Green, Water-Dispersible Photoluminescent On-Off-On Probe for Selective Detection of Fluoride Ions

A Review of Nanotechnology-Enabled Fluorescent Chemosensors for Environmental Toxic Ion Detection

This review examines the utilization of nanotechnology-based chemosensors for identifying environmental toxic ions. Over recent decades, the creation of nanoscale materials for applications in chemical sensing, biomedical, and biological analyses has emerged as a promising avenue. Nanomaterials play a vital role in improving the sensitivity and selectivity of chemosensors, thereby making them effective tools for monitoring and evaluating environmental contamination. This is due to their highly adjustable size- and shape-dependent chemical and physical properties. Nanomaterials possess distinct surface chemistry, thermal stability, high surface area, and large pore volume per unit mass, which can be harnessed for sensor development. The discussion encompasses different types of nanomaterials utilized in chemosensor design, LOD, their sensing mechanisms, and their efficacy in detecting specific toxic ions. Furthermore, the review explores the progress made, obstacles faced, and future prospects in this rapidly evolving field, highlighting the potential contributions of nanotechnology to the creation of robust sensing platforms for environmental monitoring.

Improving anion sensing ability of the indolocarbazole-based fluorescence turn-on sensor by increasing salicylaldehyde response unit

Detection abilities on tested subjects of sensors should be closely connected to the sensing unit numbers. Herein, two anion sensors ICZ-o-1S and ICZ-o-2S were synthesized by using indolo (2,3-a) carbazoles as fluorescent chromophore and salicylaldehyde as recognition site. Though UV-Vis and fluorescent ways, it demonstrated that F^- can induce the sensor solutions becoming colored from colorless to yellow green, and can endow them with bright green turn-on fluorescence, proving their sensitive and selective sensing on F^-. Accordingly, the F ion sensing studies including anti-interference abilities against to other anions on fluorescence response, stoichiometric ratios of sensor-F^- in 1 : 1 and 1 : 2, -OH deprotonation sensing mechanism confirmed by ¹H NMR titration and theoretical calculation were fully covered. Most importantly, fluoride ion detection limits achieved by ICZ-o-1S and ICZ-o-2S were 1.8 × 10^-7 M and 6.0 × 10^-8 M, respectively, the latter with two sensing units exhibited 3 times lower detection limit outcompeted to the former with only one sensing unit, rendering the sensor design strategy of improving detecting ability by increasing sensing unit number was rational. The practical application of F^- detection in water-containing environment calibrated from the standard curve between the fluorescence intensity of sensor-F^- system and the changing F^- concentration was conducted. In addition, the accuracy of the sensor on detecting F^- was evaluated by the spiked recovery experiment, therefore, the fast and convenient F^- concentration detection based on the fluorescence color RGB values of the tested sensor-sample mixture was investigated. Consequently, the results obtained by these two sensors should deliver effective supports on designing high-performance sensors featuring naked-eye and fluorescence turn-on anion sensing by altering the response unit numbers.

A portable and intelligent logic detector for simultaneous and in-situ detection of Al3+ and fluoride in groundwater

To develop a convenient and intelligent detector for simultaneous and in-situ detection of Al³⁺ and F^- in groundwater, a novel organic probe called RBP has been prepared. With the increase of Al³⁺, RBP showed a significant fluorescence enhancement at 588 nm, and the detection limit was 0.130 mg/L. After combining with fluorescent internal standard CDs, the fluorescence of RBP-Al-CDs at 588 nm was quenched due to the replace of F^- for Al³⁺, while the CDs at 460 nm remained unchanged, and the detection limit was 0.0186 mg/L. For convenient and intelligent detection, an RBP-based logic detector has been developed for simultaneous detection of Al³⁺ and F^-. Within the ultra-trace, low concentration, and high concentration range of Al³⁺ and F^-, the logic detector can achieve rapid feedback on their concentration levels ("U", "L" and "H") through different output modes of the signal lamps. The development of logical detector is of great significance for studying the in-situ chemical behavior of Al³⁺ and F^- and for daily household detection.

