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A magnetically recoverable RuCo bimetallic catalyst was reported for the catalytic hydrogenation of furfural to furfuryl alcohol under ambient H2 pressure. The magnetic catalyst was prepared by H2 treatment of the RuCo composite precursor from a facile one-pot hydrolysis of Co and Ru salts by NaBH4 solution. This catalyst can totally convert furfural to 98-100% furfuryl alcohol at 120 °C under 1 bar H2 in isopropanol or water using only molecular H2 as hydrogen source. Moreover, the catalyst showed excellent stability during recycling test and can be easily and completely recovered by magnet from reaction solution. The influence of Ru/Co ratio and H2-treatment temperature was studied, which were shown to be important for the structural evolution and the metal interaction in RuCo active sites, based on the comprehensive characterizations including XRD, TGA, TEM, XPS, H2-TPR, CO adsorbed DRIFT-IR. It was demonstrated that the cooperative Ru0-Co0 bimetallic active sites in strong interaction can significantly promote activity and selectivity of the catalyst due to an enhanced adsorption and activation of furfural and H2, and simultaneously created a strong magnetism in the RuCo catalyst for simple physical separation.

The development of a facile synthesis and controllable layer stacking approach for covalent organic frameworks (COFs) is an important issue for modulating their properties and realizing their application diversity. Herein, three COF isomers with different stacking models (eclipsed AA, staggered AB, and ABC stacking) were obtained by modulating the reaction temperature and solvent medium. Experimental and theoretical calculations show that the ABC stacking isomer obtained at room temperature is the kinetic product, while the AA stacking isomer prepared by the solvothermal method is a thermodynamic product. Owing to the tautomerism involved in the reaction process, these isomers possess different ratios of enol and keto forms. Thus, they exhibit different generation efficiencies of Type I and Type II reactive oxygen species (ROS). The ABC stacking isomers could be employed as metal-free heterogeneous photocatalysts for visible-light-induced oxidation of amines to imines, owing to the highest generation efficiency of Type I ROS.

The base-free aerobic oxidation of 5-hydroxymethylfurfural (HMF) in water to 2,5-furandicarboxylic acid (FDCA) is a sustainable upgrading process for cellulosic carbohydrates. A mesoporous NiO-supp...

Cysteine is widely used as a stabilizer for the preparation of fluorescent gold nanoclusters (Au NCs) with different fluorescence properties. Herein, by using cysteine as a stabilizer and controlling the synthesis conditions, a new non-fluorescent cysteine stabilized gold nanocluster (Cys-Au NCs) probe was prepared and a new strategy for "turning on" the fluorescence of the Cys-Au NCs was studied for rapid and selective detection of silver ions. In this strategy, the addition of silver ions to non-fluorescent Cys-Au NCs solution could quickly induce a visible fluorescence "turn on" phenomenon in 30 s. Further studies indicated that this fluorescence "turn on" phenomenon is specific for silver ions and the "turn on" fluorescence intensity has a linear relationship with the amount of silver ions in the range from 3.0 to 30.0 μM. Therefore, the non-fluorescent Cys-Au NCs were applied to the detection of silver ions in environmental water samples and a limit of detection (LOD) of 0.26 μM was obtained. This research sheds light on new applications of Au NCs and proposes a simple, rapid, sensitive, and visual method for the detection of metal ions.

The effective control of particle size and electron density of metal active sites is challenging yet important for supported nanoparticles, as size effects and promoter effects play vital roles in ...

A highly sensitive enzyme-induced metallization-based electrochemical signal amplification strategy was developed based on the integration of the enzyme-induced metallization reaction, Au nanoparticles (AuNPs)-induced silver deposition, chemically modified electrode and highly sensitive stripping voltammetry detection. The presence of alkaline phosphatase (ALP) catalyzed ascorbic acid 2-phosphate into ascorbic acid, which reduced Ag+ to Ag0 on the surface of the AuNPs/multi-walled carbon nanotubes/polyethyleneimine/glassy carbon electrode (AuNPs/MWNTs/PEI/GCE). As a result, the enzyme-generated product was accumulated on the surface of the AuNPs/MWNTs/PEI/GCE by means of silver deposition via this signal amplification strategy, which enhanced the detection signal dramatically. Amounts as low as 1 × 10–8 U/mL (corresponding to 10 aM) ALP can be detected using this strategy, which is about 4−7 orders of magnitude more sensitive than with other reported methods for ALP determination. In addition, this strategy can be applied to ALP detection in real complex samples, which shows great potential in the early diagnosis of diseases.

