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This study calculates China’s provincial total factor productivity (TFP) and decomposition indexes. Then, a system of indicators is constructed to measure digitization, and an empirical analysis is conducted. The results show that (1) digitization can significantly improve TFP, especially technical efficiency, largely due to the increase in factor allocation efficiency and the quality of technological innovation resulting from digitization, a finding that remains valid even after a series of robustness tests. (2) The effect of digitization on the improvement of TFP is more pronounced in the central and western regions of China than in the east and more pronounced when economic development is in the service stage. The existence of a digital divide can diminish the positive effects of digitization. The regression results by industry show that digitization has a more significant positive impact on TFP in the secondary and tertiary industries than in the primary industries. (3) Further analysis shows that the process of digitization in raising TFP is nonlinear and that the positive effect of digitization on TFP is stronger when the level of industrial structure crosses the threshold. The findings of this paper bear some beneficial policy implications.

Green technological innovation is an overarching approach to tackling environmental pollution, and mitigating the inequality in green technological innovation between regions can contribute to environmental equity. This study measures the inequality in green technological innovation via an index and examines the influence of digital finance on that inequality using data from 285 cities in China from 2011 to 2018. The results are as follows: (1) Digital financial development alleviates the inequality in green technological innovation, and the greater the inequality is, the stronger the effect of digital finance. The development of digital finance can help regions lagging behind in terms of green technology to catch up. (2) When the financial supervision and environmental restrictions within a region are strict, the development of digital finance is more effective at reducing the inequality in green technological innovation; a higher capacity for governance in the local government and a smaller digital divide strengthen the positive effects of digital finance. (3) The development of digital finance alleviates interregional inequality in green credit, reduces market segmentation, and increases spending on environmental protection, thus narrowing the gap in the capacity for green innovation between regions. These findings not only enrich the literature on digital finance and green technological innovation but also serve as a reference for governmental departments as they optimize their strategy for developing digital finance and coordinating green development across regions.

In this study, polyacrylic acid functionalized N-doped porous carbon derived from shaddock peels (PAA/N-SPCs) was fabricated and used as a solid-phase microextraction (SPME) coating for capturing and determining volatile halogenated hydrocarbons (VHCs) from water. Characterizations results demonstrated that the PAA/N-SPCs presented a highly meso/macro-porous hierarchical structure consisting of a carbon skeleton. The introduction of PAA promoted the formation of polar chemical groups on the carbon skeleton. Consequently, large specific surface area, highly hierarchical structures, and abundant chemical groups endowed the PAA/N-SPCs, which exhibited superior SPME capacities for VHCs in comparison to pristine N-SPCs and commercial SPME coatings. Under the optimum extraction conditions, the proposed analytical method presented wide linearity in the concentration range of 0.5–50 ng mL−1, excellent reproducibility with relative standard deviations of 5.8%–7.2%, and low limits of detection varying from 0.0005 to 0.0086 ng mL−1. Finally, the proposed method was applied to analyze VHCs from real water samples and observed satisfactory recoveries ranging from 75% to 116%. This study proposed a novel functionalized porous carbon skeleton as SPME coating for analyzing pollutants from environmental samples.

Herein, novel, loose, and porous graphite phase carbon nitride/porous carbon (g-C3N4@PC) composites were prepared by decorating cellulose nanocrystals (CNCs). The characterization results demonstrate that the as-prepared composites presented high specific surface areas, porous structures, and abundant chemical groups, with the modification of CNCs. In view of the unique advantages, g-C3N4@PC was used as the coating material for the solid-phase microextraction (SPME) of organochlorine pesticides (OCPs) in water and juice samples. The g-C3N4@PC-coated fibers showed better extraction efficiencies than commercial fibers (100/7 μm PDMS and PA) toward the OCPs, with the enrichment factors of the g-C3N4@PC-coated fibers 5–30 times higher than the latter. Using a gas chromatography–mass spectrometry (GC-MS) instrument, the g-C3N4@PC-coated fibers exhibited a gratifying analytical performance for determining low concentrations of OCPs, with a wide linear range (0.1–1600 ng L−1 for water; 0.1–1000 ng L−1 for juice), low limits of detection (0.0141–0.0942 ng L−1 for water; 0.0245–0.0777 ng L−1 for juice), and good reproducibility and repeatability in optimal conditions. The established method showed good sensitivity and recovery in the determination of OCPs in the water and fruit juice samples, which displayed broad prospects for analyzing organic pollutants from environmental samples.

