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As vital microenvironmental indicators, hypochlorite and viscosity levels can be applied to diagnose diseases. Thus, real time and in situ monitoring of hypochlorite and viscosity has gained increasing attentions. A fluorescence probe named JDK was developed by using a novel acceptor of 2-(2-(5-(dimethylamino)thiophen-2-yl)vinyl)-1,3,3-trimethyl-3H-indol-1-ium fluorophore basing on FRET and TICT system. JDK possessed large Stokes shift, broad emission peak gap, prominent photostability and biocompatibility. JDK could track hypochlorite with rapid response time (within 1 min) and low detection limit (28.5 nM). Meaningfully, JDK was favor to append on mitochondria where physiological processes can be disrupted deriving from the abnormal concentrations of hypochlorite and viscosity. Successfully, JDK could visualize endogenous hypochlorite and viscosity in living cells and zebrafish.

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The ultrasensitive detection of hepatitis C virus (HCV) nucleic acid is crucial for the early diagnosis of hepatitis C. In this study, by combining Ag@Au core/shell nanoparticle (Ag@AuNP)-based surface-enhanced Raman scattering (SERS) tag with hybridization chain reaction (HCR), a novel SERS-sensing method was developed for the ultrasensitive detection of HCV nucleic acid. This SERS-sensing system comprised two different SERS tags, which were constructed by modifying Ag@AuNP with a Raman reporter molecule of 4-ethynylbezaldehyde, two different hairpin-structured HCR sequences (H1 or H2), and a detection plate prepared by immobilizing a capture DNA sequence onto the Ag@AuNP layer surface of the detection wells. When the target nucleic acid was present, the two SERS tags were captured on the surface of the Ag@AuNP-coated detection well to generate many "hot spots" through HCR, forming a strong SERS signal and realizing the ultrasensitive detection of the target HCV nucleic acid. The limit of detection of the SERS-sensing method for HCV nucleic acid was 0.47 fM, and the linear range was from 1 to 105 fM.

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Copper ion (Cu2+) detection remains an important task for monitoring water quality because of its specific toxicity. Herein, a new dual-signal fluorescent probe was developed by combining zeolitic imidazolate framework-8 (ZIF-8) and lanthanide for the detection of Cu2+ for the first time. The lanthanide coordination polymer (guanosine monophosphate and Eu3+, GMP/Eu) was initially incorporated into ZIF-8 to yield ZIF-8/GMP/Eu nanomaterials with extremely weak single emission fluorescence at 618 nm. It was found that the resulted nanomaterials could display a dual emission fluorescence at 515 nm and 618 nm after the introduction of tetracycline (TC) due to the synergistic effect of aggregation-induced emission effect (AIE, TC induced by ZIF-8) and antenna effect (AE, between TC and GMP/Eu). Interestingly, in the presence of Cu2+, the AIE of TC was destroyed because of the interaction of Cu2+ with ZIF-8 and TC. The AE between TC and GMP/Eu disappeared due to the formation of complex between TC and Cu2+. A dual-signal fluorescent probe of ZIF-8/GMP/Eu/TC was thereby established for sensing Cu2+ in the range of 0.5-100 µM. Such a dual-signal response strategy that intelligently utilized the "ON"/"OFF" of AIE and AE can not only eliminate the background interference, but also ensure the improved selectivity of Cu2+ sensing. Subsequently, the dual-signal fluorimetric strategy was applied for the detection of Cu2+ in environmental water samples, indicating the potential feasibility of applications for water quality monitoring.

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A Ag@AuNP-functionalized capillary-based surface-enhanced Raman scattering (SERS) sensing platform for the interference-free detection of glucose using SERS tags with a built-in nitrile signal has been proposed in this work. Capillary-based SERS capture substrates were prepared by connecting 4-mercaptophenylboronic acid (MBA) to the surface of the Ag@AuNP layer anchored on the inner wall of the capillaries. The SERS tags with a built-in interference-free signal could then be fixed onto the Ag@AuNP layer of the capillary-based capture substrate based on the distinguished feature of glucose, which can form a bidentate glucose-boronic complex. Thus, many "hot spots" were formed, which produced an improved SERS signal. The quantitative analysis of glucose levels was realized using the interference-free SERS intensity of nitrile at 2222 cm-1, with a detection limit of about 0.059 mM. Additionally, the capillary-based disposable SERS sensing platform was successfully employed to detect glucose in artificial urine, and the new strategy has great potential to be further applied in the diagnosis and control of diabetes.

