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Fluorescent carbon dots (CDs) have been reported as an artificial antenna to amplify the harvesting ability of light and enhance photosynthesis in plants. However, the main mechanism of this promotive effect and contributions of CDs' structure are unclear. Herein, CDs and nitrogen (N)-doped CDs (N-CDs) with blue fluorescence were synthesized, and they could promote photosynthesis and growth of corn at an application concentration of 50 mg·L-1 or lower, compared to the control. Foliar application of N-CDs (5 mg·L-1) on corn could increase the net photosynthesis rate (21.51%), carbohydrate content (66.43% in roots and 42.03% in shoots), fresh weight (24.03% in roots and 34.56% in shoots), and dry weight (72.30% in roots and 55.75% in shoots), which were much higher than those of CDs. Principal component analysis and density functional theory calculation demonstrated that, compared with undoped CDs, N doping enhanced the light conversion and electron supply via altering the structure of CDs, making N-CDs effective light conversion materials and electron donors to promote the photoelectron transfer rate. Furthermore, foliar application of N-CDs could increase the yield and 1000-grain weight by 24.50 and 15.03%, respectively. Therefore, the application of N-CDs could be a promising approach for increasing agricultural production.

Pollution of toxic heavy-metal ions such as mercury ions (Hg2+) is well known to severely threaten ecological environment and human health. Correspondingly, development of a fast and sensitive method for detecting heavy-metal ions is urgently needed and has been received widespread attention in recent years. In this study, carbon nanodots (CDs) with strong blue fluorescence were synthesized by a microwave-assisted hydrothermal method. The as-prepared blue fluorescent CDs not only have excellent stability (e.g. photostability, salt stability and pH stability), but also have extremely high selectivity and sensitivity for probing Hg2+ via fluorescence quenching. Specifically, fluorescence of CDs is gradually quenched along with the increase in Hg2+ concentration, and a low concentration of Hg2+ can be identified (with low detection limit, 15 nM). Therefore, the novel fluorescent CDs could be developed for detecting Hg2+ in aqueous conditions, and have great potential for fast probing Hg2+ in environmental samples.

A novel visual and fluorometric-sensor paper is prepared for the monitoring of atmospheric humidity and ethanol. The paper contains a combination of copper nanoclusters (CuNCs) and carbon dots (CDs), immobilized on a filter paper. This makes it a dual-emission system. The visual sensor shows bright fluorescence and has a diameter of ∼8 cm with uniform and homogeneous surface. The detection mechanism of the sensing paper is based on the fluorescence intensity variation of CuNCs in different environments. Desirable linear relationship is observed between fluorescence intensity ratio (red/blue) and humidity. Visible color transformation of this sensor paper is observed in the humidity range ∼40-80%, implying utility for easy and facile atmospheric humidity determination. Furthermore, due to the water and ethanol have different impacts on the spectrum, this paper-based fluorescent probe shows excellent response to ethanol. Therefore dual-emitting sensing paper, when suitably calibrated, shows promise for visual and fluorometric sensing platforms aimed at humidity or ethanol detection.

Nitrogen doping can effectly adjust the compositions and structures of carbon dots and hence enhance their fluorescence. In this work, we report a fast and low-cost route for synthesis of nitrogen-doped carbon dots (N-CDs) by microwave pyrolysis of citric acid and ammonium within 7 min. The as-prepared N-CDs contain plentiful oxygen and nitrogen functional groups, and dispaly intense fluorescence with high quantum yield of ca. 44.3% and have an average size of 1.8 nm. The obtained N-CDs exhibit highly stable against photobleaching, ionic strengths, and can be used for selective and sensitive detection of Fe(III). It is postulated that the Fe3+-mediated fluorescence quenching is attributed to the charge transfer between N-CDs and Fe3+. In particular, the emission peaks from blue to red region can be tuned by interparticle distance of N-CDs, simply by increasing the concentration of N-CDs in aqueous solution, which indicates its potential applications as a promising optical image probe in multicolor cellular imaging.

