Coordination polymer nanoparticles (CPNs) formed by self-assembly of metal ions (or clusters) and organic bridging ligands through coordination bonds provide a unique platform for designing multifunctional nanoparticles. In this work, we report a ratiometric fluorescent probe for Zn2+ based on CPNs, which were prepared from AIE fluorophore HDBB molecules with metal ions. The CPNs are composed of HDBB molecules with Tb3+ (named Tb-HDBB-CPNs) which displayed a matrix coordination-induced emission peak at a wavelength of 590 nm, while CPNs formed by HDBB molecules and Zn2+ (named Zn-HDBB-CPNs) showed a distinctive fluorescent property with a blue emission peak wavelength of 470 nm. Based on the cation exchange process of Tb-HDBB-CPNs with Zn2+, a highly selective ratiometric fluorescent probe for the determination of Zn2+ in aqueous solution was developed with a linear range from 0.1 to 60 μM and a detection limit of 50 nM. Our approach using AIE molecules as organic ligands for the construction of CPNs paves a way toward AIE functionalized materials with ratiometric fluorescence response and will find wide applications in chemical sensing.

•An ion-imprinted sensor method for determination of Pd(II) was developed.•An electrochemical sensor was constructed by Pd(II)-IIM modified G/GCE.•One-step in situ polymerization method was used to form ion imprinted membrane.•The sensor was successfully applied to detect Pd(II) in catalyst and plant samples.In this work, an amperometric sensor was developed for the selective recognition and sensitive determination of palladium in complex matrices using a glassy carbon electrode (GCE) modified with a novel ion-imprinted membrane (IIM) and graphene. Graphene enhanced the sensor's electron transfer and sensitivity. The electrode surface was first directly modified with graphene through the electrodeposition of graphene oxide. An ion-imprinted polymer membrane was subsequently synthesized on this modified surface via in situ polymerization in acetonitrile using allylurea (NAU) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent, and azobisisobutyronitrile as an initiator at a molar ratio of template (PdCl2) to NAU to EGDMA of 1:4:40. Amperometric i-t curves were measured for the determination of palladium. The designed modified electrode was shown a linear response to Pd(II) ions in the range of 2.0 × 10− 8–2.0 × 10− 4 mol L− 1 of Pd(II) ion with a detection limit of 6.4 × 10− 9 mol L− 1. Metal ions present at concentrations 15 times higher than that of Pd(II) did not interfere with the determination of Pd(II). The sensor was successfully applied to determine palladium in catalyst and plant samples with a relative standard deviation (RSD) of less than 3.3% (n = 5) and recoveries in the range of 99.2–106.5%.A novel amperometric sensor was constructed by in situ polymerization of Pd(II)-imprinted membranes on the surface of graphene modified glassy carbon electrode using allyluread (NAU) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent. The electrochemical characteristic of the sensor was characterized by CV and i-t curve. The sensor exhibited a good selectivity, high sensitivity.

A dual-emission pH-sensitive fluorescent probe was developed, which displays green fluorescence in alkaline after deprotonation, while orange emission in acid at aggregated state. This novel probe allows the specific light-on in acidic lysosomes of cancer cells and tumors in nude mice, which indicates its potential application in cancer diagnosis.

Coordination nanoparticles (CNPs) are becoming attractive platforms for chemical sensing applications because their unique adjustable properties offer the opportunity to design various luminescent nanoprobes. Here, we present a CNP-based fluorescent nanoprobe, in which fluorophores (rhodamine B, RB) and quenchers (methylene blue, MB) were spontaneously enfolded by coordination networks self-assembled of adenine, biphenyl-4,4′-dicarboxylic acid (BDA) and zinc ions. The aggregation of fluorophores and quenchers in CNPs resulted in a quenched state fluorescence of RB. RB and MB could be released from CNPs in the presence of phosphate, which triggered the fluorescence of RB. On the basis of recognition-driven disassembly principle, a novel turn-on fluorescent probe for the determination of PO43− with a wide response range (0.5–50 μM) has been successfully applied in the detection of phosphate in human serum samples. This work not only develops a probe for phosphate but also provides a general strategy for designing nanoprobes or nanocarriers towards various targets by altering organic linkers or metal ions.

