Search

Detecting hexavalent chromium (Cr(VI)) is important for human health and environmental protection due to its high toxicity, carcinogenicity and persistence, but developing a sensor to selectively detect Cr(VI) remains challenging. Here, we proposed a selective fluorescent sensor for Cr(VI) detection using cetyltrimethylammonium chloride (CTAC) modified N-doped carbon dots (N-CDs–CTAC) synthesized via a post-modification strategy. Specifically, the introduced CTAC molecules could self-assemble into micelles for encapsulating fluorescent N-CDs, causing the aggregation of N-CD particles and then displaying enhanced fluorescence emission owing to the aggregation-induced emission effect. Moreover, the positively charged CTAC can interact with negatively charged Cr(VI) in the form of an anion (Cr2O72−), boosting the ability of the selective recognition of Cr(VI). Thus, a N-CDs–CTAC fluorescent probe was designed to selectively monitor Cr(VI) with an ultralow detection limit down to 40 nM, and was further used for Cr(VI) detection in real environmental samples. The fluorescence quenching mechanism of N-CDs–CTAC by Cr(VI) was attributed to dynamic quenching. The proposed assay opens an avenue for the selective detection of Cr(VI) in the environmental monitoring field. [ABSTRACT FROM AUTHOR]

The development and construction of fluorescent sensors with high sensitivity for nitroaromatics explosives detection is of great significance for national security and public environmental issue. Herein, the mechanism of photoinduced electron transfer (PET) was utilized to design a newly amino-functionalized luminescent Zr-based metal-organic framework (NU-1000-NH 2) for ultra-sensitive fluorescent detection of nitroaromatic explosives, like 2,4,6-trinitrotoluene, 2,4-dinitrotoluene and 2-nitrotoluene. The amino constructed in cavities of NU-1000-NH 2 can be served as recognition site to capture and bind the nitroaromatic molecules. Thus the rational design of NU-1000-NH 2 has been proven an effective route to recognize the electron-deficient nitroaromatic explosives, causing fluorescence quenching of NU-1000-NH 2 due to the electron donor (–NH 2)–acceptor (-NO 2) interaction. Moreover, hydrogen-bonding effect of intermolecular N –H···O analyte between NU-1000-NH 2 and analytes was also found assisting for binding and recognizing of nitroaromatic explosives molecule. And the density functional theory (DFT) calculations were conducted to further investigate and quantitatively assess the molecule orbitals (MOs), interaction energies and electrostatic potential map, revealing the electron transfer process from conduction band (CB) of MOF to LUMO of nitro analytes and stronger interaction effect was obtained with more nitro groups of NEs. This study provided a feasible idea to design functionalized fluorescent MOFs for nitroaromatic explosives sensing based on PET and hydrogen-bonding effect. [Display omitted] • Fluorescence quenching mechanism of PET is successfully applied in the functionalized MOF design for fluorescent sensing. • DFT theoretical calculation is used to discuss molecule orbitals, hydrogen bonding and electrostatic interaction effect. • Interaction effect of host-guest hydrogen bonding could be evaluated by experiments and theoretical calculation. • Highly sensitive detection of Higher K sv and lower limits of detection (LODs) for multiple nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

A novel fluorescence turn-off sensing strategy for I− ions detection was developed based on the internal filtering effect between CDs and iodide-induced aggregation His-AuNCs. [Display omitted] • An ultrasensitive sensing strategy for iodide detection was proposed. • His-AuNCs and iodide form ground-state complexes that block the CDs' fluorescence. • A new insight into I− ions determination with CDs/His-AuNCs is presented. In this work, a novel fluorescence turn-off sensing strategy for I− ions detection was developed. The fluorescence of CDs/His-AuNCs hybrid probes was effectively turned off by I− ions. It was attributed to the internal filtration effect between the fluorescence emission peak of CDs and the absorption spectrum of His-AuNCs enhanced by I− ions. Quantitative analysis of I− ions can be achieved by analyzing the fluorescence quenching degree of CDs/His-AuNCs. Under the optimal experimental conditions, it exhibited good linearity in two concentration ranges of I− ions: 0.1–5.0 μM and 5.0–60.0 μM (low detection limit = 34 nM). The established sensing platform has been successfully exploited for the detection of I− ions in practical water samples. This work provided new insight into the determination of anions using fluorescent nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Cu-NCDs exhibited stronger fluorescence emission peaks benefiting from the Cu doping. • Selective and sensitive detection of Fe3+ and TC were achieved based on Cu-NCDs. • The total Fe in the detection system was realized by adding H 2 O 2 into the Cu-NCDs. • The Cu-NCDs were applied in the detection of Fe3+ and TC in real water samples. This paper synthesized carbon dots (Cu-NCDs) doped with nitrogen and copper, which could be used as a sensor for measurement of Fe3+ and tetracycline (TC). The average particle sizes of CDs and Cu-NCDs were determined as 3.9 nm and 4.8 nm, respectively. The presence of carbon, oxygen, nitrogen and Cu atoms was confirmed in the structure of Cu-NCDs. Both CDs and Cu-NCDs exhibited a strong fluorescence (FL) emission peak at 450 nm, but the doping of Cu and N makes the surface of Cu-NCDs positively charged, which enhances the fluorescence intensity. The carbon dots doped with copper had more significant optical effects than those doped with other metals, and the relative quantum yield (QY) of the Cu-NCDs was as high as 53.6%. Cu-NCDs can be used as multi-functional fluorescent probes to selectively detect Fe3+ and TC based on fluorescence quenching. The limit of detection of Fe3+ and TC separately was found as 1.189 µM and 0.416 µM. This probe is also suitable for the indirect determination of Fe2+ because the Fe2+ is oxidated to Fe3+ by H 2 O 2. The mechanisms of the quenching process for Fe3+ and TC were explored that is the complex process of dynamic quenching and static quenching based on internal filtration effect (IFE), respectively. The fabricated sensors were successfully applied to determine Fe3+ and TC in tap and lake water samples, suggesting a promising application in environment analysis. [ABSTRACT FROM AUTHOR]

