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1.
We prepared four differently shaped Te nanomaterials (NMs) as antibacterial reagents against Escherichia coli. By controlling the concentrations of hydrazine (N2H4) as reducing agent, NaCl, and temperature, we prepared Te nanowires, nanopencils, nanorices, and nanocubes. These four Te NMs resulted in a live/dead ratio of E. coli cells of less than 0.1, which is smaller than that of Ag nanoparticles. The order of antibacterial activity against E. coli is nanocubes ≈ nanorices > nanopencils ≈ nanowires. This is in good agreement with the concentration order of tellurite (TeO32−) ions released from Te NMs in E. coli cells, revealing that TeO32− ions account for the antibacterial activity of the four Te NMs. We found that spherical Te nanoparticles (32 nm in diameter) with TeO32− ions were formed in the E. coli cells. Compared to Ag nanoparticles that are commonly used as antibacterial reagents, Te NMs have higher antibacterial activity and lower toxicity. Thus, Te NMs hold great practical potential as a new and efficient antibacterial agent.  相似文献   

2.
A novel antimicrobial nanohybrid based on near‐infrared (NIR) photothermal conversion is designed for bacteria capture, separation, and sterilization (killing). Positively charged magnetic reduced graphene oxide with modification by polyethylenimine (rGO–Fe3O4–PEI) is prepared and then loaded with core–shell–shell Au–Ag–Au nanorods to construct the nanohybrid rGO–Fe3O4–Au–Ag–Au. NIR laser irradiation melts the outer Au shell and exposes the inner Ag shell, which facilitates controlled release of the silver shell. The nanohybrids combine physical photothermal sterilization as a result of the outer Au shell with the antibacterial effect of the inner Ag shell. In addition, the nanohybrid exhibits high heat conductivity because of the rGO and rapid magnetic‐separation capability that is attributable to Fe3O4. The nanohybrid provides a significant improvement of bactericidal efficiency with respect to bare Au–Ag–Au nanorods and facilitates the isolation of bacteria from sample matrixes. A concentration of 25 μg mL?1 of nanohybrid causes 100 % capture and separation of Escherichia coli O157:H7 (1×108 cfu mL?1) from an aqueous medium in 10 min. In addition, it causes a 22 °C temperature rise for the surrounding solution under NIR irradiation (785 nm, 50 mW cm?2) for 10 min. With magnetic separation, 30 μg mL?1 of nanohybrid results in a 100 % killing rate for E. coli O157:H7 cells. The facile bacteria separation and photothermal sterilization is potentially feasible for environmental and/or clinical treatment.  相似文献   

3.
Herein we describe the preparation and structure‐activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin‐resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12–0.25 μg mL?1 and against Staphylococcus spp. with MICs ranging from 2–4 μg mL?1. The derivative 17 showed increased activity with MICs of 0.06–0.25 μg mL?1 against M. catarrhalis and 0.12–1 against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 μg mL?1 and clindamycin with MICs of ≤0.5 μg mL?1. As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development.  相似文献   

4.
Heterasumanenes 4 – 6 containing chalcogen (S, Se, and Te) and phosphorus atoms have been synthesized in a one‐pot reaction from trichalcogenasumanenes 1 – 3 by replacing one chalcogen atom with a P=S unit. The P=S unit makes 4 – 6 almost planar and shrinks the HOMO–LUMO gap as compared to 1 – 3 . The bonding between Ag+ and S atom on P=S brings about a distinct change to the optical properties of 4 – 6 ; 4 in particular shows a selective fluorescence response toward Ag+ with LOD of 0.21 μm . Compounds 4 – 6 form complexes with AgNO3 to be ( 4 )2?AgNO3, ( 5 )2?AgNO3, and ( 6 )2?(AgNO3)3. In complexes, the coordination between Ag+ and P=S is observed, which leads to shrinkage of C?P and C?X (X=S, Se, Te) bond lengths. As a result, 4 , 5 , and 6 are all bowl‐shaped in complexes with bowl‐depths reaching to 0.66 Å, 0.42 Å, and 0.40 Å, respectively. There are Ag?Te dative bonds between Ag+ and Te atom on telluorophene in ( 6 )2?(AgNO3)3.  相似文献   

