Fluorescent Quantum Dots Research Articles

Combining CdTe/CdS/ZnS Quantum Dot Fluorescence Temperature Measurements with Double-Helix Point Spread Function Axial Location for Intracellular 3D Thermograms

Combining CdTe/CdS/ZnS Quantum Dot Fluorescence Temperature Measurements with Double-Helix Point Spread Function Axial Location for Intracellular 3D Thermograms

(Invited) Highly Emissive CdTe Quantum Dots Passivated with Novel Branched Ligands as Fluorescent Sensors

Fluorescent-based sensors attract enormous attention due to their facile nature, simplicity, superior selectivity and sensitivity, and better reproducibility and reliability. The sensing parameters, such as detection limit, dynamic range, and the possibility for multiplexed detection, rely hugely on the physicochemical properties of the fluorophore used. Therefore, the choice and rational design of fluorescent probes demand considerable attention. The growing interest in highly fluorescent semiconductor quantum dots as sensors or imaging probes is evident from the numerous reports available in the literature. Unlike conventional organic dyes, novel fluorescent quantum dots-inorganic nanocrystals have manifold advantages. QDs have symmetric and narrow emission profiles, high absorption efficiency in the UV region, high quantum yields, especially in the NIR region, exorbitant photo and temporal stability, and shallow photo-bleaching effect. The optical properties of QDs are primarily defined by the nature of constituent materials, size and shape, surface chemistry, and the nature of dangling bonds. The applicability of CdTe QDs was limited in the biological realm mainly due to the highly toxic nature of its constituent materials. The use of benign ligands is one procedure to be adopted to overcome this impediment. Also, the stability of the QDs warrants the limited bleaching of the material. The aqueous solubility of the material is another requirement to be satisfied. The functional groups in ligands also play a significant role in determining the stability of QDs and the utility of the QDs synthesized, as it can advocate the possibility of reactions and recognition of suitable analytes in sensing schemes. This talk will discuss the choice of organic ligands with side methyl chains that can supplement or be used in alternatives to the existing ligands for synthesizing QDs. We have employed easy and facile colloidal synthetic procedures for an extended period for manipulating the size of QDs formed, which can be further implemented for the sensing of various analytes. The side methyl chain added several benefits for the QDs synthesis, such as providing better stability of the QDs and in the sensing scenario.

A fluorescent quantum dot conjugate to probe the interaction of Enterolobium contortisiliquum trypsin inhibitor with cancer cells

Serine proteases play crucial biological roles and have their activity controlled by inhibitors, such as the EcTI, a serine protease inhibitor purified from Enterolobium contortisiliquum seeds, which has anticancer activity. This study aimed to conjugate EcTI with quantum dots (QDs), fluorophores with outstanding optical properties, and investigate the interaction of QDs-EcTI nanoprobe with cancer cells. The conjugation was evaluated by fluorescence correlation spectroscopy (FCS) and fluorescence microplate assay (FMA). EcTI inhibitory activity after interaction with QDs was also analyzed. From FCS, the conjugate presented a hydrodynamic diameter about 4× greater than bare QDs, suggesting a successful conjugation. This was supported by FMA, which showed a relative fluorescence intensity of ca. 3815% for the nanosystem, concerning bare QDs or EcTI alone. The EcTI inhibitory activity remained intact after its interaction with QDs. From flow cytometry analyses, approximately 62% of MDA-MB-231 and 90% of HeLa cells were labeled with the QD-EcTI conjugate, suggesting that their membranes have different protease levels to which EcTI exhibits an affinity. Concluding, the QD-EcTI represents a valuable nanotool to study the interaction of this inhibitor with cancer cells using fluorescence-based techniques with the potential to unravel the intricate dynamics of interplays between proteases and inhibitors in cancer biology.

Biomass-Derived Carbon Dots as Nanoprobes for Smartphone-Paper-Based Assay of Iron and Bioimaging Application.