•The cases of in-situ polymerization of ART-imprinted membranes on the surface of graphene modified glassy carbon electrode were discussed.•The calibration graph for the determination of artemisinin by the sensor was linear in the range of 1.0×10−8–4.0×10−5 mol L−1 with the detection limit of 2.0×10−9 mol L−1.•The sensor could retain more than 94% of its original response after used at least 80 times or stored in water at room temperature for 60 days.To develop a rapid and simple method for sensitive determination of artemisinin (ART) in complicated matrices, a novel electrochemical sensor was constructed by in-situ polymerization of ART-imprinted membranes (ART-MIMs) on the surface of graphene (G) modified glassy carbon electrode (GCE) using acrylamide (AM) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent after the experimental parameters for the preparation of ART-MIMs such as functional monomer, molar ratio of template, monomer and cross-linking agent together with extraction condition were optimized. Under the optimal conditions, the sensor named as ART-MIM/G/GCE exhibited a good selectivity, high sensitivity and considerably better resistance against some analogs of artemisinin such as dihydroartemisinin (DHA), artemether (ARM) and artesunate (ARTS). The calibration graph for the determination of artemisinin by the sensor was linear in the range of 1.0×10−8 mol L−1 to 4.0×10−5  mol L−1 with the detection limit of 2.0×10−9 mol L−1. Meanwhile, this sensor possessed of good regeneration, stability and practicability. It could retain more than 94% of its original response after used at least 80 times or stored in water at room temperature for 60 days. The obtained sensor was successfully applied to determine the contents of artemisinin in the extract of Artemisia annua L. with the relative standard deviation (RSD) of less than 3.5% (n=5).

•Developed a new colorimetric method for ascorbic acid detection.•The colorimetric detection of ascorbic acid is rapid, sensitive and selective.•Photo-synthesized silver NCs are powerful for growth of silver nanoparticles.In this work, we report a colorimetric method for detection of ascorbic acid based on growth of silver nanoparticles by a simple and green photo-catalytic route. This route contains two steps, photo-synthesis of silver nanoclusters (NCs) with papain under UV irradiation, and catalytic growth of silver nanoparticles (NPs) in the presence of ascorbic acid. The produced silver NCs at the first step is excellent catalyzer that could quickly catalyze the growth of silver NPs by Ag+ and ascorbic acid in 1 min at room temperature. And thus, in the second step, the color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. We found that the absorbance changes at 420 nm have a good relationship with ascorbic acid concentration, and established a spectrophotometric method for the sensing of ascorbic acid in the range from 0.25 to 50.0 μM, with a limit of detection (LOD) as low as 79.2 nM. We also established a colorimetric assay of ascorbic acid by analyzing the yellow value (Y%) of the silver NPs photographs using cyan, magenta and yellow (CMY) color mode. The lowest detection concentration of ascorbic acid for colorimetric assay by the photographs could be estimated to ∼1 μM. Moreover, the method for ascorbic acid detection also has high selectivity. Potential interferes, such as glucose, dopamine, uric acid and cysteine will not affect the detection of ascorbic acid.

To develop a convenient method for sensitive and selective determination of platinum in complicated matrices, an ion-imprinted electrode was studied by in situ polymerization of Pt(IV) ion-imprinted membranes (Pt(IV)-IIMs) on the surface of a glassy carbon electrode (GCE). After the experimental parameters for the preparation of Pt(IV)-IIMs such as functional monomer, molar ratio of template, monomer and cross-linking agent together with extraction condition were optimized, an electrode with good regeneration, high stability and specific recognition to Pt(IV) was obtained by modifying GCE with Pt(IV)-IIMs prepared in acetonitrile using allylurea (NAU) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent, azobisisobutyronitrile (AIBN) as initiator under the molar ratio of template (H2PtCl6), NAU and EGDMA as 1:4:40. The resulting electrode named as Pt(IV)-IIMs/GCE exhibits high response sensitivity to Pt(IV) in phosphate buffer (pH 5.29). The calibration graph for the determination of Pt(IV) by Pt(IV)-IIMs/GCE is linear in the range of 2.0 × 10−8 ∼ 2.5 × 10−4 mol L−1 with a detection limit of 4.0 × 10−9 mol L−1. No metal ions tested at a concentration 25 times higher than that of Pt(IV) interfered in the determination. The electrode was successfully applied to determine platinum in catalyst and plant samples with a relative standard deviation (RSD) of less than 3.0% (n = 5) and recoveries in the range of 97.8–103.6%.

•Demonstrated a new colorimetric strategy for iodide detection by silver nanoplates.•The colorimetric strategy is to find the critical color in a color change process.•The colorimetric strategy is more accurate and sensitive than common colorimetry.•Discovered a new morphological transformation phenomenon of silver nanoplates.In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 μM of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis.

