Functionalized CdTe Quantum Dots Research Articles

Dual-mode immunochromatography based on Ti3C2Tx functionalized CdTe quantum dots for chloramphenicol detection in animal-derived foods

In this study, Ti3C2Tx was coupled with CdTe quantum dots via plyethylenimine (PEI) mediation to form composite nanomaterials with dual colorimetric and fluorescent properties, which had strong pH, high ion strength, and organic solvent resistance. Then, this novel Ti3C2Tx@CdTe was firstly applied to develop a dual-mode immunochromatographic assay (ICA) for chloramphenicol (CAP) detection in animal-derived foods. The limits of detection of the colorimetric and fluorescent modes for CAP in milk/chicken/fish were 0.01 and 0.005 μg/kg, the limits of quantification were 0.025 and 0.016 μg/kg, the recovery rates were between 85.7% and 129.0% and 84.0%-119.2%, with the corresponding variations ranged from 6.5% to 14.8% and 6.4%-14.9%, respectively. The sensitivity of fluorescence mode was up to 100-fold higher than that of the reported ICA for CAP detection. The results of the confirmatory experiment on 30 samples showed good consistency with that of our established method (R2>0.93). The above results indicated that Ti3C2Tx@CdTe had superior detection performance and can provide a dual-mode signal calibration, high stability and sensitivity selection for immunoassay detection platforms.

Modeling and optimization of the ratio of fluorophores: a step towards enhancing the sensitivity of ratiometric probes.

In the ratiometric fluorescent (RF) strategy, the selection of fluorophores and their respective ratios helps to create visual quantitative detection of target analytes. This study presents a framework for optimizing ratiometric probes, employing both two-component and three-component RF designs. For this purpose, in a two-component ratiometric nanoprobe designed for detecting methyl parathion (MP), an organophosphate pesticide, yellow-emissive thioglycolic acid-capped CdTe quantum dots (Y-QDs) (analyte-responsive), and blue-emissive carbon dots (CDs) (internal reference) were utilized. Mathematical polynomial equations modeled the emission profiles of CDs and Y-QDs in the absence of MP, as well as the emission colors of Y-QDs in the presence of MP separately. In other two-/three-component examples, the detection of dopamine hydrochloride (DA) was investigated using an RF design based on blue-emissive carbon dots (B-CDs) (internal reference) and N-acetyl L-cysteine functionalized CdTe quantum dots with red/green emission colors (R-QDs/G-QDs) (analyte-responsive). The colors of binary/ternary mixtures in the absence and presence of MP/DA were predicted using fitted equations and additive color theory. Finally, the Euclidean distance method in the normalized CIE XYZ color space calculated the distance between predicted colors, with the maximum distance defining the real-optimal concentration of fluorophores. This strategy offers a more efficient and precise method for determining optimal probe concentrations compared to a trial-and-error approach. The model's effectiveness was confirmed through experimental validation, affirming its efficacy.

Influence of different functionalized CdTe quantum dots on the accumulation of metals, developmental toxicity and respiration in different development stages of the zebrafish (Danio rerio).

