Cysteine–Ag Cluster Hydrogel Confirmed by Experimental and Numerical Studies

The native cysteine (Cys)‐Ag₃ cluster hydrogel is approved for the first time by both experimental and theoretical studies. From the detailed molecular structure and energy information, three factors are found to ensure the self‐assembly of Cys and Ag₃, and result in the hydrogel. First, the Ag–S bonds make Cys and Ag₃ form Cys‐Ag₃‐Cys monomer. Second, intermolecular hydrogen bonds between carboxyl groups of adjacent monomer push them self‐assembled. Third, more monomer precisely self‐assemble to produce the –[Cys‐Ag₃‐Cys]_n multimer, e.g., a single molecular chain with the left‐handed helix conformation, via a benign thermodynamic process. These multimers entangle together to form micro‐network to trap water and produce hydorgel in situ. The hydrogen bonds of hydrogel are sensitive to thermal and proton stimuli, and the hydrogel presents lysosome targeting properties via fluorescent imaging with biocompatibility.     

Preoperative Detection and Intraoperative Visualization of Brain Tumors for More Precise Surgery: A New Dual‐Modality MRI and NIR Nanoprobe

In clinical practice, it is difficult to identify tumor margins during brain surgery due to its inherent infiltrative character. Herein, a unique dual‐modality nanoprobe (Gd‐DOTA‐Ag₂S QDs, referred as Gd‐Ag₂S nanoprobe) is reported, which integrates advantages of the deep tissue penetration of enhanced magnetic resonance (MR) imaging of Gd and the high signal‐to‐noise ratio and high spatiotemporal resolution of fluorescence imaging in the second near‐infrared window (NIR‐II) of Ag₂S quantum dots (QDs). Due to the abundant tumor angiogenesis and the enhanced permeability and retention effect in the tumor, a brain tumor (U87MG) in a mouse model is clearly delineated in situ with the help of the Gd assisted T1 MR imaging and the intraoperative resection of the tumor is precisely accomplished under the guidance of NIR‐II fluorescence imaging of Ag₂S QDs after intravenous injection of Gd‐Ag₂S nanoprobe. Additionally, no histologic changes are observed in the main organs of the mouse after administration of Gd‐Ag₂S nanoprobe for 1 month, indicating the high biocompatibility of the nanoprobe. We expect that such a novel “Detection and Operation” strategy based on Gd‐Ag₂S nanoprobe is promising in future clinical applications.     

Quantitative Analysis of Multiple Proteins of Different Invasive Tumor Cell Lines at the Same Single‐Cell Level

Tumor cell invasion is pivotal to the development, metastasis, and prognosis of tumors. It is reported that the invasive ability of tumor cells is mainly dependent on the expression levels of membrane type‐1 matrix metalloproteinase (MT1‐MMP) and integrin α_Vβ₃ proteins on cell membranes. To precisely distinguish between tumor cells with different invasive abilities, it is important to establish a highly sensitive and precise quantification method to differentiate the expression levels of MT1‐MMP and integrin α_Vβ₃ in the same single tumor cell at the same time. Herein, two functional peptides to construct red‐emissive Au₂₆ clusters and green‐emissive Ag₁₂ clusters are reported. Moreover, the Au₂₆ clusters and Ag₁₂ clusters have the ability to specifically target MT1‐MMP and integrin α_Vβ₃, respectively, in the same single cell at the same time. By utilizing the fluorescent properties and metallic compositions of metal clusters, the MT1‐MMP and integrin α_Vβ₃ levels of the more invasive SiHa cells or the less invasive HeLa cells are simultaneously and quantitatively differentiated via laser ablation inductively coupled plasma mass spectrometry. This method of quantitatively detecting multiple invasive proteins on the same cell is of great value for accurately diagnosing aggressive tumors and monitoring the invasiveness of these tumors.     