Development of luminescence carbon quantum dots for metal ions detection and photocatalytic degradation of organic dyes from aqueous media

In the present study, fish scale waste was used for the organic synthesis of luminescence CQDs by the hydrothermal method. The impact of CQDs on improved photocatalytic degradation of organic dyes and metal ions detection is examined in this study. The synthesized CQDs had a variety of characteristics that were detected, such as crystallinity, morphology, functional groups, and binding energies. The luminescence CQDs showed outstanding photocatalytic effectiveness for the destruction of methylene blue (96.5%) and reactive red 120 dye (97.8%), respectively after 120 min exposure to visible light (420 nm). The high electron transport properties of the CQDs edges, which make it possible to efficiently separate electron-hole pairs, are attributed to the enhanced photocatalytic activity of the CQDs. These degradation results prove that the CQDs are the outcome of a synergistic interaction between visible light (adsorption); a potential mechanism is also suggested, and the kinetics is analyzed to use a pseudo-first-order model. Additionally, the metal ions detection of CQDs was studied by various metal ions (Hg²⁺, Fe²⁺, Cu²⁺, Ni²⁺, and Cd²⁺) in an aqueous solution and results revealed that the PL intensity of CQDs in presence of cadmium ions decreased. Studies show that the organic fabrication of CQDs are effective photocatalyst and may one day serve as the ideal material to reduce water pollution.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2

In this work, CDs@Eu-UiO-66(COOH)₂ (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu³⁺ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu²⁺ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu²⁺. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu²⁺. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

Nitrogen-doped carbon dots coupled with morin-Al3+: Cleverly design an integrated sensing platform for ratiometric optical dual-mode and smartphone-assisted visual detection of fluoride ion

Ratiometric fluorescence sensor has high selectivity and good sensitivity; however, its development is limited by intricate design, tedious synthesis, etc. Herein, a facile and effective ratiometric fluorescence sensing platform for fluoride ion (F^-) detection was developed by simply combining nitrogen-doped carbon dots (N-CDs) and morin-Al³⁺ based on inner filter effect (IFE). The competitive binding of F^- to Al³⁺ obviously decreased morin-Al³⁺ fluorescence and increased N-CDs fluorescence, attributing to the inhibition of IFE between N-CDs and morin-Al³⁺. The as-constructed ratiometric fluorescence sensing platform can be used for F^- detection with a wide linear range (0.5-150 μM) and a low detection limit (55.8 nM). Interestingly, with the introduction of F^- into the N-CDs/morin-Al³⁺ sensing platform, a distinguishable change in fluorescence color from green to blue enabled the N-CDs/morin-Al³⁺ system to be used as a smartphone-assisted visual sensing platform for F^- detection with a detection limit of 2.09 μM. This platform was successfully applied for the onsite monitoring of F^- in various water samples with satisfying results. These findings provide a novel guidance for the facile construction of a ratiometric optical dual-mode and smartphone-assisted sensing platform based on CDs, revealing the broad application prospect of CDs in environmental monitoring field.

Versatile Sensing Platform of Innovative Copper Oxide Assisted Cu-Phenolic Coordination Nanosheet mediated Fluorophore tagged GT-rich SSA based Fluorescence ON-OFF Biosensor for Subsequent Detection of Cd2+ and S2− Ions

Increased levels of toxic metal/non-metal ions Cadmium (Cd2+) and Sulfide (S2−) in the environment can be detrimental to human health. Given the circumstances, the detection and measurement of Cd2+ and...

Amino acid-functionalized carbon quantum dots for selective detection of Al3+ ions and fluorescence imaging in living cells

Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al³⁺ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al³⁺ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al³⁺ in the range of 1-20 μmol L^-1; the limit of detection (3σ) was only 0.32 μmol L^-1. Furthermore, an AA-CQD probe was also utilized for detection of Al³⁺ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al³⁺ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research.