A strategy was designed for the molecular imprinting of magnetic nanoparticles with boric acid affinity (MNPs@MIP) which were then used for the selective recognition and isolation of glycoproteins. Fe3O4 nanoparticles were prepared by a solvothermal method and direct silanization by the condensation polymerization of aminopropyltriethoxysilane (APTES). Subsequently, phenylboric acid was functionalized by reductive amination between 2,3-difluoro-4-formyl phenylboric acid (DFFPBA) and the amido group. The resultant Fe3O4@SiO2–DFFPBA was then used for the selective adsorption of a glycoprotein template. Finally, a molecularly imprinted layer was covered on the surface nanoparticles by the condensation polymerization of tetraethyl orthosilicate (TEOS). The adsorption capacities of the resultant MNPs@MIP–HRP and MNPs@MIP–OVA to horseradish peroxidase (HRP) or ovalbumin (OVA) were significantly higher than non-imprinted particles (MNPs@NIP). Moreover, the adsorption capacities of MNPs@MIP–HRP and MNPs@MIP–OVA on non-template protein and non-glycoprotein bovine serum albumin (BSA) were significantly lower than those of their respective template proteins, thus indicating that both of the prepared MNPs@MIP exhibited excellent selectivity.

Here, a new 1D helical chain coordination polymer with enhanced chemical stability and fluorescence emission was prepared by introducing a benzimidazole molecule into Ag12 clusters. This coordination polymer demonstrated an increased fluorescence intensity with increasing polarity of alcohol solution, revealing its potential application in alcohol sensing.

Ce–Ni mixed oxides with different Ni/Ce molar ratios, promoted by a rather low amount of Pd (0.2 wt%), were prepared by a simple one-pot precipitation method. The thus-synthesized CeNiXOY and Pd–CeNiXOY catalysts were applied respectively to the direct N-alkylation of amine and alcohol via oxidative coupling, under O2 in the absence of basic additives. The CeNiXOY catalyst could provide a >99% yield of imine in the model alkylation reaction of aniline with benzyl alcohol at 100 °C. The Pd-promoted Pd–CeNiXOY catalyst surprisingly showed an enhanced imine yield (>99%) at a mild temperature of 60 °C. This catalyst exhibited good reusability, and moreover, demonstrated high performance towards imine synthesis from various amines with alcohols. The presence of Pd species and the Ni/Ce molar ratio showed a synergistic impact on the conversion of aniline, as well as on the product selectivity, which was believed to be related to the improvement on the intrinsic activity of the oxidation of benzyl alcohol to benzaldehyde. Various physicochemical techniques, including ICP-MS, XRD, N2 adsorption–desorption, UV-Raman, H2-TPR, TEM, EPMA and XPS, were employed to study mainly the composition, structure and redox properties of the catalysts. The proportion of Ce3+ species and oxygen vacancies, which can be manipulated by the Ce–Ni redox system and the interaction between Ce and Ni, was crucial to the selective activation of alcohols in the presence of reactive amines. The activation of alcohol on the highly reactive Pd0 species was the other crucial factor.

Nanocatalysts and single-atom catalysts are both vital for heterogeneous catalysis. They are recognized as two different categories of catalysts. Nevertheless, recent theoretical works have indicated that Au nanoparticles/clusters release Au single atoms in CO oxidation, and they co-catalyze the oxidation. However, to date, neither experimental evidence for the co-catalysis nor direct observations on any heterogeneous catalysis process of single-atom catalysts are reported. Here, the dynamic process of nanoporous Au to catalyze methane pyrolysis is monitored by in situ transmission electron microscopy with high spatial–temporal resolutions. It demonstrates that nanoporous Au surfaces partially disintegrate, releasing Au single atoms. As demonstrated by DFT calculation, the single atoms could co-catalyze the reaction with nanoporous Au. Moreover, the single atoms dynamically aggregate into nanoparticles, which re-disintegrate back to single atoms. This work manifests that under certain conditions, the heterogeneous catalysis processes of nanocatalysts and single-atom catalysts are not independent, where their dynamic co-catalysis exists., Nanocatalysts and single‐atom catalysts are generally considered as two categories with distinct performances. Here, in situ TEM study of catalytic methane pyrolysis over nanoporous Au reveals a highly dynamic process where co‐catalysis exists among various catalyst forms.