This paper investigates the spatial effect of environmental decentralization on innovation using the spatial Durbin model from 2006 to 2015 in China. The results not only confirm the local effect of environmental decentralization on innovation, but also exists the spatial effect after introducing the spatial weighed matrix. We also note that different types of environmental decentralization have different effects on innovation. The impact of the environmental decentralization of governance on innovation is stronger than that on finance in the local effect, while the spatial impact is opposite to the local effect. The policy implication is that the government should apply a special type of environmental decentralization to increase innovation. Enhancing environmental decentralization of finance for local and neighbor innovation and decreasing the environmental decentralization of governance are better for increasing innovation.

The aim of this paper is to analyze the impact of environmental regulation on regional environmental efficiency convergence using the fixed effects model and threshold regression model. The results show that the differences in environmental efficiency have a convergence trend in China, as well as in the eastern, central and western regions. The effect of environmental regulation on regional environmental efficiency is inhibition first and then promotion, research and development investment and outward foreign direct investment have a positive transmission effect; when environmental regulation intensity exceeds a certain threshold, the growth rate of environmental efficiency in the central and western regions will be significantly higher than that in the eastern regions.

In this study, a cooling assisted solid-phase microextraction technique (CA-SPME) was proposed and used for identifying volatile and semi-volatile compounds in edible oil innovatively coupled to gas chromatography-mass spectrometry. Compared with regular SPME technique, CA-SPME presented significantly higher extraction efficiencies for analytes in edible oil due to its synergistic effect of heating and cooling. After optimization of the extraction conditions including heating temperature, cooling temperature, extraction time, and added amount of edible oil, thirty-eight, thirty-six, twenty-nine, and thirty-three kinds of compounds in peanut oil, olive oil, canola oil, and soybean oil were successfully identified, respectively, using DVB/CAR/PDMS coating with extraction time of 30 min and edible oil amounts of 20 μL. Principal component analysis, partial least squares discriminant analysis, and hierarchical clustering analysis (HCA) were performed to evaluate the potential of proposed method in discriminating edible oils adulteration (peanut oil adulterated with canola oil, peanut oil adulterated with soybean oil, olive oil adulterated with canola oil) subsequently. Results demonstrated that the method was useful in successful discrimination of pure and adulterated edible oils with adulteration percentages ranging from 0.5 to 10%. Furthermore, volatiles contributing to classifications between pure and adulterated edible oils were also illustrated based on variable importance for the projection analysis and distributions of volatiles in HCA heatmaps. The proposed method provided a novel strategy for sensitive detection of edible oil adulteration without any other sample pretreatment.

A simple and rapid microwave heating approach was reported for the preparation of water soluble carbon dots (CDs) using peptone as carbon source with the assistance of ethylenediamine. Several characterization techniques such as transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were employed to analyze CDs. The optical properties of synthesized CDs were examined by UV-vis and fluorescence spectroscopy. The CDs exhibit strong blue emission under 365 nm UV lamp and have the excitation and pH (2.0-12.0) dependent emission behavior. The fluorescence intensity of CDs can be selectively quenched by Co

This paper investigates the distributional effects of globalization on innovation using 86 countries data from 1986 to 2016. Our results derived from the dynamic panel quantile regression technique show that overall globalization has a positive influence on national innovation in the least innovative countries. Similar evidences are found when utilizing globalization (de jure) and social globalization indices. Subsample analysis shows that globalization leads to better innovation performance in the medium innovative countries among OECD countries. Therefore, our findings contribute to the existing literature in identifying the changing effect of globalization on innovation.

In this work, carbon dot-decorated graphite carbon nitride composites (CDs/g-C3N4) were synthesized and innovatively used as a SPME coating for the sensitive determination of chlorobenzenes (CBs) from water samples, coupled with gas chromatography–mass spectrometry. The CDs/g-C3N4 coating presented superior extraction performance in comparison to pristine g-C3N4, owing to the enhancement of active groups by CDs. The extraction capacities of as-prepared SPME coatings are higher than those of commercial coatings due to the functions of nitrogen-containing and oxygen-containing group binding, π–π stacking, and hydrophobic interactions. Under optimized conditions, the proposed method exhibits a wide linearity range (0.25–2500 ng L−1), extremely low detection of limits (0.002–0.086 ng L−1), and excellent precision, with relative standard deviations of 5.3–9.7% for a single fiber and 7.5–12.6% for five fibers. Finally, the proposed method was successfully applied for the analysis of CBs from real river water samples, with spiked recoveries ranging from 73.4 to 109.1%. This study developed a novel and efficient SPME coating material for extracting organic pollutants from environmental samples.

