Simple synthesis of silver nanocluster composites AgNCs@PE-g-PAA by irradiation method and fluorescence detection of Cr^(3+)

Silver nanoclusters(AgNCs)are a new type of nanomaterials with similar properties to molecules and unique applications.The applications of AgNCs can be significantly expanded by combining them with different matrix materials to obtain AgNC composites.Using irradiation techniques,we developed a simple two-step method for preparing silver nanocluster composites.First,polyacrylic acid(PAA)chains were grafted onto the surface of a PE film as templates(PE-g-PAA).Subsequently,silver ions were reduced in situ on the surface of the template material to obtain the AgNC composites(AgNCs@PE-g-PAA).The degree of AgNC loading on the composite film was easily controlled by adjusting the reaction conditions.The loaded AgNCs were anchored to the carboxyl groups of the PAA and wrapped in the graft chain.The particle size of the AgNCs was only 4.38±0.85 nm,with a very uniform particle size distribution.The AgNCs@PE-g-PAA exhibited fluorescence characteristics derived from the AgNCs.The fluorescence of the AgNCs@PE-g-PAA was easily quenched by Cr^(3+)ions.The composite can be used as a fluorescence test paper to realize visual detection of Cr^(3+).

MOLECULAR DYNAMICS SIMULATION OF STRUCTURE STABILITY OF SILVER NANOCLUSTERS

The structures of Ag clusters with sizes n=13 to 1157 are studied by tight binding molecular dynamics simulation. It is found that the stable structures of Ag clusters follow the sequence amorphous-crystalline-amorphous-crystalline with the cluster size increasing from 13 to 1157. Furthermore, all the shells of Ag clusters are different from the structure of the corresponding bulk Ag.

Ag7(MBISA)6 Nanoclusters Conjugated with Quinacrine for FRET-Enhanced Photodynamic Activity under Visible Light Irradiation

Singlet oxygen(1 O2) plays an important role in various applications, such as in the photodynamic therapy(PDT) of cancers,photodynamic inactivation of microorganisms, photo-degradation of toxic compounds, and photo-oxidation in synthetic chemistry. Recently,water-soluble metal nanoclusters(NCs) have been utilized as photosensitizers for the generation of highly reactive 1 O2 because of their high water solubility, low toxicity, and surface functionalizability for targeted substances. In the case of metal NC-based photosensitizers, the photo-physical properties depend on the core size of the NCs and the core/ligand interfacial structures. A wide range of atomically precise gold NCs have been reported; however, reports on the synthesis of atomically precise silver NCs are limited due to the high reactivity and low photostability(i.e., easy oxidation) of Ag NCs. In addition, there have been few reports on what kinds of metal NCs can generate large amounts of 1 O2. In this study, we developed a new one-pot synthesis method of water-soluble Ag7(MBISA)6(MBISA= 2-mercapto-5-benzimidazolesulfonic acid sodium salt) NCs with highly efficient 1 O2 generation ability under the irradiation of white light emitting diodes(LEDs). The molecular formula and purity were determined by electrospray ionization mass spectrometry and gel electrophoresis. To the best of our knowledge, this is the first report on atomically precise thiolate silver clusters(Agn(SR)m) for efficient 1 O2 generation under visible light irradiation. The 1 O2 generation efficiency of Ag7(MBISA)6 NCs was higher than those of the following known water-soluble metal NCs: bovine serum albumin(BSA)-Au25 NCs,BSA-Ag8 NCs, BSA-Ag14 NCs,Ag25(dihydrolipoic acid)14 NCs,Ag35(glutathione)18 NCs,and Ag75(glutathione)40 NCs. The metal NCs examined in this study showed the following order of 1 O2 generation efficiency under white light irradiation: Ag7(MBISA)6 > BSA-Ag14 > Ag75(SG)40 > Ag35(SG)18 >BSA-Au25 >>BSA-Ags(not detected) and Ag2 s(DHLA)14(not detected). For further improving the 1 O2 generation of Ag7(MBISA)6 NCs, we developed a novel fluorescence resonance energy transfer(FRET) system by conjugating Ag7(MBISA)6 NCs with quinacrine(QC)(molar ratio of Ag NCs to QC is 1 : 0.5). We observed the FRET process,from QC to Ag7(MBISA)6 NCs,occurring in the conjugate. That is,the QC works as a donor chromophore,while the Ag NCs work as an acceptor chromophore in the FRET process. The FRET-mediated process caused a 2.3-fold increase in 1 O2 generation compared to that obtained with Ag7(MBISA)6 NCs alone. This study establishes a general and simple strategy for improving the PDT activity of metal NC-based photosensitizers.