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A target-responsive ratiometric fluorimetric sensing strategy for Hg2+ has been rationally designed. The sensing probe was established based on a functionalized metal-organic framework, which was prepared with 3,5-dicarboxyphenylboronic acid (DCPB) as the functional ligand and Eu3+ as the metal junction. The porous nano-spheres of Eu-MOF with an arylboronic acid as the functional recognition group for Hg2+ exhibited tunable optical properties with dual emission fluorescence signals at 338 nm and 615 nm. In the presence of Hg2+, arylmercury was formed by a specific transmetalation reaction between Hg2+ and arylboronic acid groups, which blocks the energy transfer between the ligand and Eu3+. Thereby, the fluorescence signal of Eu-MOF/BA at 615 nm decreased, while the fluorescence signal at 338 nm remained almost constant. The ratiometric fluorimetric sensing for Hg2+ was achieved by calculating the peak intensity ratio of F615/F338 based on the reference signal at 338 nm and the response signal at 615 nm. The detection limit of Hg2+ was as low as 0.0890 nM, and the recovery rate of the actual environmental water sample ranged from 90.92% to 118.50%. Therefore, the excellent performance of the ratiometric fluorimetric sensing method for Hg2+ makes it attractive for the detection of heavy metal ions in environmental monitoring.

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A microdots array-based fluoremetric method with superwettability profile has been developed for the simultaneous and separate detection of Fe3+ and Cu2+ ions in red wine samples. A wettable micropores array was initially designed with high density by using polyacrylic acid (PAA) and hexadecyltrimethoxysilane (HDS), followed by the NaOH etching route. Zinc metal organic frameworks (Zn-MOFs) were fabricated as the fluorescent probes to be immobilized into the micropores array to obtain the fluoremetric microdots array platform. It was found that the fluorescence of Zn-MOFs probes could decrease significantly in the presence of Fe3+ and/or Cu2+ ions towards their simultaneous analysis. Yet, the specific responses to Fe3+ ions could be expected if using histidine to chelate Cu2+ ions. Moreover, the developed Zn-MOFs-based microdots array with superwettability profile can enable the accumulation of targeting ions from the complicated samples without any tedious pre-processing. Also, the cross-contamination of different samples droplets can be largely avoided so as to facilitate the analysis of multiple samples. Subsequently, the feasibility of simultaneous and separate detection of Fe3+ and Cu2+ ions in red wine samples was demonstrated. Such a design of microdots array-based detection platform may promise the wide applications in analyzing Fe3+ and/or Cu2+ ions in the fields of food safety, environmental monitoring, and medical diseases diagnostics.

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Covalent organic frameworks (COFs) were fabricated with a hierarchical flower-like hollow structure, possessing a large specific surface area, high porosity, and excellent environmental stability. In situ growth of noble silver nanoparticles (AgNPs) onto COFs was conducted yielding COF-Ag nanozymes. The structural advantages of COFs can ensure the uniform dispersion and effective size control of AgNPs. More interestingly, the oxidase-like catalytic activity of the obtained COF-Ag nanozymes could be enhanced in the presence of Hg2+ ions, which could specifically interact with AgNPs to form Ag-Hg alloys. A COF-Ag catalysis-based colorimetric platform was thereby constructed for highly selective and sensitive analysis of Hg2+ ions, showing a linear concentration range from 0.050 to 10.0 µM, with a limit of detection of about 3.7 nM. Besides, the developed colorimetric strategy was successfully applied for detecting Hg2+ ions in human blood with favorable detection recoveries, indicating its potential for applications in the biomedical analysis, environmental monitoring, and food safety fields.

