbent for preconcentration of copper residue in Thai food ingredients: Optimization of ultrasound-assisted magnetic solid phase extraction

Fe3O4/hydroxyapatite/graphene quantum dots (Fe3O4/HAP/GQDs) nanocomposite was synthesized and used as a novel magnetic adsorbent. This nanocomposite was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetization property. The Fe3O4/HAP/GQDs was applied to pre-concentrate copper residues in Thai food ingredients (so-called “Tom Yum Kung”) prior to determination by inductively coupled plasma-atomic emission spectrometry. Based on ultrasound-assisted extraction optimization, various parameters affecting the magnetic solid-phase extraction, such as solution pH, amount of magnetic nanoparticles, adsorption and desorption time, and type of elution solvent and its concentration were evaluated. Under optimal conditions, the linear range was 0.05–1500ngmL−1 (R2>0.999), limit of detection was 0.58ngmL−1, and limit of quantification was 1.94ngmL−1. The precision, expressed as the relative standard deviation of the calibration curve slope (n=5), for intra-day and inter-day analyses was 0.87% and 4.47%, respectively. The recovery study of Cu for real samples was ranged between 83.5% and 104.8%. This approach gave the enrichment factor of 39.2, which guarantees trace analysis of Cu residues. Therefore, Fe3O4/HAP/GQDs can be a potential and suitable candidate for the pre-concentration and separation of Cu from food samples. It can easily be reused after treatment with deionized water.

A molecularly imprinted polymer-coated CdTe quantum dot nanocomposite for tryptophan recognition based on the Förster resonance energy transfer process

A new ‘turn-on’ Förster resonance energy transfer (FRET) nanosensor for l-tryptophan based on molecularly imprinted quantum dots (QDs) is proposed. The approach combines the advantages of the molecular imprinting technique, the fluorescent characteristics of the QDs and the energy transfer process. Silica-coated CdTe QDs were first synthesized and then molecularly imprinted using a sol–gel process without surfactants. The final composite presents stable fluorescence which increases with the addition of l-tryptophan. This ‘turn-on’ response is due to a FRET mechanism from the l-tryptophan as donor to the imprinted QD as acceptor. QDs are rarely applied as acceptors in FRET systems. The nanosensor shows selectivity towards l-tryptophan in the presence of other amino acids and interfering ions. The l-tryptophan nanosensor exhibits a linear range between 0 and 8 µM concentration, a detection limit of 350 nM and high selectivity. The proposed sensor was successfully applied for the detection of l-tryptophan in saliva. This novel sensor may offer an alternative approach to the design of a new generation of imprinted nanomaterials for the recognition of different analytes.

One pot synthesis of gold – carbon dots nanocomposite and its application for cytosensing of metals for cancer cells

Cytosensing of biological transition metals is paramount important for cancer research. One-pot synthesis of the nanocomposite of carbon dots (CDs) and gold nanoparticles (AuNPs) is reported and has been applied for metal cytosensing. The nanocomposite (GCDs) is synthesized using citric acid (CA) and L-cysteine as precursors in the presence of chloroauric acid. The synthesis procedure exhibits many advantages including simple one step, green approach (solvent free method) and requires cheap chemical precursors. The current procedure produces uniform carbon dots (<3nm) and assist the formation of AuNPs without using extra reducing agent. GCDs nanoparticles have UV absorbance matching with the wavelength of N2 laser (337nm). The synergistic effect of the large surface area of GCDs and the maximum absorbance at 337nm offers an effective and promising application for surface enhanced laser desorption/ionization mass spectrometry (SELDI-MS) of biological metals (Fe2+, Fe3+ and Cu2+ ions) for cancer cells. SELDI-MS using GCDs offers a sensitive method, shows selective detection, and provides simultaneous cytosensing of biological metals (Fe2+, Fe3+ and Cu2+) of cancer cells. The metals are detected after complexation with mefenamic acid (MFA) which provides multi-functions (chelating agent, internal calibrant and co-matrix) for LDI-MS.