Enzyme-mimicking nanomaterials (nanozymes) have been used to catalyze enzyme-like reactions for various applications. Despite these favorable properties, peroxidase-mimicking nanozymes suffer from the optimum reaction occurring in acidic solutions, which greatly limits their applications in biological systems. Herein, we demonstrate that copper Metal–Organic Polyhedra (Cu-MOP) nanorods exhibit high peroxidase-mimicking activity at a physiological pH value. Cu-MOP nanorods catalyze the generation of strong chemiluminescence signals in the presence of luminol/H2O2 and the oxidation of 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate acid) (ABTS) by H2O2 produces a green color reaction in a neutral pH solution. The Cu-MOP nanorod driven generation of color reactions is applied to develop a H2O2 sensor, and furthermore is implemented to develop a glucose detection platform.

International audience; Mn-Ce mixed oxides-supported Ru nanoparticles (Ru/MnXCe1OY) with enhanced oxygen mobility and strong metal-support interaction were prepared and applied to the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) without addition of any base additives. Oxygen and water were used as green oxidant and solvent, respectively. The catalysts were characterized in depth by XRD, H2-TPR, O2-TPD, UV–Vis DRS, XPS and TEM, to reveal materials properties from bulk to surface. The influence of Mn/Ce molar ratios in support materials and reaction parameters (i.e., HMF/Ru ratio, O2 pressure, reaction temperature and time) was systematically studied and optimized. The reaction route and rate-determining step for oxidation of HMF to FDCA over the Ru/MnXCe1OY catalysts were investigated by kinetic analysis. Well-dispersed metallic Ru nanoparticles with a mean size of 4.4 nm deposited on the support were found essential to activate and oxidize the HMF molecule. The Mn/Ce molar ratio was found to affect not only conversion of HMF but also distribution of products. The Ru/Mn6Ce1OY catalyst demonstrated an exceptional yield (≥99%) of FDCA, which corresponds in our conditions to one of the best productivity (5.3 molFDCA·molRu−1·h−1) ever reported in literature. The superior activity of the Ru/Mn6Ce1OY catalyst was mainly associated with (i) the strong metal-support interaction and (ii) the synergistic effect between manganese and cerium oxides. This catalyst showed the highest surface concentrations in Mn4+ and Ce3+ among the series, which, as a consequence, enhanced the availability and mobility of active oxygen species. This catalyst was shown resistant to deactivation during eight recycling uses thanks to a strong metal-support interaction between Ru nanoparticles and the Mn-Ce mixed oxide used as a support.

To develop a convenient method for sensitive and selective determination of Ce3+ in aqueous phase with complicated matrices, a carbon paste electrode (CPE) modified with ion imprinted polymers (IIPs) were fabricated. The polymers were prepared by precipitation polymerization using Ce3+ as template, allyl phenoxyacetate (APA) as monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker and azobisisobutyronitrile (AIBN) as initiator under the molar ratio of Ce3+, APA and EGDMA as 1:4:40, respectively. Ce3+ was detected directly by differential pulse adsorptive stripping voltammetry (DPASV) and its oxidation peak appears at about 0.93 V. All parameters affecting the sensor's response are optimized and a calibration curve is plotted at a linear range of 1.0 × 10−6–1.0 × 10−5 mol/L and 1.0 × 10−5–2.0 × 10−4 mol/L with the detection limit of 1.5 × 10−7 mol/L. All other rare earth ions have no interference with the determination of Ce3+ even at a concentration 500 times higher than that of Ce3+. This sensor was successfully applied to determination of Ce3+ in two catalyst sample solutions with RSD≤3.3% (n = 5) and recoveries in the range of 99.2%–106.5% at our optimal conditions.

As a result of the increasing applications in different fields, europium has become a threat to the environment and human health. Thus, it is necessary to develop a simple and rapid method for determination of europium in trace level. In this paper, a sensor for determination of Eu3+ was established by modifying a screen printed electrode (SPE) successively with poly catechol as signal amplifying element and Eu(III) ion-imprinted membrane fabricated by sol-gel method as the recognition material. After the factors influenced the sensitivity of the sensor for Eu3+ was optimized in detail, Eu3+ can be determined by differential pulse adsorptive stripping voltammetry (DPASV) in the concentration range of 3.0 × 10−7–1.0 × 10−3 mol L−1 with the detection limit of 1.0 × 10−7 mol L−1. The fabricated sensor owns outstanding selectivity, perfect stability and good regeneration. 50-fold excess concentration of rare earth ions such as Ce3+, Tb3+, Ho3+, Dy3+, Er3+, Gd3+, Pr3+, Nd3+, Yb3+ and 100-fold excess concentration of other metal ions such as Fe3+, Ni3+, Cu2+, Zn2+ and Co2+ have no influence on the determination of 1.0 × 10−5 mol L−1 Eu3+. The obtained sensor, which can maintain >90% of its original response after used >60 times or stored in the water for 2 months, has been satisfactorily used to detect Eu3+ in water samples with the relative standard deviation (RSD) of

