Water-soluble Quantum Dots Research Articles

Labeling of liver cells with CdSe/ZnS quantum dot-based fluorescence probe below freezing point

In this paper, CdSe/ZnS quantum dots (QDs) with particle size of 5.5 ~ 9.3 nm were synthesized, and the fluorescence emission ranged from 545 ~ 616 nm. When the volume fraction of ethanol was 30%, the water-soluble QD dispersion system remained liquid under −20 °C freezing conditions, the fluorescence intensity increased with a decrease in temperature, and the quantum yield reached 79% at −20 °C. The endothelial cell adhesion molecule CD31 antibody (anti-CD31) was used as the primary antibody, QDs were coupled with IgG as the secondary antibody (QD-Ab), and effective labeling of hepatic sinusoid endothelial cells was achieved at −20 °C. Fluorescence imaging and flow cytometry analysis showed that the labeling efficiency was as high as 97%, indicating that QDs have an important application prospect in microscopic section tomography of the liver.

Water-soluble CdSe quantum dots synthesis via facile seed-mediated approach and their characterization studies

In this paper, we are reporting the water-soluble quantum dots exhibiting emission in visible range from 550 to 650 nm. These have been synthesized by a simple seed-mediated approach using cadmium chloride, sodium borohydrate, selenium powder and thioglycolic acid as precursors. The as-prepared cadmium selenide (CdSe) quantum dots were characterized by UV-Vis spectroscopy (UV-Vis), photo luminescence (PL) spectroscopy, Fourier transfer infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The obtained water-soluble quantum dots exhibited excellent composition, spherical geometry, strong emission and good stability which can be suitable for biomedical imaging applications.

A facile green synthesis of functionalized carbon quantum dots as fluorescent probes for a highly selective and sensitive detection of Fe3+ ions

In this study, we have reported an economical, easy, greener and non-toxic synthesis route of water soluble carbon quantum dots (CQDs) through hydrothermal treatment using gelatin as precursor. Under the UV lamp of wavelength 365 nm, the as-prepared CQDs exhibit strong blue fluorescence along with CIE coordinate index of (0.17, 0.14) and possess a quantum yield of 22.7% with rhodamine B as standard. The morphology of as-synthesized CQDs as investigated by TEM measurement confirmed their spherical shape and also revealed that their sizes varied in the scale of 0.5–5 nm. Furthermore, the CQDs showed excitation dependent fluorescence emission behaviour in range of 280 nm to 420 nm as a result of quantum confinement effect. Apart from this, in CQDs solution, the addition of Fe3+ ion lead to fluorescence quenching effect. These results revealed that the as-synthesized CQDs have a sensitive response towards the Fe3+ ion. The calculated limit of detection (LOD) is 0.2 μM with correlation coefficient R2 = 0.996 in the concentration range 0 to 50 μM. More remarkably, the application of CQDs for monitoring the trace level of Fe3+ ion in tap water yielded acceptable recoveries (103.33%-105%). Therefore, this work provides a novel additional fluorescent probe for the detection of Fe3+ ion in real world.

Embedment of Quantum Dots and Biomolecules in a Dipeptide Hydrogel Formed In Situ Using Microfluidics.

As low‐molecular‐weight hydrogelators, dipeptide hydrogel materials are suited for embedding multiple organic molecules and inorganic nanoparticles. Herein, a simple but precisely controllable method is presented that enables the fabrication of dipeptide‐based hydrogels by supramolecular assembly inside microfluidic channels. Water‐soluble quantum dots (QDs) as well as premixed porphyrins and a dipeptide in dimethyl sulfoxide (DMSO) were injected into a Y‐shaped microfluidic junction. At the DMSO/water interface, the confined fabrication of a dipeptide‐based hydrogel was initiated. Thereafter, the as‐formed hydrogel flowed along a meandering microchannel in a continuous fashion, gradually completing gelation and QD entrapment. In contrast to hydrogelation in conventional test tubes, microfluidically controlled hydrogelation led to a tailored dipeptide hydrogel regarding material morphology and nanoparticle distribution.

Interplay of Multiexciton Relaxation and Carrier Trapping in Photoluminescent CdS Quantum Dots Prepared in Aqueous Medium

A comprehensive understanding of exciton dynamics of water-soluble quantum dots (QDs), especially those synthesized directly in aqueous media, is critical for devising their applications. Trapping ...

