Thioglycolic Acid Capped CdTe Quantum Research Articles

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.

Luminescent diagnostics and quantitative assessment of malaria based on a lateral flow immunoassay with cdte quantum dots

A lateral flow immunoassay (LFI) is a simple, low-cost and rapid diagnostic tool to identify various diseases by detecting analytes such as antibodies, parasites, or other relevant biomarkers. However, most LFIs can only confirm the presence or absence of a target analyte being applied as qualitative diagnostic tools. In addtion, the conventional LFIs, which require visual inspection of the test line, may demonstrate insufficient sensitivity for the mild form or early detection of infections and for this reason, the result can be falsely negative. This study presents the results of employing thioglycolic acid capped CdTe quantum dots as a probe to enhance luminescence and subsequently detection sensitivity in LFIs for diagnosis of malaria. The chemical route synthesis of thioglycolic acid capped CdTe quantum dots was optimized systematically by probing optical properties of the quantum dots. These optimized quantum dots of thioglycolic acid capped CdTe have been conjugated with the anti-malaria antibodies against HRP2 protein (P. falciparum) and were then incorporated into LFIs. Further, an image processing code has been developed to carry out the quantification of malaria parasites in terms of the ratio on intensities of control and test lines on the LFIs. The results have been compared with those obtained using the standard, colloidal gold based LFIs. It has been demonstrated that sensitivity and lower detection limits of malaria under low parasite concentration increase significantly due to enhanced luminescence of control and test lines under UV light, owing to the presence of thioglycolic acid capped CdTe quantum dots. It has also been shown that the image processing based quantification of malaria will likely minimize the chances of false negative results under low parasite concentration and assist in early diagnosis of malaria.

Thioglycolic Acid Capped CdTe Quantum Dots as Sensors for the Detection of Hazardous Heavy Metal Ion Cu2+ in Water

Thioglycolic Acid Capped CdTe Quantum Dots as Sensors for the Detection of Hazardous Heavy Metal Ion Cu2+ in Water

A highly selective and simple fluorescent probe for salbutamol detection based on thioglycolic acid-capped CdTe quantum dots.

In this paper, a highly fluorescent water-soluble CdTe quantum dots (CdTe QDs) stabilized with thioglycolic acid (TGA) were synthesized for the quantitative and selective determination of salbutamol (SAL). When ten different of 2.09×10-6 mol L-1 alpha-2 adrenoceptor agonist were added to 4.38×10-4 mol L-1CdTe QDs solution, the fluorescence signal of the CdTe QDs quenched obviously by SAL with 57.32% and 0.815% - 7.00% for other nine kinds of veterinary medicine, such as tulobuterol, fenoterol, phenylethanamine A, simatero, penbutolol, clenbuterol, ractopamine, terbutaline and clorprenaline. The result shows that the CdTe QDs is highly sensitive sensor for SAL. The quenching mechanism has been investigated by absorption spectroscopy and KSV at different temperatures, and shew a static quenching process than dynamic quenching. Under the optimal conditions, respectively the straight line equation (F0/F=0.1491×106 C+1.3078) was found between the relative fluorescence intensity and the concentration of SAL was in the range of 6.27×10-8 to 2.09×10-7 mol L-1, and the limit of detection was 4.2×10-8 mol L-1. The proposed method has been applied to the determination of SAL in pig urine samples.

Aptamers-Based Sensing Strategy for 17β-Estradiol Through Fluorescence Resonance Energy Transfer Between Oppositely Charged CdTe Quantum Dots and Gold Nanoparticles.