When rare earth meets carbon nanodots: mechanisms, applications and outlook

Rare earth (RE) elements are widely used in the luminescence and magnetic fields by virtue of their abundant 4f electron configurations. However, the overall performance and aqueous stability of single-component RE materials need to be urgently improved to satisfy the requirements for multifunctional applications. Carbon nanodots (CNDs) are excellent nanocarriers with abundant functional surface groups, excellent hydrophilicity, unique photoluminescence (PL) and tunable features. Accordingly, RE-CND hybrids combine the merits of both RE and CNDs, which dramatically enhance their overall properties such as luminescent and magnetic-optical imaging performances, leading to highly promising practical applications in the future. Nevertheless, a comprehensive review focusing on the introduction and in-depth understanding of RE-CND hybrid materials has not been reported to date. This review endeavors to summarize the recent advances of RE-CNDs, including their interaction mechanisms, general synthetic strategies and applications in fluorescence, biosensing and multi-modal biomedical imaging. Finally, we present the current challenges and the possible application perspectives of newly developed RE-CND materials. We hope this review will inspire new design ideas and valuable references in this promising field in the future.

Fluorescence detection of fluorine ions in biological fluids based on aggregation-induced emission

Traditional chemical and biological sensors developed through aggregation-induced emission (AIE) are mainly based on “Turning on” pattern of fluorescence enhancement, which often has poor selectivity and can be easily interfered with by other substances. On this basis, an AIE-based tetraphenyl ethylene (TPE) derivative (TPE-COOH) was prepared in this study and aggregated by adding Al³⁺, so as to form the TPE-COOH/Al³⁺ polymer. TPE-COOH fluorescence was enhanced through AIE principle, thus realizing the “Turning on” state. F⁻ could bind to Al³⁺ after the addition of F⁻ ions which would result in the decomposition of TPE-COOH/Al³⁺ aggregate, dissolved state of TPE-COOH and gradual reduction of fluorescence intensity of the system, thus realizing “Turning off” state. Moreover, F⁻ ions in biological fluid were analyzed and detected through such AIE-based “Turning on-off” pattern. The linear range of this method for F⁻ detection was 3–12 μM and the detection limit was 0.9 μM.

Schematic diagram of fluorescence detection of F⁻ ions in biological fluids based on TPE-COOH/Al³⁺ polymer Aggregation-Induced Emission (AIE) “Turning on–off” mode.

Novel synthesis of Cu2CoSnS4-carbon quantum dots nano-composites potential light absorber for hybrid photovoltaics

A novel and simple synthesis of the absorber layer is indispensable in order to reduce the cost and processing of quantum solar cells. In this work, we developed novel Cu₂CoSnS₄-carbon quantum dot (CCTS:CQD) nano-composite as an absorbing material for solar cell applications. CCTS:CQD nano-composites were prepared by direct pyrolysis of CCTS precursors and citric acid. The proportions of citric acid precursor to CCTS were varied from 0.1 to 0.7. The properties of the synthesized nano-composite were studied using a UV-vis spectrophotometer in the wavelength range of 300-900 nm. CCTS:CQD has a property of dynamic photoluminescence that depends on the excitation wavelength. The results of the x-ray diffraction revealed that the CCTS:CQD nano-composites were predominantly polycrystalline in nature. The formation of CCTS:CQD was confirmed by a high-resolution transmission electron microscope (HRTEM), which exhibits the size ∼3 nm. The thin films of CCTS:CQD nano-composites were deposited on glass/ITO substrates by spray pyrolysis technique at 170 °C. Current-voltage (I-V) measurements carried out in dark and light conditions revealed CCTS: CQD thin films with good photo-response. The purpose of the present study is to develop CCTS: CQD nano-composite p-type absorber layer suitable for thin film solar cells.

Detection of toxic fluoride ion via chromogenic and fluorogenic sensing. A comprehensive review of the year 2015-2019

Fluoride ion (F^-) contamination can be accumulated along the water and the food chain and cause serious risk to public health. It is of the greatest importance that selects the suitable chromophores and fluorophores for the design and synthesis of outstanding selective, sensitive chromogenic and fluorogenic probes for detection of fluoride ion. In this review is mainly focused on the current progress of fluoride ion detection according to their receptors into several categories like anthracene, azo, benzothiazole, BODIPY, calixarene, coumarin, imidazole, diketopyrrolopyrrole, hydrazone, imidazole, naphthalene, naphthalimide, quantum dots, Schiff base and urea group sensing in the year 2015-2019.