Near‐Infrared Fluorescent Ag2Se–Cetuximab Nanoprobes for Targeted Imaging and Therapy of Cancer

Theranostic nanoprobes integrated with diagnostic imaging and therapy capabilities have shown great potential for highly effective tumor therapy by realizing imaging‐guided drug delivery and tumor treatment. Developing novel high‐performance nanoprobes is an important basis for tumor theranostic application. Here, near‐infrared (NIR) fluorescent and low‐biotoxicity Ag₂Se quantum dots (QDs) have been coupled with cetuximab, a clinical antiepidermal growth factor receptor antibody drug for tumor therapy, via a facile bioconjugation strategy to prepare multifunctional Ag₂Se–cetuximab nanoprobes. Compared with the Ag₂Se QDs alone, the Ag₂Se–cetuximab nanoprobes display faster and more enrichment at the site of orthotopic tongue cancer, and thus present better NIR fluorescence contrast between the tumor and the surrounding regions. At 24 h postinjection, the NIR fluorescence of Ag₂Se–cetuximab nanoprobes at the tumor site is still easily detectable, whereas no fluorescence is observed for the Ag₂Se QDs. Moreover, the Ag₂Se–cetuximab nanoprobes have also significantly inhibited the tumor growth and improved the survival rate of orthotopic tongue cancer‐bearing nude mice from 0% to 57.1%. Taken together, the constructed multifunctional Ag₂Se–cetuximab nanoprobes have achieved combined targeted imaging and therapy of orthotopic tongue cancer, which may greatly contribute to the development of nanotheranostics.     

Self‐Destruction of Cancer Induced by Ag2S Amorphous Nanodots

Studies on distinctive performances and novel applications of amorphous inorganic nanomaterials are becoming attractive. Herein, Ag₂S amorphous and crystalline nanodots (ANDs and CNDs) are prepared via facile methods. In vitro and in vivo studies indicate that Ag₂S ANDs, rather than CNDs, can induce the self‐destruction of tumors, which can be attributed to their distinctive chemical properties, e.g., the higher electrochemical active surface area and lower redox potential well matching with the redox reaction requirement in the tumor microenvironment. Ag₂S ANDs can be oxidized by intracellular reactive oxygen species (ROS) to release Ag⁺, which further stimulates high generation of intracellular ROS. This mutual stimulation damages the mitochondria, induces apoptosis, and leads to the self‐destruction of the tumor. Moreover, Ag₂S ANDs do not show observable in vitro and in vivo side effects. These findings provide a promising self‐destructive strategy for cancer therapy by utilizing distinctive chemical properties of inorganic nanomaterials, while avoiding complicated external assistance.     

Ultrasmall Pb:Ag2S Quantum Dots with Uniform Particle Size and Bright Tunable Fluorescence in the NIR‐II Window

Ag₂S quantum dots (QDs) are well‐known near‐infrared fluorophores and have attracted great interest in biomedical labeling and imaging in the past years. However, their photoluminescence efficiency is hard to compete with Cd‐, Pb‐based QDs. The high Ag⁺ mobility in Ag₂S crystal, which causes plenty of cation deficiency and crystal defects, may be responsible mainly for the low photoluminescence quantum yield (PLQY) of Ag₂S QDs. Herein, a cation‐doping strategy is presented via introducing a certain dosage of transition metal Pb²⁺ ions into Ag₂S nanocrystals to mitigate this intrinsic shortcoming. The Pb‐doped Ag₂S QDs (designated as Pb:Ag₂S QDs) present a renovated crystal structure and significantly enhanced optical performance. Moreover, by simply adjusting the levels of Pb doping in the doped nanocrystals, Pb:Ag₂S QDs with bright emission (PLQY up to 30.2%) from 975 to 1242 nm can be prepared without altering the ultrasmall particle size (≈2.7–2.8 nm). Evidently, this cation‐doping strategy facilitates both the renovation of crystal structure of Ag₂S QDs and modulation of their optical properties.     

Facile Aqueous‐Phase Synthesis of Biocompatible and Fluorescent Ag2S Nanoclusters for Bioimaging: Tunable Photoluminescence from Red to Near Infrared

Low toxicity and fluorescent nanomaterials have many advantages in biological imaging. Herein, a novel and facile aqueous‐phase approach to prepare biocompatible and fluorescent Ag₂S nanoclusters (NCs) is designed and investigated. The resultant Ag₂S NCs show tunable luminescence from the visible red (624 nm) to the near infrared (NIR; 724 nm) corresponding to the increasing size of the NCs. The key for preparing tunable fluorescent Ag₂S NCs is the proper choice of capping reagent, glutathione (GSH), and the novel sulfur‐hydrazine hydrate complex as the S^2? source. As a naturally occurring and readily available tripeptide, GSH functions as an important scaffold to prevent NCs from growing large nanoparticles. Additionally, GSH is a small biomolecule with several functional groups, including carboxyl and amino groups, which suggests the resultant Ag₂S NCs are well‐dispersed in aqueous solution. These advantages make the as‐prepared Ag₂S NCs potentially applicable to biological labeling as well. For example, the resultant Ag₂S NCs are used as a probe for MC3T3‐EI cellular imaging.     