Near-infrared (NIR) fluorescent metal nanodots may have significant advantages in biological detection and bioimaging. Herein, we introduce tunable near-infrared fluorescent gold nanodots (AuNDs) protected by branched polyethylenimine (PEI) modified by surface segmental attachment of sulfhydryl groups (PEI-SH), abbreviated as PEI-SH-AuNDs, for simultaneous gene delivery and cell imaging. The modified PEI endows the resultant PEI-SH-AuNDs with the following excellent advantages. Sulfhydryl groups of PEI-SH anchor to the surface of AuNDs, and such polycations with amine groups give PEI-SH-AuNDs remarkable stability. The cationic polymer PEI-SH with positive charges enables PEI-SH-AuNDs to perform gene delivery, and the gene transfection efficiency can reach 22.8%. Moreover, the fluorescence of PEI-SH-AuNDs is tunable from visible red light (wavelength 609 nm) to NIR light (wavelength 811 nm) via an increase in the size of AuNDs. PEI-SH-AuNDs yielded gene transfection efficiency similar to that of commercial PEI, but showed much lower cytotoxicity and much greater red-shift fluorescence. With excellent photoluminescent properties, such multifunctional fluorescent PEI-SH-AuNDs hold promise in applications to bioimaging and as ideal fluorescent probes for tracking gene transfection behavior.

Fluorescence-based nanothermometers have potential to offer accuracy in the measurement of temperature using non-contact approaches. Herein, a C-dot/C-dot based dual-emission temperature sensing platform is fabricated through the electrostatic self-assembly of two kinds of fluorescent CDs with opposite charges. This dual-emission platform consists of several nearly-spherical CDs with two emission centers in blue (440 nm) and orange (590 nm) regions. The orange fluorescence exhibits discernible response to external temperatures in the range of ∼15 to 85 °C; on the other hand, the blue fluorescence remains nearly constant. A continuous fluorescence color change in response to temperature from orange to blue can be clearly observed by the naked eye. Thus, the as-prepared C-dot based dual-emission nanospheres can be used for optical thermometry with high reproducibility and sensitivity (0.93%/°C). Detailed characterization shows that temperature (in the 15-85 °C window) impacts the surface states of orange emissive CDs, leaving the blue emissive CDs unaffected. A model is proposed to explain the observations. Finally, by taking advantage of the excellent biocompatibility and stability, the CD based fluorescent nanothermometer is successfully used for the visual measurement of intracellular temperature variations.

The authors described gold nanoclusters (AuNCs) for use on an “on − off − on” NIR fluorescent probe for the determination of citrate and Cu(II) ion. The AuNCs were prepared by a microwave-assisted method using BSA as both the stabilizing and reducing agent. The resulting BSA-capped AuNCs display NIR fluorescence peaking at 680 nm under 500 nm excitation, a quantum yield of ~6.0%, an average size of 2.8 ± 0.5 nm, water-dispersibility, stability and biocompatibility. The on−off probe for Cu(II) is based on the interaction between Cu(II) and BSA which causes the fluorescence of the BSA−AuNCs to be quenched. The quenched fluorescence is recovered on addition of vitamin C (VC), obviously due to complexation of Cu(II) by citrate. The probe was employed to image Cu(II) and citrate in HeLa cells and in aqueous solutions. The method works in the 20 nM to 0.1 mM concentration range for Cu(II), and in the 8 nM to 120 μM concentration range for VC.

The preparation and applications of fluorescent Ag nanoclusters (AgNCs) have been developed rapidly. However, the poor stability and time-consuming in synthesis process limit their further application. Herein, a rapid sonochemical route is used to synthesize fluorescent AgNCs using hydrazine hydrate as reducing agent and glutathione (GSH) as capping agent. The AgNCs would be formed quickly (∼15 min) due to presence of ultrasonic wave, which show red fluorescence (λem = 645 nm), small size (∼2 nm) and good dispersion in aqueous solution. Moreover, GSH, as protecting agent on the surface of resultant AgNCs, has many functional groups including carboxyl and amino groups which make NCs show high photo-, time-, metal- and pH-stability. Then a stable Ag nanoclusters-based nano-sensor is designed for highly sensitive and selective label-free detection of Pb2+. This nanosensor shows a potential application as probe for monitoring Pb2+ not only in aqueous solution but also in living cells. Thus, these stable and fluorescent AgNCs could work as an alternative to conventional fluorescence probes for biolabeling, sensing and other applications.