N,S co-doped carbon dots as a dual-functional fluorescent sensor for sensitive detection of baicalein and temperature

In this work, nitrogen and sulfur dual-doped CDs (N,S-CDs) were prepared via a facile one-pot hydrothermal method from citric acid and N-acetyl-L-cysteine with a high quantum yield (QY) of 49%. As-fabricated N,S-CDs had a size around 2.5 nm and exhibited excitation-independent emission and excellent luminescent properties. The fluorescent sensor based on the N,S-CDs showed a highly sensitive detection of baicalein with a detection limit (LOD) of 0.21 μmol L^-1 in the linear range from 0.69 to 70.0 μmol L^-1. The fluorescence of the N,S-CDs could be effectively quenched by baicalein based on static quenching. In addition, the temperature sensor based on the synthesized N,S-CDs showed a good linear relationship between temperature and fluorescence (FL) intensity with a temperature range from 5 °C to 75 °C. Furthermore, the synthesized N,S-CDs were successfully applied to the measurement of baicalein in real samples. In a word, the N,S-CDs had great potential to be worked as fluorescence sensors to monitor the concentration of baicalein and temperature.

DNA-templated copper nanoclusters as a fluorescent probe for fluoride by using aluminum ions as a bridge

A selective fluorescent on-off-on probe has have designed for the detection of fluoride (F^-) ions based on DNA-templated copper nanocluster (CuNCs) and by using aluminum(III) ions as a bridge. A 40-mer polythymine acts as a template for the reduction of Cu(II) to Cu(0) by ascorbic acid. This result is the formation of red fluorescent CuNCs, with excitation/emission peaks at 340/640 nm. After addition of Al³⁺ ions, the fluorescence of CuNCs is quenched because the interaction of Al³⁺ and DNA disturbs the formation of DNA-templated CuNCs. Fluorescence is restored on addition of fluoride to the system. This is due to the desorption of Al³⁺ from the DNA and the formation of the Al(OH)₃F^- complex. This system displays a fast fluorometric response to fluoride, with high selectivity over other anions. Fluorescence increases linearly in the 2 to 150 μM F^- concentration range, and the detection limit is 1.0 μM. This probe has been successfully used for the detection of F^- ions in four brands of toothpaste. The method is rapid, cost-effective, selective, and does not require toxic solvents and reagents. Graphical abstract Schematic presentation of a method for fluorometric determination of fluoride by using DNA-templated copper nanoclusters (CuNCs) and using aluminum(III) as a bridge. The red fluorescence of the CuNCs is quenched in the presence of Al(III) ions but restored after addition of fluoride.

Revisiting the fluoride binding behaviour of dipyrrolylquinoxaline in aqueous medium: a copper ion mediated approach

An ion detection methodology employing synergistic interaction between copper(ii) ions and fluoride with 2,3-dipyrrol-2′-yl-quinoxaline (SR1) is investigated with a particular target to detect fluoride in an aqueous environment.

Hydrothermal synthesis of N-doped carbon dots from an ethanolamine–ionic liquid gel to construct label-free multifunctional fluorescent probes for Hg2+, Cu2+ and S2O32−

N-Doped carbon dots were synthesized and used to construct multifunctional fluorescent probes for Hg²⁺, Cu²⁺ and S₂O₃²⁻.