In this study, a molecularly imprinted electrochemical sensor based on graphene/Au nanoparticles (G@AuNPs) compound materials and molecularly imprinted membrane (MIM) modified glassy carbon electrodes (GCEs) was developed for the sensitive detection of colchicine in pharmaceuticals and serum (MIM/G@AuNPs/GCE). The film was formed by the in situ polymerization of colchicine-imprinted membranes on the G@AuNPs-modified GCE using methacrylic acid as the functional monomer. The specific surface area, catalytic performance, and electrical conductivity of the electrode increased on account of the formation of G@AuNPs compound materials, thereby improving the sensitivity of the sensor. The MIM as a preconcentrator exhibited chemical selectivity. Under optimal conditions, the MIM/G@AuNPs/GCE sensor exhibited high selectivity and high anti-interference ability. Moreover, good linearity was obtained in the range of 1.2 × 10−8 to 1.2 × 10−6 mol L−1 and 1.2 × 10−6 to 1.0 × 10−4 mol L−1 of colchicine with a detection limit of 4.8 × 10−9 mol L−1. The sensor was successfully applied for the direct determination of colchicine in colchicine tablets and human serum samples, with a relative standard deviation of less than 3.1% (n = 5) and recoveries ranging from 97.5% to 110.0%.

The aerobic oxidation of bio-platform compound 5-hydroxymethylfurfural (HMF) to value-added 2,5-furandicarboxylic acid (FDCA) was studied over hydroxyapatite supported ruthenium (Ru/HAP) nanocatalyst without extra addition of soluble base. Molecular oxygen and water were used as the oxidant and solvent, respectively. Various dominant reaction parameters, including HMF/Ru molar ratio, O2 pressure, reaction temperature and reaction time were systematically investigated. When HMF/Ru molar ratio was of 25, Ru/HAP catalyst exhibited the optimal catalytic performance, i.e., total conversion of HMF and 99.6% yield of FDCA were achieved at 120 °C and 1 MPa O2. Kinetic study revealed that the oxidation of HMF to FDCA followed a tandem pathway and the oxidation of carbonyl group in 5-formylfuran-2-carboxylic acid (FFCA) was found as the rate-determining step. Besides, well-dispersed uniformly-small metallic Ru0 nanoparticles and the acidic-basic sites presented on HAP surface were both essential to drive this base-free oxidation process. During the kinetic-controlled range (i.e., initial 1 h of reaction), the activity of the catalyst can be almost remained after five consecutive cycles; afterwards a minor decline in activity was observed mainly due to the partial oxidation of surface metallic Ru species, but the activity can be entirely recovered by a hydrogen reduction at 350 °C.

5-Hydroxymethylfurfural (HMF) production from catalytic dehydration of fructose was studied over mesoporous silica heterogenized perfluorosulfonic acid resin (Aquivion@silica) catalyst. Amphiphilic Aquivion PFSA was used as both acidic and template agent for the sol–gel synthesis of amorphous mesoporous silica which was found very appropriate to effectively immobilize Aquivion resin by using an impregnation method. Various characterizations including elemental analysis, acid-base titration, XRD, FTIR, Raman, N2 adsorption–desorption, SEM and TEM revealed that Aquivion@silica catalyst presented large surface area, sufficient porosity and afforded highly accessible sulfonic acid groups. Efficient and productive HMF production from the dehydration of fructose was achieved in the polar dimethyl sulfoxide (DMSO) solvent at low temperature of 90 °C, i.e. 85% yield of HMF and 43 molHMF molH+ productivity of HMF. The influence of reaction time, reaction temperature, Aquivion loading, catalyst dosage and solvent on the dehydration process was systematically investigated. The catalyst could be regenerated through a simple ion-exchange method and a stable HMF yield was maintained after being used four times.

A new photocatalytic synthesis strategy for rapid preparation of BSA-Au nanoclusters (NCs) with tunable fluorescence was developed and used for the highly selective detection of silver ion. In this strategy, the silver ion was firstly photo-reduced to Ag NCs under UV light illumination. Then, the produced Ag NCs would further reduce HAuCl4 to Au NCs stabilized in BSA molecules. In this process, silver ion not only acted as a photocatalyst to accelerate the formation of fluorescent Au nanocluster but also as a regulator to tune the fluorescence emission color of the BSA-Au NCs from orange to red. The maximum emission peak of BSA-Au NCs fluorescence could be tuned from 570 to 620 nm in different experimental conditions. Furthermore, a fluorescence emission peak red-shifts of the as-prepared BSA-Au NCs could also be observed by subsequent adding of silver ion. Thus, a quantitative analytical method for silver ion detection could be established in the range from 5.0 to 60.0 μM with a detection limit (LOD) of 0.226 μM (3σ). The method had high selectivity that other common metal ions and small biological molecules did not have similar phenomena. It had great potential for applying for environmental water sample analysis.

Selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was studied using molecular oxygen without addition of any soluble base. A new, cheap and robust support ( i.e. hydrotalcite-activated carbon composite, HT-AC) was prepared by physical milling of home-made HT and commercial AC, which required using less chemical consumption and simpler chemical protocol. Au/HT-AC catalyst showed superior catalytic performance for aerobic oxidation of HMF in water under mild conditions compared to Au/HT and Au/AC catalysts, respectively. It was found that the HT-AC support with the optimal ratio (2:1 in mass ratio) significantly enhanced FDCA yield and catalytic stability. After 12 h at 100 °C, 99.5% FDCA yield was achieved using O 2 at 0.5 MPa. Moreover, 99% FDCA yield was obtained using air as oxidant after 18 h. The catalyst demonstrated remarkable stability during recycling up to six times. The influence of different reaction parameters was studied and optimized. Furthermore, the properties of catalysts were characterized by ICP-MS, N 2 isotherms, XRD, XPS and TEM.

A highly selective and rapid analytical method was proposed to detect cysteine in aqueous solution by using poly(thymine)-templated copper nanoparticles. In a neutral aqueous condition, the fluorescence of poly(thymine)-templated copper nanoparticles could be quenched by cysteine in 10 min effectively coexisting with common biological small molecules. Under the optimal experimental condition, the present assay allowed for the selective determination of cysteine in the range of 12.5–100 µM, with a detection limit of 7.3 µM. The results indicated that the poly(thymine)-templated copper nanoparticles probe would find potential application in bioanalysis.

A hydrothermal method was applied to the synthesis of green-emitting gold nanoclusters (Au NCs) which are shown to be viable fluorescent probes for 4-nitrophenol (4-NP). The Au NCs were prepared by using thiol-β-cyclodextrin as a template. Under 365 nm excitation, their green fluorescence has a peak at 502 nm, with a narrow emission bandwidth of only 30 nm. The fluorescence and composition of the Au NCs were characterized and the mechanism of the nanocluster formation is discussed. Due to host-guest recognition of β-cyclodextrin and 4-NP, fluorescence is quenched. The probe can selectively recognize 4-NP among other nitrophenols. A fluorometric and colorimetric assay was developed for 4-NP that works in the 0.1 to 100 μM concentration range and has a detection limit of 90 nM (at 3σ). Graphical abstractSchematic representation of hydrothermal synthesis of green-emitting gold nanoclusters using thiol-β-cyclodextrin. Fluorescence is quenched and the absorption of the nanoclusters is increases in the presence of 4-nitrophenol.

Porous coordination polymers or metal-organic frameworks with reversible phase-transition behavior possess some attractive properties, and can respond to external stimuli, including physical and chemical stimuli, in a dynamic fashion. Their phase transitions can be triggered by adsorption/desorption of guest molecules, temperature changes, high pressure, light irradiation, and electric fields; these mainly include two types of transitions: crystal-amorphous and crystal-crystal transitions. These types of porous coordination polymers have received much attention because of their interesting properties and potential applications. Herein, reversible phase transition porous coordination polymers are summarized and classified based on different stimuli sources. Corresponding typical examples are then introduced. Finally, examples of their applications in gas separation, chemical sensors, guest molecule encapsulation, and energy storage are also presented.

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.

A high sensitive electrochemical signal transduction amplification strategy was constructed based on the integration of the target-triggered silver deposition and the high sensitive stripping voltammetry detection. The Au-nanoparticles (AuNPs), multi-walled carbon nanotubes (MWNTs) and polyethyleneimine (PEI) modified glassy carbon electrode (AuNPs/MWNTs/PEI/GCE) was prepared and used as the working electrode which could also amplify the electrochemical signal dramatically due to the excellent electronic property of the electrode and the Au-nanoparticles induced silver deposition reaction. This strategy was applied to the high sensitive ascorbic acid (AA) determination and a detection limit as low as 15 fM was achieved, which was 6–9 orders of magnitude more sensitive than other reported methods for AA determination. The proposed method has good selectivity and anti-interference ability, which could be applied to AA detection in real complex 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%.