A facile one-step carbonization approach is reported herein for the sustainable hydrothermal synthesis of fluorescent blue nitrogen-doped carbon quantum dots (NCQDs) using banana petioles obtained as biomass waste. These NCQDs were used to design a "turn-off" fluorescent probe, which exhibited excellent sensing capability toward the selective detection of micronutrient, Fe3+ ion, with a limit of detection (LOD) of 0.21 nM. The turn-off process involves the formation of a nonradiative charge transfer complex via a photoinduced electron transfer process. The sensor showed a linear range from 5 to 200 nM and was used for the estimation of Fe3+ ions in real plant samples. Further, a paper-based assay was developed for the quantitative estimation of Fe3+ with LOD values of 0.47 nM for solution-based assay and 0.94 nM for paper-based assay using a smartphone-based readout for potential on-field applications in precision agriculture. Bioimaging studies on banana leaf cells using NCQDs revealed the selective staining of stomata openings on leaf lamella. Therefore, this work provides a way for the valorization of biomass waste into functional nanomaterials without using any extra chemicals.

Highly reflective and fluorescent TiO2 quantum dots modified asphalt coating: Engineering characterizations and microclimatic modelling

Conventional asphalt absorbs and stores a large quantity of solar radiation, contributing to urban heat island (UHI) phenomenon. TiO2 quantum dots (QDs) are one of the important zero-dimensional nanocrystals with remarkable light reflection and fluorescence. In this study, the highly reflective and fluorescent asphalt binder modified with TiO2 QDs was proposed as an innovative UHI mitigation strategy. Optical and Superpave performance characterizations were employed on TiO2 QDs modified asphalt binder while its cooling potential was assessed by implementing microclimatic modelling. The results show that solar reflectance of asphalt binder increases from 12% to 17% when doping 5–30% TiO2 QDs compared to 3% of traditional asphalt binder. Meanwhile, fluorescent intensity of modified asphalt binder is increased by 43–289%. Compared to conventional asphalt binder, TiO2 QDs modified asphalt binder exhibits superior rutting resistance. The microclimatic modelling using ENVI-met simulation tool has revealed that asphalt coating with TiO2 QDs brings air temperature reduction by up to 2.9 °C. Moreover, economic analysis has shown that asphalt coating withTiO2 QDs could achieve desirable cost-effectiveness.

Composite molecularly imprinted ratiometric fluorescent sensor based on carbon dots and CdTe quantum dots for visual detection of ciprofloxacin in seawater

As a commonly used antibiotic, the residues of ciprofloxacin (CIP) enter the environment owing to its abuse and it is of great significance for environmental protection and human health to develop a fast and selective sensor for the determination of trace CIP. In this work, composite imprinted ratiometric fluorescent nanoparticles of CdTe/CQDs@SiO2@MIPs that can efficiently and rapidly detect ciprofloxacin (CIP) in seawater samples were synthesized by sol-gel method. The blue fluorescence of carbon quantum dots (CQDs) at 436 nm was the reference, and the orange yellow fluorescence of CdTe QDs at 547 nm was sensitive to CIP. The sensor showed satisfying linear relationship till to 20 μmol L−1 (R2 = 0.9963) with limit of detection (LOD) of 0.09 μmol L−1 and recoveries of 96.2–103.1% in seawater. It was successfully applied to the detection of CIP in seawater after pretreatment by solid phase microextraction. The sensor exhibited a “green-blue” color change window visible to the naked eye under 365 nm UV light. This method provides a fluorescence imprinting strategy for the visualization and in situ detection of CIP in environmental water.