One-pot synthesis of NiFe2O4 integrated with EDTA-derived carbon dots for enhanced removal of tetracycline

Recently, carbon-based nanomaterials especially carbon dots (CDs) show as the promising candidates for organic contaminant removal because of their abundant functional groups, easy-of-preparation and high surface area. However, the difficulties in separation and recycle of CDs arising from its high water solubility and low molecular weight limit its application in this area. Herein, we demonstrate a one-pot solvothermal method for fabricating NiFe2O4-carbon dot (NiFeC) nanocomposites, which solve its limitations and mitigate the usual fabrication drawbacks by self-assembly such as relatively weak interaction, time-consuming and lack of recycling potential. Series characterizations confirmed the successful fabrication of NiFeC nanocomposites with great uniformity in morphology and exhibited excellent dispersibility in water. The adsorption behavior of the as-prepared nanocomposites was systematically studied using kinetic and equilibrium experiments. Owing to abundant hydroxy and carboxyl groups introduced from CDs, NiFeC nanocomposites offered significantly enhanced tetracycline (TC) removal ability with the maximum adsorption capacity of 591.72mgg−1, as well as the excellent regenerability. Moreover, XPS and FT-IR analysis revealed the adsorption mechanism was attributed to surface complexation, cation exchange and electrostatic interaction between TC and the NiFeC. With the higher adsorption capacity and simpler synthesis method than traditional adsorbents, NiFeC nanocomposites have promising potential for the removal of TC from wastewater.

Tuning Electrical Transport Mechanism of Polyaniline–Graphene Oxide Quantum Dots Nanocomposites for Potential Electronic Device Applications

In this report, we study the tuning of the electrical transport dimensionality of polyaniline–graphene oxide quantum dots nanocomposites (PANI-GOQD) for electronic device applications. We focused this study on the microstructure and its correlations with electrical transport properties. X-ray diffraction and small-angle X-ray scattering analyses showed the effect that caused the addition of GOQD on the structural and microstructural properties of polyaniline. Confocal Raman spectroscopy revealed that the presence of GOQD leads to a notorious decrease of the polaron population of polyaniline. In relation to this experimental evidence, a significant increase in resistivity was observed for PANI-GOQD nanocomposites with respect to pure polyaniline. Electrical transport showed a typical Arrhenius behavior at relatively high temperatures and a broad transition with a logarithmic dependence of the activation energy with temperature for the intermediate temperature regime. Additionally, PANI-GOQD showed an incre...

A Prussian blue/carbon dot nanocomposite as an efficient visible light active photocatalyst for C-H activation of amines.

A Prussian blue/carbon dot (PB/CD) nanocomposite was synthesised and used as a visible-light active photocatalyst for the oxidative cyanation of tertiary amines to α-aminonitriles by using NaCN/acetic acid as a cyanide source and H2O2 as an oxidant. The developed photocatalyst afforded high yields of products after 8 h of visible light irradiation at room temperature. The catalyst was recycled and reused several times without any significant loss in its activity.

Rapid fabrication of carbon quantum dots as multifunctional nanovehicles for dual-modal targeted imaging and chemotherapy.

In this manuscript, we reported a facial, rapid, and environmental friendly method to fabricate hetero atoms including gadolinium, nitrogen, and sulfur doped multi-functional magnetofluorescent carbon quantum dots (GdNS@CQDs) nanocomposite. These multifunctional GdNS@CQDs were conjugated with a folic acid for targeting dual modal fluorescence/magnetic resonance imaging. Additionally, an anticancer drug, doxorubicin, was incorporated into the nanocomposite forming FA-GdNS@CQDs-DOX, which enables targeted drug delivery. We have developed GdNS@CQDs with integrated functions for simultaneous in vitro cell imaging, targeting, and pH-sensitive controlled drug release in HeLa cells. Furthermore, we successfully demonstrated the use of this material for in vivo fluorescence imaging, using zebrafish as an animal model.

Designing an ultra-sensitive aptasensor based on an AgNPs/thiol-GQD nanocomposite for TNT detection at femtomolar levels using the electrochemical oxidation of Rutin as a redox probe

In this paper, for the first time a highly sensitive and low-cost electrochemical aptasensor was fabricated based on a silver nanoparticles/thiol functionalized graphene quantum dot (AgNPs/thiol-GQD) nanocomposite for the measurement of 2,4,6-Trinitrotoluen (TNT) as a nitroaromatic explosive. For the first time Rutin (RU) as a biological molecule with inherent properties was used as the redox probe in the development of the TNT aptasensor was used. The system was based on a TNT-binding aptamer which is covalently attached onto the surface of a glassy carbon electrode (GCE) modified with the nanocomposite for the formation of a sensing layer and improving the performance of the aptasensor. Using the proposed nanocomposite provides a specific platform with increased surface area which is capable of loading more Aptamer (Ap) molecules as a receptor element of TNT on the electrode surface. So, TNT molecules is in an upward position to be measured and the obtained results indicate that the aptasensor exhibits two wide linear ranges and an unprecedented LOD compared with previously reported analytical methods for TNT detection. Applicability of the developed aptasensor to easily detect TNT in real samples was evaluated. It seems that the proposed strategy can be expanded to other nanoparticles and is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.