Core-shell structured Fe2O3/CeO2@MnO2 microspheres were fabricated and used as solid-phase microextraction coating for determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. XPS spectra demonstrated the generation of abundant surface oxygen on Fe2O3/CeO2@MnO2 microspheres, which provided binding sites for enhancement of analyte extraction. Under optimized conditions, the proposed method presented good linearity in the concentration range 0.04–100 ng mL−1, with low limits of detection varying from 0.38 to 3.57 ng L−1 for eight PAHs. Relative standard deviations for a single fiber and five batches of fibers were in the ranges of 4.1–8.2% and 7.1–11.4%, respectively. The proposed method was successfully used for determination of PAHs in real river water samples with recoveries ranging from 87.1 to 115.9%. The proposed method using as-prepared Fe2O3/CeO2@MnO2 microspheres as SPME coating exhibit significant potential for real sample analysis due to its excellent reproducibility, high sensitivity, and good linearity.

Core-shell structured Fe

Lotus-like Ni@NiO embedded porous carbons (Ni@NiO/PCs) were fabricated by pyrolysis of MOF-74/cellulose nanocrystal hybrids, and used as a solid phase microextraction (SPME) coating for ultrasensitive determination of chlorobenzenes (CBs) from water combined with gas chromatography-mass spectrometry. Owing to its abundant chemical groups, high porosity, and excellent thermal stability, the as-prepared Ni@NiO/PCs presented superior extraction performance compared to commercial SPME coatings. Notably, Ni@NiO/PCs derived from MOF-74/CNC hybrids presented higher extraction efficiencies towards CBs than that derived from pristine CNC and MOF-74 due to the formation of micro/mesopores and more abundant oxygen-containing groups. Under the optimum extraction conditions, the proposed analytical method presented wide linearity range (0.5-1500 ng L

Using panel data from 30 Chinese provinces (excluding Tibet, Hong Kong, Macao, and Taiwan) over the 2006 to 2016 period, this research analyzes the impact of private investment on natural resource utilization efficiency. We find that private investment improves natural resource utilization efficiency both directly and via technological innovation.

To further clarify the relationship between environmental regulation and green technology innovation and discuss how environmental regulation affects green technology innovation through import trade, this paper analyzes the impacts of environmental regulation and import trade on green technology innovation and the transmission effect of import trade based on panel data for 30 provinces in China for 2008 to 2017. The results show that (1) environmental regulation first plays a role in promoting green technology innovation and then restrains it, and import trade can significantly promote green technology innovation; (2) under the constraints of stronger environmental regulations, import trade has a significantly positive effect on green technology innovation; and (3) environmental regulation can further enhance the technology spillover effects of import trade in regions with high absorptive capacity and regions with high levels of R&D investment. This paper analyzes the impact of environmental regulation on green technology innovation from the perspective of import trade and makes up for the deficiencies of existing research. It also lays a foundation for scholars to study the relationship between environmental regulation and green technology innovation in the midst of heterogeneous government regulation capabilities and industries in the future.

In this paper, utilizing the same recognition group dinitrophenyl and hydroxyl functional NIR fluorophore hemicyanine, directly-linked probe CyNO2 and self-immolative probe CyBNO2 were developed for evaluation of sensing PhSH. Though CyNO2 was easily synthesized and sensitive to mercapto, the probe CyBNO2 showed higher selectivity, broader linear range from 1.0 × 10−7 to 7.0 × 10−6 M with lower detection limit of 22 nM for PhSH. Moreover, CyBNO2 was successfully applied for monitoring PhSH in living cells and in vivo, indicating the great potential of self-immolative probes.

In the present study, a simple strategy was developed for Ni/Co layered double hydroxides (LDHs) as a substitute for natural peroxidase. The obtained Ni/Co LDHs exhibited ease of preparation, low-cost, and water-solubility; importantly, this material showed high catalytic activity in neutral pH solutions (phosphate buffer, Tris–HCl buffer, and even water). Benefitting from Ni/Co LDHs having a similar pH and temperature with specificity oxidase, such as glucose oxidase, choline oxidase, acetylcholinesterase, etc., a novel one-step method for a biosensor was developed in water. Glucose detection was selected as an application model system to evaluate the performance of this method, which showed a linear detection range from 0.5 μM to 100 μM with a detection limit (DL) of 0.1 μM. We also extended the one-step method to detect acetylcholine (ACh) by taking advantage of the specific catalytic reaction of acetylcholinesterase (AChE) and choline oxidase (ChOx). The linear detection range was from 10 μM to 150 μM with the DL of 1.62 μM. The proposed method had ease of operation, simple steps, and was rapid for glucose and ACh detection in real samples. On the basis of these advantages and virtues, Ni/Co LDHs could become attractive nanozymes in biotechnology and bioassays, and create a great influence on the next generation of enzyme mimetic systems.