Synthesis of highly fluorescent carbon quantum dots from rubber seed shells for the adsorption and photocatalytic degradation of dyes

The potentials of biomass-based carbon quantum dot (CQD) as an adsorbent for batch adsorption of dyes and its photocatalytic degradation capacity for dyes which are congo red (CR) and methylene blue (MB) have been conducted in this study. The CQDs properties, performance, behaviour, and photoluminescence characteristics were assessed using batch adsorption experiments which were carried out under operating conditions including, temperature, pH and dosage. The morphological analysis revealed that CQDs are highly porous, uniform, closely aligned and multi-layered. The presence of hydroxyl, carboxyl and carbonyl functional groups indicated the significance of the oxygenated functional groups. Spectral analysis of photoluminescence for CQDs confirmed their photoluminescent quality by exhibiting high excitation intensity and possessing greenish-blue fluorescence under UV radiation. The removal percentage of the dyes adsorbed for both CR and MB dyes was 77% and 75%. Langmuir isotherm and pseudo-second-order models closely fitted the adsorption results. Thermodynamics analysis indicated that the adsorption process was exothermic and spontaneous, with excellent reusability and stability. The degradation efficiency of CQDs on both dyes was more than 90% under sunlight irradiation and obeyed the first-order kinetic model. These results demonstrated CQDs to be an excellent adsorbent and outstanding photocatalyst for organic dye degradation.

Optimizing scalable synthesis of high-quality FeSe quantum dot in organic and aqueous states

A typical layered transition metal chalcogenide nanostructure, FeSe quantum dots (QDs) have recently begun to attract for their unique optical properties, i.e., multicolored excitation dependent emission (MEDE) property that breaks conventional Kasha - Vavilov rule as well as their potential applications in biological, and optical/electronic sensing and imaging. In this article, we present robust and optimized protocols for the scalable synthesis of FeSe QDs either in aqueous or organic syntheses. The synthesis conditions were carefully compared to obtain insistent synthesis parameters, e.g., solvents, precursors, stabilizers, pH, temperature, concentration, and reaction time after reproduction experiments. Furthermore, post-treatment procedures, i.e., phase transition and PEGylation are also optimized for further potential environmental and biological applications. In the scale-up experiments, a 5-liter reactor was utilized to produce approximately 55 g of QDs per batch, showing a robust optical MEDE property. The most optimized experimental condition reached quantum yield (QY) up to 60 % at the typical synthesis conditions of pH 9.0, 95 °C for 4 h of reflux, and the production yield of ca. 20%. These high fluorescent QDs can be potentially applied for biological fluorophores as well as next-generation QD displays.

Dual metal ion (Fe3+ and As3+) sensing and cell bioimaging using fluorescent carbon quantum dots synthesised from Cynodon dactylon

In this study, water dispersible fluorescent carbon quantum dot (CQD) has been synthesised, having an average size of 8.6 ± 0.4 nm using Cynodon dactylon (CD) following microwave assisted green synthetic one-step method. As-prepared CQD fluoresces strongly at 444 nm having a quantum yield of 1% in water when excited at 350 nm. This fluorescence of CQD is sensitive toward As3+ and Fe3+ metal ions. These CQD are utilized for dual metal ion fluorescence sensing; turn-on fluorescence sensing for As3+ and turn-off fluorescence sensing for Fe3+ ions. Limit of detection for As3+ and Fe3+ ions has been found to be 19 nM and 0.10 μM respectively, which is the lowest value reported for As3+ without any functionalization. The adsorption kinetics of As3+ and Fe3+ ions on CQD have been examined using pseudo-first-order-kinetic model revealing that physical adsorption is dominant over chemical processes in this work. For 0.41 g/L and 1.90 g/L dose of CQD, the equilibrium adsorption capacity was found to be 1.57 × 10−6 mg/g, 2.91 × 10−7 mg/g, and 1.01 × 10−5 mg/g, 1.69 × 10−6 mg/g respectively for As3+ and Fe3+ ions. Despite having low quantum yield in water, as-prepared CQD showed low cytotoxicity and good tolerance against photodegradation of biological cells at concentrations lower than 62.5 μg/mL and when the cells are illuminated up to 12 h. Owing to this, the synthesised CQD have been utilized as fluorescent probes for in itro cell imaging.