A novel aptamers-based fluorescence resonance energy transfer (FRET) assay was developed employing the oppositely charged thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) and cysteamine-stabilized gold nanoparticles (cysteamine-AuNPs). The fluorescence of TGA-CdTe QDs was significantly quenched with addition of cysteamine-AuNPs via the FRET. The FRET process can be modulated by 17β-estradiol in that the specific recognition between 17β-estradiol and aptamers could show different effects on the aptamers-mediated aggregation of cysteamine-AuNPs, and correspondingly adjust the FRET process. The feasibility of the method has been demonstrated by carrying out the detection of 17β-estradiol with the wide linear range from 0.5·ng mL-1 to 150 ng·mL-1 and the low detection limit of 0.057 ng·mL-1. The established assay exhibited favorable selectivity towards 17β-estradiol over other endocrine disrupting compounds and probably coexisting chemicals in real samples. Furthermore, the assay has been successfully applied to detect 17β-estradiol in real tap water samples and feeds samples with good performance. The results were in full consistence with those from HPLC method, indicating the reliability of the detection system. The aptamers-based FRET assay is expected to offer a new opportunity for the rapid analysis of 17β-estradiol in real samples.

Boric Acid-Based Dual Modulation Photoluminescent Glucose Sensor Using Thioglycolic Acid-Capped CdTe Quantum Dots

Most luminescent glucose sensors based on the interaction of glucose with organic boric acids or borates. Herein, a new luminescent glucose sensor is designed using thioglycolic acid-capped CdTe quantum dots in the presence of cheap inorganic boric acid. Both peak position and intensities change upon the addition of glucose because of the interaction of boric acid with glucose and thioglycolic acid-capped CdTe quantum dots, which enables glucose detection by either color change or intensity change. The luminescent intensities change linearly with glucose concentrations in the ranges from 0.03 to 1 mM and 1–25 mM with a detection limit of 10 µM (S/N = 3). Moreover, glucose concentrations can be conveniently detected by color change in the range from 1 mM–25 mM. It displays a highly selective response to glucose over other interfering but biologically important saccharides, amino acids, and common ions. A thioglycolic acid-capped CdTe QD-based sensor can detect glucose with wide linear range by change in intensity or color in the presence of cheap inorganic boric acid.

Flow-based determination of methionine in pharmaceutical formulations exploiting TGA-capped CdTe quantum dots for enhancing the luminol-KIO4 chemiluminescence

A novel flow-injection chemiluminescence method (FI-CL) was established for the determination of methionine in this paper, based on its strong enhancement on CL intensity of the luminol-KIO4 system catalyzed by thioglycolic acid-capped CdTe quantum dots in alkaline media. Under the optimized conditions, the relative CL intensity was in proportion to methionine concentration in the range from 1.0×10−8 to 1.0×10−5gmL−1 with a detection limit of 6.6×10−9gmL−1 (3σ). The relative standard deviation (RSD) of the CL intensity for 1.0×10−6gmL−1 standard methionine solution was 0.97% (n=11). The proposed method was successfully applied to determine methionine in commercial pharmaceutical formulations with recoveries between 98.0% and 101.9%. The possible CL mechanism was discussed as well.

Sensitive arginine sensing based on inner filter effect of Au nanoparticles on the fluorescence of CdTe quantum dots

Arginine plays an important role in many biological functions, whose detection is very significant. Herein, a sensitive, simple and cost-effective fluorescent method for the detection of arginine has been developed based on the inner filter effect (IFE) of citrate-stabilized gold nanoparticles (AuNPs) on the fluorescence of thioglycolic acid-capped CdTe quantum dots (QDs). When citrate-stabilized AuNPs were mixed with thioglycolic acid-capped CdTe QDs, the fluorescence of CdTe QDs was significantly quenched by AuNPs via the IFE. With the presence of arginine, arginine could induce the aggregation and corresponding absorption spectra change of AuNPs, which then IFE-decreased fluorescence could gradually recover with increasing amounts of arginine, achieving fluorescence “turn on” sensing for arginine. The detection mechanism is clearly illustrated and various experimental conditions were also optimized. Under the optimum conditions, a decent linear relationship was obtained in the range from 16 to 121μgL−1 and the limit of detection was 5.6μgL−1. And satisfactory results were achieved in arginine analysis using arginine injection, compound amino acid injection, even blood plasma as samples. Therefore, the present assay showed various merits, such as simplicity, low cost, high sensitivity and selectivity, making it promising for sensing arginine in biological samples.