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A ratiometric fluorimetric sensing strategy with Zeolitic imidazolate framework-8 (ZIF-8) has been developed for the analysis of tetracycline (TC) in environmental water samples. ZIF-8 with polyhedral structure was synthesized at room temperature exhibiting blue fluorescence at 445 nm. Especially, the as-prepared ZIF-8 could conduct the aggregation-induced emission (AIE) effect in the presence of TC through electrostatic, hydrogen bond, π-π stacking, and coordination interactions. As a result, a strong yellow-green fluorescence appeared and a new fluorescence peak at 505 nm was observed, although the initial fluorescence peak at 445 nm of ZIF-8 was almost unchanged. A ZIF-8-based fluorimetric platform was thereby designed for sensing TC by using ZIF-8 as the fluorescent probe with the peak at 445 nm as the reference and the one at 505 nm as the changing signal, which should increase with the increasing concentrations of TC. Moreover, the quantitative analysis of TC could be carried out through the ratiometric peak intensities of F505/F445, with a detection limit as low as 14.7 nM. Additionally, the ratiometric fluorescent analysis method was successfully employed to detect TC in environmental water samples, indicating that ZIF-8 might be a good luminescent sensor for probing the pollutants in the environmental water.

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Rational construction of heterogeneous interfaces that maximize carrier flux and allow carrier separation for achieving efficient photocatalytic CO2 reduction still remain a challenge. In this work, high-throughput and intimate interfaces that allow efficient carrier separation and flux are designed by depositing high-density CeO2 nanoparticles on large-area Ti3C2TX (T = terminal group) nanosheets. Oxygen-containing functional groups of Ti3C2TX nanosheets facilitate the anchoring of CeO2 nanoparticles on the nanosheets via the formation of interfacial Ce-O-Ti bonds, which serve as effective channels for reverse and synergistic migration of electrons and holes to achieve spatial separation. The light absorption of the CeO2@Ti3C2TX composites is extended to the infrared (IR) region due to narrow bandgaps of Ti3C2TX. High-density lateral and basal interfaces enhance carrier migration, which ultimately aids the CeO2@Ti3C2TX composites to exhibit excellent activity for reducing CO2 to alcohols (i.e., methanol and ethanol) under both visible (vis) and IR irradiations. The total amount of produced alcohol under visible irradiation is 109.9 µmol•gcatal-1 (methanol and ethanol: 76.2 and 33.7 µmol•gcatal-1, respectively), which is 4.3 times higher than that obtained using CeO2 (methanol and ethanol: 19.8 and 6 µmol•gcatal-1, respectively). The yields of methanol and ethanol using the optimized CeO2@Ti3C2TX were 102.24 and 59.21 µmol•gcatal-1, respectively, after 4 h under the vis-IR irradiation.

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It is a challenge to regulate charge flow synergistically at the atomic level to modulate gradient hydrogen migration (H migration) for boosting photocatalytic hydrogen evolution. Herein, a self-adapting S vacancy (Vs) induced with atomic Cu introduction into ZnIn2S4 nanosheets was fabricated elaborately, which can tune charge separation and construct a gradient channel for H migration. Detailed experimental results and theoretical simulations uncover the behavior mechanism of Vs generation with Cu introduction after substituting a Zn atom tendentiously. Cu-S bond shrinkage and Zn-S bond distortion are presented around Vs areas. Besides, Vs induced by Cu introduction lowers the internal electric field to restrain electron transmission between layers, which are enriched on the Vs area because of the lower surface electrostatic potential. Atomic Cu and Vs show a synergistic effect for regulating regional charge separation due to the Cu dopant being a hole trap and Vs being an electron trap. The channels for H migration with gradient ΔGH0 are constructed by different S atom sites, which are modulated by Vs. Gradient H migration driven by a photothermal effect occurs on an identical surface without striding across a heterogeneous interface, which is a valid pathway with lower resistance for boosting H2 release. Ultimately, 5 mol % Cu confined in ZnIn2S4 nanosheets achieves an optimum photocatalytic hydrogen evolution activity of 9.8647 mmol g-1 h-1, which is 14.8 times higher than 0.6640 mmol g-1 h-1 for ZnIn2S4, and apparent quantum efficiency reaches 37.11% at 420 nm. This work demonstrates the behavior mechanism of atomic substitution and provides cognition for hydrogen evolution mechanism deeply.