Multiple functions incorporated in one single component material offer important applications in biosystems. Here we prepared a divalent state of rare earth EuS nanocrystals (NCs), which provides luminescent and magnetic properties, using both 1-Dodecanethiol (DT) and oleylamine (OLA) as reducing agents. The resultant EuS NCs exhibit controllable shapes, uniform size, and bright luminescence with a quantum yield as high as 3.5%. OLA as a surface ligand plays an important role in tunable morphologies, such as nanowires, nanorods, nanospheres et al. Another attractive nature of the EuS NCs is their paramagnetism at room temperature. In order to expand the biological applications, the resultant EuS NCs were modified with amphiphilic block copolymer F127 and transferred from oil to water phase. The excellent biocompatibility of EuS NCs is demonstrated as well as preservation of their luminescence and paramagnetic properties. The EuS NCs offer multifunction and great advantages of bright luminescence, paramagnetic, controllable morphologies, and good biocompatibility promising applications in the field of simultaneous magnetic resonance and fluorescence bioimaging.

A series of dual-emission fluorescent probes was prepared from copper nanoclusters (Cu NCs) and carbon dots (CDs). They show two emission peaks (blue at 469 nm and red at 622 nm) when photoexcited at 365 nm. Upon exposure to sulfide, the Cu NCs will be deteriorated because they react with sulfide to form CuS. This results in the quenching of the red fluorescence of the Cu NCs, while the blue fluorescence of the CDs remains constant. Thus, the color of the nanocomposite changes from red to blue. The ratio of the fluorescences at the two wavelengths decreases linearly in the 2–10 ppb (26–128 nM) sulfide concentration range, and the limit of detection is 0.33 ppb (4.3 nM). The nanocomposite also was placed in an agar gel and then incorporated into a paper strip for fluorometric monitoring of gaseous hydrogen sulfide.

The use of carbon-dot-based dual-emission fluorescent nanohybrids (DEFNs) as versatile nanothermometry devices for spatially resolved temperature measurements in living cells is demonstrated. The carbon dots (CDs) are prepared in the organic phase and display tunable photoluminescence (PL) across a wide visible range by adjusting the excitation wavelengths and extend of N-doping. DEFNs are formed in a straightforward fashion from CDs (emitting blue PL) and gold nanoclusters (AuNCs, emitting red PL). The DEFNs display ideal single-excitation, dual-emission with two well-resolved, intensity-comparable fluorescence peaks, and function in optical thermometry with high reliability and accuracy by exploiting the temperature sensitivity of their fluorescence intensity ratio (blue/red). Furthermore, the DEFNs have been introduced into cells, exhibiting good biocompatibility, and have facilitated physiological temperature measurements in the range of 25-45 °C; the DEFNs can therefore function as "non-contact" tools for the accurate measurement of temperature and its gradient inside a living cell.

In this paper, a novel “turn-on” chemosensor for detecting temperature and Fe3+ has been designed. This nanosensor is based on the aggregation-induced emission enhancement (AIEE) properties of fluorescent carbon dots (CDs). The CDs prepared by a facile hydrothermal route show blue emission (λem = 505 nm) with a quantum yield of 4.7%. The resultant CDs are modified by glutathione (GSH) on the surface through the carbodiimide-activated coupling reaction. The as-prepared GSH-CDs show good dispersion, high fluorescence and AIEE phenomenon. Resultant GSH-CDs would be aggregated by Fe3+ ions in aqueous solution which results in enhanced fluorescence. Therefore, such GSH-CDs would be excellent candidates as fluorescent probes for the label-free detection of Fe3+ ions with a limit of detection of 0.1 μM. Moreover, the PL intensity of GSH-CDs increases progressively with increasing temperature and they could be used in optical thermometry over a wide temperature range (25–80 °C) with small temperature resolution (∼0.5 °C). Using MC3T3-E1 cells as the model, the resultant nanosensor is demonstrated to monitor temperature and Fe3+ ions in cells. Thus, resultant GSH-CDs could be used as a “turn-on” sensor for highly sensitive and selective detection of temperature and Fe3+ ions in aqueous solution and biosystems.