5.
Heterasumanenes 4 – 6 containing chalcogen (S, Se, and Te) and phosphorus atoms have been synthesized in a one‐pot reaction from trichalcogenasumanenes 1 – 3 by replacing one chalcogen atom with a P=S unit. The P=S unit makes 4 – 6 almost planar and shrinks the HOMO–LUMO gap as compared to 1 – 3 . The bonding between Ag+ and S atom on P=S brings about a distinct change to the optical properties of 4 – 6 ; 4 in particular shows a selective fluorescence response toward Ag+ with LOD of 0.21 μm . Compounds 4 – 6 form complexes with AgNO3 to be ( 4 )2?AgNO3, ( 5 )2?AgNO3, and ( 6 )2?(AgNO3)3. In complexes, the coordination between Ag+ and P=S is observed, which leads to shrinkage of C?P and C?X (X=S, Se, Te) bond lengths. As a result, 4 , 5 , and 6 are all bowl‐shaped in complexes with bowl‐depths reaching to 0.66 Å, 0.42 Å, and 0.40 Å, respectively. There are Ag?Te dative bonds between Ag+ and Te atom on telluorophene in ( 6 )2?(AgNO3)3.  相似文献   

6.
MOF-5 that sometimes called IRMOF-1 has been intensively studied in recent years to develop efficient photocatalyst to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, Ag/Ag3PO4 nanoparticles incorporated in IRMOF-1 was successfully prepared via hydrothermal approach. The antibacterial activity of synthesized materials (IRMOF-1, Ag/Ag3PO4 nanoparticles and Ag/Ag3PO4-IRMOF-1 nanocomposite was compared against two types of bacteria (Escherichia coli (E. coil) as Gram negative and Staphylococcus aureus (S. aureus) as Gram-positive bacteria). The deactivation of the bacteria by the prepared material was measured in the dark and under visible light irradiation. The antibacterial activity of synthesized samples was investigated by determining the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), growth inhibition assay and inhibition zone. The Ag/Ag3PO4-IRMOF-1 nanocomposite exhibited stronger antibacterial activities than the Ag/Ag3PO4 nanoparticles and IRMOF-1 at all tested bacteria types. Based on inhibition zone, without any light irradiation, Ag/Ag3PO4-IRMOF-1 nanocomposite showed activity toward E. coil, but in presence of light nanocomposite depicted activity toward S. aureus. The results demonstrated that antibacterial activity of all synthesized samples in the dark and light against S. aureus bacteria was more than E. coil bacteria. The antibacterial activity mechanism was due to sustained-release of silver ions in the dark and reactive oxygen species (ROS) under visible light. The bioactivity of IRMOF-1 was related to the degradation of the its structure and the release of Zn2+ ions into the culture medium that bind to the cell wall and deactivation bacteria.  相似文献   

7.
A facile method was used to prepare hollow mesoporous TiO2 and Au@TiO2 spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl4? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO2 core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO2 spheres with Au NPs inside the TiO2 shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO2 shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO2 spheres.  相似文献   

8.
An assembly strategy for metal nanoclusters using electrostatic interactions with weak interactions, such as C?H???π and π???π interactions in which cationic [Ag26Au(2‐EBT)18(PPh3)6]+ and anionic [Ag24Au(2‐EBT)18]? nanoclusters gather and assemble in an unusual alternating array stacking structure is presented. [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]? is a new compound type, a double nanocluster ion compound (DNIC). A single nanocluster ion compound (SNIC) [PPh4]+ [Ag24Au(2‐EBT)18]? was also synthesized, having a k‐vector‐differential crystallographic arrangement. [PPh4]+ [Ag24Au(2,4‐DMBT)18]? adopts a different assembly mode from both [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]? and [PPh4]+ [Ag24Au(2‐EBT)18]?. Thus, the striking packing differences of [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]?, [PPh4]+ [Ag24Au(2‐EBT)18]? and the existing [PPh4]+ [Ag24Au(2,4‐DMBT)18]? from each other indicate the notable influence of ligands and counterions on the self‐assembly of nanoclusters.  相似文献   