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As the dominant hazardous waste discharged from petroleum industry, the pyrolysis features of the upstream oily sludge (UOS) were scrutinized by way of TGA/DSC. The pyrolysis kinetics model of UOS was systematically constructed by sectionalized single-step reaction approach (SSRA) and distributed activation energy model (DAEM), and the data reproducibility was further evaluated. The results showed that when the pyrolysis operation temperature interval was set from 380 K to 1170 K, two weigh loss step, two endo/exothermic regions and three significant mass-loss peak were respectively emerged in TG, DSC and DTG curves, based on which the TG curves could be sectionalized into three stages. Attributing to the ∆E/Eα¯ value of each stage was higher than 10% but lower than 20% derived from the activation energy assessment, it is not only revealed three multi-step reactions were carried out in sequence with an individual dominant single-step reaction which was sufficient for the SSRA utilization, but also displayed a well fitted by the Gaussian distribution which satisfied the requirement of DAEM implementation. Based on the five-step construction procedure introduced in this paper, pyrolysis kinetics model of UOS could be successful established and interpret as SSRA-based and DAEM-based piecewise function. The latter exhibited a better performance on the data reproduction than the former because the nRSS value of the reproduced data derived from DAEM-based model was lower than 1.86%. The higher mathematical flexibility of DAEM-based model function was the major attribution to a better data reproducibility, also, it possessed a potential ability in predicting the reaction rate at an arbitrary reaction temperature once the heating ratio was preset.

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Z-scheme photocatalyst preserved with superior oxidicability is an innovative photocatalyst system that can be used for efficient photocatalytic detoxification of antibiotics. In this study, Z-scheme Ag3PO4@ZnIn2S4 photocatalyst was constructed by decorating Ag3PO4 nanoparticles on ZnIn2S4 nanoscopariums. ZnIn2S4 nanoscopariums were prepared by self-templated strategy and given hierarchical structures. The hierarchical Ag3PO4@ZnIn2S4 provides more active sites for generating photogenerated carriers and large surface area for capturing tetracycline. The study results show that Ag3PO4@ZnIn2S4 performed excellently well in the photocatalytic degradation of tetracycline and also in protecting Ag3PO4 nanoparticles from photo-corrosion. The highest removal efficiency (up to 92.3%) was achieved from the optimal composites of Ag3PO4 and ZnIn2S4. In stability tests, Ag3PO4@ZnIn2S4 did not reduce the photocatalytic activity of degrading tetracycline after five successive runs. Active radical identification proves that the transfer behavior of electron and hole over Ag3PO4@ZnIn2S4 follows a direct Z-scheme mechanism. Furthermore, the transformation pathway for degrading tetracycline was proposed by combining the Fukui index prediction with Mass Spectra identification of intermediates. This work presents in-depth sights into a regulated degradation pathway from theoretical prediction and practical identification based on innovative Z-scheme photocatalyst.

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Despite the existence of numerous photocatalyst heterostructures, their separation efficiency and charge flow precision remain low due to the poor study on interfacial properties. The photocatalysts with confined defects can effectively control the photogenerated carrier migration, but the metastability of such defects considerably decreases the photocatalyst stability. Meanwhile, the introduction of defective region can increase the coordinative unsaturation and delocalize local electrons to promote their interactions with the molecules/ions in that region. The selective growth of modulated heterogeneous interface by defect-induced strategy may not only increase the stability of defective structures, but also enhance the migration of interfacial charges. Using this method, photocatalytic heterostructures with low contact resistances and intimate interfaces are constructed to achieve the optimal charge migration in terms of efficiency and accuracy. In this work, the point, linear, and planar heterogeneous interfaces and related defect engineering techniques are discussed. Particularly, it is focused on the external, defect-induced interfacial heterogeneities with various spatial and dimensional configurations, which exhibit modulated and controllable interfacial properties. Furthermore, the main aspects of fabricating photocatalyst heterostructures by the defect-induced strategy, including the i) controllable generation of defects, ii) advanced characterization methods, and iii) elaborate construction of the minimal interface, are described.