Water dispersible ZnSe/ZnS quantum dots: Assessment of cellular integration, toxicity and bio-distribution

Quantum dots (QDs) comprise an emerging group of materials with innumerable number of possibilities in biological research including cellular labelling. Among the leading members in this category, ZnSe/ZnS quantum dots (QDs) hold greater attractive possibilities in imaging primarily due to their higher biocompatibility and dispersibility. Nevertheless, the inherent toxicity of ZnSe/ZnS QDs is not yet completely explored which largely compromise most of their biomedical application potential. Strong blue emitting water soluble QDs effectively synthesized by aqueous phase route. Synthesized QDs further subjected to various optical and physicochemical characterization. Approximately 5–6 nm sized ZnSe/ZnS QDs illuminated bluish green fluorescence under UV lamp. Present study addresses possible adverse effects of ZnSe/ZnS QDs in hepatic system using HepG2 cells; which is the routinely employed in vitroliver cell model. A bundle of assays wasperformed out to reveal the cytotoxic nature of ZnSe/ZnS QDs and the mechanism behind it. Herein, absorption, distribution, metabolism, excretion and toxicity (ADME and T) of ZnSe/ZnS in mice were profiled in detail followed by intravenous (i.v.) and intraperitoneal (i.p.) administration at a dose of 10 mg/kg body weight. In a short review, it could be state that ZnSe/ZnS QDs did not exhibit any significant in vivo toxicity outcome in mice.

Water Soluble Silicon Quantum Dots Grafted with Amoxicillin as a Drug Delivery System.

Water soluble silicon quantum dots (Si QDs) are prepared and used for the measurement of the efficiency for the controlled release drug delivery. Amoxicillin, antibiotics, is covalently grafted with Si QDs through a surface derivatization reaction. Si QDs are embedded in hydrogel polymer. The release of amoxicillin has been measured by using Ultra violet-visible (UV-vis) absorption spectrometer. Amoxicillin-embedded hydrogels exhibit a burst release for 1 h, however covalently loaded Amoxi-Si QDs hydrogel composite exhibited very slow release. Absorption analysis reveals that the Si QDs exhibits a great potential candidate for controlled release of drug. The controlled drugrelease profiles depend on the hydrolysis of amoxicillin from the surface of Si QDs.

Monodisperse and Water-Soluble Quantum Dots for SWIR Imaging via Carboxylic Acid Copolymer Ligands.

Compared to the visible and near-infrared, the short-wave infrared region (SWIR; 1000-2000 nm) has excellent properties for in vivo imaging: low autofluorescence, reduced scattering, and a low-absorption cross-section of blood or tissue. However, the general adoption of SWIR imaging in biomedical research will be enhanced by a broader availability of versatile and bright contrast materials. Quantum dots (QDs) are bright and compact SWIR emitters with narrow size distributions and emission spectra, but their use is limited by the shortcomings of established ligand systems for SWIR QDs. Established ligands often result in SWIR probes with either limited colloidal stability, large size, or broad size distribution or a combination of all three. We present a polymeric QD ligand designed to be compatible with oleate-coated QDs. Our polymeric acid ligand is a copolymer bearing carboxylic acid anchoring groups and PEG-550 chains to solubilize the QD-ligand construct. After a mild and rapid ligand exchange, the resulting constructs are compact (<11 nm hydrodynamic diameter) and have narrow size distribution. Both qualities are preserved for several months in isotonic saline. The constructs are bright in vivo, and to demonstrate their suitability for imaging, we perform whole-body imaging and lymphatic imaging, including visualization of lymphatic flow.

One-Step Synthesis of Water-Soluble Quantum Dots from Ag2S and AgInS2 QDs

Water-soluble quantum dots (QDs) have attracted much attention because of their excellent optical stability and biocompatibility. Here we report a simple, easy to operate, safe, and nontoxic method...

Enhanced Photocatalytic H2 -Production Activity of CdS Quantum Dots Using Sn2+ as Cocatalyst under Visible Light Irradiation.

Herein, oil-soluble CdS quantum dots (QDs) are first prepared through a solvent-thermal process. Then, oil-soluble CdS QDs are changed into water-soluble QDs via ligand exchange using mercaptopropionic acid as capping agent at pH 13. The photocatalytic performance is investigated under the visible light irradiation using glycerol as sacrificial agent and Sn2+ as cocatalyst. No H2 -production activity is observed for oil-soluble CdS QDs. Water-soluble CdS QDs exhibit significantly enhanced hydrogen evolution rate. When the concentration of cocatalyst Sn2+ increases to 0.2 × 10-3 m, the rate of hydrogen evolution reaches 1.61 mmol g-1 h-1 , which is 24 times higher than that of the pristine water-soluble CdS QDs. The enhanced H2 -production efficiency is attributed to the adsorption of Sn2+ ions on the surface of CdS QDs that are further reduced to Sn atoms by photogenerated electrons. The in situ generated Sn atoms serve as photocatalytic cocatalyst for efficient hydrogen generation.