The development of full-color/white carbon-dot-based light-emitting diodes (LEDs) has been achieved, which show promising applications in full-color and flexible displays, backlights, and novel lighting sources. The gram-level synthesis of these full-color carbon dots (CDs) from citric acid by controlling the temperature has been achieved. By increasing the temperature from 120 to 180 °C, two, four, and six light-emitting CDs can be obtained, for which the emission wavelength shifts from 440 to 585 nm. This result reveals that temperature has a huge impact on the evolution of surface states, that is, increasing the temperature brings about enhanced surface functionalization and passivation, resulting in a red shift of the emission wavelength and enhancement of quantum yield. Then, full-color CDs/polymer composite phosphors are fabricated for efficient phosphor-based LED devices with quench-resistant solid-state fluorescence. By regulating the proportion of various CDs/polymer phosphors, white LEDs are realized with Commission Internationale de L'Eclairage coordinates of (0.32, 0.33) and a color rendering index of 82.7. The as-prepared CD-based full/white color LEDs can prove to be promising candidates for alternative light sources.

A fast, sensitive, and convenient dual-emission water detector was robustly fabricated. This detector was prepared with blue fluorescent carbon dots (CDs) and red fluorescent Cu nanoclusters (NCs), and showed two well-resolved and intensity-comparable fluorescence peaks under a single excitation wavelength. Moreover, it showed strong red fluorescence in organic solvent due to the aggregation-induced emission enhancement (AIEE) properties of the Cu NCs, but the red fluorescence was gradually quenched with an increasing amount of water, whereas the blue fluorescence remained constant. The differences in response result in a continuous fluorescence color change from red to blue that can be clearly observed by the naked eye. Thus, as-prepared Cu NC-based dual-emission nanomaterials can be used for ratiometric fluorescence detection of trace amounts of water in organic solvents by taking advantage of the water sensitivity of their fluorescence intensity ratios (red/blue) and their low detect limits (

In this paper, fluorescent carbon dots (CDs) loaded on silica (SiO2) spheres are synthesized by the one-pot hydrothermal route, and then folic acids (FA) are covalently conjugated on the surface of SiO2 spheres. The formed SiO2@CDs-FA composites can target specific tissues, e.g., cancer. The key of this method is the employment of (3-aminopropyl)trimethoxysilane as bridge joint, which not only serves as surface passivation agents allowing the large scale synthesis of CDs with high quantum yield, but also enables SiO2@CDs composites further covalent conjugation of FA. The resultant SiO2@CDs composites have many advantages such as easy separation and purification, highly stable, well water-soluble, and biocompatible. Moreover, the SiO2@CDs-FA could be used as fluorescent probes for biological imaging in vitro. The uptake of the SiO2@CDs-FA into HeLa cells is receptor-mediated endocytosis, which is confirmed by a comparative study using FR-negative 293T cells. Findings from this study suggest that the SiO2@CDs-FA composites could be used as a platform for cancer diagnosis studies in various biological systems.

Herein, a facile and one-step hydrothermal route is designed to synthesize fluorescent carbon dots (CDs) with citric acid (CA) as a carbon source and hyperbranched polyethyleneimine (PEI) as a surface passivation agent. The resultant CDs display strong blue fluorescence with a quantum yield up to 24.3 %. The resultant CDs show excellent photoluminescence properties with high photo- and metal-stability, which are attributed to PEI, a surface passivation agent that would form a protecting layer. Due to the water solubility and low toxicity, the as-prepared CDs possess potential applications in biological labelling. Additionally, PEI is a functional polycationic polymer with various amine groups, which makes the CDs exhibit pH-responsive optical properties. The resultant CDs have been used as pH sensors due to the reversible pH-responsive fluorescence from acidic (pH 3) and basic solutions (pH 11). Moreover, the fluorescence intensity increases with increasing concentrations of CDs.