Preparation and multicolored fluorescent properties of CdTe quantum dots/polymethylmethacrylate composite films

A new simple route was presented for the preparation of stable fluorescent CdTe/polymethylmethacrylate (CdTe/PMMA) composite films by using hydrophilic thioglycolic acid capped CdTe quantum dots (TGA-CdTe QDs) and polymethylmethacrylate (PMMA) as raw materials. The TGA-CdTe QDs were firstly exchanged with n-dodecanethiol (DDT) to become hydrophobic DDT-CdTe QDs via a ligand exchange strategy, and then incorporated into PMMA matrix to obtain fluorescent CdTe/PMMA composite films. The structure and optical properties of DDT-CdTe QDs and CdTe/PMMA composite films were investigated by XRD, IR, UV and PL techniques. The results indicated that the obtained DDT-CdTe QDs well preserved the intrinsic structure and the maximum emission wavelength of the initial water-soluble QDs and the resulting 6.10 wt% CdTe/PMMA composite film exhibited significantly enhanced PL intensity. Furthermore, the multicolored composite films with green, yellow-green, yellow and orange light emissions were well tuned by incorporating the CdTe QDs of various maximum emission wavelengths. The TEM image demonstrated that the CdTe QDs were well-dispersed in the PMMA matrix without aggregation. Superior photostability of QDs in the composite film was confirmed by fluorescence lifetime measurement. Thermo-gravimetric analysis of CdTe/PMMA composite films showed no obvious enhancement of thermal stability compared with pure PMMA.

Characterization of the interaction of FTO protein with thioglycolic acid capped CdTe quantum dots and its analytical application

CdTe quantum dots (QDs) were synthesized in aqueous solution using thioglycolic acid (TGA) as stabilizing agents. The interaction between TGA-CdTe QDs and fat mass and obesity-associated (FTO) protein was investigated by fluorescence, UV–visible absorption, synchronous fluorescence and three-dimensional fluorescence spectroscopy. Results revealed that TGA-CdTe QDs could strongly quench the intrinsic fluorescence of FTO protein with a static quenching procedure. Both the van der Waals and hydrogen bonding played a major role in stabilizing the complex. The binding constant and thermodynamic parameters at different temperatures were obtained. In addition, we found that the fluorescence intensity of QDs was significantly enhanced by the addition of FTO protein. Based on this, a sensitive method for detecting FTO protein was obtained in the linear range of 5.52×10−9–6.62×10−7molL−1 with the detection limit of 1.14×10−9molL−1. The influences of factors on the interaction between FTO protein and TGA-CdTe QDs were studied.

CdTe quantum dots and gold nanoparticle based spectral methods for determination of lincomycin

Two novel and convenient methods for the determination of lincomycin (LCM) in aqueous solutions have been developed. The first method was based on the enhanced fluorescence of thioglycolic acidcapped CdTe quantum dots (TGA-CdTe QDs) by LCM. For the second method, the introduction of LCM could induce the aggregation of gold nanoparticles (AuNPs), displaying distinct changes in color and in UVvis spectra. Under optimal conditions, the enhanced fluorescence intensity was linearly proportional to LCM concentration in the range of 1–240 μg mL−1 with a detection limit of 2.63 × 10−1 μg mL−1. The second platform is capable of determining LCM in ranges from 1.00 × 10−3 to 2.00 × 10−2 μg mL−1 and from 3.00 × 10−2 to 1.20 × 10−1 μg mL−1 with a detection limit of 1.27 × 10−4 μg mL−1. Both methods were used for rapid detection of LCM in real samples with satisfactory results. Comparisons between the two methods were made.

Determination of Tigecycline by Quantum Dots/Gold Nanoparticles-based Fluorescent and Colorimetric Sensing System

In this study, two simple and sensitive methods for detection of tigecycline are developed based on thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) and unmodified gold nanoparticles (AuNPs), respectively. The first method was based on the fluorescence quenching of CdTe QDs by the addition of tigecycline. For the second method, the introduction of tigecycline could induce the aggregation of gold nanoparticles, displaying distinct changes in color and in UV-vis spectra. Under optimal conditions, the relative fluorescence intensity of CdTe QDs decreased linearly with the increasing concentration of tigecycline in the range of 0.11-35.56 ug mL-1 with a detection limit of 3.93×10-2 ug mL-1. While the colorimetric sensor could detect tigecycline in linear range from 5.98×10-3 to 1.44×10-1 ug mL-1 and from 0.30 to 2.99 ug mL-1 with a detection limit of 1.07×10-3 ug mL-1. Moreover, both the proposed methods were applied to real sample with satisfactory results. Finally, comparisons between these two methods were made. Keywords: Colorimetric, fluorescence quenching, gold nanoparticles, quantum dots, tigecycline.