Introduction: The bioaccumulation and differential effects of cadmium tellurium quantum dot (CdTe QDs) nanomaterials with different functional groups are poorly understood in aquatic organisms. This study aimed to investigate the metal uptake, developmental effects, and respiratory effects of CdTe QDs with different functional groups (COOH, NH3, and PEG) on zebrafish embryos. Methods: Zebrafish embryos were exposed to carboxylate (COOH), ammonia (NH3), and polyethylene glycol (PEG) functionalized CdTe QDs at nominal concentrations of 0.5, 2, 4, 6, and 20 mg QDs/L. The materials were characterized in E3 exposure media and the metal uptake, developmental effects, and respiratory effects of zebrafish embryos were recorded. Results: The total Cd or Te concentrations in the larvae could not be explained by the metal concentrations or dissolution of the materials in the exposure media. The metal uptake in the larvae was not dose-dependent, except for the QD-PEG treatment. The QD-NH3 treatment caused respiration inhibition at the highest exposure concentration and hatching delays and severe malformations at low concentrations. The toxicities observed at low concentrations were attributed to particles crossing the pores in the chorion, and toxicities at higher concentrations were linked to the aggregation of particle agglomerates to the surface of the chorion impairing respiration. Developmental defects were recorded following exposure to all three functional groups, but the QD-NH3 group had the most severe response. The LC50 values for embryo development of QD-COOH and QD-PEG groups were higher than 20 mg/L, and the LC50 of the QD-NH3 group was 20 mg/L. Discussion: The results of this study suggest that CdTe QDs with different functional groups have differential effects on zebrafish embryos. The QD-NH3 treatment caused the most severe effects, including respiration inhibition and developmental defects. These findings provide valuable information for understanding the effects of CdTe QDs on aquatic organisms and highlight the need for further investigation.

A Novel L-Arginine Functionalized CdTe Quantum Dots Fluorescence Probe for Pyrophosphate Anion Detection.

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74-, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30μM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging.

Rare-earth ions coordination enhanced ratiometric fluorescent sensing platform for quantitative visual analysis of antibiotic residues in real samples

Levofloxacin (LVFX) as a representative drug of quinolone antibiotics is widely used in clinical, and its residues enriched in water bodies and sideline products seriously damage human health. It is imperative to develop a real-time/on-site sensing method for monitoring residual antibiotics. Here, we report a portable sensing platform by utilizing a composite fluorescent nanoprobe constructed by the cerium ions (Ce3+) coordination functionalized CdTe quantum dots (QDs) for the visual and quantitative detection of LVFX residues. This fluorescent probe provides a distinct color variation from red to green, which shows a good linear relationship to LVFX residues concentrations in the range of 0-6.0 µmol/L with a sensitive limit of detection (LOD) of 16.3 nmol/L. The smartphone platform with Color Analyzer App installed, which could accomplish quantified detection of LVFX in water, milk, and raw pork with a LOD of 27.9 nmol/L. The facile sensing method we proposed realizes rapid visualization of antibiotics residual in the environment and provides a practical application pathway in food safety and human health.

Reversible Ratiometric Electrochemiluminescence Biosensor Based on DNAzyme Regulated Resonance Energy Transfer for Myocardial miRNA Detection.

Myocardial miRNAs in peripheral blood are closely related to the pathogenic process of myocardial infarction. Rapid identification and accurate quantification of myocardial miRNAs are of great significance to clinical interventions for treating cardiovascular lesions. Therefore, a ratiometric electrochemiluminescence (ECL) biosensor integrating DNAzyme with a resonance energy transfer (RET) system was designed to detect myocardial miRNA. The dual-signal system was composed of rA marked substrate strand functionalized CdTe quantum dots (QDs) as reductive-oxidative (R-O) emitters and Cy5-labeled strand-functionalized Ru(bpy)32+-filled silica nanoparticles (RuSi NPs) as oxidative-reductive (O-R) emitters. In the presence of target miRNA, DNAzyme was activated to cut substrate strands on the CdTe QDs and release triggers for opening hairpin probes. Then, the Cy5 molecule-labeled hairpin DNA on the RuSi NPs was opened to introduce Cy5 molecules and RuSi NPs into the system. The R-O ECL was quenched by ECL-RET between CdTe QDs and Cy5 molecules and the O-R ECL was introduced by the RuSi NPs. In this way, based on the simultaneous changing of the ECL signal, the dual-potential dynamic signal ratiometric ECL sensing platform was developed. By measuring the ratio of O-R ECL signal to R-O ECL signal, the concentration of miRNA-499 was accurately quantified in the range of 10 fM to 10 nM, and the detection limit was as low as 2.44 fM (S/N = 3). This DNAzyme guided dual-potential ratiometric ECL method provides a sensitive and reliable method for myocardial miRNA detection, and it has great potential in clinical diagnosis and treatment.