In this work, we develop a novel dual-emitting hollow TiO2 microsphere with high stability and attractive thermal sensitivity, which could work as nanosensor for accurately measuring temperature. This nanosensor is prepared through coating gold nanocluster (AuNCs) on the surface of carbon dots-doped hollow TiO2 microsphere. As-prepared nanosensor shows characteristic dual-emitting property of carbon dots (CDs, blue fluorescence) and AuNCs (red fluorescence) under a single excitation wavelength. Moreover, upon increasing the temperature, the intensity of red emission from the AuNCs continuously quenched, whereas that of blue emission from the CDs remained nearly constant. The different response results in a continuous fluorescence color change from red to purple that can be clearly observed by the naked eyes. Thus, as-prepared dual-emitting hollow TiO2 microsphere could be used as optical thermometry by taking the advantage of the temperature sensitivity of their fluorescence intensity ratio (red/blue) with high reliability and accuracy, which change considerably over the wide temperature range (20–80 °C) with small temperature resolution (∼0.5 °C). Additionally, this nanosensor is successfully applied in 10 mM buffered saline (PBS) solution with physiological temperature ranging from 20 to 45 °C, which suggests as-prepared dual-emitting microspheres have promising applications in vivo temperature sensing.

Although the synthesis of two-dimensional (2D) layered MoS2 nanomaterials has been developing rapidly, there are many technical issues in preparing MoS2 quantum dots (QDs) with photoluminescence properties. Herein, we design a facile colloidal chemical route to prepare photoluminescent MoS2 QDs using ammonium tetrathiomolybdate ((NH4)2MoS4) as a precursor and oleyl amine as a reducing agent. The optical properties and structure of as-prepared MoS2 QDs are investigated systematically. The resultant MoS2 QDs exhibit fluorescence (λmax = 575 nm; quantum yield, 4.4%), spherical morphology with a uniform thickness of ∼3 nm and an excitation-dependent PL phenomenon. Moreover, the resultant MoS2 QDs show size-dependent tunable photoluminescence in the wide visible region. With the help of amphiphilic compounds, the resultant MoS2 QDs could be transferred from an organic to an aqueous phase. MoS2 QDs in aqueous solution have many advantages, such as good dispersion, low toxicity and photoluminescent properties, which make them promising materials for application in optoelectronic and biological fields. In this study, the 293T cells are used as a model to evaluate the fluorescence imaging of MoS2 QDs. The results confirm that the fluorescent signal appears in the cytoplasm which demonstrates that as-prepared MoS2 QDs could be used as a probe for real-time optical cellular imaging.

A one-pot sonochemical reaction of Cu(NO3)2 with glutathione (GSH), the latter functioning as a reducing agent and a stabilizing agent, rapidly affords Cu nanoclusters (NCs). The as-prepared GSH-CuNCs possess a small size (∼2.2 ± 0.2 nm), red luminescence with quantum yield (5.3%), and water-dispersibility. Moreover, the fluorescence of the as-prepared GSH-CuNCs is responsive to pH so that the intensity of fluorescence increases rapidly with decreasing pH from 9 to 4. Besides, the GSH-CuNCs would be aggregated by Pb(2+) ions in aqueous solution which results in quenching of the fluorescence. Therefore, such GSH-CuNCs would be excellent candidates as fluorescent probes for the label-free detection of Pb(2+) with the limit of detection at 1.0 nM. Importantly, CAL-27 cells are used as models to achieve potential application as probes for monitoring Pb(2+) in living cells. Thus, these fluorescent CuNCs could work as an alternative to conventional fluorescent probes for biolabeling, sensing and other applications.