To obtain an electrochemical sensor with high sensitivity and good selectivity for determination of podophyllotoxin (PPT), a kind of graphene composite (rGO@TiO2) with multi-layer structure and excellent conductivity was prepared by hydrothermal treatment of reduced graphene oxide (rGO) and TiO2 nanoparticles. The composite was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and a sensor using rGO@TiO2 as a signal amplification element was fabricated by in-situ polymerization of PPT imprinted membrane (PPT-MIM) on the rGO@TiO2 modified glassy carbon electrode (PPT-MIM/rGO@TiO2/GCE). The structure and electrochemical performance of PPT-MIM/rGO@TiO2/GCE as well as the mechanism with superior conductivity of rGO@TiO2 exceeding the ones of the mixture of TiO2 and rGO (TiO2-rGO) or the pure TiO2 and rGO were explained with different technologies. Under the optimal conditions, the present sensor showed a linear response for the determination of PPT by differential pulse voltammetry (DPV) in the range of 1.0 × 10−9 − 1.0 × 10−7 mol L−1 (R2 = 0.9980) and 1.0 × 10−7 − 3.0 × 10−4 mol L−1 (R2 = 0.9991) with the limit of quantification is 1.0 × 10−9 mol L−1 and the limit of detection of 3.0 × 10−10 mol L−1. The sensor not only possesses high sensitivity and good selectivity, but also exhibits excellent repeatability and stability. It has been used to detect PPT in real samples (including Podophyllum hexandrum, human urine and human whole blood) with satisfied recoveries of 92.0%–102.3%.

A bifunctional Ru/(AlO)(ZrO)n catalyst was reported for efficient hydrogenation of levulinic acid to γ-valerolactone, an important and environmental-benign upgrading process of bio-platform compound. The optimal Ru/(AlO)(ZrO)0.1 catalyst showed 100% yield to γ-valerolactone in water at 120 °C under 1 MPa H2, one of the best performances among Ru catalysts under mild conditions. And this catalyst also presented good stability and reusability. PXRD, TEM, XPS, CO chemisorption, CO adsorption DRIFT-IR, NH3-TPD and pyridine adsorption IR gave insights into the acidic property and surface synergy of the catalysts. Highly active electron-rich Ru0 sites stabilized by strong metal-support interaction (SMSI) can effectively adsorb and activate molecular H2 and C O bond in levulinic acid. Varying Zr/Al ratio and calcination temperature can rationally control the acid strength and acid sites distribution of support, and (AlO)(ZrO)0.1 calcined at 400 °C exhibited the maximal proportion of Lewis acid sites. Ru0 species and Lewis acid sites synergistically enhanced the conversion of levulinic acid and facilitated the intramolecular dehydration of 4-hydroxypentanoic acid as intermediate to γ-valerolactone (i.e., the rate-limiting step).

A hydrogel was directly assembled from a Cu-MOP by a facile procedure without adding any polymers for the first time, and it exhibited excellent antibacterial activity towards both Gram-negative and Gram-positive bacteria.

Fluorescent DNA-stabilized Ag nanoclusters (DNA/Ag NCs) plays significant roles in biochemical detections due to their high fluorescence quantum yield, high stability and good biocompatibility. In this paper, two guanine-enhanced fluorescence DNA-stabilized silver nanoclusters were designed to study the effect of guanine coating degree on silver nanoclusters fluorescence and their interactions with small biological molecules. The results indicated that the degree of guanine coating had a slight influence on the fluorescence of the two DNA/Ag NCs, however, the two DNA/Ag NCs had different fluorescence response when interacting with different small biological molecules. The fluorescence of the DNA/Ag NCs wrapped in the guanine-rich strand could be quenched by small biomolecules such as ascorbic acid, dopamine and cysteine, while the fluorescence of the DNA/Ag NCs approached to the guanine-rich strand could only be quenched by dopamine and cysteine. Based on this interesting phenomenon, an analytical method for recognition of ascorbic acid, dopamine and cysteine from other small biological molecules can be established by measuring the fluorescence change of DNA/Ag NCs and a method for selective detection of ascorbic acid in the absence of dopamine and cysteines can be achieved by combining the two DNA/Ag NCs probe.

