Search

The example of a lanthanide based hybrid nanoprobe has been developed through functionalization of carbon dots with the organic pendant arms (ethylenediaminetetraaceticdianhydride). This assay has been designed for the highly specific recognition of an anthracis biomarker (2,6-pyridinedicarboxylic acid, DPA) in pure aqueous medium and the improved red emissions increase with the addition of DPA. In the next stage, this nanosystem demonstrates high selectivity for the determination of copper ions in terms of the switch-off effect. Furthermore, the presence of thiols such as glutathione (GSH) has induced large enhancements of the red luminescence. The corresponding detection limits are determined to be 137 nM for DPA, 80 nM for Cu(II) and 50 nM for GSH respectively. The employments of organic solvents, separation treatments and advanced instrumentations have been ruled out during the detection processes. The luminescence changes can be realized with the bare eye observation under the irradiation of a portable UV lamp. The results reported here may open the new way for designing multiple tailor-made sensing systems by finely tuning the features of both organic moieties and carbon nanostructures. [ABSTRACT FROM AUTHOR]

The antibiotic type organic structure pefloxacin binds well with europium (III) ions as a useful scaffold for assembling optical probes and allows energy transfer from ligand to metal ions through coordination linkages. This water-soluble chemosensor demonstrated significant 'off-on (red)' changes from an alkaline to a neutral environment (pH 14-8). The emission changed from red to blue under acidic conditions (pH 7-2). The whole process was completely reversible and effective within the pH range 2 to 14. Moreover, this probe system exhibited distinct luminescence quenching upon the addition of Cu2+ or Fe3+. This general modular route will permit easy detection and the concept can be extended to a variety of quinolones for sensing purposes. [ABSTRACT FROM AUTHOR]

Abstract A simple, rapid and low-cost solar irradiation method to prepare highly fluorescent carbon dots has been demonstrated by using citric acid and o -phenylenediamine as precursors. The whole concentrated light sintering process is completed within 2 min and this nitrogen doped carbon quantum dots exhibit striking blue luminescence. Except the conventional ultra-violet (378 nm) pumped emissions, the specific up-converted photoluminescence signal is able to extend the excitation sources to near-infrared range (750 nm). Moreover, carbon dots are very sensitive and selective to the presence of Hg2+ ions. Two different responsive ways (down-conversion and up-conversion) have been employed for the first time and the limits of detection are determined to be 1.3 nM and 0.06 nM respectively. Its pH dependence has been discussed and the evolution curves indicate such carbon-based nanomaterial possess unique features within a wide pH range. This study focuses on efficient solar energy conversion and provides new insights of carbon dots with multi-modal sensing capabilities. Highlights • Concentrated solar irradiation was used to prepare carbon dots. • Blue carbon dots were synthesized within 2 min. • Up-conversion feature was explored. • Hg2+ ions sensing experiments were investigated. [ABSTRACT FROM AUTHOR]

Abstract A robust, one-pot synthesis of polymeric nanocluster in polar medium has been reported based on the assembly of polyethyleneimine (PEI) and p-phenylenediamine (PPDA). A number of process parameters including molecular weights of PEI, ratios between PEI and PPDA, reaction time, pH condition and solvent polarity have been discussed. This novel nanomaterial can exhibit striking blue-greenish emissions upon the excitation at 377 nm. More importantly, it is highly sensitive to the titration of copper ions and detection limit has been determined to be as low as 11.27 nmol. These results will pave the way for constructing next generation of polymeric devices. [ABSTRACT FROM AUTHOR]