Developing an approach for targeting and detecting cancer cells has long been a challenge. Herein, the folic acid (FA) conjugated gold nanodots (Au NDs) are designed for specifically targeting and imaging folate receptor (FR) positive cancerous cells. Fluorescent small Au NDs were synthesized using stable Ag NPs with size above 50 nm and GSH as capping agent. This method solves the problems of low stability and difficulty in purification of small Ag NDs as templates. The resulting Au NDs display pink fluorescence with an emission peak at 582 nm. As-prepared Au NDs provide tunable fluorescence with a significant red shift (∼60 nm) with increase in the amount of GSH. In addition, GSH acts as a protecting layer, which could provide original functional groups (thiol, carboxyl and amine) and make Au NDs exhibit outstanding properties such as dispersibility in water, high stability, good biocompatibility and surface bioactivity. These characteristics make them suitable for further conjugation with FA. FA-conjugated Au NDs show the specific target HeLa cancer cells compared with 293T normal cells. These properties provide Au NDs with potential applications in distinguishing FR-positive cancer cells from normal cells.

Low toxicity and near infrared (NIR) fluorescent nanomaterials have many advantages in biological imaging. Herein, based on metal-enhanced fluorescence (MEF), novel NIR fluorescent nanocomposites (Au/SiO2/Ag2S core–shell microspheres) are designed and investigated. Characterization with UV, PL, TEM, FTIR and XPS confirms the fact that NIR Au/SiO2/Ag2S nanocomposites were prepared. The effects on the MEF including the metal core size (gold nanoparticles), and the distance between the fluorescent molecules (Ag2S nanoclusters (NCs)) and the metal core are systematically studied. The results show that the developed nanocomposites can effectively enhance the NIR fluorescence signal of the Ag2S NCs. A maximum enhancement is obtained when the nanocomposites contain a 25 nm gold nanoparticle core and a 34 ± 2 nm silica spacer. SiO2 as an important scaffold which could prevent NC aggregation and can be easily modified with functional groups (thiol, carboxyl and amine). These characteristics are beneficial for the further conjugation with folic acid (FA). FA-conjugated Au/SiO2/Ag2S nanocomposites show specific targeting of HeLa cells compared with 293T cells. With these properties provided, these nanocomposites have potential applications in distinguishing folate receptor-positive cancer cells from normal cells.

The authors describe strongly red-emitting carbon dots (CDs) which were obtained via microwave synthesis using phenylenediamine as the carbon source. The structural and optical properties of the resultant CDs are studied in some detail. The CDs possess (a) longwave emission (peaking at 620 nm under 470 nm excitation), (b) a quantum yield of ~15%, (c) a size of typically 3.8 nm; and (d) good photostability. The CDs have a pH-dependet response that covers the pH 5 to 10 range, and their fluorescence is quenched by ferric ions. The CDs can detect ferric ions in aqueous samples in the 0 to 30 μM concentration range with a lower detection limit of 15 nM. The CDs were also used to image pH values and ferric ions in E. coli bacteria. Graphical abstract The red-emitting carbon dots with high stability are synthesized which show dual response to pH-values and ferric ions in aqueous solution and biological media simultaneously.

We report on the preparation of water-soluble and fluorescent silver/gold alloy nanoclusters (Ag/Au NCs) by a galvanic replacement reaction. The alloy NCs have an average diameter of 1.5 nm and are shown to be viable fluorescent probes for the determination of lead(II) due to aggregation-induced quenching of fluorescence. The alloy NCs are characterized in terms of photoluminescence spectrum, photoluminescence excitation spectrum, transmission electron microscopy and X-ray photoelectron spectroscopy which confirm the presence of alloy NCs. Bovine serum albumin, a well known stabilizing agent, has a high-affinity site for Pb2+ ion, and the resulting complex acts as a quencher of fluorescence. This finding has led to a method for selective determination of Pb2+ with a limit of detection of about 2 nM.

The development of functional copper nanoclusters (Cu NCs) is becoming increasingly widespread in consumer technologies due to their applications in cellular imaging and catalysis. Herein, we report a simple protein-directed synthesis of stable, water-soluble and fluorescent Cu NCs, using BSA as the stabilising agent. Meanwhile, in this study, hydrazine hydrate (N₂H₄·2H₂O) was used as the reducing agent. N₂H₄·2H₂O was a mild reducing agent suggesting that all processes could be operated at room temperature. The as-prepared Cu NCs showed red fluorescence with a peaking center at 620 nm (quantum yield 4.1%). The fluorescence of the as-prepared BSA-Cu NCs was responsive to pH in that the intensity of fluorescence increased rapidly by decreasing the pH from 12 to 6. Besides, with an arresting set of features including water-dispersibility, red fluorescence, good biocompatibility, surface-bioactivity and small size, the resultant BSA-Cu NCs could be used as probes for cellular imaging and catalysis. In this study, CAL-27 cells and the reaction of oxidation of styrene are used as models to achieve fluorescence imaging and elucidate the catalytic activity of the as-prepared BSA-Cu NCs.

