Protein‐Directed Synthesis of Mn‐Doped ZnS Quantum Dots: A Dual‐Channel Biosensor for Two Proteins

Proteins typically have nanoscale dimensions and multiple binding sites with inorganic ions, which facilitates the templated synthesis of nanoparticles to yield nanoparticle–protein hybrids with tailored functionality, water solubility, and tunable frameworks with well‐defined structure. In this work, we report a protein‐templated synthesis of Mn‐doped ZnS quantum dots (QDs) by exploring bovine serum albumin (BSA) as the template. The obtained Mn‐doped ZnS QDs give phosphorescence emission centered at 590 nm, with a decay time of about 1.9 ms. A dual‐channel sensing system for two different proteins was developed through integration of the optical responses (phosphorescence emission and resonant light scattering (RLS)) of Mn‐doped ZnS QDs and recognition of them by surface BSA phosphorescent sensing of trypsin and RLS sensing of lysozyme. Trypsin can digest BSA and remove BSA from the surface of Mn‐doped ZnS QDs, thus quenching the phosphorescence of QDs, whereas lysozyme can assemble with BSA to lead to aggregation of QDs and enhanced RLS intensity. The detection limits for trypsin and lysozyme were 40 and 3 nM , respectively. The selectivity of the respective channel for trypsin and lysozyme was evaluated with a series of other proteins. Unlike other protein sensors based on nanobioconjugates, the proposed dual‐channel sensor employs only one type of QDs but can detect two different proteins. Further, we found the RLS of QDs can also be useful for studying the BSA–lysozyme binding stoichiometry, which has not been reported in the literature. These successful biosensor applications clearly demonstrate that BSA not only serves as a template for growth of Mn‐doped ZnS QDs, but also impacts the QDs for selective recognition of analyte proteins.     

Aptamer‐Based Turn‐On Detection of Thrombin in Biological Fluids Based on Efficient Phosphorescence Energy Transfer from Mn‐Doped ZnS Quantum Dots to Carbon Nanodots

This paper presents the first example of a sensitive, selective, and stable phosphorescent sensor based on phosphorescence energy transfer (PET) for thrombin that functions through thrombin–aptamer recognition events. In this work, an efficient PET donor–acceptor pair using Mn‐doped ZnS quantum dots labeled with thrombin‐binding aptamers (TBA QDs) as donors, and carbon nanodots (CNDs) as acceptors has been constructed. Due to the π–π stacking interaction between aptamer and CNDs, the energy donor and acceptor are taken into close proximity, leading to the phosphorescence quenching of donors, TBA QDs. A maximum phosphorescence quenching efficiency as high as 95.9 % is acquired. With the introduction of thrombin to the “off state” of the TBA‐QDs‐CNDs system, the phosphorescence is “turned on” due to the formation of quadruplex‐thrombin complexes, which releases the energy acceptor CNDs from the energy donors. Based on the restored phosphorescence, an aptamer‐based turn‐on thrombin biosensor has been demonstrated by using the phosphorescence as a signal transduction method. The sensor displays a linear range of 0–40 nM for thrombin, with a detection limit as low as 0.013 nM in pure buffers. The proposed aptasensor has also been used to monitor thrombin in complex biological fluids, including serum and plasma, with satisfactory recovery ranging from 96.8 to 104.3 %. This is the first time that Mn‐doped ZnS quantum dots and CNDs have been employed as a donor–acceptor pair to construct PET‐based biosensors, which combines both the photophysical merits of phosphorescence QDs and the superquenching ability of CNDs and thus affords excellent analytical performance. We believe this proposed method could pave the way to a new design of biosensors using PET systems.     