9.
A two‐step optimization strategy is used to improve the thermoelectric performance of SnTe via modulating the electronic structure and phonon transport. The electrical transport of self‐compensated SnTe (that is, Sn1.03Te) was first optimized by Ag doping, which resulted in an optimized carrier concentration. Subsequently, Mn doping in Sn1.03?xAgxTe resulted in highly converged valence bands, which improved the Seebeck coefficient. The energy gap between the light and heavy hole bands, i.e. ΔEv decreases to 0.10 eV in Sn0.83Ag0.03Mn0.17Te compared to the value of 0.35 eV in pristine SnTe. As a result, a high power factor of ca. 24.8 μW cm?1 K?2 at 816 K in Sn0.83Ag0.03Mn0.17Te was attained. The lattice thermal conductivity of Sn0.83Ag0.03Mn0.17Te reached to an ultralow value (ca. 0.3 W m?1 K?1) at 865 K, owing to the formation of Ag7Te4 nanoprecipitates in SnTe matrix. A high thermoelectric figure of merit (z T≈1.45 at 865 K) was obtained in Sn0.83Ag0.03Mn0.17Te.  相似文献   

10.
Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL1) and 2‐[(5‐methyl‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL2), and their Pd(II), Ni(II) and Co(II) complexes were prepared and characterized using 1H NMR, 13C NMR, infrared and UV–visible spectroscopic techniques, elemental analysis, magnetic susceptibility, thermogravimetry and molar conductance measurements. The infrared spectral data showed that the chelation behaviours of the ligands towards the transition metal ions were through one of the carbonyl oxygen and deprotonated nitrogen atom of the secondary amine group. Molar conductance results confirmed that the complexes are non‐electrolytes in dimethylsulfoxide. The geometries of the complexes were deduced from magnetic susceptibility and UV–visible spectroscopic results. Second‐order perturbation analysis using density functional theory calculation revealed a stronger intermolecular charge transfer between ligand and metal ion in [NiL1(H2O)2(CH3COO‐)] and CoL1 compared to the other complexes. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities. [NiL1(H2O)2(CH3COO‐)] exhibited the best antibacterial results with a minimum inhibitory concentration of 50 μg mL?1. The molecular interactions of the compounds with various drug targets of some bacterial organisms were established in a bid to predict the possible mode of antibacterial action of the compounds. The ferrous ion chelating ability of the ligands indicated that HL1 is a better Fe2+ ion chelator, with an IC50 of 29.79 μg mL?1, compared to HL2 which had an IC50 of 98.26 μg mL?1.  相似文献   

11.
Synthesis of atom‐precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18]? cluster (SR: thiolate) using a pure [Ag25(SR)18]? cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag25?xAux(SR)18]?, x=1–8. Mass spectrometry and crystallography of [Ag24Au(SR)18]? reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single‐atom level.  相似文献   

12.
A polymeric silver(I) complex, [Ag4(μ-pydc)2(μ-pm)2]n (1) (pydc = pyridine-3,5-dicarboxylate and pm = pyrimidine), has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. X-ray crystallographic data of 1 revealed that pydc exhibits two different coordinaton modes that play a key role in the construction of the 3-D crystal network including Ag–carboxylate clusters in which close Ag–Ag distances exist. The magnitudes of close Ag–Ag interactions in second-order energy (E2) have been revealed by natural bond orbital analysis performed with single point energy calculation using the experimental geometry of 1. Furthermore, the luminescent properties of 1 show strong fluorescence with two emission maxima in the visible region. Also, 1 has antifungal activity on Candida albicans (MIC value, 4 μg mL?1) and good antibacterial activity on micro-organisms (MIC value, 64–256 μg mL?1).  相似文献   