Nitrogen, phosphorus co-doped carbon dot has been synthesized via a hydrothermal method and it gives rise to bright green emission at 504 nm and the excitation-dependent behavior is monitored. Such nanoplatform displays rapid and highly selective detection to nitrite ions in water. Carbon nanomaterials have aroused considerable interests due to excellent optical performances, but most of achieved carbon dots possess blue luminescence under UV-light irradiations. Herein, we report the preparation of phosphorus and nitrogen co-doped carbon quantum dots (PNCQDs) via hydrothermal method by employment of 1,3-phenylenediamine, citric acid and H 3 PO 4 as precursors. The particle size of the water-soluble PNCQDs is in the range between 4 and 6 nm and the average diameter is determined to be 4.75 nm. The resulted quantum dots give rise to bright green emission at 504 nm and the excitation-dependent behavior has been found. Moreover, it demonstrates luminescence stability toward a broad pH range from 1 to 10. Fluorometric titration studies reveal that close interactions occur between carbon dots and nitrite ions and a switched off effect has been achieved. In addition, prospective application of the quantum dots in tap water and live cells has also been demonstrated. [ABSTRACT FROM AUTHOR]

Abstract Efficient ways for the trace level monitoring of Cr 2 O 7 2− have generated considerable attention in the fields of medical diagnosis and environmental protection. In current research, the water-soluble carbon dots (CDs) have been developed via the precursors of 1,3-phenylenediamineand citric acid. The quantum dots with particle size of 3–4 nm have been prepared based on a simple one-pot ultrasonic irradiation method and demonstrate bright blue emission at 440 nm. Its excitation-dependent feature has been explored and the achieved emission evolves from blue (440 nm) to green luminescence (528 nm). Photophysical studies support that CDs can be remarkably quenched by the presence of chromate due to inner filter effect. In addition, the absorption curves demonstrate that carbon dots possess highly selective and sensitive responses to Cr 2 O 7 2− through color changes. The dual sensing modes (fluorescence and colorimetric detection) can be well-established for the recognition of chromate and the detection limits are calculated to be as low as 140 nM and 410 nM respectively. To further evaluate the analytical potentials of such nano-platform, the concentration of Cr 2 O 7 2− have been determined in real water and river samples. Highlights • Ultrasonic irradiation was used to assemble carbon dots. • Blue-emissive carbon dots were prepared. • Excitation-dependent feature was explored. • Dual sensing modes were developed. [ABSTRACT FROM AUTHOR]

Abstract An efficient strategy for the synthesis of excitation-independent carbon nanodots has been provided. This functional nano-scale particle has been assembled by using citric acid and urea as raw materials through a microwave irradiation process in the absence of further surface modifications. The achieved nanomaterial demonstrates intensive green emissions and can be dispersible in aqueous environment. In particular, cerium (III) ion is able to quench its fluorescence emission intensity selectively and an " on-off " change has been observed. A good linearity between the concentration range of 10−6–10−4 M has been realized and the detection limit is determined to be 0.7 μM. More importantly, we report a color-evolution based paper sensor for effective monitoring of Ce3+ by incorporating fluorescent nanoprobe onto the cellulose paper substrate. Graphical Abstract Green-emissive nano-scale particle has been assembled by using citric acid and urea as raw materials through a microwave irradiation process. Cerium (III) ion is able to quench its fluorescence emission intensity selectively and an " on-off " change has been observed. Unlabelled Image Highlights • A novel carbon dot nanomaterial has been designed. • Its green emissions are irrespective to excitations. • Cerium (III) ion was able to quench its fluorescence selectively. [ABSTRACT FROM AUTHOR]

Highlights • The synthesized tetraphenylethene (TPE)-based derivative exhibited weak emission at 580 nm in water. • Hyaluronic acid (HA) induced the emission recovery due to electrostatic interaction. • Fluorescence quenching has been observed in the presence of hyaluronidase (HAase). • Quantitative evaluation of HAase in human urine samples has been realized. Abstract The development of nanoprobes with high sensitivity and specificity for tumor marker detection has gained increasing attention in biological applications. Here, we have designed and synthesized a novel 4,4',4”,4”'-(ethene-1,1,2,2-tetrayltetrakis(benzene-4,1-diyl))tetrakis (1-(4-bromobenzyl)pyridin-1-ium) bromide (TPE-4N+) based aggregation induced emission (AIE) fluorescent sensor and it gives rise to electrostatic adsorption towards hyaluronic acid (HA), resulting in an effective emission recovery in yellow-greenish region. In the presence of hyaluronidase (HAase), the enzymatic digestion between HA and HAase induces the fluorescence quenching and this “ on-off ” change has been analyzed by two consecutive linear equations. The low detection limit is determined to be 0.02 U/mL by quantitative evaluation and its practical application has been verified by detecting human urine samples. It is promising that this new approach can be utilized to study a wide variety of other depolymerization reactions. [ABSTRACT FROM AUTHOR]