Solvent-free analysis of organic pollutants from a complex matrix has attracted significant attention. In this work, we designed and fabricated a facile cooling-assisted solid-phase microextraction device (CA-SPME) that could be used for the solvent-free extraction of volatile and semivolatile compounds from a complex matrix using a commercial SPME probe. Determination of polycyclic aromatic hydrocarbons (PAHs) from soil samples was carried out to evaluate the performance of the designed CA-SPME device. The effects of heating temperature, cooling temperature, extraction time, and moisture content in soil on extraction efficiency were investigated. To enhance the extraction efficiency of the targeted analytes, the matrix solid-phase dispersion technique (MSPD) by grinding soil with silica gels was applied. The results showed that grinding with silica gels promoted the release of PAHs from the soil matrix to the headspace by disrupting the matrix structure, which then facilitated the extraction efficiency. Under optimized conditions, for all of the targeted PAHs, the method exhibited good linearity (40–4000 ng g−1) with regression coefficients (R2) ranging from 0.9586 to 0.9964. The limits of detection and limits of quantification ranged from 4.2 to 8.5 ng g−1 and 14.0–28.5 ng g−1, respectively. Relative standard deviations corresponding to the analysis of spiked soil samples (n = 5) were 8.1–13.4%. The solvent-free analysis of the certified soil sample using the proposed method demonstrated satisfactory results.

Nanozymes are more stable, economical, and easier to produce than natural enzymes; however, their low activity in non-acidic environments and lack of substrate selectivity severely limit the applications of nanozymes. In this study, we developed Co- and N-doped carbon dot nanozymes (CoNCDs) that specifically exhibited peroxidase-like activity toward o-phenylenediamine in a non-acidic environment. Based on the peroxidase-like activity and fluorescence property of CoNCDs in a neutral environment, a one-pot multi-mode sensing platform (colorimetric and ratiometric fluorescence imaging) was developed to detect cholesterol and xanthine in solution and human serum samples. This platform was simple to operate, and the CoNCDs demonstrated a reduced detection time and an improved analytical performance compared to most of the reported nanozymes. Moreover, the improved peroxidase activity at neutral pH, good biocompatibility, and photostability of CoNCDs facilitated their use for monitoring endogenous H2O2 levels in vivo. This study not only provides a novel approach for developing an acid pH-independent and substrate selectivity nanozyme but also demonstrates the application of ratiometric fluorescence imaging using the developed CoNCDs both in vitro and in vivo.

To remove the pollutant methylene blue (MB) from water, a sheet-like skeleton carbon derived from shaddock peels (SPACs) was prepared by NaOH activation followed by a calcination procedure under nitrogen protection in this study. Characterization results demonstrated that the as-prepared SPACs displayed a hierarchically porous structure assembled with a thin sheet-like carbon layer, and the surface area of SPAC-8 (activated by 8 g NaOH) was up to 782.2 m2/g. The as-prepared carbon material presented an ultra-fast and efficient adsorption capacity towards MB due to its macro-mesoporous structure, high surface area, and abundant functional groups. SPAC-8 showed ultrafast and efficient removal capacity for MB dye. Adsorption equilibrium was reached within 1 min with a removal efficiency of 99.6% at an initial concentration of 100 mg/g under batch adsorption model conditions. The maximum adsorption capacity for MB was up to 432.5 mg/g. A pseudo-second-order kinetic model and a Langmuir isotherm model described the adsorption process well, which suggested that adsorption rate depended on chemisorption and the adsorption process was controlled by a monolayer adsorption, respectively. Furthermore, column adsorption experiments showed that 96.58% of MB was removed after passing through a SPAC-8 packed column with a flow rate of 20 mL/min, initial concentration of 50 mg/L, and adsorbent dosage of 5 mg. The as-prepared adsorbent displays potential value in practical applications for dye removal due to its ultrafast and efficient adsorption capacity.

The synthesized NiCo2O4 mesoporous spheres (MS) displayed intrinsic peroxidase and oxidase-like activity were firstly reported. The catalytic mechanism of the oxidase-like activity of NiCo2O4 MS was analyzed in detail using the electron spin resonance (ESR) method. It is found that NiCo2O4 MS could directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) but did not produce 1O2 and ·OH. And the mechanism of the peroxidase-like activity of NiCo2O4 MS was also verified that the oxidation of TMB stemmed from not only ·OH but also 1O2. Based on the NiCo2O4 MS showed excellent peroxidase-like activity over a broad temperature range, especially at normal body temperature, a detection tool was designed for glucose determination in diabetics' serum samples. And this detection method based on NiCo2O4 MS gave a lower limit of detection than the method using Co3O4 NPs and NiO NPs, as the single-component oxides of NiCo2O4. Our study may open up the possibility to make a great influence on the next generation of enzyme mimetics system.