A facile, economical and one-step hydrothermal method was used to synthesize fluorescent carbon dots by utilizing citric acid as carbon source and phenylalanine to provide nitrogen. The as-prepared fluorescence carbon dots had strong blue light emission around 440 nm. As confirmed by UVvis absorption, X-ray photoelectron spectroscopic, Fourier transform infrared spectroscopy and transmission electron microscope characterization, the carbon dots were small and very stable in water for using as a fluorescent probe. It was also found that the fluorescence of the carbon dots could be quenched in the presence of Fe3+ ions, and the quenching rate was linear with the concentration of Fe3+ ions. We here proposed a static quenching mechanism about the fluorescence of the Phe-CDs could be selectively quenched by Fe3+ ions, which was because these Fe3+ ions could easily combine with the hydroxyl or carboxyl groups on the surface of Phe-CDs and induced aggregation. In addition, the pH had little effect on the fluorescence intensity of the Phe-CDs and maintained excellent fluorescence intensity even under extreme pH value conditions and could be used for the detection of Fe3+ ions. We have demonstrated that the method using the carbon dots for Fe3+ ions detection was rapid, reliable, and selective with a detection limit as low as 0.720 μM and a dynamic range from 5.0 to 500.0 μM. Moreover, the results of determination Fe3+ ions in tap water samples indicated that the presented method has potential for practical application in environmental metal analysis.

A HDBB@ZIF-8 fluorescent probe has been developed by encapsulating the aggregation-induced emission (AIE) molecule 4,4’-(hydrazine-1,2-diylidenebis(methanylylidene)) bis(3-hydroxybenzoic acid) (HDBB) into the nanochannels of zeolitic imidazolate frameworks-8 (ZIF-8) for distinguishing small alcohol solvent molecules. The crystal structure and morphology of ZIF-8 are well maintained after the encapsulation of HDBB molecules. Encapsulation of HDBB into the confined nanospace of ZIF-8 not only triggered new green fluorescent emission but also endowed them with unique carbon chain length-dependent fluorescence intensity for alcohols, which has not been observed in pure HDBB and ZIF-8. This property could be attributed to the alcohol–water sorption selectivity of host ZIF-8. Moreover, a linear relationship is obtained between the fluorescent intensity of these composites and the concentrations of ethanol with a wide linear range, which could be employed as a chemosensor to detect the content of ethanol in the real wine sample.

Commercial pseudo-boehmite was modified, and a series of mesoporous aluminas (MA) with different textural properties were synthesized using selected group of surfactants including sodium dodecylsulphate (SDS), cetyltrimethyl ammonium bromide (CTAB), and polyethylene glycol (PEG) in aqueous solution. The structure and morphology of samples were evaluated, and the catalytic activity for the methane combustion was also discussed. The results suggested that sample templated by PEG exhibited a high pore volume and surface area when calcined at 1050 °C. This considerably improved the catalytic performance for methane combustion. The light-off (T10) and final (T90) combustion temperatures were as low as 305 °C and 400 °C.

An ultrasensitive liquid crystal biosensor is described for multicolor visualization of the activity of alkaline phosphatase (ALP) based on the controlled growth of silver nanoparticles. The enzymatic product is accumulated on the surface of the LC sensing film by means of silver deposition, and the birefringent signal (observed with a polarizing microscope) is strongly enhanced as a result. The presence of AuNPs also enhances the sensitivity by about 4 orders of magnitude. The bright spots in polarized optical microscopy (POM) images increase with increasing activities of ALP. The signal intensities of the spots are then calculated by using Photoshop software and by multiplying the average brightness of the spots by the pixel value. The detection limit for ALP is 1.2 nU·mL-1, which is 5-7 orders of magnitude lower than other colorimetric or fluorometric methods. The method was applied to a highly sensitive immunoassay for the carcinoembryonic antigen (CEA) by integrating immunomagnetic separation. The immunoassay was applied to the analysis of complex samples without tedious sample pretreatment, and a detection limit as low as 0.35 pg·mL-1 of CEA was achieved. The method has attractive features in that it provides an ultrasensitive multicolor visualization approach for enzymes such as ALP, but also paves the way to a new kind of immunoassay coupled to immunomagnetic separation. Graphical abstract A signal enhanced liquid crystal (LC)-based multicolor immunosensor is described that is based on immunomagnetic separation and biometallization. Alkaline phosphatase (ALP) and carcinoembryonic antigen (CEA) can be easily visualized by bare eyes using the polarized optical microscopy (POM) images of LCs.