EDTA-bonded multi-connected carbon-dots and their Eu3+ complex: preparation and optical properties

EDTA-bonded multi-connected carbon-dots (EDTA–C-dots) were prepared from carbon dot precursors and complexed with Eu³⁺ to give Eu³⁺-coordinated EDTA-bonded multi-connected carbon dots (Eu–EDTA–C-dots). Whereas EDTA–C-dots were readily soluble in DMSO, Eu–EDTA–C-dots could not be easily dissolved in DMSO, water, or other common organic solvents. The newly prepared materials were thoroughly characterized. The X-ray diffraction results showed that no crystalline phase of Eu oxides (europium oxide or europium hydroxide) could be observed in Eu–EDTA–C-dots. The infrared and UV-Vis spectra showed that coordination with Eu³⁺ ions did not damage the structure of the EDTA–C-dots. It was found that EDTA could be easily grafted on the surface of carbon dots and EDTA had minimal influence on the photoluminescence of the carbon dot matrix. In contrast, the existence of Eu³⁺ ions strongly quenched the photoluminescence of Eu–EDTA–C-dots. The measured and fitted decay lifetime indicated that Eu–EDTA–C-dots possessed two photoluminescence decay processes, i.e., radiative recombination and non-radiative recombination.

EDTA-bonded multi-connected carbon-dots (EDTA–C-dots) were prepared from carbon dot precursors and complexed with Eu³⁺ to give Eu³⁺-coordinated EDTA-bonded multi-connected carbon dots (Eu–EDTA–C-dots).

Biomass-derived nitrogen-doped carbon quantum dots: highly selective fluorescent probe for detecting Fe3+ ions and tetracyclines

Nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized using rice residue and glycine as carbon and nitrogen sources by one-step hydrothermal method. High quantum yield (23.48%) originated from the effective combination of nitrogen with various functional groups (CO, NH, CN, COOH and COC). The N-CQDs showed a fluorescence with the wavelength varied from 420 to 500 nm and the maximum emission wavelength being at 440 nm. N-CQDs have been importantly applied as probe to detect Fe³⁺ and tetracycline (TCs) antibiotics with remarkable performance. Using the linear relationship between fluorescence intensity and Fe³⁺ concentration, the N-CQDs could be employed as a simple, efficient sensor for ultrasensitive Fe³⁺ detection ranging from 3.32 to 32.26 µM, with a limit of detection (LOD) of 0.7462 µM. The N-CQDs showed the applicability to detect TCs. The detection limits of tetracycline, terramycin and chlortetracycline were 0.2367, 0.3739 and 0.2791 µM, respectively. The results of TC by fluorescence method in real water samples were in good agreement with standard Ultraviolet-visible (UV-vis) method. The N-CQDs have various potential applications including sensitive and selective detection of Fe³⁺ and TCs, and cellular imaging with low cytotoxicity, good biocompatibility and high permeability.

On-off-on luminescent pyrophosphate probe based on the use of Mn-doped ZnS quantum dots and using Eu(III) as a mediator

A selective phosphorescent on-off-on probe with long decay lifetime has been designed for the detection of pyrophosphate ions (PPi). The detection scheme is based on the use of europium(III)-modulated Mn(II)-doped ZnS quantum dots capped with N-acetyl-L-cysteine. Both the aggregation of quantum dots and electron transfer induced by Eu(III) ions cause phosphorescence to be quenched ("off" state). Phosphorescence is, however, restored on addition of PPi to the system ("on" state). The effect is attributed to the removal of Eu(III) from the carboxy groups on the surface of the quantum dots owing to the stronger interaction between PPi and Eu(III). A linear relationship exists between phosphorescence intensity (best measured at excitation/emission wavelengths of 316/594 nm) and PPi concentration in the 400 nM to 6000 nM with a detection limit of 145 nM. An additional attractive feature is provided by the long-lived phosphorescence (1920 μs) of the quantum dots. It can be used to eliminate interference by short-lived fluorescence in biological samples by performing time resolved measurements. The probe was applied to the determination of PPi in spiked in urine samples and gave recoveries in the range from 98 to 105% with RSDs of <2.0%. Graphical abstract Schematic of a long-lived phosphorescent on-off-on probe for the sensitive and selective detection of pyrophosphate ions (PPi). It is based on the use of Eu(III)-modulated Mn(II)-doped ZnS quantum dots (QDs). Phosphorescence is quenched of QDs after the addition of Eu³⁺but restored after the addition of PPi.