Study on AgInZnS-Graphene Oxide Non-toxic Quantum Dots for Biomedical Sensing.

In recent years, non-toxic quantum dot has caught the attention of biomedical fields. However, the inherent cytotoxicity of QDs makes its biomedical application painful, and is a major drawback of this method. In this paper, a non-toxic and water-soluble quantum dot AgInZnS-GO using graphene oxide was synthesized. A simple model of state complex was also established, which is produced through a combination of quantum dots and protein. The interaction between AIZS-GO QDs and human serum albumin (HSA) has significant meaning in vivo biological application. Herein, the binding of AIZS-GO QDs and HSA were researched using fluorescence spectra, Uv-visible absorption spectra, FT-IR spectra, and circular dichroism (CD) spectra. The results of fluorescence spectra demonstrate that AIZS-GO QDs have an obvious fluorescence quenching effect on HSA. The quenching mechanism is static quenching, which implies that some type of complex was produced by the binding of QDs and HSA. These results were further proved by Uv-visible absorption spectroscopy. The Stern-Volmer quenching constant Ksv at various temperatures (298 K, 303 K, 308 K) were acquired from analyzing Stern-Volmer plots of the fluorescence quenching information. The Van't Hoff equation could describe the thermodynamic parameters, which demonstrated that the van der Waals and hydrogen bonds had an essential effect on the interaction. FT-IR spectra and CD spectra further indicate that AIZS-GO QDs can alter the structure of HSA. These spectral methods show that the quantum dot can combine well with HSA. The experimental results showed that AgInZn-GO water-soluble quantum dots have good biocompatibility, which can be combined with proteins to form new compounds which have no cytotoxicity and biological practicability. It provides an important basis for the combination of quantum dots and specific proteins as well as fluorescent labeling.

Cytotoxicity, fluorescence tagging and gene-expression study of CuInS/ZnS QDS - meso (hydroxyphenyl) porphyrin conjugate against human monocytic leukemia cells

The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum dots (QDs) has hindered their wide applications hence the advent of non-toxic ternary quantum dots. These new group of quantum dots have been shown to possess some therapeutic action against cancer cell lines but not significant enough to be referred to as an ideal therapeutic agent. In this report, we address this problem by conjugating red emitting CuInS/ZnS QDs to a 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin -photosensitizer for improved bioactivities. The glutathione capped CuInS/ZnS QDs were synthesized in an aqueous medium using a kitchen pressure cooker at different Cu: In ratios (1:4 and 1:8) and at varied temperatures (95 °C, 190 °C and 235 °C). Optical properties show that the as-synthesized CuInS/ZnS QDs become red-shifted compared to the core (CuInS) after passivation with emission in the red region while the cytotoxicity study revealed excellent cell viability against normal kidney fibroblasts (BHK21). The highly fluorescent, water-soluble QDs were conjugated to 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP) via esterification reactions at room temperature. The resultant water-soluble conjugate was then used for the cytotoxicity, fluorescent imaging and gene expression study against human monocytic leukemia cells (THP-1). Our result showed that the conjugate possessed high cytotoxicity against THP-1 cells with enhanced localized cell uptake compared to the bare QDs. In addition, the gene expression study revealed that the conjugate induced inflammation compared to the QDs as NFKB gene was over-expressed upon cell inflammation while the singlet oxygen (1O2) study showed the conjugate possessed large amount of 1O2, three times than the bare porphyrin. Thus, the as-synthesized conjugate looks promising as a therapeutic agent for cancer therapy.

Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media.

Fluorescent graphene quantum dots (GQDs) are nanomaterials which possess unique properties that show great potential in different applications. In this work, GQDs were synthesized using graphene oxide (GO) as precursor via thermal treatment at high temperature. The obtained GQDs were highly fluorescent and were suitable for the determination of heavy metal ions. X-ray diffraction, FTIR spectroscopy, and UV visible spectroscopy confirm the formation of GQDs. TEM images show that formed GQDs have size ranging from 2 to 10nm. Emission profile of aqueous GQDs was taken by exciting GQDs at different wavelength. The intensity of GQDs remains the same for 4-5months. Furthermore, as prepared, GQDs were used for selective recognition of Fe3+, Pb+2, and Cr3+ from the bunch of different metal ions in aqueous media. Lower limit of detection obtained for Fe3+, Cr3+ and Pb2+ using GQDs were 50, 100 and 100 nM, respectively, which indicatesthat the GQDs canbe utilized as a promising material for sensing of the heavy metal ions. Graphical abstract.