13.
Au core Ag shell composite structure nanoparticles were prepared using a sol method. The Au core Ag shell composite nanoparticles were loaded on TiO2 nanoparticles as support using a modified powder–sol method, enabling the generation of Au @ Ag/TiO2 photocatalysts for photocatalytic decomposition and elimination of ozone. The sols were characterized by means of ultraviolet–visible light (UV–Vis) reflection spectrometry, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The activity of the Au @ Ag/TiO2 photocatalysts for photocatalytic decomposition and elimination of ozone was evaluated and the effect of Cl? anions on the photocatalytic activity of the catalysts was highlighted. Results showed that Au @ Ag/TiO2 prepared via the modified powder–sol route in the presence of an appropriate amount of NaCl solid as demulsifier had better activity in the photocatalytic decomposition and elimination of ozone. At the same time, Au @ Ag/TiO2 catalysts had better ability to resist poisonous Cl? anions than conventional Au/TiO2 catalyst. The reasons could be, first, that NaCl was capable of reducing the concentration of free Ag+ by adsorption on the surface of Ag particles forming AgCl and enhancing the formation of Au core Ag shell particles, leading to a better resistance to Cl? anions of the catalysts, and, second, AgCl took part in the photocatalytic decomposition of ozone together with Au @ Ag/TiO2 catalysts and had a synergistic effect on the latter, resulting in better photocatalytic activity of Au @ Ag/TiO2 catalysts.  相似文献   

14.
Two spectrophotometric methods, a photochemical and a non-photochemical, for the determination of ascorbic acid in soft drinks and beer using a flow-injection system are proposed. The non-photochemical method is based on the redox reaction that takes place between ascorbic acid and Fe(III), yielding dehydroascorbic acid and Fe(II). Fe(II) reacts with 1,10-phenantroline, originating the reddish orange Fe(phen)3 2+ complex (ferroin). This complex is spectrophotometrically monitored at 512 nm, and the signal is directly related to the concentration of ascorbic acid in the sample. The photochemical method has the same basis, nevertheless, uses the irradiation with visible light to enhance the redox reaction and so achieve higher sensitivities in the analysis. The non-photochemical method shows a linear range between 5 and 80 μg mL?1, with a relative standard deviation of 1.6% (n = 11), a detection limit of 2.7 μg mL?1 and a sample throughput of ¶60 samples h?1. The photochemical method shows a linear range between 1 and 80 μg mL?1, with a relative standard deviation of 1.0% (n = 11), a detection limit of 0.5 μg mL?1 and a sample throughput of 40 samples h?1.  相似文献   

15.
In a tannic acid assisted synthesis of mesoporous TiO2, tannic acid was used as a cost effective and non‐toxic template for pore formation. Meanwhile, a gold nanoparticles (Au NPs) deposited TiO2 nanocomposite was coated on an indium tin oxide electrode for the fabrication of a photoelectrochemical (PEC) biosensing system. Upon the formation of anatase structure, the electrode was coated with MoS2 for effective visible light absorption. The mesoporous structure led to an enhanced surface area by improving Au NPs and glucose oxidase adsorption. Incorporation of Au NPs led to an enhanced photonic efficiency due to the generation of Schottky barriers. The obtained nanocomposite was used for the light‐driven, real‐time, and selective PEC glucose sensing. Under visible light irradiation, the enzyme immobilized electrodes yielded significant photocurrent improvement owing to the releasing electron donor H2O2. The obtained PEC biosensor demonstrated acceptable reproducibility and stability with a sensitivity of 4.42 μA mM?1 cm?2 and a low detection limit of 1.2 μM glucose. Also, the linear measurement range was found to be 0.004–1.75 mM glucose. The results indicated that the proposed production method of mesoporous TiO2 will pave the way for a green chemistry based porous material production, along with the extension of the implementation of semiconductors in PEC biosensing systems.  相似文献   

16.
Abstract

The chemical composition of Tussilago farfara L. essential oil from the Saguenay-Lac-St-Jean region of Quebec, Canada was analyzed by gas chromatography–flame ionisation detector (GC-FID) and gas chromatography–mass spectrometry (GC-MS), and the antibacterial activity of the oil was tested against Escherichia coli and Staphylococcus aureus. Forty-five (45) compounds were identified from the GC profile. The main components were 1-nonene (40.1%), α-phellandrene (26.0%) and ρ-cymene (6.6%). The essential oil demonstrated antibacterial activity against E. coli (MIC50 = 468 µg·mL?1; MIC90 = 6869 µg·mL?1) and S. aureus (MIC50 = 368 µg·mL?1; MIC90 = 773 µg·mL?1). Dodecanoic acid was found to be active against both bacteria having a MIC50 and MIC90 of 16.4 µg·mL?1 and 95 µg·mL?1, respectively for E. coli and a MIC50 and MIC90 of 9.8 µg·mL?1 and 27.3 µg·mL?1, respectively for S. aureus. In addition, 1-decene and (E)-cyclodecene were also found to be active against E. coli.  相似文献   