A Curated Graphene Quantum Dot-Porphyrin-Based Photosensitizer for Effective Singlet Oxygen Generation through Energy Transfer.

Porphyrin-based photosensitizers are proven generators of reactive oxygen species (ROS), such as singlet oxygen, and used as anti-cancer therapeutic agents. However, most of these compounds suffer from potential drawbacks due to limited photostability, hydrophobicity, aggregation propensity, and low cellular uptake. Ultrasmall fluorescent graphene quantum dots (GQDs) have emerged as the next-generation carriers for drugs and have gained reputation in the pharmaceutical domain. Considering the various limiting factors in porphyrin-based ROS generation and cellular internalization, here, we have developed a method to generate tetrakis(m-nitrophenyl) porphyrin (TNPP)-GQD exciplexes. This allows resonance energy transfer (RET) from GQDs to TNPP. The calculated overlap integrals for GQD-TNPP and AGQD-TNPP (1.001 × 1018 and 1.257 × 1017 M-1 cm-1 nm4, respectively) assured 95 and 71% energy transfer. The optimum donor-acceptor distances in these couples are 59.82 and 62.65 Å, respectively, which yielded the rate constant of RET as 4.09 and 0.56 ns-1, respectively. The efficient RET helped in subsequent generation of singlet oxygen. The singlet oxygen quantum yields (SOQY) of around 0.435 and 0.464 for GQD-TNPP and AGQD-TNPP, respectively, are comparable to those of different porphyrin derivatives where the SOQY ranges from 0.55 to 0.70 when used with Triton X-100. The data show that non-conjugated amine- and amide-functionalized GQDs (AGQDs) are better candidates in this case because of the special properties of the amine groups. The systems could be excited at 450 nm for FRET, which favors biological usage.

A review on characterization of carbon quantum dots

AbstractCarbon quantum dots (CQDs) are a new blooming carbon containing nanoparticles having size of less than 10 nm. They have wide range of application in the field of sensing of inorganic analytes, bio sensing, cell imaging, studying biological processes in living cells and also for drug delivery. These nanoparticles of carbon are playing important roles due to their interesting qualities like small particle size, biocompatibility, fluorescing, etc. Sometimes it shows excitation wavelength dependent, which may be more than 100 nm, and sometimes excitation wavelength independent fluorescent property. CQDs are highly photo stable (stable for hours), compared to the conventional fluorescent semiconductor quantum dots. To apply such carbon quantum dots, it is necessary to characterize the CQDs first. Most of the time they are characterized by photophysical and structural property using UV‐VIS spectroscopy, fluorescence spectrophotometry, FT‐IR, XRD, XPS, Raman spectroscopy, TCSPC, HRTEM, etc. In this review article we demonstrate how these tools are used to characterize newly synthesized CQDs, monitor the synthesis process along with finding its application in numerous fields.

Fluorescence quenching detection of p-nitrophenol in river water using functional perovskite quantum dots

p-Nitrophenol (p-NP) is a chemical compound that produces pesticides and pharmaceuticals. Improper handling can lead to water pollution and pose risks to the environment. Considerable attention has been given to the research and development of methods for detecting water pollutants to achieve Sustainable Development Goal 6. This study used highly fluorescent perovskite quantum dots (PVSK QDs) to detect p-NP in water. To enhance the stability of the PVSK QDs, we performed surface modification using 3-triethoxysilylpropylamine, resulting in functionalized amine-PVSK QDs. This enables the amine-PVSK QDs to maintain a high fluorescent quantum yield of 88.8% after 30 days of storage in ethanol. The detection of p-NP in water is achieved through the fluorescence quenching resulting from the reaction between the amino groups on the amine-PVSK QDs and p-NP. The detection limit for p-NP was 160 nM, lower than the US EPA permissible concentration limit for potable water. The amine-PVSK QDs detected p-NP in two river water samples with a relative standard deviation of 0.31–2.49% range. These findings demonstrate that amine-PVSK QDs can serve as a fast and sensitive fluorescent detection platform for the qualitative and quantitative identification of aqueous p-NP, addressing environmental sustainability issues.