Sensitive detection of influenza a virus based on a CdSe/CdS/ZnS quantum dot-linked rapid fluorescent immunochromatographic test

Prevention is the most effective management strategy for influenza A infection in humans. In this study, we developed a CdSe/CdS/ZnS quantum dot (QD) fluorescent dye for rapid and sensitive detection of two common subtypes (H1N1 and H3N2) of influenza A virus, and examined its utility. CdSe/CdS/ZnS QD was conjugated with antibody (Ab) after conjugation with latex, making QD conjugate of QD + Latex + Ab. A stable photoluminescence of QD conjugate and advantage of CdSe/CdS/ZnS QD used was characterized in this study. The performance of a rapid fluorescent immunochromatographic test (FICT) employing QD conjugate (QD-FICT) in detecting influenza A/H1N1 was 8-fold and 64-fold higher than that of a europium nanoparticle-based FICT and a rapid diagnostic test (RDT; Standard Diagnostics BIOLINE Influenza A/B), respectively. For influenza A/H3N2, QD-FICT showed 8-fold and 128-fold higher performance than europium nanoparticle-based FICT and RDT, respectively. In clinical evaluations, QD-FICT showed 93.75% clinical sensitivity [45/48; 95% confidence interval (95% CI): 82.80–98.69], 100% clinical specificity (117/117; 95% CI: 96.90–100.00), and strong correlation (kappa; 0.98) with rRT-PCR (20 ≤ Ct ≤ 40). Europium nanoparticle-linked FICT showed 79.17% clinical sensitivity (38/48; 95% CI: 65.01–89.53) and 100% clinical specificity (117/117; 95% CI: 96.90–100.00), whereas RDT showed 77.08% sensitivity (37/48; 95% CI: 62.69–87.97), 100% specificity (117/117; 95% CI: 96.90–100.00), and reasonably good correlation with rRT-PCR (kappa; 0.93). Water-soluble QDs can therefore be used as an effective material for developing fluorescent diagnostic systems for rapid detection of human influenza A virus in clinical specimens.

Highly efficient energy transfer from a water soluble zinc silver indium sulphide quantum dot to organic J-aggregates.

The present work has been carried out with the aim to design and develop an efficient light harvesting inorganic-organic hybrid nanoscale material by employing a less toxic, environment friendly inorganic substance and also to understand the mechanism of inter-particle electronic interaction between the inorganic and organic components of the nanomaterial. Specifically, the inorganic-organic hybrid associate has been made by integrating water soluble semiconductor (zinc-silver-indium-sulfide (ZAIS)) QDs and organic J-aggregates of a cyanine dye (S2165). The fabrication of the present nano-hybrid system has been achieved via electrostatically driven self-assembly of organic dyes over ZAIS QDs. The interaction between QD and J-aggregates has been investigated by using steady state and time resolved fluorescence measurements. Zeta potential measurements have also been performed to understand the role of electrostatic interaction and thermodynamic feasibility of the association process. The investigations have revealed that the energy transfer (ET) process between QD and J-aggregates was mediated through a dipole-dipole mechanism. Interestingly, data analysis based on Förster theory has further revealed that the ET from QD to J-aggregates is very high, indicating efficient electronic coupling between the inorganic QD and the organic J-aggregates. Zeta potential measurements and thermodynamic calculations have demonstrated that the interaction between QD and organic dye is electrostatically driven and the association of organic dyes over QDs is thermodynamically feasible. The outcome of the present study is expected to be helpful in designing efficient nanoscale light harvesting devices. Additionally, fluorescence microscopy and toxicity studies on the QDs have also shown their suitability for biological applications.

Amplified light harvesting for enhancing Italian lettuce photosynthesis using water soluble silicon quantum dots as artificial antennas.

Maximizing the utilization of the ultraviolet portion in the solar radiation spectrum has always been a goal for plant growth in order to minimize the harm and harvest the benefits. For this reason, fluorescent, amine-functionalized, and water-soluble silicon quantum dots (SiQDs) were fabricated with a mono-dispersed size of 2.4 nm. The SiQDs were used as artificial antennas to amplify the light harvesting ability and consequently enhance the photosynthesis in Italian lettuce. Upon ultraviolet excitation, the intense blue emission from the quantum dots matched very well to the absorption of the chloroplasts, allowing for the ultraviolet portion in solar radiation to be effectively utilized. The consumed optical energy enhanced the photosystem II activity, which made the amplification of photosynthesis possible. More importantly, in vivo, the quantum dots significantly promoted Italian lettuce seedling growth at concentrations below 30 mg L-1 on the root length, seedling height, and biomass by increasing the soluble sugar and water content by 49.8% and 40.9%, respectively. Interestingly, the chlorophyll a and b content increased to 41.0 and 114.8%, respectively, with no inhibition, even at the highest dose of 200 mg L-1. This study provides a new perspective on the use of quantum dots to amplify the utilization of ultraviolet light in agriculture.