CdTe quantum dots incorporated in CoNiAl layered double hydroxide interlayer spaces as a highly efficient visible light driven photocatalyst for degradation of an azo dye and Bisphenol A

The photocatalytic application of CdTe quantum dots (QDs) is restricted by the charge carriers recombination and tendency to aggregate in suspended systems. Novel functionalized CdTe (F-CdTe) QDs and CoNiAl layered double hydroxide (LDH) nanocomposite have been prepared to utilize the unique advantages of CdTe QDs. The nanocomposite is prepared via in situ synthesis of LDH in the presence of as-prepared F-CdTe QDs where the QDs partially intercalated in the interlayer spaces of LDHs. As a result of the effective electronic coupling between F-CdTe QDs and CoNiAl LDH, the light-harvesting ability has been enhanced and the absorption edge expands toward the higher visible light wavelengths. Moreover, the charge carriers recombination in nanocomposite has been considerably suppressed compared to the pristine CoNiAl LDH and F-CdTe QDs. Also, the nanocomposite shows remarkable enhancing in photocatalytic degradation of Acid Red 14 (AR14) and Bisphenol A (BPA) as the sample pollutants. The photogenerated holes and hydroxyl radicals have a determining role in the degradation of AR14. The plausible mechanism is proposed based on the experimental results and theoretical calculations. The prepared nanocomposite represents superior photocatalytic activity after 5 consecutive runs. So, the CdTe QDs can be effectively utilized in photocatalytic applications through the proposed promising approach.

Thermodynamic and kinetic insights into the interactions between functionalized CdTe quantum dots and human serum albumin: A surface plasmon resonance approach

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA–QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA−CdTe@TGA]‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (Ea−TGA‡= 65.10 and T∆Sa−TGA‡= 28.62 kJ mol−1) than the formation of [HSA−CdTe@MPA]‡ (Ea−MPA‡ = 38.13 and T∆Sa−MPA‡ = 0.53kJ mol−1). While the [HSA−CdTe@MPA]° dissociation required higher energy and lower entropy loss (Ed−MPA‡ = 49.96 and T∆Sd−MPA‡ = − 32.18kJ mol−1) than the [HSA−CdTe@TGA]° dissociation (Ed−TGA‡= 30.78 and T∆Sd−TGA‡= − 51.12 kJ mol−1). The stability of [HSA−QDs]° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH° = − 11.83 and TΔS° = 32.72 kJ mol−1) with TGA (ΔH° = 34.31 and TΔS° = 79.73 kJ mol−1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA−QDs]°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA–QD interaction, thus their application.

Paper-Based Simplified Visual Detection of Cry2Ab Insecticide from Transgenic Cottonseed Samples Using Integrated Quantum Dots-IgY Antibodies.

In the present study, an easy to use field-deployable methodology was developed for onsite detection of pesticidal crystal protein Cry2Ab from transgenic cotton crops to reduce seed adulteration. Anti Cry2Ab IgG and IgY antibodies were developed against recombinant Cry2Ab protein in New Zealand white rabbits and in white leg horn chickens, respectively. Carboxyl-functionalized CdTe quantum dots (QDs) were used as revealing probes, and nitrocellulose paper was used as an assay matrix. Recombinant Cry2Ab was generated in the lab and used for immunization of chicken and rabbits. After successful immunization and attaining the desired titer values (1:32 000 for IgY and 1:64 000 for IgG), eggs and hyperimmune sera were collected. Anti Cry2Ab IgY was purified as per the standardized protocols, and anti Cry2Ab IgG was purified using protein A affinity chromatography. Sensitivity of the generated antibodies was examined using indirect ELISA methods against recombinant Cr2Ab protein. Specificity evaluation was carried out against other Cry proteins including Cry2Ab, Cry4b, Cry4a, Cry1Ec, and Cry1Ac. Functionalized CdTe QDs were characterized for structure and shape as well as fluorescence properties using standard laboratory techniques. A field-deployable paper-based detection methodology was developed where IgG acted as the capturing antibody and IgY-linked CdTe QDs were used as revealing probes. The limit of detection (LOD) and quantification (LOQ) were found to be 2.91 ng/mL and 9.71 ng/mL, respectively. The effect of matrix interference was assessed on the different plant crude extracts of cottonseed materials.