Highly fluorescent papain stabilized gold nanoclusters (NCs) have been synthesized through a simple wet chemical route. Papain was used for the first time as an effective capping and reducing agent for these clusters. The optimal conditions for the synthesis of the gold nanoclusters, including the concentrations of papain and NaOH, reaction time and temperature, were investigated. The as-prepared Au clusters show intense red emission at ∼660nm (QY ∼4.3%) and are uniform in size. The clusters are quite stable and the intense red emission remained unchanged at a buffer pH range of 6-12. The fluorescent Au NCs were then used as a label-free probe for the sensitive detection of Cu(2+). A limit of detection of 3nM was obtained. The sensing strategy is also highly selective against the various potential interference ions.

In this work, we first report the application of fluorescent polymer brushes film as a device for ultrasensitive and selective detection of TNT. As positively charged fluorescent molecules of quaternary ammonium tetraphenylethylene derivatives (d-TPE) were self-assembled on the brushes of poly(acrylic acid) (PAA) by coulomb forces, we obtained a novel fluorescent polymer brushes film with excellent photoluminescent properties, and the emission could be quantitatively and sensitively responsive to 2,4,6-trinitrotoluene (TNT) due to the electron transfer between d-TPE and TNT. The limit of detection of TNT was established to be 0.1 ppb in water. The fluorescent device could also be used repeatedly for TNT detection, which indicated a promising application in trace explosive detection.

The fluorescent nanomaterials play an important role in cellular imaging. Although the synthesis of fluorescent metal nanoclusters (NCs) have been developing rapidly, there are many technical issues in preparing metal alloy NCs. Herein, we used a facile galvanic replacement reaction to prepare Ag/Au alloy NCs. The characterizations of UV, PL, HRTEM, EDX and XPS confirm one fact the Ag/Au alloy NCs are carried out. As-prepared Ag/Au alloy NCs display near-infrared (NIR) fluorescence centered at 716 nm and show tunable luminescence from visible red (614 nm) to NIR (716 nm) by controlling the experimental Ag/Au ratios. Moreover, as-prepared Ag/Au alloy NCs are protected by glutathione (GSH) whose some functional groups including thiol, carboxyl and amino groups make the as-prepared alloy NCs exhibit good dispersion in aqueous solution, high physiological stability and favorable biocompatibility. Together with NIR fluorescence, these advantages make alloy NCs be promising candidate in biological labeling.

Temperature measurement in biology and medical diagnostics is of great importance. Herein, a novel carbon nanodot (CND) based fluorescent nanothermometry device for spatially resolved temperature measurements is demonstrated. The fluorescence CNDs are prepared by a simple one-pot solvothermal method using sucrose as carbon source. Resultant CNDs show stable green fluorescence at 520 nm with high quantum yield (≈6%). The fluorescence of resultant CNDs exhibits a reversible linear response to temperature in a wide range of 20–85 °C. Moreover, the temperature resolution better than 0.5 °C and high sensitive variation of ≈1.3% °C−1 are observed in a broad physiological temperature range of 20–40 °C. Therefore, the as-prepared CNDs possess high water solubility, stable fluorescence, small size, and good biocompatibility, which make them promising candidate for thermometry and cell imaging in biological media.