Angle-sensitive and fast photovoltage of silver nanocluster embeded ZnO thin films induced by 1.064-μm pulsed laser

Silver nanocluster embedded ZnO composite thin film was observed to have an angle-sensitive and fast photovoltaic effect in the angle range from -90° to 90° , its peak value and the polarity varied regularly with the angle of incidence of the 1.064-μm pulsed Nd：YAG laser radiation onto the ZnO surface. Meanwhile, for each photovoltaic signal, its rising time reached -2 ns with an open-circuit photovoltage of -2 ns full width at half-maximum. This angle-sensitive fast photovoltaic effect is expected to put this composite film a candidate for angle-sensitive and fast photodetector.

Preparation of antibacterial non-woven AgNCs@PP-g-PAA via radiation method

With the growing threat of airborne epidemics,there has been an increasing emphasis on personal protection.Masks serve as our primary external defense against bacteria and viruses that might enter the respiratory tract.Hence,it’s crucial to develop a polypropylene(PP)nonwoven fabric with quick antibacterial capabilities as a key component for masks.This study introduces silver nanoclusters(AgNCs)into non-woven PP using radiation technology to infuse antibacterial properties.Initially,a solid ligand(PP-g-PAA)was procured via radiation grafting of the ligand polyacrylic acid(PAA),which was incorporated into the nonwoven PP with the aid of a crosslinking agent at a lower absorbed dosage.Subsequently,AgNCs were synthesized in situ on PP-g-PAA via an interaction between PAA and AgNCs,leading directly to the formation of AgNCs@PP-g-PAA composites.Owing to the hydrophilicity of PAA,AgNCs@PP-g-PAA maintains good moisture permeability even when the voids are heavily saturated with PAA gel,preventing droplet aggregation by diffusing droplets on the surface of the material.This feature enhances the comfort of the masks.Most importantly,due to the incorporation of AgNCs,AgNCs@PP-g-PAA demonstrates outstanding antibacterial effects against Escherichia coli and Staphylococcus aureus,nearly achieving an instant“touch and kill”outcome.In conclusion,we synthesized a modified nonwoven fabric with significant antibacterial activity using a simple synthetic route,offering a promising material that provides improved personal protection.

以卡托普利为模板银纳米团簇的制备及生物硫醇的检测研究

生物硫醇在生物体内的代谢过程中起着重要作用,如体内半胱氨酸(Cys)和谷胱甘肽(GSH)含量异常会引发一系列疾病。为了建立一种快速、定量检测生物硫醇的荧光分析方法,本文以卡托普利(Captopril,Capt)为模板,采用湿化学还原法成功合成了发红色荧光的银纳米团簇(Capt-Ag NCs),对Capt-Ag NCs的形貌、结构、元素组成和光学性能等进行了表征。基于生物硫醇小分子对Capt-Ag NCs的荧光猝灭作用建立了定量检测Cys和GSH的新方法,在最佳实验条件下,Cys和GSH的线性范围分别为1~100μmol/L和2~180μmol/L,检出限分别为0.054μmol/L和0.23μmol/L。该方法可用于人血浆中Cys的测定,回收率为95.3%~103.3%。实验结果表明,CaptAg NCs作为一种新型信号关闭荧光探针,可用于Cys和GSH等生物硫醇的检测。