Four-channel fluorescent sensor array based on various functionalized CdTe quantum dots for the discrimination of Chinese baijiu

As a special carrier of traditional Chinese culture, baijiu is rich in terms of types and ingredients. Its quality analysis and control are always important and complex issues that urgently need reliable evaluation methods. In this study, four different modified CdTe quantum dots (QDs) were used to characterize their sensing performance to various baijiu. A sensor array was then constructed through the complementary properties of differential fluorescence signals. To achieve an accurate and rapid evaluation of different baijiu types, a linear discriminant analysis (LDA) was introduced to extract and process spectral information. And the array was able to distinguish commercial baijiu samples with different aroma-types, brands, qualities and storage years with a recognition rate of 100%. In addition, according to the heat map, the organic acids in baijiu were shown to be the main components causing the fluorescence change through electron transfer (hydrogen bond) and resonance energy transfer among QDs and acids. Furthermore, using the partial least squares regression (PLSR) model, five representative organic acids were accurately quantified with a quantitative range of 10 μmol/L-80 μmol/L with a high selectivity. This QDs fluorescence sensing strategy provides an accurate, simple, and fast baijiu sensing method, which provides a potential use for on-line baijiu monitoring.

Functionalized CdTe fluorescence nanosensor for the sensitive detection of water borne environmentally hazardous metal ions

In this work, we have investigated the possibility of using COOH functionalized CdTe quantum dots (QDs) as fluorescent nanosensor for the detection of some environmentally hazardous metal ions ($\rm{Cr^{3+}}$, $\rm{Pb^{2+}}$, $\rm{Cu^{2+}}$, $\rm{Zn^{2+}}$ and $\rm{Co^{2+}}$) in aqueous phase. COOH-CdTe QDs are prepared in aqueous medium and characterized by UV-visible, photo luminescence and FTIR spectrometry. Optical response of CdTe nanosensor is observed to be time and temperature dependent. A strong "Turn-Off" fluorescence response of CdTe is observed in presence of all metals ions ($\rm{X^{n+}}$). The output of Stern volmer relation, graphical Job's plot and FTIR data established the existence of strong 1:1 complexation ($\rm{X^{n+}: ^{-}OOC-CdTe)}$ between CdTe and metal ions. CdTe shows its efficient sensing ability for $\rm{Pb^{2+}}$, $\rm{Cr^{3+}}$ and $\rm{Cu^{2+}}$ ions up to concentration $\rm{10^{-14}}$ M which was established by its low detection of limit (LOD)validation. Further, strong appearance of $\frac{F-F_{0}}{F_{0}}$ establishes the better sensing capability of CdTe QDs for $\rm{Cr^{3+}}$, $\rm{Pb^{2+}}$, $\rm{Cu^{2+}}$ ions which are far better than the existing fluorescent sensors available in industry. The proposed optical techniques and principal component analysis of sensing were successfully applied for testing of dissolved metal ions in real samples like: paint, river water, rain water etc which validates the applicability of COOH functionalized CdTe nanosensor as a effective successful optical sensor for water dissolved metal ions which are responsible for water pollution.