Hemicyanine dyes including hemi-indocyanine and hemi-benzindocyanine have been attracted considerable attentions to develop near infrared probes for in vivo fluorescence imaging. However, hemi-benzothiazolecyanine dye (MTR) is rarely reported for detection analytes. In this work, to extend the sensing applications of MTR, we present an optimized route for facile preparation of the dye. And as a proof-of-concept, a self-immolative NIR probe MTR-HH based on hemi-benzothiazolecyanine dye was designed and synthesized for H2O2. The probe exhibited a 284-fold fluorescent enhancement to H2O2 with a detection limit of 0.32 μM over other biospecies. Moreover, MTR-HH was successfully applied for visualizing endogenous H2O2 in living cells and mice.

A ultrafast one-step microwave-assisted method was developed for the synthesis of nitrogen–sulfur co-doped carbon nanodots (N,S-CDs) by using ethylenediamine as the carbon source and sulfamic acid as the surface passivation reagent. The morphology and the properties of N,S-CDs were explored by a series of techniques, such as high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis absorption and fluorescence spectroscopy. The prepared N,S-CDs exhibit bright blue photoluminescence with a high fluorescence quantum yield (FLQY) up to 28%, and high stability and excellent water solubility. A N,S-CDs-based fluorescent probe was developed for sensitive detection ascorbic acid (AA) in the presence of Cu2+, based on the mechanism that AA reduces Cu2+ to Cu+, then Cu+ quenches the fluorescence of N,S-CDs through electron or energy transfer due to the interaction between Cu+ and thiol ligand on the N,S-CDs surface. The observed linear response concentration range was from 0.057 to 4.0 μM to AA with a detection limit as low as 18 nM. The probe exhibited a highly selective response toward AA even in the presence of possible interfering substances, such as uric acid and citric acid. Moreover, these promising features made the sensing system used for the analysis of human serum and urine samples.

Ascorbic acid (AA) serves as a key coenzyme in many metabolic pathways, and its abnormal level is found to be associated with several diseases. Therefore, monitoring AA level in living systems is of great biomedical significance. In comparison with one-photon excited fluorescent probes, two-photon (TP) excited probes are more suitable for bioimaging, as they could afford higher imaging resolution with deeper imaging depth. Here, we report for the first time an efficient TP fluorescence probe for turn-on detection and imaging of AA in living cells and tissues. In this nanosystem, the negatively charged two-photon nanoparticles (TPNPs), which were prepared by modifying the silica nanoparticles with a two-photon dye, could adsorb cobalt oxyhydroxide (CoOOH) nanoflakes which carried positive charge by electrostatic force, leading to a remarkable decrease in their fluorescence intensity. However, the introduction of AA could induce the fluorescence recovery of the nanoprobe because it could reduce CoOOH into Co(2+) and result in the destruction of the CoOOH nanoflakes. The nanosystem exhibits a high sensitivity toward AA, with a LOD of 170 nM observed. It also shows high selectivity toward AA over common potential interfering species. The nanoprobe possessed both the advantages of TP imaging and excellent membrane-permeability and good biocompatibility of the silica nanoparticles and was successfully applied in TP-excited imaging of AA in living cells and tissues.

A fluorescent probe has been developed for the determination of guanine based on the quenched fluorescence signal of Cu(2+)/eosin Y. Cu(2+) interacted with eosin Y, resulting in fluorescence quenching. Subsequently, with the addition of guanine to the Cu(2+)/eosin Y system, guanine reacted with Cu(2+) to form 1:1 chelate cation, which further combined with eosin Y to form a 1:1 ternary ion-association complex by electrostatic attraction and hydrophobic interaction, resulting in significant decrease of the fluorescence. Hence, a fluorescent system was constructed for rapid, sensitive and selective detection of guanine with a detection limit as low as 1.5 nmol L(-1) and a linear range of 3.3-116 nmol L(-1). The method has been applied satisfactorily to the determination of guanine in DNA and urine samples with the recoveries from 98.7% to 105%. This study significantly expands the realm of application of ternary ion-association complex in fluorescence probe.

In the present work, unmodified carbon nanodots (CDs) can act as fluorescent probes for detection and measurement of guanine concentration. CDs were synthesized by using a facile one-step microwave-assisted method with dl -malic acid and ethylenediamine as the precursors. The fluorescence of CDs can be obviously quenched by copper(II) ions through nonradiative electron transfer. Meanwhile, due to the coordination of copper(II) ions with guanine, the fluorescence of the CDs was restored reversibly by the addition of guanine. Under optimized conditions, the prepared CDs demonstrate a linear range from 1.31 × 10−8 to 7.27 × 10−7 mol L−1 with the detection limit of 0.67 × 10−8 mol L−1. The new fluorescence system has been applied for the determination of guanine in urine and DNA samples with the recoveries from 98.1% to 103.0%.