Fluorescent Quantum Dots and Its Composites for Highly Sensitive Detection of Heavy Metal Ions and Pesticide Residues: A Review

Quantum dots nanomaterials have attracted extensive interest for fluorescence chemical sensors due their attributes, such as excellent optical characteristics, quantum size effects, interface effects, etc. Moreover, the fluorescence properties of quantum dots can be adjusted by changing their structure, size, morphology, composition, doping, and surface modification. In recent years, quantum dots nanomaterials have been considered the preferred sensing materials for the detection of heavy metal ions and pesticide residues by the interactions between quantum dots and various analytes, showing excellent sensitivity, selectivity, and interference, as well as reducing the cost of equipment compared with traditional measurement methods. In this review, the applications and sensing mechanisms of semiconductor quantum dots and carbon-based quantum dots are comprehensively discussed. The application of semiconductor quantum dots, carbon quantum dots, graphene quantum dots, and their nanocomposites that are utilized as fluorescence sensors are discussed in detailed, and the properties of various quantum dots for heavy metal ion and pesticide residue determination are also presented. The recent advances in and application perspectives regarding quantum dots and their composites are also summarized.

A dual-ratio fluorescent probe with a single excitation triple-signal to synchronously detect PTK7 and miRNA-21 for breast cancer early diagnosis

The measurement of tumor biomarker levels is of great significance for early diagnosis of breast cancer. The combination diagnosis of multiple tumor biomarkers will significantly improve the accuracy of early diagnosis. Here, we successfully developed a dual-ratio fluorescent sensing platform for the detection of breast cancer biomarkers (PTK7, miRNA-21) using single excitation triple-signal detection. Introducing three types of fluorescence nanomaterials with narrow emission peaks and long Stokes shift as signal markers, the three peaks (430 nm, 530 nm and 640 nm) of which do not interfere with each other in fluorescence spectra under a single excitation (360 nm). The sensing platform linked aptamer (apt) modified green fluorescence quantum dots (gQDs-apt1) and aptamer modified red fluorescence quantum dots (rQDs-apt2) to Fe3O4-cDNA1 and Fe3O4-cDNA2, respectively, via base complementary pairing with aptamer molecules. When PTK7/miRNA-21 is present in the system, gQDs-apt1/rQDs-apt2 bound to the Fe3O4 MNPs surface will be released to recover fluorescence. Upon DNase I digestion of free apt1 and apt2, the target molecules will be released to bind to gQDs-apt1/rQDs-apt2 for signal amplification. After magnetic separation, PTK7 and miRNA-21 can be quantified using the fluorescence intensity ratio of gQDs with bCDs and rQDs with bCDs at a single excitation of 360 nm wavelength. This method has high sensitivity, good selectivity, and can quantify both PTK7 and miRNA-21 simultaneously with an LOD of 0.426 ng mL-1 and 0.072 nM, respectively. Additionally, the sensing platform was used for serum detection of health man and breast cancer patients with satisfactory results.

Development of cysteine-doped MnO2 quantum dots for spectrofluorimetric estimation of copper: applications in different matrices