荧光桃红B稳定剂制备银纳米簇及用于盐酸小檗碱的检测

本文以荧光桃红B为稳定剂,硝酸银为前驱体,硼氢化钠为还原剂,混合反应4 h制备得到具有荧光特性的银纳米簇(AgNCs)。实验显示,所合成的AgNCs的最佳激发波长为339 nm,最佳发射波长为444 nm。研究发现盐酸小檗碱(BH)能使合成的AgNCs的荧光显著猝灭,当BH浓度在1.25~12.50μmol/L范围内时,AgNCs的荧光强度的猝灭值(ΔI F)与BH浓度之间呈良好的线性关系,相关系数r为0.9958。基于此建立了一种测定BH的荧光分析方法,该方法的检出限为0.41μmol/L。同时,以紫外灯对体系进行照射时,pH浓度在3.75~12.50μmol/L范围时,溶液的颜色与pH浓度之间呈现梯度变化,因此可以建立一种更为简单的可视化检测BH的半定量检测方法。

基于银纳米簇比色传感器快速检测水果维生素C的方法

为提升水果品质分析效率,建立了基于银纳米簇比色传感器快速检测水果维生素C的方法。该方法以偏磷酸溶液萃取水果中的维生素C,以石墨化炭黑吸附干扰物质。以硝酸银水溶液和聚甲基丙烯酸钠水溶液混合加热搅拌4 h制备聚甲基丙烯酸修饰的银纳米簇材料,银纳米簇为球形,银纳米簇的平均直径为1 nm,加入维生素C以后,维生素C还原银离子从而增大了银纳米簇的尺寸并改变了银纳米簇溶液的光学性能,通过溶液颜色在感观上深浅变化和RGB色彩模式下蓝色值变化可实现维生素C含量的裸眼半定量分析和手机定量分析。在优化得到最佳检测条件后,结果表明,该检测方法可检出的维生素C最小含量为0.03 mg/kg,可定量的维生素C最小含量为0.1 mg/kg;该检测方法对葡萄糖、果糖、蔗糖、钙离子、锌离子、钾离子、叶酸等物质表现出了较好的抗干扰能力;该检测方法成功应用于橙、葡萄和梨果实维生素C的分析。将银纳米簇材料应用于水果的品质分析,有助于加快检测速度,降低检测成本,实现水果的精准快速分级。

沸石限域银纳米团簇发光材料的研究进展

沸石限域银纳米团簇具有制备方法简单、成本低、发光性能优异和稳定性好等优点,是一类具有广阔前景的新型发光材料,在发光二极管(Light emitting diode,LED)照明、防伪和传感等高新技术领域具有较高的应用价值,近来逐渐受到中外学者的广泛关注。本文总结了近年来沸石限域银纳米团簇的研究进展,重点讨论了这类发光材料的制备方法、发光性能调控以及它们在白光LED照明和小分子荧光检测方面的应用。此外,本文对该领域未来的发展进行了展望。

酪蛋白-金银合金纳米簇的制备及其对金霉素的荧光检测

以酪蛋白为保护剂和还原剂,采用优化的一锅加热合成方法,成功制备一种新型金银合金纳米簇(Au-AgNCs@casein)。产物在325 nm最佳激发波长下有双荧光发射峰,通过红外光谱、透射电子显微镜等方法对其进行结构表征。在常见离子或氨基酸存在下,金霉素(CTC)可明显增强比率型探针Au-AgNCs@casein的荧光,其结构类似物却无明显影响。因此,本研究中制备的纳米簇可快速、灵敏、选择性检测CTC。

Superatomic Ag_(58) nanoclusters incorporating a [MS_(4)@Ag_(12)]^(2+)(M = Mo or W) kernel show aggregation-induced emission