Near-infrared (NIR) fluorescent probes are attractive molecular tools for bioimaging because of their low autofluorescence interference, deep tissue penetration, and minimal damage to sample. However, most previously reported NIR probes exhibit small Stokes shift, typically less than 30 nm, and low fluorescence quantum yield, strictly limited contrast and spatial resolution for bioimaging. Herein, by expanding the π-conjugated system of rhodamine B, while, at the same time, keeping its rigid and planar structure, we reported an efficient NIR dye, HN7, with large stokes shift of 73 nm and fluorescence quantum yield as high as 0.72 in ethanol, values superior to those of such traditional cyanine NIR dyes as Cy5. Using HN7, living cells, tissues and mice were imaged, and the results showed significantly enhanced contrast, improved spatial resolution, and satisfactory tissue imaging depth when compared to Cy5. Moreover, the nonfluorescent spirocyclic structure of rhodamine B is an inherent component of HN7; therefore, our strategy provided a universal platform for the design of efficient NIR turn-on bioimaging probes for various targets. As a proof-of-concept, two different NIR probes, HN7-N2 and HN7-S for NO and Hg2+, respectively, were designed, synthesized, and successfully applied for the imaging of NO and Hg2+ in living cells, tissues and mice, respectively, demonstrating the potential bioimaging applications of the new probes. In sum, this new type of dye may present new avenues for the development of efficient NIR fluorescent probes for contrast-enhanced imaging in biological applications.

Nitrogen-doped carbon quantum dots (N-CDs) have become a current focus of chemical research due to their superior photoluminescence (PL) properties and high fluorescence quantum yield (QY). In this paper, we reported a facile, simple and low-cost approach for the synthesis of highly fluorescent and stable N-CDs by hydrothermal treatment of maleic acid and ethylenediamine. The as-prepared N-CDs emitted strong blue fluorescence with an absolute QY of up to 45%, and exhibited pH-independent behavior in a wide pH range from 1 to 13 and good water solubility. In addition, the fluorescence of the N-CDs can be significantly quenched by p-nitrophenol (4-NP) through an electron-transfer-induced dynamic quenching mechanism, leading to 4-NP being sensed optically. The sensor presented a good linearity with 4-NP concentration in the range of 0.10–11 μg mL−1. The detection limit of 22 ng mL−1 4-NP could be obtained, which is lower than the 60 ng mL−1 limit allowed in drinking water by the U. S. Environmental Protection Agency. The sensor exhibited rapid recognition and distinguished selectivity to 4-NP over other structural analogues of phenols. Moreover, the sensing system was successfully applied for the determination of 4-NP in environmental water samples.

Selenocysteine (Sec, pKa 5.8) is genetically encoded 21st amino acid into the active site of selenoproteins, which have broad functions relevant to various diseases, tissues or organs and subcellular organelles. However, many selenoproteins involved cellular functions still remains unclear. In addition, since biothiols such as glutathione (GSH, pKa 8.3), possessing similar chemical properties with Sec, commonly exist in living systems at high levels. Thus, it is of great importance and high challenge to identify novel probes for selectively monitoring Sec over biothiols. In this paper, we proposed a smart strategy which allowed us to develop a lysosome targetable probe for specifically sensing Sec. By restricting weak acidic microenvironment, the probe shows a specific detection for Sec with 85-fold fluorescence enhancement owing to the remaining high activity of Sec at pH 5.0. Moreover, being low cytotoxicity to the cells verified by MTS assay, the probe was then successfully applied for imaging exogenous and endogenous Sec in lysosomes, indicating its potential for the biological investigation of Sec in subcellular organelles.

In this study, facile fabrication of three-dimensional (3D) pompon-like gold/zinc oxide (Au/ZnO) porous microspheres by hydrothermal procedure was investigated. These microspheres were utilized as solid phase microextraction (SPME) coating for determination of volatile fatty acids (VFAs) from foot odor coupling with gas chromatography-mass spectrometry (GC-MS). SEM and TEM characterizations showed that as-prepared material was composed of 1D porous nanowires and presented a uniform coating on stainless-steel wire. The extraction of VFAs including propanoic acid, butyric acid, isobutanoic acid, isovaleric acid, hexanoic acid, and heptylic acid was carried out by headspace model after sampling from human foot using cotton wool strips. Following optimization of extraction parameters including extraction temperature and time and desorption temperature and time, the as-prepared SPME coating presented better extraction efficiency than commercial DVB/CAR/PDMS fiber towards all the VFAs due to its excellent properties. Under the optimized conditions, the method exhibited good linearity (0.5–200 ng) with regression coefficients (R2) ranging from 0.9836 to 0.9981 for all the analytes. The limits of detection ranged from 0.017 to 0.098 ng. Single fiber repeatability varied from 6.5% to 11.2% and the fiber-to-fiber reproducibility ranged from 8.6% to 12.3%. The proposed method was successfully applied for extraction and determination of VFAs from foot odor after sampling using cotton wool strips.