Aptamer based lysozyme assay using fluorescent CuInS2 quantum dots and graphene oxide, and its application to inhibitor screening

We report on a widely applicable approach for protein detection by using triple-helix DNA mediated CuInS2 quantum dot (QD) and graphene oxide (GO) nanocomposite. The CuInS2 QDs were coated with mercaptopropionic acid and then covalently linked to a hairpin aptamer against lysozyme (HLA). Single-stranded DNA (triple helix-forming oligonucleotide; THFO) readily absorbs on the surface of GO via π-stacking interaction, and this results in the formation of THFO-GO. If HLA-CuInS2 QDs are added to the THFO-GO system, the fluorescence of HLA-CuInS2 QDs (at excitation/emission wavelengths of 590/665 nm) is quenched. Lysozyme has a higher affinity for HLA than THFO. Therefore, in the presence of lysozyme, it will bind to the HLA-CuInS2 QD and displace the THFO-GO. This results in the restoration of fluorescence that is related to the concentration of lysozyme. The fluorescence of the QDs is turned on. The calibration plot is linear in the 0.01 to 1.8 ng·mL‾1 concentration range, with a 3 pg·mL‾1 detection limit (at a signal-to-noise ratio of 3). The method was also applied to study the inhibition of lysozyme by Ivy Ec . In our perception, this method has a wide scope in that it may become applicable to any protein for which an appropriate aptamer is available.

Enhanced Solar Hydrogen Generation by a Heterojunction of Perovskite-type La2 Ti2 O7 Nanosheets Doped with CdS Quantum Dots.

A heterojunction of a perovskite-type La2 Ti2 O7 (LTO)/CdS quantum dot (QD) nanocomposite was prepared by the chemical bath deposition method. The solar-light-driven H2 generation results show that this CdS QDs/LTO heterojunction exhibits great improvement in the photocatalytic H2 production and its photoelectrochemical properties in comparison with pure CdS QDs and LTO nanosheets. A possible enhanced mechanism of photoinduced interfacial charge transfer between CdS and LTO is proposed for the heterojunction. The shift of the CdS conduction band (CB) edge can enlarge the CB potential difference between CdS QDs and LTO, enhancing transferred driven force of the interfacial electrons and finally improving the two components' separation activity of photogenerated carriers. This study provides a promising method for constructing an efficient photoinduced interfacial charge transfer over LTO and CdS QD heterojunctions for photocatalytic hydrogen production.

Optimizing the Photovoltaic Properties of CdTe Quantum Dot–Porphyrin Nanocomposites: A Theoretical Study

By using the self-consistent charge density functional tight binding method, we explore the photovoltaic properties of CdTe quantum dot (CdTeQD)–porphyrin nanocomposites. It is well-known that for dye-sensitized solar cell (DSSCs) applications, the composite system should have a type-II band alignment that hinders the recombination of charge carriers, thereby improving the photovoltaic performance. The emphasis of our tight-binding calculations is to find the suitable CdTeQD–porphyrin nanocomposites that can offer better performance for solar energy conversion. By analyzing the electronic energy levels of the composite systems we have shown that the axially coordinated Zn-tetraphenylporphyrin (ZnTPP) functionalized CdTe quantum dot (ZnTPP–CdTeQD) nanocomposites are really promising materials for application in DSSCs, as they produce type-II band alignment for all the composites irrespective of the size of CdTeQDs. The time-dependent density functional theory (TDDFT) calculations demonstrate that the size ...