CdTe量子点功能化玻片的制备及其对Pb2+浓度的检测

通过羟基化和氨基硅烷化处理,得到表面接枝氨基的玻片载体。水相合成巯基乙酸修饰的CdTe量子点（CdTe-TGA）,采用EDC/NHS活化反应,将量子点偶联到氨基化玻片表面,制备出具有荧光性能的功能化玻片。考察了量子点与EDC的量比、活化时间、偶联温度以及偶联时间对偶联效果的影响。结果表明,在量子点与EDC的量比为1∶30、活化时间1 h、偶联温度30℃、偶联时间4 h条件下获得的功能化玻片具有最佳的荧光性能。将该条件下制备的功能化玻片用于水溶液中Pb2＋的浓度检测,得到玻片相对荧光猝灭强度随Pb^2＋浓度变化的线性曲线,线性范围为1.0×10^-9-4.0×10^-8mol·L^-1,检出限为3.8×10^-9mol·L^-1,且具有良好的选择性。该方法可以灵敏而准确地检测Pb2＋浓度。

Investigation of ultrafast relaxation dynamic process of water-soluble TGA-CdTe quantum dots

In the present paper, we study the average fluorescence lifetimes, detected by using the time-correlated single-photon-counting (TCSPC) technique, of three thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs), which are ～6 ns, ～9 ns and ～11 ns; and the fluorescence kinetic process includes two parts:the slow process and the fast process. With the increase of the particle size, the slow process becomes longer, but the fast process becomes shorter. Afterwards, by using both femtosecond transient absorption and fluorescence up-conversion time-resolved spectrum techniques, we have investigated the interband relaxation process of three TGA-CdTe QD samples, with the nanoparticle diameters of 2.3, 2.8 and 3.5 nm. Investigation indicates that for the three QD samples, exciton filling rate becomes slower in the highest excited state and the lowest excited state, among them, the time of exciton filling increases from 0.33 to 0.79 ps for the highest excited state, while the time of exciton filling increases from 0.53 ps to 1 ps for the lowest excited state. Moreover, the two kinds of experiment provide complementary information and obtain the full image of interband relaxation process. Result shows that the bleach recovery of the 1 S transition shows an initial rise, but the fluorescence up-conversion signal for the 1 S transition is slower in rise time, which can provide help in the application of optoelectronic devices.

“Turn-on-off-on” fluorescence switching of quantum dots–cationic porphyrin nanohybrid: a sensor for DNA

In this article, we describe a new platform for probing double stranded DNA (dsDNA) by tracing the "on-off-on" fluorescence signals of quantum dots-cationic porphyrin utilizing fluorescence and synchronous fluorescence measurements. Electrostatic interaction between the negatively charged thioglycolic acid capped CdTe quantum dots (CdTe-TGA QDs) and positively charged porphyrin surfaces leads to drastic quenching (turning off) of the donor by an effective electron transfer process. Interestingly, after the addition of calf thymus DNA (CtDNA), the porphyrins peel off from the quantum dot surface and bind to dsDNA, resulting in the restoration of fluorescence intensity of quantum dots (turning on). Consequently, this can be utilized for the selective sensing of dsDNA via optical responses. Experimental results show that the increase in fluorescence intensity is proportional to the concentration of CtDNA within the range of 6.5 × 10(-9) M to 29.6 × 10(-8) M under the optimized experimental conditions. Furthermore, the peel off mechanism was confirmed by atomic force measurement.