Copper (Cu) plays a role in maintaining healthy nerve cells and the immune system. Osteoporosis is a high-risk factor for Cu deficiency. In the proposed research, unique green, fluorescent cysteine-doped MnO2 quantum dots (Cys@MnO2 QDs) were synthesized and assessed for the determination of Cu in different food and hair samples. The developed quantum dots were synthesized with the help of cysteine using a straightforward ultrasonic approach to create 3D fluorescent Cys@MnO2 QDs. The resulting QDs’ morphological and optical characteristics were carefully characterized. By adding Cu ions, the intensity of fluorescence for the produced Cys@MnO2 QDs was found to be dramatically reduced. Additionally, the applicability of Cys@MnO2 QDs as a new luminous nanoprobe was found to be strengthened by the quenching effect grounded on the Cu–S bonding. The concentrations of Cu2+ ions were estimated within the range of 0.06 to 7.00 µg mL−1, with limit of quantitation equal to 33.33 ng mL−1 and detection limit equal to 10.97 ng mL−1. The Cys@MnO2 QD technique was applied successfully for the quantification of Cu in a variety of foods, including chicken meat, turkey, and tinned fish, as well as in human hair samples. The chance that this novel technique could be a useful tool for figuring out the amount of cysteine in bio-samples is increased by the sensing system’s remarkable advantages, which include being rapid, simple, and economical.Graphical abstract

O-phenylenediamine Derived Fluorescent Carbon Quantum dots for Detection of Hg(II) in Environmental Water.

With the expansion of human activities, the consequent influx of mercury (Hg) into the food chain and the environment is seriously threatening human life. Herein, nitrogen and sulfur co-doped fluorescent carbon quantum dots (yCQDs) were prepared via a hydrothermal method using o-phenylenediamine (OPD) and taurine as precursors. The morphological characteristics as well as spectral features of yCQDs indicated that the photoluminescence mechanism should be the molecular state fluorophores of 2, 3-diaminophenothiazine (oxOPD), which is the oxide of OPD. The as-synthesized yCQDs exhibited sensitive recognition of Hg2+. According to the investigation in combination of UV-Vis absorption spectra, time-resolved fluorescence spectra and quantum chemical calculations, the abundant functional groups on the surface of yCQDs allowed Hg2+ to bind with yCQDs through various interactions, and the formed complexes significantly inhibited the absorption of excitation light, resulting in the static fluorescence quenching of yCQDs. The proposed yCQDs was utilized for Hg2+ sensing with the limit of detection calculated to be 4.50 × 10- 8M. Furthermore, the recognition ability of yCQDs for Hg2+ was estimated in tap water, lake water and bottled water, and the results indicated that yCQDs have potential applications in monitoring Hg2+.

Highly fluorescent nitrogen-doped graphene quantum dots (N-GQDs) synthesized from Pennisetum purpureum for selective and sensitive detection of Fe3+ ions

The synthesis of nitrogen-doped Graphene Quantum Dots (N-GQDs) employing Pennisetum purpureum (elephant grass) as the carbon precursor and ethylenediamine (EDA) as the nitrogen source was conducted. This study highlights the potential applications of nitrogen-doped multi-fluorescent graphene quantum dots (N-GQDs) in the detection of Fe3+. The synthesized N-GQDs have been studied using UV–vis spectrophotometry, fluorescence spectrometry, Raman spectrometry, FT-IR spectrometry, x-ray spectroscopy, selected-area electron diffraction, transmission and high-transmission electron microscopy. The acquired N-GQDs were observed to have an almost hexagonal shape with a lateral size of 2.42 nm and exhibited a comparable quantum yield of approximately 26%. The N-GQDs that have been prepared with consistent size distribution and a significant amount of nitrogen and oxygen-based functional groups showcase outstanding water dispersity. The N-GQDs exhibited the capability to identify the Fe3+ ions in a broad range concentration of 1–600 μM by creating an N-GQDs-Fe3+ complex through the occurrence of functional groups like nitrogen, carbonyl, and carboxyl on N-GQDs surface, has a lower limit of detection at approximately 60 nM. Our study provides evidence that the N-GQDs produced a strong and persistent fluorescence, which is highly soluble in water, notably the precise and selective detection of Fe3+ in water-based solutions.

Clinical Evaluation of Polymerase Chain Reaction Coupled with Quantum Dot Fluorescence Analysis for Diagnosis of Candida Infection in Vulvovaginal Candidiasis Practice.