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The abnormal expression of some miRNAs is often closely related to the development of tumors. Available detection methods or biosensors that can simultaneously quantify multiple miRNAs in a single sample have rarely been reported. Herein, a novel catalytic hairpin self-assembly (CHA)-based surface-enhanced Raman scattering (SERS) sensor array was developed to simultaneously measure multiple miRNAs associated with cancer in one sample. The sensor array with four different sensing units was constructed by immobilizing one of four different hairpin-structured DNA sequence 1 (hp1) onto one of four Au/Ag alloy nanoparticle (AuAgNP)-coated detection wells. When target miRNA is present, the SERS tags, which were prepared by modifying AuAgNPs with a Raman reporter molecule of 4-mercaptobenzonitrile (MPBN) and the related hairpin-structured DNA sequence 2 (hp2), were captured onto the corresponding sensor unit through a repeated specific CHA reaction. This generated many "hot spots" because of interactions between the SERS tags and the AuAgNP layer-coated surface of the sensor, which ultimately produced a strong SERS signal that allowed the detection of target miRNAs with the detection limit of 0.15 pM. Using this SERS sensor array, multiple cancer-associated miRNAs (miR-1246, miR-221, miR-133a, and miR-21) were successfully determined in buffer, serum, and cellular RNA extracts.

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A ratiometric surface-enhanced Raman scattering (SERS) based method is described for the determination of the activity of hyaluronidase (HAase). Gold nanorods (AuNRs) were functionalized with 4-thiobenzonitrile (TBN) to act as the Raman reporter (TBN-AuNRs), and 4-thiophenylacetylene-functionalized gold-silver alloy nanoparticles (TPA-AuAgNPs) were used as the reference. Hyaluronic acid (HA) acts as the HAase recognition element. The TBN-modified AuNRs aggregate in the presence of HA due to the strong electrostatic interaction between the positively charged TBN-AuNRs and negatively charged HA. This strongly enhances the Raman signal of TBN at 2220 cm-1. However, HA has no significant effect on the dispersion of the modified AuAg NPs which are electroneutral. Hence, no change can be seen in the Raman intensity of TPA at 1974 cm-1. In the presence of HAase, HA is digested into smaller fragments. This results in good dispersion of the TBN-AuNRs and a weaker TBN Raman signal. Hence, the ratio of the Raman peaks at 1974 and 2220 cm-1 increases. Under the optimized conditions, the ratio changes in the 5-70 U mL-1 HAase activity range, and the detection limit is 1.7 U mL-1 (based on the 3σ rule). Moreover, this method has been successfully applied in the determination of the activity of HAase in artificial urine and it is expected to be a new method for the diagnosis of cancer, especially bladder cancer.

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On the basis of a target microRNA (miRNA)-responsive DNA hydrogel, a novel surface-enhanced Raman scattering (SERS) sensor array with nine sensor units that can detect multiple cancer-related miRNAs in one sample was developed. The target miRNA-responsive DNA hydrogel was first formed in each sensor unit to realize the construction of the DNA hydrogel-based SERS sensor array. Initially, because of the blocking of the streptavidin (SA)-modified sensor units by the formed DNA hydrogel, the SERS tags (biotin/4-mercaptobenzonitrile-functionalized AuAg alloy nanoparticles (B/M-AuAgNPs)) could not pass through the hydrogel and bind to the SA-modified sensor surface; thus, obvious Raman signals could not be observed. After the introduction of the target miRNA, DNA hydrogels of the corresponding sensor unit were disintegrated accordingly, and SERS tags were able to pass through the hydrogel to be captured onto the SA-modified detection surface, thus resulting in strong Raman signals and the detection of target miRNA. The assay is validated under clean buffer conditions as well as in serum. This target miRNA-responsive DNA hydrogel-based SERS sensor array has attractive application prospects in cancer typing via blood miRNA measurements.