Structural, optical, and electrical properties of thioglycolic acid-capped CdTe quantum dots thin films

Water-soluble cadmium telluride (CdTe) quantum dots (QDs) were synthesized using thioglycolic acid as capping agent; this reaction was carried out at pH = 10.2 and refluxed at 100°C for 18 h. The CdTe QDs prepared at various reflux times from 1 to 18 h were coated on the glass substrates to obtain thin films of the CdTe QDs with the same thickness. The CdTe thin films were characterized by X-ray diffraction, ultraviolet-vis spectroscopy, and photoluminescence spectroscopy. The absorption thresholds of the CdTe thin films are blueshifted by about 0.65 eV with respect to the bulk value (1.5 eV), due to the quantum size effect as expected from the nanocrystalline nature of the CdTe QDs. X-ray diffraction showed that the films consisted of small CdTe nanocrystallites, 2.91 to 3.57 nm in size, showing quantum size effects. The effects of temperature on the electrical properties of the films were studied in detail. Electrical resistivity measurements were carried out for different films in the temperature range from 343 to 463 K. It is shown that activation energy increases by increasing the reflux time.

Highly selective detection of dopamine in the presence of ascorbic acid and uric acid using thioglycolic acid capped CdTe quantum dots modified electrode

In this work, cadmium telluride (CdTe) quantum dots (QDs) have been successfully applied for construction of a novel chemically modified electrode for determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). The small CdTe QDs were synthesized by using a wet chemical routes in the presence of thioglycolic acid (TGA), as capping agent at pH 9.5, having particle diameters of 1–3nm. The synthesized QDs were immobilized on the surface of gold disk electrode by self assembly method in dark conditions for 30h and electrochemically characterized. The modified CdTe QDs-based electrode afforded the simultaneous detection of these three compounds with wide peak separations, which allowed the interferences to be masked with applied potential. Using a potential window of 0–350mV, where only dopamine was electroactive, a detection limit of 8.27×10−9M and 1.30×10−9M were calculated from square wave voltammetry and amperometry, respectively.

Spectral method determination of kanamycin sulfate using both gold nanoparticles and quantum dots

Two novel methods for the determination of kanamycin sulfate (Kan) have been developed. The first method was based on the enhanced fluorescence of thioglycolic acid-capped CdTe quantum dots by Kan in aqueous solutions. The second method was a simple colorimetric method to detect trace amounts of Kan with unmodified gold nanoparticles as the sensing probe. Under optimal conditions, the relative fluorescence intensity was linearly proportional to the concentration of Kan between 1.80 × 10−2 μg mL−1 and 8.00 × 10−1 μg mL−1. The linear ranges of the colorimetric sensor for Kan were from 3.75 × 10−3 μg mL−1 to 4.25 × 10−2 μg mL−1 and from 4.40 × 10−2 μg mL−1 to 9.88 × 10−2 μg mL−1, respectively. Comparisons between the two methods were made. Both methods were used for rapid detection of Kan in real samples with satisfactory results.

Electrochemical reduction of dioxygen on a thioglycolic acid-capped CdTe quantum dots modified glassy carbon electrode

A novel modified electrode was constructed by immobilizing thioglycolic acid-capped CdTe quantum dots (QDs) on a glassy carbon electrode (GCE) using Nafion ionomers. The results obtained by electrochemical impedance spectroscopy, cyclic voltammetry, and rotating disk electrode using the modified QDs–Nafion/GCE in a 0.20 M phosphate buffer of pH 7.0 revealed that the QDs act as effective mediators for the electrocatalytic reduction of dioxygen.

Suppressed blinking behavior of thioglycolic acid capped CdTe quantum dot by amine functionalization

Prepared water soluble thioglycolic acid capped CdTe quantum dots (QDs) were further surface functionalized by ethylene diamine (EDA). Amine functionalized CdTe QDs demonstrate enhanced luminescence intensity at ensemble measurements and suppressed luminescence intermittency behavior at the single molecule level. A clear decrease in the power law exponent for “on” time behavior is observed in amine modified CdTe QDs. Our results show that surface of CdTe QDs modified by EDA can lead to an important physical mechanism to enhance fluorescence intensity, reduce blinking, and increase photostability.