Simultaneous Adjustment of Size and Helical Sense of Chiral Nanospheres and Nanotubes Derived from an Axially Racemic Poly(phenylacetylene)

Nanospheres and nanotubes with full control of their size and helical sense are obtained in chloroform from the axially racemic chiral poly(phenylacetylene) poly‐(R)‐ 1 using either Ag⁺ as both chiral inducer and cross‐linking agent or Na⁺ as chiral inducer and Ag⁺ as cross‐linking agent. The size is tuned by the polymer/ion ratio while the helical sense is modulated by the polymer/cosolvent (i.e., MeCN) ratio. In this way, the helicity and the size of the nanoparticles can be easily interconverted by very simple experimental changes.     

Influence of implanted Fe on the Kerr effect of Co6Ag94 granular films

A magneto-optical chip of Fe–(Co₆Ag₉₄) granular films was fabricated by using of combinatorial Fe ions implanting into co-sputtered Co₆Ag₉₄ films and 16 units with different Fe content were prepared via binary masking scheme. The structures and surface morphologies of as-prepared and annealed Fe–Co₆Ag₉₄ films were analyzed by X-ray diffraction and atomic force microscopy respectively. It reveals that the Co, Fe and FeCo granules precipitate, grow and then form nanoparticles embedded in the Ag matrix during annealing. In addition, the measurement of the magneto-optic polar Kerr effect shows that Kerr rotation increases with increasing Fe content, which contributes to the magnetic moment. Precipitation and growth of the magnetic granules during annealing also increase the Kerr rotation due to the size effects. Further, Mössbauer study confirms that the formation of granules with certain size plays a principal role in the enhancement of magneto-optic polar Kerr effect.     

Room temperature synthesis and electrochemical application of imidazoline surfactant-modified Ag2S nanocrystals

Well-dispersed Ag₂S nanocrystals with size of about 20~30 nm were prepared in distilled water at room temperature with the assistance of imidazoline surfactant quaternary ammonium salt of 2-undecyl-1-dithioureido-ethyl-imidazoline (SUDEI) prepared in-house. The products were characterized by TEM, XRD, and FT-IR, respectively. The influence of SUDEI concentration on the dispersion of Ag₂S products was briefly discussed. Furthermore, the obtained Ag₂S nanocrystals product was applied into DNA hybridization analysis, and the results indicated that the detection limit of target ssDNA was up to pmol/L, showing that the DNA probe labeled with Ag₂S nanoparticles is of promising application value in electrochemical DNA detection analysis and biosensors.     

Synthesis of SERS active Ag2S nanocrystals using oleylamine as solvent,reducing agent and stabilizer

Semiconductor Ag₂S nanocrystals have been prepared via a facile solution growth method, in which AgNO₃ and sulfur (S) powder are used as precursors, oleylamine is used and can function as both reducing agent and stabilizer during the synthetic process. The experimental results demonstrate that the as-synthesized Ag₂S nanocrystals, which have uniform size are monoclinic Ag₂S. Furthermore, surface-enhanced Raman scattering (SERS) spectrum of rhodamine 6G can be obtained on the Ag₂S nanocrystals modified substrate, indicating novel optical response of Ag₂S nanocrystals. The SERS effect of Ag₂S nanocrystals should attract much interest in fundamental physics as well as device application points of view.     