Time-consuming culture methods and wet-mount microscopy (WMM) with low sensitivity have difficulties in diagnosing Vulvovaginal candidiasis (VVC). Rapid and highly sensitive polymerase chain reaction coupled with quantum dot fluorescence analysis (PCR-QDFA) for the diagnosis of VVC has not been reported to date. This study was the first to evaluate the performance of PCR-QDFA for diagnosis of Candida strains in the leukorrhea samples from patients with suspected VVC. Leukorrhea samples from all visited patients were taken from the vagina using vaginal swabs by clinicians. We evaluated patients admitted with suspected VVC who completed WMM for diagnosis and reported the diagnostic effectiveness of PCR-QDFA and Candida culture (gold standard) when testing leucorrhea samples. A total of 720 leukorrhea samples from 387 VVC-positive patients and 333 VVC-negative patients were included in this study. Of the 387 leukorrhea samples from the VVC-positive patients, 391 Candida strains were identified by culture. 99.23% (388/391) Candida strains were included in the PCR-QDFA list. The 388 Candida strains belonged to four different species of Candida, including C. albicans (n = 273, 70.36%), C. glabrata (n = 85, 21.91%), C. tropicalis (n = 16, 4.12%), and C. krusei (n = 14, 3.61%). PCR-QDFA diagnosed Candida strains in 340/384 (88.54%) of the leucorrhea samples with Candida strains infection. The sensitivity of PCR-QDFA for C. albicans, C. glabrata, C. tropicalis, and C. krusei was 89.01%, 85.88%, 81.25% and 92.86%, respectively. The specificity of PCR-QDFA for C. albicans, C. glabrata, C. tropicalis and C. krusei was 93.69%, 99.37%, 99.71%, and 99.57%, respectively. The highly sensitive and specific PCR-QDFA technique can be exploited as a rapid (approximately 4 h) diagnostic tool for common Candida strains of leucorrhea samples from patients with suspected VVC.

Long wavelength emission multicolor fluorescent carbon quantum dots for the detection of pH, amino acids, and metal ions

Carbon quantum dots are widely used in the field of analysis and detection due to their excellent optical properties. At present, many studies have focused on the preparation of multi-color fluorescent quantum dots by simple methods. Inspired by this, carbon quantum dots with green (G-CQDs) and yellow fluorescence (YN-CQDs) emission were prepared by hydrothermal method using PTCDA and urea as precursors. After characterizing their morphology, structure, and optical properties, fluorescent probes for different purposes were constructed according to their different fluorescence characteristics. Since green G-CQDs are sensitive to acidic environments, pH detection kits are developed. In addition, G-CQDs can also efficiently detect Asp. YN-CQDs are used to detect metal ions and can specifically detect Fe3+. Both of them were applied to the detection of actual samples, showing high efficiency and reliability. It provides a new idea for the multi-purpose detection of carbon quantum dot fluorescent probes.

Anti-crosstalk device based on a Novel Micro-LED structure design

Herein, the crosstalk problem of display pixels and color subpixels is solved according to the optical design requirements of a large half-beam angle and highly uniform far-field light distribution to obtain improved display effects. A new chip micro-light emitting diode (LED) + quantum dot (QD) fluorescence mode is presented. The design optical principle uses the Monte Carlo method to prevent the light emitted from the chip from entering the QD film in adjacent pixels. Implementation is achieved by adjusting the distance between the QD film and the chip. The results are obtained by optimizing the distance between the micro-LED and the QD phosphor. When the distance between the QD fluorescent film and the chip is constant, the intensity of the light received by the QD fluorescent film decreases at increasing distances between the subpixel chips, and its contrast increases. The analyzed results suggest that anti-crosstalk micro-LED optical devices can reduce the illuminance on the receiving surface of adjacent pixels to the original 0%. Thus, the crosstalk between display pixels is effectively addressed.