A simple boronic acid-based fluorescent probe for selective detection of hydrogen peroxide in solutions and living cells

An approach of high sensitivity and selectivity for hydrogen peroxide (H₂O₂) detection is highly demanded due to its important roles in regulating diverse biological process. In this work, we introduced an easily synthesized fluorescent "turn off" probe, BNBD. It is designed based on the core structure of 4-chloro-7-nitrobenzofurazan as a fluorophore and incorporated with a specific H₂O₂-reactive group, aryl boronate, for sensitive and selective detection of H₂O₂. We demonstrated its selectivity by incubating the probe with other types of ROS, and measured the limit of detection of BNBD as 1.8 nM. BNBD is also conducive to H₂O₂ detection at physiological conditions. We thus applied it to detect both exogenous and endogenous changes of H₂O₂ in living cells by confocal microscopy, supporting its future applications to selectively monitor H₂O₂ levels and identify H₂O₂-related physiological or pathological responses from live cells or tissues in the near future.

A Cu(ii) mediated approach for colorimetric detection of aqueous fluoride in ppm level with a Schiff base receptor

Inspired by the importance of fluoride detection in aqueous environment, a new methodology is demonstrated by employing the synergistic reaction of fluoride and Cu(ii) salts with a designed Schiff base receptor.

Novel carbon quantum dots for fluorescent detection of phenol and insights into the mechanism

Phenol is considered as one of the most important pollutants in the water environment, and thus its detection plays a cardinal role in environmental assessment and treatment.

Microwave-assisted synthesis of water-soluble Eu3+ hybrid carbon dots with enhanced fluorescence for the sensing of Hg2+ ions and imaging of fungal cells

Eu³⁺ ion hybrid carbon dots as a novel fluorescent probe for the assay of Hg²⁺ ions and cellular imaging of Fomitopsis sp.

Implementation of a logic gate by chemically induced nitrogen and oxygen rich C-dots for the selective detection of fluoride ions

The widespread pollution of fluoride ions in the environment badly affects the ecological system due to their high toxicity, mobility and the difficulty of their degradation.

Nanomaterials for the optical detection of fluoride

Overexposure to fluoride ions (F^-) causes serious diseases in human beings. Extensive efforts have been made to develop sensitive and selective approaches for F^- detection and a variety of F^- sensors have been constructed recently. The burgeoning nanotechnology has provided novel materials for F^- analysis due to the extraordinary properties of nanomaterials. In this review, we present the recent advances in different nanomaterials-based approaches for the optical F^- detection via colorimetric, fluorescent and chemiluminescent responses. The materials include gold nanomaterials, CeO₂ nanoparticles, semiconductor quantum dots, carbon quantum dots, metal-organic frameworks, upconversion nanoparticles, micellar nanoparticles, polymer dots, SiO₂ nanoparticles and graphene oxide. The recent trends and challenges in the optical detection of F^- with various nanomaterials are also discussed.

Electron-Transfer-Mediated Uranium Detection Using Quasi-Type II Core-Shell Quantum Dots: Insight into Mechanistic Pathways

Uranium is one of the most toxic and important elements present in the environment, and because of its high toxicity, ultra-trace-level detection is of utmost importance. Many methods were reported earlier for this purpose, but each has its own limitations such as high cost, sophisticated instrumentation, sample processing, and so forth. Herein we have demonstrated an alternate method that is much simpler and can be used for the ultra-trace-level detection of uranium. We have synthesized 3-mercaptopropionic acid (MPA)-capped CdSe/CdS core-shell quantum dots (CSQDs) and used its photoluminescence properties to detect uranium in solution. Steady-state emission studies suggest the luminescence quenching of CSQDs in the presence of uranium. Redox levels of CSQDs and uranium suggests that the electron-transfer process from photoexcited CSQDs to uranium is a thermodynamically viable process, which has subsequently been confirmed by time-resolved studies. A Stern-Volmer plot of CSQDs with uranium suggests that the detection limit of this method is 74.5 ppb. The method has an advantage over other reported methods for being simple and low cost and requiring a small amout of sample processing. To the best of our knowledge, we are reporting for the first time uranium detection using quasi-type II CSQDs and proposing the mechanistic path through luminescence spectroscopy, which in turn helps us to design an efficient detection method.