Nanozymes’ activities could be regulated by a simple and effective pH change in an in situ manner. In this work, for the first time, the peroxidase-like activity of Ni/Co layered double hydroxides (LDHs) was regulated via the alkaline-promoted reaction of fluorogenic substrate homovanillic acid and H2O2, and a promising tool for pH sensing was developed over the pH range of 8.3–9.6. As peroxidase nanozyme model, Ni/Co LDHs showed ease of preparation, low-cost, and water-solubility, which played an important role in this luminescence system. Based on the pH-dependent regulation of the Ni/Co LDHs activity, we constructed the bioassay platform for the determination urea, urease, penicillin G, and penicillinase with a wide linear range of 17–1000 µM, 3.3–270 mU mL−1, 3.3–1300 µM and 3.3–100 mU mL−1, respectively. This study not only demonstrated the alkaline-promoted modulation the nanozymes’ activities, but also established a facile approach to develop novel bioassays.

Hypochloric acid (HClO) is mainly distributed in acidic lysosomes of phagocytes and closely associated with numerous physiological and pathological processes, especially inflammatory response. Fluorescent probe has become an important tool for imaging HClO in lysosomes, but suffered from interference from autofluorescence in vivo , phototoxicity to biosamples and photobleaching phenomenon due to their short-wavelength excitation and emission. Unfortunately, up to now, no near-infrared (NIR) lysosome-targetable fluorescent probe has been reported for imaging HClO. In this paper, a near-infrared fluorescent probe Lyso - NIR - HClO for imaging lysosomal HClO was reported for the first time. Lyso - NIR - HClO based on Si-rhodamine is consisted of a morpholine unit as a lysosome-targetable group and a HClO-mediated cyclization reaction site as a response group, which was applied for highly selective and sensitive detection and imaging for endogenous and exogenous HClO in lysosomes, with a linear range from 5.0 × 10 −8 to 1.0 × 10 −5 M and a detection limit of 2.0 × 10 −8 M in vitro . Attributed to NIR emission and excellent photostability of Si-rhodamine, Lyso - NIR - HClO exhibits excellent performances in vivo , such as low interference from intracellular autofluorescence, stable and persistent fluorescence signal and good tissue penetration, which are in favor of accurate, time-lapse and long-term imaging for HClO. Finally, we applied the probe Lyso - NIR - HClO to visualize endogenous HClO during lysosome-involved inflammatory response including bacteria-infected cells and inflamed mouse model with satisfactory results. The above results proved that Lyso - NIR - HClO would be a potentially useful tool for the study of biological functions and pathological roles of HClO in lysosomes, especially role of lysosome in the inflammatory response.

A novel fluorescence method for the determination of guanine was developed based on the fluorescence enhancement of Cu(2+)-nuclear fast red complex in the presence of guanine in Tris-HCl buffer. The complex of Cu(2+) with nuclear fast red resulted in a dramatic quenching of the fluorescence intensity. Nuclear fast red were dissociated from the complex with the addition of guanine due to the strong interaction between guanine and Cu(2+), which caused the fluorescence enhancement. The enhanced fluorescence intensity was well proportional to the concentration of guanine in the range of 4.96 × 10(-8)-1.09 × 10(-6)mol/L with the limit of detection 1.9 × 10(-8)mol/L. The method has been applied successfully to the determination of guanine in serum and DNA samples, and the recoveries were from 96.0% to 104.8%.

Nanomaterial-based peroxidase-mimetics are an emerging research field that promises to produce alternatives to horseradish peroxidase for a variety of applications. Generally, some peroxidase-mimetics substrates are used in acidic condition (pH ≤ 7). Then, it is necessary to screen some peroxidase-mimetics substrates suitable for basic condition because that some peroxidase-mimetics leached ions in acidic solution. In this paper, using Ni/Co layered double hydroxides (LDHs) as a nano-peroxidase mimic model, we evaluated three fluorogenic substrates suitable for basic condition though experimental conditions, reaction kinetic and glucose detection assay. And the detection of glucose method based on homovanillic acid (HVA) as fluorescent substrate gave wide linear range (0.02–20 μM) and low detection limit (0.01 μM). We also developed a novel platform that could study the inhibitory effects of ascorbic acid and glutathione based on the system of Ni/Co LDHs-HVA-H2O2.