CuO–ZnO Micro/Nanoporous Array‐Film‐Based Chemosensors: New Sensing Properties to H2S

CuO–ZnO micro/nanoporous array‐films are synthesized by transferring a solution‐dipped self‐organized colloidal template onto a device substrate and sequent heat treatment. Their morphologies and structures are characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectrum analysis. Based on the sensing measurement, it is found that the CuO–ZnO films prepared with the composition of [Cu²⁺]/[Zn²⁺]=0.005, 0.01, and 0.05 all show a nice sensitivity to 10 ppm H₂S. Interestingly, three different zones exist in the patterns of gas responses versus H₂S concentrations: a platform zone, a rapidly increasing zone, and a slowly increasing zone. Further experiments show that the hybrid CuO–ZnO porous film sensor exhibits shorter recovery time and better selectivity to H₂S gas against other interfering gases at a concentration of 10 ppm. These new sensing properties may be due to a depletion layer induced by p–n junction between p‐type CuO and n‐type ZnO and high chemical activity of CuO to H₂S. This work will provide a new construction route of ZnO‐based sensing materials, which can be used as H₂S sensors with high performances.     

基于硫堇掺杂的聚乙烯醇薄膜的光波导传感器检测硫化氢气体

采用旋转甩涂法将硫堇掺杂的聚乙烯醇薄膜固定在K⁺交换玻璃光波导表面,研制出一种高灵敏硫化氢气体传感器。 传感膜与硫化氢(H₂S)气体作用时,薄膜颜色从紫色变为无色,从而降低薄膜对倏逝波的吸收,使传感器的输出光强度（信号）增强。 采用流动注射法对H₂S气体进行检测。 实验结果表明,H₂S传感器对浓度在0.14~56 mg/m3范围的H₂S气体具有良好的线性响应（r=0.99667）,检出限为0.11 mg/m³(S/N=3),相对标准偏差为4.0%,响应时间（t90）＜2 s。 该传感器具有灵敏度高、响应快、可逆性和重复性好等特点。     

Dual‐Reactable Fluorescent Probes for Highly Selective and Sensitive Detection of Biological H2S

Hydrogen sulfide (H₂S) is an important endogenous signaling molecule with a variety of biological functions. Development of fluorescent probes for highly selective and sensitive detection of H₂S is necessary. We show here that dual‐reactable fluorescent H₂S probes could react with higher selectivity than single‐reactable probes. One of the dual‐reactable probes gives more than 4000‐fold turn‐on response when reacting with H₂S, the largest response among fluorescent H₂S probes reported thus far. In addition, the probe could be used for high‐throughput enzymatic assays and for the detection of Cys‐induced H₂S in cells and in zebrafish. These dual‐reactable probes hold potential for highly selective and sensitive detection of H₂S in biological systems.     

Ascorbic Acid Induced Enhancement of Room Temperature Phosphorescence of Sodium Tripolyphosphate‐Capped Mn‐Doped ZnS Quantum Dots: Mechanism and Bioprobe Applications

Although quantum dot (QD)‐based room temperature phosphorescence (RTP) probes are promising for practical applications in complex matrixes such as environmental, food and biological samples, current QD‐based‐RTP probes are not only quite limited but also exclusively based on the RTP quenching mechanism. Here we report an ascorbic acid (AA) induced phosphorescence enhancement of sodium tripolyphosphate‐capped Mn‐doped ZnS QDs, and its application for turn‐on RTP detection. The chelating ability allows AA to extract the Mn and Zn from the surface of the QDs and to generate more holes which are subsequently trapped by Mn²⁺, while the reducing property permits AA to reduce Mn³⁺ to Mn²⁺ in the excited state, thereby enhancing the excitation and orange emission of the QDs. The enhanced RTP intensity of the QDs increases linearly with the concentration of AA in the range of 0.05–0.8 μM . Thus, a QD‐based RTP probe for AA is developed. The proposed QD‐based turn‐on RTP probe avoids tedious sample pretreatment, and offers good sensitivity and selectivity for AA in the presence of the main relevant metal ions and other molecules in biological fluids. The limit of detection (3s) of the developed method is 9 nM AA, and the relative standard deviation is 4.8 % for 11 replicate detections of 0.1 μM AA. The developed method is successfully applied to the analysis of real samples of human urine and plasma for AA with quantitative recoveries from 96 to 105 %.     