Magnetic nanoparticles embedded with graphene quantum dots and multiwalled carbon nanotubes as a sensing platform for electrochemical detection of progesterone

Results of this paper related to fabrication of a simple, reproducible, stable and sensitive electrochemical sensing platform of progesterone (P4) based on graphene quantum dots (GQDs) nanocomposite. GQDs, Fe3O4 nanoparticles and functionalized multi–walled carbon nanotubes (f–MWCNTs) modified glassy carbon electrode (Fe3O4@GQD/f–MWCNTs/GCE) were constructed and the electrocatalytic properties of the modified electrode toward the oxidation of P4 were analyzed. GQDs with the size of about 15nm were prepared by a facile and low expense bottom–up method by carbonization of citric acid and dispersing the carbonized products into alkaline solution. The characterization of the sensor was studied by transmission electron microscopy (TEM), X–ray diffraction (XRD), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FT–IR) and voltammetry techniques. Electrochemical studies suggested that as–prepared sensor revealed some advantages in terms of high effective surface area, more reactive sites and excellent electrochemical catalytic activity toward the oxidation of P4. After optimization of analytical conditions, the peak currents for P4 were found to vary linearly with its concentrations in the wide range of 0.01–0.5 and 0.5–3.0μM. The estimated detection limit and sensitivity of the electrode were 2.18nM and 16.84μAμM−1, respectively. This sensor exhibited excellent stability, selectivity, sensitivity and reproducibility and could be successfully applied for determination of P4 in human serum samples and pharmaceutical products with excellent recoveries and without the interferences of coexisting substances.

Abstract 2196: Improving cytotoxicity against cancer cells by chemo-photodynamics combined modalities using silver/graphene quantum dots/doxorubicin nanoconjugates

Abstract Tumor microenvironment complexity render chemotherapy and radiotherapy ineffective to eradicate highly aggressive tumors. For this reason, we are interested to find new avenues that can improve clinical outcomes. Recently, different nanomaterials such as Graphene Quantum Dots (GQDs) have been explored in treatments for a broad range of diseases, including cancer therapeutics. GQDs are nanometer-sized fragments (2-20 nm) of graphene, which have shown unique electrical, optical and mechanical properties. We hypothesize that the unique physical and chemical properties of the Graphene Quantum Dots (GQDs) along with the anticancer properties of silver (Ag) can provide an alternative to the challenges presently encountered in traditional cancer therapy regimens. In this study functionalized silver decorated graphene quantum dots (Ag-GQDs) nanocomposites were synthesized by a bottom-up approach by the pulsed laser irradiation of a liquid hydrocarbon precursor containing silver ions. The Ag-GQDs were characterized by UV-Vis spectroscopy, transmission electron microscopy, and Fourier transform IR spectroscopy. The Ag-GQD nanocomposites were tested in the treatment of cervical cancer HeLa cells and prostate cancer cells DU-145. The Ag-GQD nanocomposites demonstrated high potential in the delivery of Doxorubicin to cancer cells and an anticancer activity boost due to their intrinsic properties. Interestingly, we observed an increase in the activity of caspase-3/7 in DU145 and HeLa when treated with such nanoparticles. The photo-activation of Ag-GQDs with 425 nm radiation increased the levels of Reactive Oxygen Species (ROS) in both cell lines, inducing cell death by DNA damage. The combination of the chemo-photodynamic therapies using Ag-GQDs conjugated with DOX remarkably enhanced the treatment efficacy of HeLa and DU145, as compared to treatment by using each modality alone. HeLa. Fluorescence imaging results showed that Ag-GQDs deliver DOX to the nucleus of cancer cells, which suggests they may deliver other cargos. Also, to confirm whether the decrease in the cells viability upon treatment with Ag-GQDs was caused by toxicity, we tested a non-transformed cell line. The data suggest that the effect is due to the intrinsic effect of Ag-GQDs and not by toxicity. The Ag-GQDs thus offer a general platform for incorporating multiple therapeutic modalities for treating different types of cancer and they represent a significant breakthrough in nanomedicine for potential translation to the clinic. Further studies are necessary to elucidate the exact mechanism(s) of Ag-GQDs in releasing their cargo, and to test them in vivo. In summary, we developed a novel, multi-functional, and biocompatible PEGylated Ag-GQDs nanocomposites that combines two therapeutic modalities, chemotherapy and photodynamic therapy, into one platform for treatment of different type of cancers. Citation Format: Joel Encarnación-Rosado, Khaled Habiba, Kenny García-Pabón, Brad R. Weiner, Gerardo Morell. Improving cytotoxicity against cancer cells by chemo-photodynamics combined modalities using silver/graphene quantum dots/doxorubicin nanoconjugates. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2196.