The synthesized NiCo

The interaction of clomifene citrate with nuclear fast red and sodium dodecyl benzene sulfonate (SDBS) was investigated by absorption and resonance rayleigh scattering (RRS) spectrometry. Clomifene citrate can react with nuclear fast red and sodium dodecyl benzene sulfonate to from a ternary complex, resulting in the enhancement of RRS intensity and the appearance of new RRS peaks. Based on that, a novel method is proposed for the determination of clomifene citrate by RRS technique. On the optimum conditions, there was good linearship between the increments of RRS intensity and the concentration of clomifene citrate in the range of 0.25 to 20.0 μg/mL, with the detection limit of 29 ng/mL. The proposed method was applied to assay the clomifene citrate tablets and capsules in agreement with the method in Chinese Pharmacopeia. In addition, the method was also applied to detect clomifene citrate in serum and urine samples with satisfactory results. The studies indicate that clomifene citrate acts as a bridge to band with nuclear fast red and SDBS by virtue of electrostatic attraction to form ion-association complexes.

A sequential injection analysis (SIA) system is described for the determination of phenoxybenzamine hydrochloride and metoclopramide using spectrophotometer as detector. The method is based on the detection of an unstable red intermediate compound resulting from the reaction of phenoxybenzamine hydrochloride or metoclopramide with the diazotizating product of p-phenylenediamine with sodium nitrite in hydrochloric acid medium. The sampling frequency is 69 h−1 and 75 h−1 for phenoxybenzamine hydrochloride and metoclopramide, respectively. The linear range is 10–400 μg/mL for phenoxybenzamine hydrochloride with a detection limit of 0.081 μg/mL and 20–250 μg/mL for metoclopramide with a detection limit of 0.034 μg/mL. The RSD is 1.01 and 0.45% for phenoxybenzamine hydrochloride and metoclopramide, respectively. The proposed methods were used to determine phenoxybenzamine hydrochloride and metoclopramide in pharmaceuticals. The results are compared with those obtained by pharmacopoeia method.

A novel inhibitory kinetic fluorimetric method for the determination of trace methomyl was proposed. It was shown that the Fenton reagent oxidized rhodamine B in acid medium which enabled the fluorescence quenching of the latter. The presence of trace methomyl clearly inhibited the reaction. Upon addition of EDTA, a good linear relationship between the inhibitory effect and the concentration of methomyl was observed, together with improved stabilization and sensitivity. Factors affecting the determination of trace methomyl were investigated systematically. Under the optimum conditions, the linear range for the determination of methomyl was 0.04–2.2 µg/mL; the detection limit and the quantification limit for methomyl were 0.011 and 0.037 µg/mL, respectively. The proposed method was applied to the determination of methomyl in four environmental soil samples, six environmental water samples and one synthetic sample; the results were compared with those determined by the HPLC method. The recoveries and the relative errors were 83.5–101.2 and 0.47–2.02%, respectively. The possible reaction mechanism has also been discussed. Copyright © 2009 John Wiley & Sons, Ltd.

A simple, economical, and automated spectrophotometric method for the determination of chlorpromazine hydrochloride by sequential injection analysis using ammonium metavanadate as colorimetric reagent is proposed. The various chemical and physical conditions that affected the reaction have been thoroughly investigated. The calibration curve was linear within the range 10–100 μg/mL. The detection limit (S/N = 3) was 0.7 μg/mL and the limit of quantification (S/N = 10) was 2.3 μg/mL. The sampling frequency was 22 h−1. The method has been used for the determination of chlorpromazine hydrochloride in pure form and pharmaceutical formulations. The t-test has revealed that there is no evidence of significant differences between the obtained results at the 95% confidence level. The method can be applied to the quantitative determination of chlorpromazine hydrochloride. It is also applicable in the quality control of chlorpromazine hydrochloride preparations.

A novel fluorometric method for the determination of adenine was proposed, based on the fluorescence quenching of a nuclear fast red-silver complex as a small molecule optical probe in the presence of adenine. The characteristic spectra of absorption, resonance Rayleigh scattering (RRS) and the fluorescence of the system were analysed. Adenine, Ag+ and nuclear fast red formed a sandwich-type complex. The composition of the compound and the mechanisms of fluorescence quenching were discussed. The optimal conditions for the reaction and the effects of co-existing substances were also investigated. The quenched fluorescence intensity was proportional to the concentration of adenine in the range of 0.03–0.90 µg mL−1, with the limit of detection of 0.023 µg mL−1. The method was applied satisfactorily to the determination of adenine in synthetic samples, herring sperm DNA, human sera and vitamin B4 tablets with recoveries from 95.3 % to 105 %.