Multi‐Fluorinated Azido Coumarins for Rapid and Selective Detection of Biological H2S in Living Cells

Hydrogen sulfide (H₂S) is an endogenously produced gaseous signaling molecule with multiple biological functions. In order to visualize the endogenous in situ production of H₂S in living cells in real time, here we developed multi‐fluorinated azido coumarins as fluorescent probes for the rapid and selective detection of biological H₂S. Kinetic studies indicated that an increase in fluorine substitution leads to an increased rate of H₂S‐mediated reduction reaction, which is also supported by our theoretical calculations. To our delight, tetra‐fluorinated coumarin 1 could react with H₂S fast (t_1/2≈1 min) and selectively, which could be further used for continuous enzymatic assays and for visualization of intracellular H₂S. Bioimaging results obtained with 1 revealed that d ‐Cys could induce a higher level of endogenous H₂S production than l ‐Cys in a time‐dependent manner in living cell.     

In Situ Generation of AgI Quantum Dots by the Confinement of A Supramolecular Polymer Network: A Novel Approach for Ultrasensitive Response

A novel approach for in situ generation of AgI quantum dots by the confinement of a pillar[5]arene‐based supramolecular polymer network has been successfully developed. The supramolecular polymer network ( SPN‐QP ) was constructed by using a bis‐8‐hydroxyquinoline‐modified pillar[5]arene derivative as a host ( H‐QP ) and a bis‐pyridinium‐modified decane as guest ( G‐PD ). The SPN‐QP shows ultrasensitive response for Ag⁺. The limit of detection is about 7.44×10^?9 M.^.Interestingly, when I^? was added to the SPN‐QP +Ag⁺ system, an unexpected strong warm‐white fluorescence emission was observed. After carefu investigation, we found that the strong warm‐white fluorescence emission could be attributed to the in situ formation of AgI quantum dots under the confinement of the supramolecular polymer network ( SPN‐QP ). Based on this approach, ultrasensitive detection of I^? was realized. The limit of detection for I^? is 4.40×10^?9 M. This study provides a new way for the preparation of quantum dots under the confinement of supramolecular polymer network as well as ultrasensitive detection of ions by in situ formation of quantum dots.     

Highly Selective and Sensitive Near‐Infrared‐Fluorescent Probes for the Detection of Cellular Hydrogen Sulfide and the Imaging of H2S in Mice

Herein, we report the development of two fluorescent probes for the highly selective and sensitive detection of H₂S. The probes take advantage of a Cu^II? cyclen complex, which acts as a reaction center for H₂S and as a quencher of BODIPY (boron‐dipyrromethene)‐based fluorophores with emissions at 765 and 680 nm, respectively. These non‐fluorescent probes could only be turned on by the addition of H₂S, and not by other potentially interfering biomolecules, including reactive oxygen species, cysteine, and glutathione. In a chemical system, both probes detected H₂S with a detection limit of 80 nM . The probes were successfully used for the endogenous detection of H₂S in HEK 293 cells, for measuring the H₂S‐release activity of dietary organosulfides in MCF‐7 cells, and for the in vivo imaging of H₂S in mice.     

A Nitro‐Functionalized Metal–Organic Framework as a Reaction‐Based Fluorescence Turn‐On Probe for Rapid and Selective H2S Detection

The toxic gas H₂S has recently emerged as one of the important signaling molecules in biological systems. Thus understanding the production, distribution, and mode of action of H₂S in biological system is important, but the fleeting and reactive nature of H₂S makes it a daunting task. Herein we report a biocompatible, nitro‐functionalized metal–organic framework as reaction‐based fluorescence turn‐on probe for fast and selective H₂S detection. The selective turn‐on performance of MOF remains unaffected even in presence of competing biomolecules.     