17.
α‐Synuclein (α‐SYN) is a very important neuronal protein that is associated with Parkinson’s disease. In this paper, we utilized Au‐doped TiO2 nanotube arrays to design a photoelectrochemical immunosensor for the detection of α‐SYN. The highly ordered TiO2 nanotubes were fabricated by using an electrochemical anodization technique on pure Ti foil. After that, a photoelectrochemical deposition method was exploited to modify the resulting nanotubes with Au nanoparticles, which have been demonstrated to facilitate the improvement of photocurrent responses. Moreover, the Au‐doped TiO2 nanotubes formed effective antibody immobilization arrays and immobilized primary antibodies (Ab1) with high stability and bioactivity to bind target α‐SYN. The enhanced sensitivity was obtained by using {Ab2‐Au‐GOx} bioconjugates, which featured secondary antibody (Ab2) and glucose oxidase (GOx) labels linked to Au nanoparticles for signal amplification. The GOx enzyme immobilized on the prepared immunosensor could catalyze glucose in the detection solution to produce H2O2, which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of TiO2 nanotubes upon irradiation of the other side of the Ti foil and led to a prompt photocurrent. The photocurrents were proportional to the α‐SYN concentrations, and the linear range of the developed immunosensor was from 50 pg mL?1 to 100 ng mL?1 with a detection limit of 34 pg mL?1. The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for protein detection.  相似文献   

18.
Although many plasmonic nanosenosrs have been established for the detection of mercury(Ⅱ)(Hg2+),few of them is feasible for analyzing natural samples with very complex matrices because of insufficient method selectivity.To address this challenge,we propose an epitaxial and lattice-mismatch approach to the synthesis of a unique Au/Ag2S dimeric nanostructure,which consists of an Au segment with excellent plasmonic characteristics,and a highly stable Ag2S portion wi...  相似文献   

19.
A visible light driven, direct Z‐scheme reduced graphene oxide–Ag3PO4 (RGO–Ag3PO4) heterostructure was synthesized by means of a simple one‐pot photoreduction route by varying the amount of RGO under visible light illumination. The reduction of graphene oxide (GO) and growth of Ag3PO4 took place simultaneously. The effect of the amount of RGO on the textural properties and photocatalytic activity of the heterostructure was investigated under visible light illumination. Furthermore, total organic carbon (TOC) analysis confirmed 97.1 % mineralization of organic dyes over RGO–Ag3PO4 in just five minutes under visible‐light illumination. The use of different quenchers in the photomineralization suggested the presence of hydroxyl radicals ( . OH), superoxide radicals ( . O2?), and holes (h+), which play a significant role in the mineralization of organic dyes. In addition to that, clean hydrogen fuel generation was also observed with excellent reusability. The 4 RGO–Ag3PO4 heterostructure has a high H2 evolution rate of 3690 μmol h?1 g?1, which is 6.15 times higher than that of RGO.  相似文献   

20.
Hydrogen production from coal gasification provides a cleaning approach to convert coal resource into chemical energy, but the key procedures of coal gasification and thermal catalytic water–gas shift (WGS) reaction in this energy technology still suffer from high energy cost. We herein propose adopting a solar–driven WGS process instead of traditional thermal catalysis, with the aim of greatly decreasing the energy consumption. Under light irradiation, the CuOx/Al2O3 delivers excellent catalytic activity (122 μmol gcat?1 s?1 of H2 evolution and >95 % of CO conversion) which is even more efficient than noble‐metal‐based catalysts (Au/Al2O3 and Pt/Al2O3). Importantly, this solar‐driven WGS process costs no electric/thermal power but attains 1.1 % of light‐to‐energy storage. The attractive performance of the solar‐driven WGS reaction over CuOx/Al2O3 can be attributed to the combined photothermocatalysis and photocatalysis.  相似文献   

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