Hybrid Nanoparticle Pyramids for Intracellular Dual MicroRNAs Biosensing and Bioimaging

This study strategically fabricates multifunctional nanopyramids to allow the ultrasensitive quantification of dual microRNAs (miR‐203^b and miR‐21) in living cells and their responsive bioimaging in vivo. The nanopyramids, composed of Au‐Cu₉S₅ nanoparticles (NPs), upconversion NPs (UCNPs), and Ag₂S NPs, emit two luminescent signals simultaneously with excitation at 808 nm, arising from the UCNPs at 541 nm in the visible region and from the Ag₂S NPs at 1227 nm in the second window of near‐infrared (NIR‐II) region. The upconversion luminescence has a linear relationship with miR‐203^b from 0.13 to 54.54 fmol per 10 µg_RNA and a limit of detection (LOD) of 0.09 fmol per 10 µg_RNA, whereas the Ag₂S NP luminescence has a linear relationship with miR‐21 from 0.37 to 43.56 fmol per 10 µg_RNA, with a LOD of 0.23 fmol per 10 µg_RNA. Significantly, this study demonstrates that the nanopyramids can be successfully used for miRs‐responsive bioimaging in a tumor‐bearing animal model. Furthermore, taking advantage of the photothermal capabilities of pyramids, the tumors can also be eliminated completely. These nanopyramids not only overcome the obstacles in the simultaneous detection of multiple miRs at the cellular level but also provide a cancer theranostic platform in vivo.     

Bactericidal effects of different silver-containing materials

The evaluation of the bactericidal effect of different silver-containing materials where silver is available as Ag⁺ (silver nitrate and different silver-exchanged zeolites), as metallic Ag⁰ (commercial silver nanoparticles) or as oxide (silver (I) oxide) was carried out in order to elucidate the importance of the bioavailability of silver (i.e., as free ions, metallic particles, combination of them, clusters, complexes, partially soluble or insoluble salts, etc.) on its bactericidal action.For the different materials tested, their bactericidal effect is ordered in the following sequence: AgNO₃ > Ag-ZSM-5 > Ag₂O > commercial silver-exchanged zeolite (granular) > commercial silver-exchanged zeolite (pellets) > Ag nanoparticles. In general, as the content of bioavailable ionic silver increases, the biocidal effectiveness of the corresponding silver-releasing material increases too.     

Palm‐Sized Ag+ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere

Ion implantation is an effective method for changing surface properties and inducing various functionalities. However, a high vacuum is generally necessary for ion implantation, which limits the range of applications. Here, we describe a palm‐sized Ag⁺ ion emission gun produced using a solid electrolyte. AgI–Ag₂O–B₂O₃ glass, known as a super‐ion‐conducting glass, has a Ag⁺ ion conductivity higher than 5 × 10^?3 S cm^?1 at room temperature. In addition, the melted glass has suitable viscous flow, and a sharp glass‐fiber emitter with a pyramid‐like apex can be obtained. Ag⁺ ion emission is observed from the tip of the glass fiber at accelerating voltages corresponding to electric fields above 20 kV cm^?1, even at room temperature in a non‐vacuum atmosphere. Ag nanoparticles of size 50–350 nm are precipitated on a Si target substrate. Other glass components such as boron and iodine are not detected. Electrochemical quartz crystal microbalance (EQCM) measurements show that the mass of Ag nanoparticles estimated from the emission current using Faraday's law of electrolysis is in good agreement with that estimated from the QCM frequency shift.

     

Activity Trends of Binary Silver Alloy Nanocatalysts for Oxygen Reduction Reaction in Alkaline Media

The electrocatalytic activity of Pt‐based alloys exhibits a strong dependence on their electronic structures, but a relationship between electronic structure and oxygen reduction reaction (ORR) activity in Ag‐based alloys is still not clear. Here, a vapor deposition based approach is reported for the preparation of Ag₇₅M₂₅ (M = Cu, Co, Fe, and In) and Ag_x Cu_100?x (x = 0, 25, 45, 50, 55, 75, 90, and 100) nanocatalysts and their electronic structures are determined by valence band spectra. The relationship of the d‐band center and ORR activity exhibits volcano‐shape behaviors, where the maximum catalytic activity is obtained for Ag₇₅Cu₂₅ alloys. The ORR enhancement of Ag₇₅Cu₂₅ alloys originates from the 0.12 eV upshift in d‐band center relative to pure Ag, which is different from the downshift in the d‐band center in Pt‐based alloys. The activity trend for these Ag₇₅M₂₅ alloys is in the order of Ag₇₅Cu₂₅ > Ag₇₅Fe₂₅ > Ag₇₅Co₂₅. These results provide an insight to understand the activity and stability enhancement of Ag₇₅Cu₂₅ and Ag₅₀Cu₅₀ catalysts by alloying.     