Immobilization of the Gas Signaling Molecule H2S by Radioisotopes: Detection,Quantification, and In Vivo Imaging

Hydrogen sulfide (H₂S) has multifunctional roles as a gas signaling molecule in living systems. However, the efficient detection and imaging of H₂S in live animals is very challenging. Herein, we report the first radioisotope‐based immobilization technique for the detection, quantification, and in vivo imaging of endogenous H₂S. Macrocyclic ⁶⁴Cu complexes that instantly reacted with gaseous H₂S to form insoluble ⁶⁴CuS in a highly sensitive and selective manner were prepared. The H₂S concentration in biological samples was measured by a thin‐layer radiochromatography method. When ⁶⁴Cu–cyclen was injected into mice, an elevated H₂S concentration in the inflamed paw was clearly visualized and quantified by Cerenkov luminescence and positron emission tomography (PET) imaging. PET imaging was also able to pinpoint increased H₂S levels in a millimeter‐sized infarcted lesion of the rat heart.     

Water‐Soluble Polymer Functionalized CdTe/ZnS Quantum Dots: A Facile Ratiometric Fluorescent Probe for Sensitive and Selective Detection of Nitroaromatic Explosives

A ratiometric fluorescent probe based on dual luminescence QD/CPL for selective sensing of the nitroaromatic explosive picric acid (PA) was constructed. The observed ratiometric fluorescence intensity change allows the quantitative detection of PA with a detection limit of 9 nM .     

Dimeric [Mo2S12]2− Cluster: A Molecular Analogue of MoS2 Edges for Superior Hydrogen‐Evolution Electrocatalysis

Proton reduction is one of the most fundamental and important reactions in nature. MoS₂ edges have been identified as the active sites for hydrogen evolution reaction (HER) electrocatalysis. Designing molecular mimics of MoS₂ edge sites is an attractive strategy to understand the underlying catalytic mechanism of different edge sites and improve their activities. Herein we report a dimeric molecular analogue [Mo₂S₁₂]^2?, as the smallest unit possessing both the terminal and bridging disulfide ligands. Our electrochemical tests show that [Mo₂S₁₂]^2? is a superior heterogeneous HER catalyst under acidic conditions. Computations suggest that the bridging disulfide ligand of [Mo₂S₁₂]^2? exhibits a hydrogen adsorption free energy near zero (?0.05 eV). This work helps shed light on the rational design of HER catalysts and biomimetics of hydrogen‐evolving enzymes.     

Prussian Blue Nanocubes‐SnO2 Quantum Dots‐Reduced Graphene Oxide Ternary Nanocomposite: An Efficient Non‐noble‐metal Electrocatalyst for Non‐enzymatic Detection of H2O2

Developing non‐noble‐metal electrocatalyst for non‐enzymatic H₂O₂ sensing is highly attractive. A facile, two‐step approach has been utilized for the synthesis of PBNCs/SnO₂ QDs/RGO ternary nanocomposite. TEM, SEM, XPS, and XRD techniques were used to the characterize the structural and morphological properties of synthesized ternary nanocomposite. The synthesized ternary nanocomposite has been examined as an electrode material for the electrochemical detection of H₂O₂ using the Amperometry technique. Under optimum conditions, PBNCs/SnO₂ QDs/RGO ternary nanocomposite performed very well in the electrocatalytic reduction of H₂O₂ with a linear dynamic range from 25–225 μM (R²=0.996) with a low detection limit of 71 nM (S/N=3). Compared to the recent literature, PBNCs/SnO₂QDs/RGO ternary nanocomposite based modified electrode exhibit a wider linear dynamic range with a low detection limit. Furthermore, PBNCs/SnO₂ QDs/RGO ternary nanocomposite based modified electrode showed an excellent anti‐interference ability against various common interfering agents. The practical applicability of this ternary nanocomposite based modified electrode was further extended to determine the H₂O₂ in tap water with acceptable recovery. The present performance of PBNCs/SnO₂ QDs/RGO ternary nanocomposite material towards H₂O₂ sensing might widen its application for developing a new type of non‐noble metal‐based non‐enzymatic electrochemical biosensors.     