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Here, we report a surface-enhanced Raman scattering (SERS) nanosensor for real-time ratiometric detection of carbon monoxide (CO) based on a ligand displacement mechanism. This nanoprobe consists of a gold-silver (Au-Ag) alloy nanoparticle core as the highly active SERS substrate, an alkyne/ruthenium(II) (alkyne/Ru(II)) complex immobilized on the surface as the CO-sensing element, and a porous silica shell to improve the stability and biocompatibility of the particle. Displacement of the alkyne ligand by CO results in a decrease of the alkyne vibrations and an increase of the metal carbonyl complex signals, thus allowing the effective ratiometric detection of CO in real-time. The great potential of this assay for CO detection is validated in clean buffer environments, live cells, and tissue slices.

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2 In this paper, we developed a novel surface-enhanced Raman scattering (SERS) nanoprobe via the assembly of 3,4-diaminobenzene-thiol on the surface of porous SiO2-coated Au-Ag alloy nanoparticles and successfully applied this for ratiometric imaging analysis of NO in living cells. This nanoprobe exhibits excellent biocompatibility and chemical stability, superior SERS enhancement capacity, and good signal reproducibility. To the best of our knowledge, this is the first report of a porous SiO2-coated Au-Ag alloy nanoparticle and ratiometric-based SERS nanosensor to be used for the detection of NO in living cells.

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We prepared an ultrathin porous silica shell-coated Au-Ag alloy nanoparticle (AuAg@p-SiO2NP) and developed it as a novel alkyne-based surface-enhanced Raman scattering (SERS) nanoprobe for the ratiometric Raman imaging of exogenous and endogenous H2O2 in live cells. The AuAg@p-SiO2NPs functionalized with 4-mercaptophenylboronic acid (MPBA) and 4-mercaptophenylacetylene (MPAE, 1986 cm-1) as internal standard were first incubated with dopamine (DA) to incorporate the bridging molecules through the formation of borate bond between DA and MPBA on the surface of nanoparticle. Then, the signaling alkyne molecules of 3-(4-(phenylethynyl) benzylthio) propanoic acid (PEB, 2214 cm-1) were conjugated to the surface of nanoparticle through the formation of amide bond between the carboxyl group on the PEB and the amino group on the DA, forming the ratiometric SERS nanoprobe. In the presence of H2O2, the alkynyl on the PEB is released from the surface of the Au-Ag alloy nanoparticle due to the boronate-to-phenol switch, decreasing the Raman signal at 2214 cm-1 significantly. Since the Raman signal of MPAE at 1986 cm-1 remains unchanged, quantitative analysis of H2O2 concentration can be achieved based on the ratiometric value of I1986/I2214. Under the optimized conditions, the plot of the ratiometric value of I1986/I2214 versus the H2O2 concentration in the range from 0.12 to 8 µM revealed a good linear response with a detection limit of 52 nM based on a signal-to-noise ratio of S/N = 3. The porous SiO2-coated Au-Ag alloy nanoparticle provides a novel SERS substrate with excellent biocompatibility, high stability, and effective anti-interference ability. Together with the alkynyl derivatives as internal standard, the SERS nanoprobe reported here allows the ratiometric detection of H2O2 in live cells and can be further applied to quantify many other biomolecules by using different signaling agents.

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We report a ratiometric surface-enhanced Raman scattering (SERS) nanoprobe for imaging hypoxic living cells or tissues, using azo-alkynes assembled on a single-walled carbon nanotube (SWCNT) surface-functionalized with Ag/Au alloy nanoparticles (SWCNT/Ag/AuNPs). Under a hypoxic condition, azobenzene derivatives preassembled on the surface of the nanostructures are reduced stepwise by various reductases and eventually removed from the surface of the SWCNT/Ag/AuNPs, resulting in the loss of characteristic alkyne Raman bands at 2207 cm-1. Using 2D-band of SWCNTs at 2578 cm-1 as the internal standard, we are able to determine the hypoxia level based on the ratio of two peak intensities ( I2578/ I2207) as demonstrated by the successful detection in different cell lines and rat liver tissue samples derived from hepatic ischemia surgery. By combining the outstanding anti-interference property of alkynes as SERS reporters and the distinct Raman responses of alkynes and SWCNTs in complex systems, this novel ratiometric SERS strategy holds promise in becoming a very useful tool for in vitro and in vivo monitoring of hypoxia in research and clinical settings.

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