A one-step facile method of synthesizing fluorescent carbon dots (CDs) has been demonstrated, whereby fluorescent CDs are produced through hydrothermal treatment of glucose in the presence of H3BO3 with a fluorescence quantum yield of 14.5%. It is found that spherical CDs have an average size of 3.7[Formula: see text]nm as well as good monodispersion in aqueous solution. The added Cr (VI) selectively leads to the inner filter effect (IFE)-based fluorescence quenching of the CDs. Such fluorescence responses can be used for well quantifying Cr (VI) in the range of 0.05–200[Formula: see text][Formula: see text]M. Significantly, the CDs possess negligible cytotoxicity, excellent biocompatibility and high selectivity. All these features are favorable for label-free monitoring of Cr (VI) in complex biological samples. It was then successfully applied for the fluorescence imaging of intracellular Cr (VI). As an efficient chemosensor, the CDs hold great promise in broadening their applications in biological systems.

Fluorescent gold nanodots (GNDs) are an important kind of nanoprobes. Herein, the application of galvanic replacement for the preparation of fluorescent GNDs is reported. Using presynthesized and size-controlled Ag nanodots (Ag NDs) as templates, the as-prepared GNDs have strong fluorescence (quantum yields ~10%) with high stability and surface bioactivity. The resultant GNDs show excellent photoluminescence properties with high photo-, time-, metal-, and pH-stability, which are attributed to the protective surface layer of glutathione (GSH) and the presence of Au(I)-S complexes on the surface of the gold core. GSH, a naturally occurring and readily available tripeptide with carboxyl and amino functional groups, allows good dispersion of the as-prepared GNDs in aqueous solution and favorable biocompatibility. These advantages, combined with their small size, mean that the as-prepared GNDs have potential application in biological labeling, especially as a DNA probe for the specific detection of nucleic acids. In this study, the CAL-27 cells are used as a model to evaluate the fluorescence imaging of GNDs.

Facile preparation of water- soluble and fluorescent Ag nanoclus- ters (NCs) stabilized by glutathione at room temperature is described. Al- though the glutathione layer was intro- duced to prevent the silver nanoparti- cles from decomposition and increase their water solubility, this simple sur- face optimization resulted in surpris- ingly high efficiency of selective Hg 2 + sensing, where the limit of detection (LOD) was as low as 10 10 m (0.02 ppb, 0.1 nm). This result revealed a simple and practical strategy for Hg 2 + detec- tion using fluorescent Ag NCs as sensor probe, with the lowest detecting limits reported to date.

L ow toxicity and fl uorescent nanomaterials have many advantages in biological imaging. Herein, a novel and facile aqueous-phase approach to prepare biocompatible and fl uorescent Ag 2 S nanoclusters (NCs) is designed and investigated. The resultant Ag 2 S NCs show tunable luminescence from the visible red (624 nm) to the near infrared (NIR; 724 nm) corresponding to the increasing size of the NCs. The key for preparing tunable fl uorescent Ag 2 S NCs is the proper choice of capping reagent, glutathione (GSH), and the novel sulfur-hydrazine hydrate complex as the S 2 − source. As a naturally occurring and readily available tripeptide, GSH functions as an important scaffold to prevent NCs from growing large nanoparticles. Additionally, GSH is a small biomolecule with several functional groups, including carboxyl and amino groups, which suggests the resultant Ag 2 S NCs are well-dispersed in aqueous solution. These advantages make the as-prepared Ag 2 S NCs potentially applicable to biological labeling as well. For example, the resultant Ag 2 S NCs are used as a probe for MC3T3-EI cellular imaging.

Lanthanide-doped luminescent nanoscale materials have great potential applications in biological researches. Herein, we reported a novel and mild method for one-step synthesis of chitosan/ NaGdF 4: Eu 3+ nanocomposites. The luminescent Eu 3+ ions and magnetic resonance imaging (MRI) contrast agent Gd 3+ ions were incorporated to these biocompatible nanocomposites. The resultant nanocomposites exhibited strong fluorescence and attractive magnetic features. The nanocomposites also have pure hexagonal phase with uniform size of about 65 nm. FT-IR spectra revealed that these nanocomposites were successfully coated by hydrophilic chitosan, whose amine groups conferred the nanocomposites excellent dispensability in aqueous solution. Besides, the MTT assay and laser confocal microscopy images have confirmed the good biocompatibility of the nanocomposites. These results indicated that the as-prepared nanocomposites could be used as an excellent targeted imaging agent in biological fields.