Determination of Heavy Metal Ions in Seawater by Water-Soluble Quantum Dot Fluorescence Probe

Wang, L. and Shi, Y., 2019. Determination of heavy metal ions in seawater by water-soluble quantum dot fluorescence probe. In: Li, L.; Wan, X.; and Huang, X. (eds.), Recent Developments in Practices and Research on Coastal Regions: Transportation, Environment and Economy. Journal of Coastal Research, Special Issue No. 98, pp. 146–150. Coconut Creek (Florida), ISSN 0749-0208.In recent years, many analytical methods have been applied to the detection of toxic metal ions. However, the interference caused by a matrix will make the measurement method less precise, and some drugs are difficult to determine. We must find a highly sensitive analytical method; only in this way can we effectively monitor the content of heavy metal ions. Quantum dot (QD) technology is an interdisciplinary technology with high sensitivity. The photoluminescence properties of QDs are closely related to their surface modification. Many metal ions can significantly affect the optical properties of QDs through different mechanisms of action. QDs with wide excitation, narrow emission, and high-fluorescence quantum yield have broad application prospects in the field of fluorescence imaging in biological analysis. At present, the application of QDs to detect metal ions in complex substrates is a promising method. The difficulty of using QDs to detect heavy metals lies in how to improve their anti-interference performance in complex substrates.

A high sensitive and selective fluorescent probe for dopamine detection based on water soluble AgInS2 quantum dots

Herein, a water soluble AgInS2 quantum dots (AIS QDs) with high sensitive and selective for dopamine (DA) were prepared through a clean and facile reflux method with the mercapto propionic acid (MPA) and polyethyleneimine (PEI) used as the co-modifiers. The fluorescence quench of as-fabricated AIS QDs displayed an excellent selectivity and sensitivity to the DA and they showed a good linear relationship with the low detection limit (2.84 nm) in the range of 0.5–300 μmol/L. The mechanism of fluorescence quench may attributed to the photoinduced electrons migrated from AIS QDs to dopamine quinone, which originated from the oxidization of DA by ambient O2. Our work shows a promising prospect of designing and preparing AIS QDs used as the fluorescence sensors for DA detection.

A facile one step hydrothermal synthesis of carbon quantum dots for label -free fluorescence sensing approach to detect picric acid in aqueous solution

In this work, a facile one step approach has been applied for the synthesis of nitrogen and sulphur co-doped water soluble carbon quantum dots (NS-CQDs) through hydrothermal treatment of L-Lysine and thiourea. The obtained NS-CQDs have a high quantum yield (QY) of 53.19 % and emit strong blue fluorescence under UV light excitation of wavelength 365 nm. The morphology of NS-CQDs is spherical in shape and their sizes are distributed in the range 5–8 nm with average diameter 6.86 nm. Moreover the NS-CQDs show excitation dependent emission behavior due to quantum confinement effect. Additionally, NS-CQDs serve as a fluorescent probe for the selective and sensitive detection of picric acid (PA) in aqueous solution. A good linear response to PA in the concentration range 1–10 μM with a detection limit 0.24 μM has been obtained. The high selectivity of PA by NS-CQDs is suggested to arise from fluorescence resonance energy transfer (FRET) mechanism. Finally these NS-CQDs fluorescent probes have been examined in real water sample by measuring the concentration of PA in tap water.

The size dependent thermal diffusivity of water soluble CdTe quantum dots using dual beam thermal lens spectroscopy

Abstract Size dependent thermal diffusivity of CdTe colloidal quantum dots samples has been studied using dual beam thermal lens spectroscopy. The thermal diffusivity values of the colloidal solution of CdTe quantum dots synthesized in water were found to be less than that of pure water (1.4 × 10−7 m2/s) varying from 0.63 × 10−7 m2/s to 0.15 × 10−7 m2/s. The samples with this kind of very low value of thermal diffusivity can be good thermal insulators. To the best of our knowledge there are no reports on the study of thermal diffusivity of water soluble CdTe quantum dots. The non-radiative relaxation mechanism due to defect states, Brownian motion, capping agent etc. play major roles in controlling the thermal diffusivity of the nano-colloidal sample. The thermal diffusivity is found to be in inverse correlation with the emission intensity.