In core-shell silver nanoclusters,the control of core structure presents a more formidable challenge compared to that of the shell structure.Here,we report the successful synthesis and characterization of four distinct silver thiolate nanoclusters[MS_(4)@Ag_(12)@Ag_(46)S_(24)(dppb)_(12)](M=Mo or W),each incorporating a cup-like[MS_(4)@Ag_(12)]^(2+)kernel.These nanoclusters were meticulously prepared using(NH_(4))2Mo S4or(NH_(4))_(2)WS_(4)as both a template and a controlled source of S2-ions.Remarkably,we have observed a unique configuration within these eight-electron superatomic Ag_(58) nanoclusters,where the zerovalent Ag atoms reside exclusively within the inner[MS_(4)@Ag_(12)]^(2+)kernel.This stands in contrast to other superatomic clusters possessing an Ag(0)core.Notably,the introduction of phenyl-containing compounds during the synthesis process induced a transformation in the space group symmetry from C_(2)/c to I 4ˉ.This transformative effect was found to originate from the interplay between adjacent 1,4-bis(diphenylphosphino)butane(dppb)ligands,which facilitated enhanced emission through aggregationinduced intermolecular interactions,specifically C-H···πinteractions.Collectively,our findings contribute substantively to the understanding of the intricate relationship between nanocluster structures and their corresponding properties,shedding light on the crucial roles played by templates and diphosphine ligands in this context.

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide （Ag2S） nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands （Ag44（SR）30 and Agla（GSH）9） are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag2S nanoparticles with controllable sizes （4-16 nm） and switchable solvent affinity （between aqueous and organic solvents）. This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag2S nanopartides.

How G-quadruplex topology and loop sequences affect optical properties of DNA-templated silver nanoclusters

In the study of the fabrication of DNA-templated silver nanoclusters （DNA-Ag NCs）, how templates affect the fluorescence of the nanoclusters remains undear, and it has been a challenge to understand the correlation between the properties of the DNA template and the Ag NCs. In this respect, based on the rational design of a series of structurally defined intramolecular G-quadruplexes, we prepared G-quadruplex-templated Ag NCs with a defined G-tetrad-to-silver ratio of 1：2. We evaluated the effect of G-quadruplex topology and loop sequences on the fluorescence of DNA-Ag NCs using circular dichroism, and extinction and emission spectroscopy. G-quadruplex templates with an anti-parallel topology were found to produce Ag NCs with stronger fluorescence compared with parallel and hybrid configurations. Loop bases adjacent to G-tetrads have a more significant impact on the fluorescence of Ag NCs compared with those in the middle of the loop, with adenine largely exhibiting an enhancement effect and thymine being detrimental. Generally, G-quadruplexes having an anti-parallel topology with adenine in the loop adjacent to the G-tetrad would be good templates for producing highly fluorescent Ag NCs. This is the first study to focus on the correlation between G-quadruplex topology/sequence and the optical properties of Ag NCs. We hope that the results of this study will facilitate a more in-depth understanding of correlation between G-quadruplex templates and Ag NCs, and help to understand and utilize their unique attributes.

Temperature-dependent chloride-mediated access to atom-precise silver thiolate nanoclusters

By using a unique temperature-dependent,chloride-mediated approach,two atom-precise silver nanoclusters[Cl@Ag_(14)(Tab)_(12)-(C_(5)H_(4)NCl)_(12)](PF_(6))_(13)(Cl@Ag_(14))and[Cl_(3)@Ag_(24)(Tab)_(20)(C_(5)H_(4)NCl)_(11)]Cl(PF_(6))_(20)(Cl_(3)@Ag_(24))(Tab=4-(trimethylammonio)benzenethiolate,C_(5)H_(4)NCl=3-chloropyridine)were obtained successfully.Notably,the number of chloride ions encapsulated inside the Ag-S shell could be regulated by the slow dissolution of almost insoluble KCl at various temperatures.The inclusion of additional core chloride ions results in the expansion of the surrounding Ag-S shell.This article provides a promising synthetic approach for controlling the number of Ag atoms that form a shell around the anionic core,in addition to offering a potential pathway for the introduction of other inorganic anions into silver clusters.More broadly,through the use of related ligands,the synthetic strategy offers scope for generating new families of silver thiolate clusters of varying size and composition.