Morphology, optical, and electric properties of polymer-quantum dots nanocomposites: effect of polymeric matrix

Polymer-CdTe quantum dots (QDs) nanocomposites were developed via solvent casting. Colloidal CdTe QDs, synthesized in aqueous solution, were transferred to organic media by exchanging of the original capping ligands by a long-chain thiol. Different commercial polymers (PMMA, OPS, PS, and PC), transparent in the visible spectral range, were chosen as matrices. Stock solutions of the polymers were prepared in suitable concentration (2 wt%) for the production of thin films with good quality, able to maximize the solubility of QDs, without phase separation. Studies on the morphological and optical properties were performed. The results showed that the polymer matrix has a considerable effect on QDs’ morphology, size, and electric conductivity. PMMA demonstrated to be the most promising embedding matrix, offering new possibilities for optoelectronic applications of polymer-QD nanocomposites.

A simple method for preparing ZnO foam/carbon quantum dots nanocomposite and their photocatalytic applications

ZnO foam/carbon quantum dots (CQDs) nanocomposite has been successfully synthesized by a facile process which ZnO foam prepared by combustion method was dispersed in CQDs solution. It is found that the ZnO foam is constructed by a large number of ZnO nanoparticles filling in irregular, hierarchical pores. The foam structure originates from a large amounts of gas produced in the combustion process. The obtained ZnO foam/CQDs nanocomposite shows excellent photocatalytic activities on degrading Rhodamine B (RhB), Methyl orange (MO) and Methylene blue (MB) under UV and visible light irradiation. The order of degradation efficiency is MB>RhB>MO. It is attributed to the synergistic effect of several factors, including the light-trapping effect of ZnO foam, the up-converted photoluminescence behavior and photo-induced electron transfer property of CQDs.

Silver Nanoparticles/N-Doped Carbon-Dots Nanocomposites Derived from Siraitia Grosvenorii and Its Logic Gate and Surface-Enhanced Raman Scattering Characteristics

Silver/carbon dots (CDs) nanocomposites receive significant attention for diverse applications owing to their unique physical and chemical properties. Herein, a green method is proposed for synthesizing silver nanoparticle/N-doped CDs (AgNPs/N-CDs) nanocomposites, wherein the AgNPs are grown on the surface of reduced N-CDs derived from Siraitia grosvenorii. The N-CDs were used as a reducing agent and stabilizer, no additional reducing agent and stabilizer were necessary. The as-synthesized AgNPs/N-CDs nanocomposites were characterized using ultraviolet–visible spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). An AND logic system based on the obtained N-CDs was proposed, which avoids complicated modifications and chemical labeling. The surface-enhanced Raman scattering (SERS) properties of the prepared AgNPs/N-CDs nanocomposites were also investigated, indicating the potential application for SERS detection.

Quantum yield and lifetime data analysis for the UV curable quantum dot nanocomposites.

The quantum yield (QY) and lifetime are the important parameters for the photoluminescent materials. The data here report the changes of the QY and lifetime for the quantum dot (QD) nanocomposite after the UV curing of the urethane acrylate prepolymer. The data were collected based on the water soluble CdTe QDs and urethane acrylate prepolymer. Colloidal QDs were in various concentration from 0.5×10−3 molL−1 to 10×10−3 molL−1, and 1% (wt%) 1173 was the photoinitiator. The QY before the curing was 56.3%, 57.8% and 58.6% for the QDs 510 nm, 540 nm and 620 nm, respectively. The QY after the curing was changed to 8.9%, 9.6% and 13.4% for the QDs 510 nm, 540 nm and 620 nm, respectively. Lifetime data showed that the lifetime was changed from 23.71 ns, 24.55 ns, 23.52 ns to 1.29 ns, 2.74 ns, 2.45 ns for the QDs 510 nm, 540 nm and 620 nm, respectively.

Biodegradable tough waterborne hyperbranched polyester/carbon dot nanocomposite: approach towards an eco-friendly material

A tough, self-cleaning, biodegradable waterborne hyperbranched polyester/carbon dot nanocomposite was fabricated through a facile solvent and catalyst free approach.