Carbon Quantum Dots Co‐catalyzed with ZnO Nanoflowers and Poly (CTAB) Nanosensor for Simultaneous Sensitive Detection of Paracetamol and Ciprofloxacin in Biological Samples

A novel platform based incorporation of carbon quantum dots (CQDs) and zinc oxide nanoflowers (ZnO‐NFs) decorated with poly cetyltrimethylammonium bromide (CTAB) was developed as electrochemical sensor for the sensitive and selective simultaneous detection of Paracetamol (PAR) and Ciprofloxacin (CIP) in biological samples. For this, CQDs and ZnO‐NFs were first deposited on a glassy carbon electrode (GCE) and subsequently a Poly (CTAB) layer was grown onto their surfaces through electro‐polymerization. The synthesized nanostructures and the corresponding fabricated sensor were characterized by the techniques of TEM, XRD, FE‐SEM, and EDX analysis. Moreover electrochemical characterization by CV and DPV were performed to elucidate the construction process and electron transfer abilities of the CQDs/ZnO‐NFs/Poly(CTAB)/GCE. Increased sensitivity and efficiency of this sensing system was obtained due to the synergistic effects of CQDs, ZnO‐NFs and Poly (CTAB) with multi‐signal amplification. Under the optimum conditions, the DPV response of proposed sensor to PAR and CIP was linear at 0.05–30.0 μM and 0.01–30.0 μM, with the detection limit of 2.47 nM and 1.97 nM respectively. The sensor possessed high stability, reproducibility, sensitivity, and selectivity toward PAR and CIP detection, over potential interferents and presented high recovery percentage in the real sample matrices.     

Structure and Composition of the 200 K‐Superconducting Phase of H2S at Ultrahigh Pressure: The Perovskite (SH−)(H3S+)

At ultrahigh pressure (>110 GPa), H₂S is converted into a metallic phase that becomes superconducting with a record T_c of approximately 200 K. It has been proposed that the superconducting phase is body‐centered cubic H₃S (Im m, a=3.089 Å) resulting from the decomposition reaction 3 H₂S→2 H₃S+S. The analogy between H₂S and H₂O led us to a very different conclusion. The well‐known dissociation of water into H₃O⁺ and OH^? increases by orders of magnitude under pressure. H₂S is anticipated to behave similarly under pressure, with the dissociation process 2 H₂S→H₃S⁺+SH^? leading to the perovskite structure (SH^?)(H₃S⁺). This phase consists of corner‐sharing SH₆ octahedra with SH^? ions at each A site (the centers of the S₈ cubes). DFT calculations show that the perovskite (SH^?)(H₃S⁺) is thermodynamically more stable than the Im m structure of H₃S, and suggest that the A site hydrogen atoms are most likely fluxional even at T_c .     

In Situ Growth of MnO2 Nanosheets on N‐Doped Carbon Nanotubes Derived from Polypyrrole Tubes for Supercapacitors

Nitrogen‐doped porous carbon nanotubes@MnO₂ (N‐CNTs@MnO₂) nanocomposites are prepared through the in situ growth of MnO₂ nanosheets on N‐CNTs derived from polypyrrole nanotubes (PNTs). Benefiting from the synergistic effects between N‐CNTs (high conductivity and N doping level) and MnO₂ nanosheets (high theoretical capacity), the as‐prepared N‐CNTs@MnO₂‐800 nanocomposites show a specific capacitance of 219 F g^?1 at a current density of 1.0 A g^?1, which is higher than that of pure MnO₂ nanosheets (128 F g^?1) and PNTs (42 F g^?1) in 0.5 m Na₂SO₄ solution. Meanwhile, the capacitance retention of 86.8 % (after 1000 cycles at 10 A g^?1) indicates an excellent electrochemical performance of N‐CNTs@MnO₂ prepared in this work.