Ratiometric fluorescence detection of bleomycin based on proximity-dependent fluorescence conversion of DNA-templated silver nanoclusters

We design a ratiometric fluo rescent sensing platform for bleomycin(BLM) by using proximity-dependent DNA-templated silver nanoclusters(DNA-AgNCs) probe.This ratiometric sensing system is constructed with DNA-AgNCs as single fluorophore.The proposed strategy is based on the two following facts:(1) a covert DNA can approach and transform the DNA-AgNCs with green emission(G-DNA-AgNCs) into red emission through hybridization reaction.(2) The specific cleavage of the convert DNA by BLM in the presence of Fe(Ⅱ) inhibits the discoloration of G-DNA-AgNCs.Thus,benefiting from the specific recognition of BLM and unique properties of G-DNA-AgNCs,a hignly-sensitive ratiometric sensor for BLM has been successfully developed.The detection limit is as low as 30 pmol/L.This label-free fluorescence probe possesses advantages of convenient synthetic process and low cost.Moreover,this ratiometric method has been applied to the detection of BLM in human serum samples,illustrating a promising tool for analysis of BLM in cancer therapy.

Core engineering of paired core-shell silver nanoclusters

Unlike the facile modulation of surface structure through protecting ligands,the core shielded by outer shell of silver nanoclusters is still hard to be controlled.Ligand effects may seep into the incipient growth of silver core.However,the comparable cases to validate such hypothesis are currently lacking.Herein,we shed light on two core-shell silver nanoclusters,Ag_(7)S_(6)@Ag_(48)(SD/Ag55b,SD=SunDi)and Ag_(6)S_(6)@Ag_(48)(SD/Ag54b),differing in only one silver atom in the core which varies from a pentagon-bipyramidal Ag_(7)to an octahedral Ag_(6)while keeping the Ag_(48)shielding shell almost the same.Although no direct bonding between alkynes and silver core is observed in them,we propose that the ligand effect still exerts profound influences on the size and geometry of silver core.The solution behaviours and complete ligand-exchange reaction of SD/Ag55b in CH_(2)Cl_(2)are investigated using electrospray ionization mass spectrometry.Due to more and stronger argentophilic interactions,SD/Ag55b exhibits room-temperature phosphorescence with a 40 nm red-shift compared to that of SD/Ag54b in CH_(2)Cl_(2).This work not only presents effective fabrication of silver nanoclusters via synergism of dithiophosphate and alkyne ligands,but also provides us a pair of comparable examples to understand substitution group effect of protecting ligand on the core structures and properties.

Luminescent silver nanoclusters for efficient detection of adenosine triphosphate in a wide range of pH values

In this work,polymethacrylic acid(PMAA)-templated silver nanoclusters(Ag NCs)were developed as the fluorescent probe for the efficient and sensitive detection of adenosine triphosphate(ATP)in a wide range of pH values.The fluorescence intensity of the Ag NCs could keep stable with pH values ranging from2.5 to 9.3.The detection of ATP was based on the quenching of the fluorescent Ag NCs in the presence of ATP.The fluorescence quenching of the Ag NCs with increasing ATP concentration was studied at pH 2.5,4.5,7.0 and 8.5 which involved a wide pH environment in body fluids.The limit of detection(LOD)for ATP was as low as 0.1 mmol/L in an acidic environment with pH of 2.5 and all the linear correlation coefficients were satisfactory under wide-span pH values from 2.5 to 8.5.In addition,the sensitive determination of ATP was also achieved by adding copper ions(Cu^2+).The high selectivity and rapid detection process proved that the fluorescent probe had great potential to detect ATP in biological samples under different pH conditions.