In this paper, we report a new assay for the rapid detection of Pb2+ in aqueous solution based on aggregation induced emission of Au(I)–glutathione complex. Non-fluorescent oligomeric Au(I)–glutathione complex could aggregate to form Au(0)@Au(I)–thiolate nanoclusters with ultra-bright fluorescence in the presence of high concentrations of metal ions. However, if two metal ions (e.g. Zn2+ and Pb2+) were both used for aggregating Au(I)–glutathione, there is a synergistic aggregation effect on the complex. A very low concentration of Pb2+ could induce apparent fluorescence enhancement. Under the optimal experimental conditions, the relationship between fluorescence changes (ΔF) of the aggregation system and the addition of Pb2+ (c, μM) in the range from 0.50 to 40.0 μM was measured as ΔF = 2.8 + 5.2 c, with the correlation coefficient (R2) of 0.996. Moreover, we carried out a visual fluorescence detection of Pb2+ under violet-light irradiation. The increasing fluorescence can be easily distinguished by color pictures using the naked eye.

A resonance light-scattering method (RLS) for the determination of Rh(III) was initially developed, based on the reaction among Rh(III), WO42− and ethylrhodamine B. The method possesses high sensitivity, but lacks selectivity. Therefore, a Rh(III) ion-imprinted polymer (IIP), prepared by precipitation polymerization using 2-(allylthio)nicotinic acid (ANA) as functional monomer, was used as sorbent to construct a ion-imprint based solid-phase extraction (IIP-SPE) method for separation of rhodium from complicated matrices prior to its determination by RLS. The experimental parameters affecting the extraction efficiency and selectivity of IIP-SPE were studied carefully. Under the optimal conditions, the IIP-SPE column with the enrichment factor (EF) of 10 could be used at least 20 times without decreasing its extraction recovery (above 90%) significantly. The calibration graph for the determination of rhodium by RLS coupled with IIP-SPE procedure was linear in the range of 0.06–1.5 ng mL−1 with the detection limit of 0.024 ng mL−1. There is no metal ions tested at the concentration below 10 ng mL−1 interfered in the determination of 0.8 ng mL−1 Rh(III). The proposed IIP-SPE–RLS method was successfully applied to the extraction and measurement of trace rhodium in catalyst, water and geochemical samples with the relative standard deviation (RSD) of less than 4.0% (n=4).Highlights► A resonance light-scattering(RLS) method for determination of Rh(III) was developed. ► A Rh(III) ion-imprinted polymer (IIP) was prepared as sorbent for SPE of Rh(III). ► The effects of variables on extraction efficiency and selectivity of IIP-SPE were studied. ► The RLS was coupled with IIP-SPE for separation and determination of Rh(III) in real samples.

We established a simple spectrophotometric and colorimetric method for detection of ascorbic acid based on the growth of silver nanoparticles in bovine serum albumin protected-silver nanoclusters (BSA–AgNCs) and Ag+ mixture. Due to the catalysis of BSA–AgNCs, ascorbic acid could reduce Ag+ to silver nanoparticles (NPs) at room temperature. The color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. The absorbance changes at 420 nm had a good relationship with ascorbic acid concentration. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 μM, with the corresponding limits of determination (3σ) of 0.16 μM.Graphical abstractWe found that BSA-protected silver nanoclusters had good catalysis on reducing of Ag+ to Ag0 by ascorbic acid at room temperature, generating uniform silver nanoparticles in the mixture. The strong absorption band near 420 nm, owing to surface plasmon resonance of silver nanoparticles, had good relationship with ascorbic acid concentration, and the color of the mixture changed from colorless to yellow. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 μM, with the corresponding limits of determination (3σ) of 0.16 μM.Highlights► Bovine serum albumin protected-silver nanoclusters show good catalytic activity to reduce Ag+ at room temperature. ► We proposed a new pathway of silver nanoparticles growth at mild condition. ► We established a simple colorimetric method to determine ascorbic acid. ► The influence of silver nanoparticles growth on silver nanoclusters fluorescence was studied.

In this paper, we report a new assay for the rapid detection of Pb2+ in aqueous solution based on aggregation induced emission of Au(I)–glutathione complex. Non-fluorescent oligomeric Au(I)–glutathione complex could aggregate to form Au(0)@Au(I)–thiolate nanoclusters with ultra-bright fluorescence in the presence of high concentrations of metal ions. However, if two metal ions (e.g. Zn2+ and Pb2+) were both used for aggregating Au(I)–glutathione, there is a synergistic aggregation effect on the complex. A very low concentration of Pb2+ could induce apparent fluorescence enhancement. Under the optimal experimental conditions, the relationship between fluorescence changes (ΔF) of the aggregation system and the addition of Pb2+ (c, μM) in the range from 0.50 to 40.0 μM was measured as ΔF = 2.8 + 5.2 c, with the correlation coefficient (R2) of 0.996. Moreover, we carried out a visual fluorescence detection of Pb2+ under violet-light irradiation. The increasing fluorescence can be easily distinguished by color pictures using the naked eye.