Fluorescence of DNA-templated silver nanoclusters can be enhanced by more than 100-fold by placing the nanoclusters in proximity to guanine-rich DNA sequences after hybridization. We found that the fluorescence of the guanine-enhanced silver nanoclusters is not increased with the guanine-rich DNA sequence closer to the silver nanoclusters. By studying the different numbers of mismatches in the linker sequences, we found that the presence of a single-nucleotide mismatch in the linker increases fluorescence more than the complementary nucleotide. Further study indicated the mismatch position of the linker sequence also affects the fluorescence of the hybridized DNA-Ag NCs. The evidence reported here indicated that the mismatch of the linker sequence affects the fluorescence enhancement of guanine-enhanced silver nanoclusters. We also found that DNA-Ag NCs is an excellent fluorescence sensor for cyanide, as cyanide effectively quenches the fluorescence of NCs at a very low concentration with high selectivity. Cyanide in the range from 0.10 μM to 0.35 μM could be linearly detected, with a detection limit of 25.6 nM.

Oleic acid capped Fe3O4 nanoparticles with a size range of 8–15 nm were prepared by a typical reduction method. Double bonds in the oleic acid molecules were activated and further grafted with methyl methacrylate (MMA) and hydroxyethyl acrylate (HEA) in butyl acetate to obtain acrylate copolymer-coated Fe3O4 nanoparticles. Hexamethylene diisocyanate (HDI) was used as the cross-linking agent to immobilize the surface structure of the nanoparticles. Fe3O4 templates were then disposed of with excessive concentrated HCl solution, and monodispersed ultra-fine and an ultra-light hollow polymer/iron eutectic system with a size range of 18–30 nm was thus obtained. The molecular structures, crystal information, thermal properties, and morphology of the prepared nano-particles were characterized. The results showed that the hollow nanoparticles were composed of an amorphous outer layer and a crystalline inner layer, and that the outer layer and the inner layer mainly consisted of acrylate copolymers and ordered iron oxide atoms, respectively. The cross-linked macromolecular architectures and the chemical bond between Fe atoms and polymeric chains are the main driving force to form such a hollow eutectic system that has never been reported previously. The preparation method reported in this paper firstly develops a route to synthesize hollow polymer/metal eutectic materials, and these hollow nanoparticles have large potential application in the fields of nanoreactors and catalysts.

Transformation of aggregation induced emission (AIE) molecules into functional materials can greatly tune their fluorescence properties and expand their related potential applications. Here, we demonstrate a facile strategy to modulate the fluorescence properties of AIE molecules by confining them within the nanochannels of metal–organic frameworks (MOFs). AIE molecules (4,4′-(hydrazine-1,2-diylidene bis(methanylylidene)) bis(3-hydroxybenzoic acid), HDBB) with pH-dependent emission were successfully integrated into UiO-66 resulting in a UiO-66⊃HDBB complex while maintaining the crystal structure by the host–guest process. The fluorescence properties of HDBB can be modulated by virtue of the unique nanospace confining effect. Furthermore, UiO-66⊃HDBB was used as a sensitive and selective fluorescent probe for Cu2+ detection in aqueous solution. This study provides a facile strategy for the construction of high performance AIE based luminescent materials with adjustable properties for potential applications.

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.

Assembly of anisotropic nanoparticles which need well controlling of assembly direction and spatial arrangement is more interesting than one-dimensional nanoparticles assemblies. As confirmed by observing of transmission electron microscopy images and analysis of plasmon resonance spectrum transformations, we found that silver triangular nanoplates (TNPs) without further modification could be face-to-face assembled by citrate. The face-to-face assembly of silver TNPs could be disassembled quickly by heating at a wide temperature range from 30 to 80 °C. In this process, an obvious localized surface plasmon resonance (LSPR) peak shift and a color change of solution from pink to purple could be observed. Moreover, the disassembled silver TNPs suspension is very stable that no significant peak shift of silver TNPs spectrum was observed in 8 h after removing of silver TNPs from a hearing area. Therefore, we fabricated an irreversible temperature indicator by measuring the relationship between the shift of LSPR peak and heating temperature, and by watching the color change of the solution in a certain environment. The irreversible temperature indicator has potential to develop a temperature label for revealing temperature history of a thermosensitive product which cannot expose to excessive temperature.

In this paper, chicken egg white purchased from a local market without further purification was directly used to prepare fluorescent gold nanoclusters through a one-step, simple, fast and green synthesis approach for analytical purposes. The as-prepared chicken egg white stabilized gold nanocluster probe has strong red fluorescence emission, which can be quenched by mercury ions and copper ions sensitively. By using an ethylenediaminetetraacetate (EDTA) masking method, mercury ions in the range from 0.60 to 10 μM can be linearly detected with the limit of detection (LOD, 3σ) of 0.510 μM in the presence of equivalent copper ions. Since the preparation of a chicken egg white stabilized gold nanocluster probe is fast, easy and cheap, this selective analytical method for mercury pollution monitoring in environmental waters may be widely used in daily life by ordinary people.