Assembly of a new functional organic linker, (dimethyl 4-(carbaldehyde oxime) pyridine-2,6-dicarboxylate, L1), with europium ions modified Uio-67 leads to Uio-Eu-L1, which is shown to be a new molecular-based probe with high sensitivity and selectivity for ClO − . The detection limit is calculated to be as low as 16 nM. To our knowledge, this is the first report of a sensitive europium sensor for ClO − established on the oxime isomerization reaction. The nature of organic L1 sensitizer within the complex has been demonstrated to control the photoluminescence effectively. The “off-on” signal changes can be realized by oxidative deoximation reaction induced recognition of hypochlorite. More strikingly, both continuous-mode lanthanide emission (steady-state photoluminescence measurement) and time-gated luminescence detection are collected in the presence of several interference organic dyes. This remarkable optical feature will allow easy spectral and discrimination of their emission bands from separation of noisy signals. [ABSTRACT FROM AUTHOR]

The study of fluorescent polydopamine nanoparticles (F-pDA NPs) for the purpose of sensing and cell-staining has been investigated over the past decade. However, most of general synthesis strategies include potentially dangerous process or need to use cytotoxic chemicals that restrict the application range. Inspired by the adhesive structures in mussel chemistry, we employ glutathione (GSH) as a stabilizing agent to assemble the fluorescent GSH-integrated polydopamine nanoparticles (F-GSH-pDA NPs) via a straightforward one-pot oxidation method. In contrast to common methods that rely on H 2 O 2 or specific catalyst, this novel way has been carried out through a single step based on only adjusting the pH value of GSH/Dopamine solution. The photoluminescence results demonstrated the possibility of controlling the emission wavelength from 480 to 540 nm by simply changing the excitation wavelength (from 320 to 450 nm). In particular, the emission profile shifted towards the longer wavelength region (from 493 to 525 nm) in the presence of acidic environment (pH 6 to 1). This blue-green luminescence could be switched off by the addition of Cu 2+ or Fe 3+ and the detection limits were determined to be 0.73 μM and 0.66 μM respectively. Further discrimination between Cu 2+ and Fe 3+ could be realized by absorption spectra changes. For the first time, the intracellular delivery of the functional nanoplatform has been reported and Cu 2+ or Fe 3+ recognition could be performed in two adherent cell lines (U937 and HeLa cells). [ABSTRACT FROM AUTHOR]

Construction of systems with variable electron distribution is a relatively new method in design of responsive fluorophores. Herein, 4,4′,4″,4‴-(ethene-1,1,2,2-trayltetrakis (benzene-4,1-diyl))tetrakis(1-carboxymethyl-pyridin-1-ium)bromide (LG556) is developed and its specific spectral behavior has been verified based on perturbation involving intramolecular charge transfer (ICT) via the connected electron donor and acceptor. In the presence of Ce4+ ions, the fluorescence intensity of LG556 can be efficiently quenched due to the disassembly of LG556 nanoaggregates and inner filter effect (IFE). The sensitivity is dependent on the concentration of Ce4+ with an excellent linear range 1–150 μM and a low detection limit of 0.62 μM. At this stage, the working principle behind the aggregated-induced-emission (AIE) has been employed and the difficulty lying in aggregate formation is overcome. The incorporated ascorbic acid causes the reduction of Ce4+ to Ce3+ and the re-assembly of LG556 has been realized. The detection limit has been evaluated to be 39.2 nM, which is lower than most of the reported results. Therefore, the "on-off-on" signal conversion leads to a reversible IMPLICATION logic gate and the molecular probe has been applied for the analysis of Ce4+ and ascorbic acid in pure aqueous solution with satisfactory results. • LG556 can emit yellow luminescence in water. • ICT and AIE effects controlled the fluorometric and detection process. • An "on-off-on" signal conversion leads to an IMPLICATION logic gate. [ABSTRACT FROM AUTHOR]