An aggregation-induced emission copper nanoclusters fluorescence probe (TA-CuNCs@CTAB) was designed for the detection of tetracycline (TC) based on the turn-off fluorescence intensity. [Display omitted] • An aggregation-induced emission copper nanoclusters fluorescence probe (TA-CuNCs@CTAB) was designed. • TA-CuNCs@CTAB fluorescence probe can detect TC in environment samples with high accuracy and good selectivity. • The detection mechanism is the internal filtration effect (IFE) of TA-CuNCs@CTAB induced by TC. Copper nanoclusters (CuNCs) is a promising fluorescent material for water detection with unique fluorescence characteristics and low cost. To boost the fluorescence characteristics of CuNCs, cetyltrimethylammonium bromide (CTAB) modified material has the ability to improve the sensitivity, selectivity and sensing performance of the probe. Herein, fluorescence-enhanced copper nanoclusters (TA-CuNCs@CTAB) based on the tannic acid templated is designed due to the electrostatic interaction between CTAB and TA-CuNCs, the addition of CTAB induced the aggregation of TA-CuNCs, and the enhancement of fluorescence signal was achieved using the aggregation-induced emission (AIE) mechanism. As a new fluorescent probe (TA-CuNCs@CTAB) for tetracycline (TC) turn-off detection, it has satisfactory linearity in the two ranges of 5–50 μM and 50–130 μM, with a detection limit of 65 nM. The detection mechanism is that the internal filtration effect (IFE) of TA-CuNCs@CTAB induced by TC leads to a significant fluorescence quenching. Therefore, this method is used to detect TC in actual water samples, which is more convenient to operate, has high accuracy and good selectivity, and has a good application prospect in detecting TC. [ABSTRACT FROM AUTHOR]

This work reported an economical and sensitive fluorescence sensor for mercury (II) ions based on the cetyltrimethylammonium bromide-mediated nitrogen-doped carbon dots (NCDs). The NCDs, obtained by a solvothermal method, exhibit emission with low quantum yield (6%) that can be quenched by various ions such as Cu2+, Cr6+, Co2+, and Hg2+. After adding cetyltrimethylammonium bromide (CTAB), the two produced aggregation-induced fluorescence effect, coupled with electrostatic interaction, and the quantum yield increased to 32%. The spatial structure formed by CTAB/NCDs could selectively capture Hg2+ and make interact with the surface groups of NCDs to cause fluorescence quenching. The fluorescence intensity and Hg2+ concentration showed a linear response in the range of 0.15–1 mM and 0.16–10.24 μM (R2 = 0.998), and the detection limit was 85.71 nM. The fluorescent sensor was used to determine Hg2+ in environmental waters with satisfactory results. [Display omitted] • Structure property and fluorescence performance study of CATB modified carbon dots. • NCDs functionalized by CTAB have an aggregation-induced fluorescence effect. • The fluorescence intensity and quantum yield of CTAB modified NCDs were improved. • The sensor could selectively capture Hg2+ and be applied for practical detection. [ABSTRACT FROM AUTHOR]

• The "on-off-on" S, N-CDs probe was prepared by the ultra-fast one-pot method. • The S,N-CDs/PVA film sensor with stable fluorescenceare was synthesized. • The fluorescence recognition of Cr(VI) and AA in liquid/solid media were realized. In this work, an "on-off-on" fluorescent sensor of sulfur and nitrogen co-doped carbon dots (S, N-CDs) was explored for the identification of Cr (VI) and ascorbic acid (AA), which showed a good selectivity and anti-interfere ability to more than 30 interfering substances. The fluorescence recognition was realized in liquid and solid media under optimal conditions based on the internal filtration effect (IFE). In the liquid medium, the linear dynamic range of Cr (VI) was 0.03–50 μM and the limit of detection (LOD) was 21.14 nM. The linear detection range and the LOD of AA were 1–1000 μM and 0.28 μM, respectively. For solid-phase detection, we embed S, N-CDs into polyvinyl alcohol (PVA) to synthesize a visual fluorescent film sensor, which was irradiated by 365 nm ultraviolet light, for easily and accurately detecting Cr (VI) and AA on-site. The ranges of linearity were 0.1–50 μM and 10–500 μM, respectively, and the LODs were 92.48 nM and 6.99 μM, respectively. This is of great significance such as low cost, user-friendliness, and fast response for the analysis of environmental water samples. [ABSTRACT FROM AUTHOR]