Alkynyl-anchored silver nanoclusters in lanthanide metal-organic framework for luminescent thermometer and CO_(2) cycloaddition

In this study,an alkynyl-modified aromatic dicarboxylic acid bifunctional ligand was selected to construct lanthanide compound{[Eu_(4)(ebdc)_(6)(4,4-bpy)_(0.5)(H_(2)O)_(4.5)]·(C_(2)H_(5)OH)_(1.25)(H_(2)O)}_(n)(Eu-MOF,H_(2)ebdc=5-ethynyl-isophthalic acid,4,4-bpy=4,4-bipyridine,MOF=metal-organic framework),of which the uncoordinated alkynyl group would be used to anchor silver nanoclusters(Ag NCs).The Eu-MOF exhibits double emission peaks,located at 492 and 611 nm,respectively,in which the high-energy blue emission is associated with alkynyl-modified ligand while the low-energy red emission belongs to characteristic emission of Eu3+,indicating that ligands can effectively sensitize Eu3+luminescence.The intensity ratio of the dual emission fluorescence peaks of Eu-MOF displays a good linear relationship with temperature,which realizes the detection function in the low temperature region of 75–275 K,the thermal sensitivity reaches 1.5398%·K^(−1).After anchoring the Ag NCs,the high-energy blue emission is significantly quenched,indicating that the Ag NCs are indeed confined into the framework and interact with the alkynyl group,and thus change the overall electronic distribution.This is the first case of anchoring Ag NCs by a luminescent Eu-MOF and studying nanocluster loading by using spectroscopic properties.In addition,the Ag NCs@Eu-MOF also shows a good catalytic activity for cycloaddition reaction from CO_(2)and epoxides.This study not only provides ideas for exploring the changes in optical properties of luminescent MOFs and Ag NCs caused by confinement effect,but also expands their potential applications in various fields.

基于HCR放大的无标记型荧光传感器的构建及H5N1 DNA检测

对于高致病性H5N1禽流感病毒,构建检测该病毒的高灵敏生物传感器,并与智能包装相结合用于实时监测,这对禽流感的防控具有重要意义。基于杂交链式反应(HCR)信号放大策略,以AgNCs作为荧光信号基团,构建了一种无标记“turn on”型荧光生物传感器用于检测代表H5N1病毒的H5N1基因序列。该传感器以H5N1 DNA作为触发剂引发HCR过程,使AgNCs产生强的荧光信号变化。研究表明,当H5N1 DNA浓度在0.2~800.0 nmol/L内,该传感器具有良好的响应信号,且在0.2~200.0 nmol/L之间的荧光强度与H5N1 DNA浓度呈线性相关,线性方程为y=10.982C+567.435(R^(2)=0.99273),检测限为176 pmol/L。核酸传感体系具有通用性,通过简单调整目标序列,可实现对不同目标物的特异性灵敏检测。该研究有望为高灵敏分析禽流感病毒标志物的通用传感平台设计提供思路。

Host molecule enhanced aggregation induced emission of chiral silver nanoclusters for achieving highly efficient circularly polarized electroluminescence

Chiral metal nanoclusters(MNCs)are competitive candidates for fabricating circularly polarized light-emitting diodes(CPLEDs),but the device performance is greatly limited by the poor emission of MNCs in solid thin films.Herein,host molecule enhanced aggregation induced emission(AIE)of MNCs is demonstrated for fabricating highly efficient CPLEDs.Namely,on the basis of the AIE effect of atomically precise enantiomeric(R/S)-4-phenylthiazolidine-2-thione capped silver(R/S-Ag_(6)(PTLT)_(6))NCs in solid thin films,1,3-bis(carbazol-9-yl)benzene(mCP)is introduced as a host molecule to control the orientation and packing arrangements of R/S-Ag_(6)(PTLT)_(6) NCs throughπ–πinteractions with the R/S-Ag_(6)(PTLT)_(6) NCs and further enhance the AIE.The as-fabricated Ag_(6)(PTLT)_(6) NC/mCP hybrid solid thin film shows a high photoluminescence quantum yield of 71.0%close to that of Ag_(6)(PTLT)_(6) NC single crystal.As the hybrid films are employed as the active emission layers of CPLEDs,mCP also suppresses the triplettriplet annihilation and balances the charge transport.Thus,the CPLEDs exhibit a maximum brightness of 3,906 cd/m^(2),peak external quantum efficiency of 10.0%,electroluminescence dissymmetry factors of−5.3×10^(−3)and 4.7×10^(−3).