Optical and electronic properties of CdTe quantum dots in their freezed solid matrix phase and solution phase

The present work deals with the comparison of sizes, optical and electronic properties of COOH functionalized CdTe quantum dots (QDs) in freezed solid polymeric (polyvinyl alcohol (PVA) matrix and in solution phase (water). PVA has been chosen as host material for guest CdTe QDs because of its unique properties like hydrophilicity, good thermo stability, and easy process ability. Experimental absorption, emission, X-Ray diffraction spectra and electronic band gap have been studied by UV–Vis absorption, luminescence and X-Ray diffraction spectroscopy. The smaller size of CdTe QDs in solid PVA polymer matrix (∼6 nm) and larger band gap of ∼9.5 eV validates their quantum confinement regime in freezed solid phase. The smaller particle size in solid phase compared to that of the particle size in its solution phase (8 nm) validates the non existence of agglomeration in solid phase. Appearance of high intense and wide luminescence emission in solid form proves the strong candidature of CdTe QDs as promising sensors for today’s optoelectronic and biomedical industry.

Photoinduced holes transfer based visual determination of dopamine in human serum.

A simple unexplored strategy was followed to construct ratiometric fluorescence-based sensing system for the detection of dopamine (DA) in human serum. Ratiometric fluorescence system was constructed through bonding energy transfer (TBET) by conjugating carboxyl functionalized CdTe quantum dots (QDs) and amine-capped Carbon quantum dots (CQDs). The photophysical properties of sensing system were characterized by standard methods. Photoluminescence (PL) of sensing system under excitonic wavelength (350 nm) depends on dual emission at 440 and 595 nm that corresponds to CQDs and CdTe QDs respectively. The developed sensing system was utilized for visual determination of DA, an unquenched blue fluorescence of CQDs in ratiometric system reveals the visual color differentiation for DA binding with CdTe QDs among the possible interferences (Alanine, Glycine, Glucose, Sucrose, Urea and Ascorbic acid). The limit of detection (LOD) and quantification (LOQ) was calculated as 8.1 and 27.2 nm respectively by using regression analysis. Photoinduced holes transfer (PHT) might have attributed the possible sensing mechanism for DA that quench the photoluminescence sequentially to enhance the sensing performance of QDs. The matrix interferences and reliability of the developed sensing platform were evaluated by testing DA spiked human serum and the sensing response was found to be field deployable.

Molecular Imprinting Polymers Based on Boric Acid-Modified CdTe QDs for Sensitive Detection of Glucose

In this study, a novel imprinted polymer based on 3-aminophenylboronic acid (APBA)-functionalized CdTe quantum dots (QDs) was synthesized and used to sensitively and selectively detect glucose. In the process of synthesis, the boronic acid in the APBA could combine covalently with vicinal diol compounds, directing imprinting process, and the APBA-modified CdTe QDs were used as the solid supports. By this method, the prepared molecular imprinting polymers (MIPs)-APBA/CdTe QDs show high selectivity, high sensitivity and good stability. Under optimal conditions, a linear relationship was obtained covering the linear range of 0–1.5[Formula: see text]mmol/L with a correlation coefficient of 0.99833 and a high imprinting factor about 5.71. Furthermore, the prepared MIPs-APBA/CdTe QDs were successfully applied to detect glucose in human serum samples. This work provides a new way to synthesize an excellent stability and efficient imprinted polymer based on CdTe QDs for convenient, fast and highly selective detection of glucose.

Switch-on fluorescent strategy based on crystal violet-functionalized CdTe quantum dots for detecting L-cysteine and glutathione in water and urine.