• Dual detection modes were realized for Hg2+ sensing. • Cytotoxicity of sulfur dots was evaluated. • Endocytosis mechanism concerning sulfur dots was established. • Cellular tracking of mercury ions was realized. As the standard for heavy metal sensing systems increases, it becomes more important to find out new self-indicating materials as alternatives. The traditional design of optical probe contains receptor and fluorophore as two moieties. Here a novel sulfur quantum dot as the intrinsic fluorescent sensor has been established and the signal transduction involves interaction of mercury ions with sulfur atoms which belongs to the internal system of the fluorophore. Its analytical performances can be assessed by fluorometric and colorimetric titrations simultaneously and the detection limits for Hg2+ ions are determined to be 65 nM and 1.86 μM respectively. In the presence of sulfur dots, very low cytotoxicity has been verified in two cell lines (HeLa and K562) via both cell counting kit-8 method and flow cytometry. For the first time, four sorts of chemical inhibitors have been employed to clarify the endocytosis mechanism based on sulfur quantum dots. The collected results indicate that clathrin and lipid raft mediated endocytosis play as primary roles in the internalization processes. It has been found that sulfur dots are located in the cytoplasm with intense blue emissions and the cellular tracking of mercury ions has been realized. [ABSTRACT FROM AUTHOR]

Fluorescence has been well documented and the optical feature of carbon dots generates considerable interests. Here the nitrogen-doped carbon dots with a relative quantum yield of 25% have been prepared. It displays stable blue emission based on the excitation at 355 nm. The carbon nanomaterial is highly dispersible in aqueous solution and can be employed as an effective optical probe for label-free detection of Fe3+ (0.87 μM) via a switched off change. Additionally, such sensing nanoplatform can be recovered in the presence of pyrophosphate (PPi) and an "off-on" process has been identified. It is expected that this on-off-on strategy will allow new possibilities for developing efficient sensors in industrial fields. The nitrogen-doped carbon dots with aqueous solubility display stable blue emission based on the excitation at 355 nm. It can be employed as an effective optical probe for label-free detection of Fe3+ (0.87 μM) through an "on-off" change. Furthermore, such sensing nanoplatform can be recovered in the presence of pyrophosphate (PPi) and the "off-on" process has been identified. It is expected that this on-off-on strategy will allow new possibilities for developing efficient sensors in industrial fields. Unlabelled Image • A carbon nanodot-based chemical sensor has been designed. • A stepwise assembly method has been used to generate responses. • Two targets could be determined by this functional sensor. [ABSTRACT FROM AUTHOR]

• Carbon nanoparticles derived from 3-hydroxybenzoic acid were achieved. • Lanthanide was incorporated into the nanosystem. • An "off-on" change was discovered in the presence of GSH. Selective determination of targets in live cells and the real-time detection of active species will be highly valuable in biological field. Integration of 3-hydroxybenzoic acid and europium ions under hydrothermal conditions would lead to the formation of regular carbon nanoparticles with the size of 10–20 nm. This novel nanostructure possessed striking blue luminescence and no effective lanthanide signals were detected. In the presence of glutathione (GSH), the europium incorporated nanoparticles showed intensive red luminescence and an "off-on" change was observed. It has been accepted that GSH acts as an antioxidant to protect cell via entrapping free radicals and it controls oxidative stress within living systems. The abnormal levels of GSH will be closely related to a variety of diseases. Therefore, the bio-distribution and in vitro detection of GSH were investigated in this study. The biocompatibility and cytotoxicity of the europium incorporated nanoparticles were also evaluated by MTT assay and flow cytometry. This new system will be essential to monitor the concentration of important biological compounds in living organisms. [ABSTRACT FROM AUTHOR]