The concentration of L-cysteine (Cys) and glutathione (GSH) is closely related to the critical risk of various diseases. In our study, a new rapid method for the determination of Cys and GSH in water and urine samples has been developed using a fluorescent probe technique, which was based on crystal violet (CV)-functionalized CdTe quantum dots (QDs). The original QDs emitted fluorescence light, which was turned off upon adding CV. This conjugation of CV and QDs could be attributed to electrostatic interaction between COO- of mercaptopropionic acid (MPA) on the surface of QDs and N+ of CV in aqueous solution. In addition, Förster resonance energy transfer (FRET) also occurred between CdTe QDs and CV. After adding Cys or GSH to the solution, Cys or GSH exhibited a stronger binding preference toward Cd2+ than Cd2+-MPA, which disturbed the interaction between MPA and QDs. Thus, most MPA was able to be separated from the surface of QDs because of the participation of Cys or GSH. Then, the fluorescence intensity of the CdTe QDs was enhanced. Good linear relationships were obtained in the range of 0.02-40μgmL-1 and 0.02-50μgmL-1, and the detection limits were calculated as 10.5ngmL-1 and 8.2ngmL-1, for Cys and GSH, respectively. In addition, the concentrations of biological thiols in water and urine samples were determined by the standard addition method using Cys as the standard; the quantitative recoveries were in the range of 97.3-105.8%, and relative standard deviations (RSDs) ranged from 2.5 to 3.7%. The method had several unique properties, such as simplicity, lower cost, high sensitivity, and environmental acceptability. Graphical abstract Crystal violet-functionalized CdTe quantum dots for detecting L-cysteine and glutathione with switch-on fluorescent strategy.

Boric acid functionalized ratiometric fluorescence probe for sensitive and on-site naked eye determination of dopamine based on two different kinds of quantum dots

A simple dual-emission probe based on 3-aminophenylboronic acid functionalized CdTe quantum dots (QDs) and carbon quantum dots (CQDs) was developed for the on-site naked eye detection of dopamine (DA).

Fluorescent switching technology based on fluorescence resonance energy transfer for detecting dimethoate pesticides in environmental water

Dithizone functionalized CdTe quantum dots for detecting dimethoate pesticide with switch-on fluorescent strategy.

β-cyclodextrin functionalized CdTe quantum dots for electrochemiluminescent detection of benzo[a]pyrene

β-cyclodextrin (β-CD) functionalized CdTe quantum dots (QDs) were prepared with β-CD and mercaptopropionic acid (MPA) as the stabilizers (denoted as β-CD-MPA-CdTe). The QDs capped with the dual stabilizers, β-CD and MPA, not only showed improved electrochemiluminescence (ECL) efficiency and higher ECL intensity due to the effective removal of the nonradiative surface state and deep surface trap of the QDs, but also exhibited selective response toward benzo[a]pyrene (BaP) as a consequence of specific host-guest interaction between the β-CD and BaP, resulting in decreased ECL of the QDs. On the basis of the quenching effect of BaP on the ECL of β-CD-MPA-CdTe QDs, a sensitive and selective method for the determination of BaP was developed. Under optimal conditions, a linear range from 87pM to 10nM with a detection limit of 29pM (S/N=3) was obtained for the detection of BaP.

A novel fluorescent sensor for mercury (ii) ion using self-assembly of poly(diallyl dimethyl ammonium)chloride functionalized CdTe quantum dots

A novel fluorescent sensor was constructed for selective quantitative analysis of mercury(ii) ion based on poly(diallyl dimethyl ammonium)chloride (PDDA) functionalized CdTe quantum dots.

Dopamine functionalized–CdTe quantum dots as fluorescence probes for l-histidine detection in biological fluids

In this paper, we developed dopamine functionalized–CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe–dopamine (QDs–DA) could be quenched by Ni2+ due to the strong coordination interaction between the pyrocatechol structure of QDs–DA and Ni2+. In the presence of l-histidine, Ni2+ preferred to bind with l-histidine due to high affinity of Ni2+ to l-histidine and the photoluminescence intensity of QDs–DA was recovered. The recovered photoluminescence intensity of QDs–DA was proportional to the concentration of l-histidine in the ranges of 1.0×10−6–1.0×10−4molL−1 and the detection limit was 5.0×10−7molL−1 respectively. The established method showed a good selectivity for l-histidine among other common amino acids, and it was applied for determination of l-histidine in human serum sample with satisfactory results.