Multilayer Amorphous‐Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 Membranes for Hydrogen Purification

The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H₂ can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single‐step under high temperature conditions. In the present work, the multilayer amorphous‐Si‐B‐C‐N/γ‐Al₂O₃/α‐Al₂O₃ membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H₂/CO permeance. The α‐Al₂O₃ support has a bimodal pore‐size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate γ‐Al₂O₃ layer—deposited from boehmite colloidal dispersion—has an average pore‐size of 8 nm being mesoporous. The results obtained by the N₂‐adsorption method indicate a decrease in the volume of micropores—0.35 vs. 0.75 cm³ g^?1—and a smaller pore size ?6.8 vs. 7.4 Å—in membranes with the intermediate mesoporous γ‐Al₂O₃ layer if compared to those without. The three times Si‐B‐C‐N coated multilayer membranes show higher H₂/CO permselectivities of about 10.5 and the H₂ permeance of about 1.05 × 10^?8 mol m^?2 s^?1 Pa^?1. If compared to the state of the art of microporous membranes, the multilayer Si‐B‐C‐N/γ‐Al₂O₃/α‐Al₂O₃ membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high‐temperature and high‐pressure stability.     

Enhancement of photocatalytic activity and stability of Ag2CO3 by formation of AgBr/Ag2CO3 heterojunction in mordenite zeolite

Two serious problems for semiconductor photocatalysts are their poor photocatalytic activity and low stability. In this work, Ag₂CO₃ nanoparticles incorporated in mordenite zeolite (MOR) by a facile precipitation method. Silver bromide (AgBr) with different weight percentage (20%, 40% and 50%) was coupled into Ag₂CO₃-MOR composite and producing a series of novel AgBr/Ag₂CO₃-MOR nanocomposites. The effects of AgBr on the Ag₂CO₃–MOR catalyst for the photocatalytic degradation of methyl blue (MB) under visible light irradiation have been investigated. The structure, composition and optical properties of nanocomposites were investigated by UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM). The prepared AgBr/Ag₂CO₃-MOR photocatalyst with the optimal content of AgBr (50 wt%) indicated higher photocatalytic activity than that of the Ag₂CO₃-MOR and Ag₂CO₃ for degradation of methylene blue (MB) under visible light irradiation. For studying of stability of nanocomposites, Fe⁺³ ions, as a cheap and available cocatalyst, was inserted into mordenite matrix (Fe³⁺/MOR) by impregnation method. The hybrid material (AgBr/Ag₂CO₃) was synthesized in the Fe³⁺/MOR matrix by precipitation method. The cycle experiments on the AgBr/Ag₂CO₃-Fe/MOR nanocomposite indicated that cocatalyst, not only to improve photocatalytic activity, but also enhance photoinduced stability of photosensitive silver compounds in all cycles with respect to MOR. On the basis of the experimental results, a possible mechanism for the enhanced photocatalytic activity and photoinduced stability of silver compounds by Fe³⁺ cocatalyst was proposed. The mordenite support played an important role in decreases of recombination of photogenerated electrons-holes and increases of MB absorption. The Fe cocatalyst reduced photocorrosion of silver compounds.     

Controllable preparation of Ag2S quantum dots with size-dependent fluorescence and cancer photothermal therapy

Although Ag₂S quantum dots (QDs) have attracted extensive attention in the fields of diagnosis and therapy, it is still a challenge to prepare Ag₂S QDs with well-controlled size distribution. Herein, size-tunable Ag₂S QDs with glutathione (GSH) as ligands were prepared via a facile aqueous precipitation method. The QDs are precisely prepared through carefully controlled growth of Ag2S QDs by varying the heating time. Morphology and structure characterization verify that Ag₂S QDs with 2.0–5.8 nm in diameter are coordinated with GSH through thiol group. The as-prepared Ag₂S QDs exhibit broad absorption spectra and narrow fluorescence emission spectra in the near-infrared region. Meanwhile, the QDs perform excellent and stable photothermal effect with a photothermal conversion efficiency up to 58.6%. More importantly, it is found that the size of Ag₂S QDs has a significant influence on the fluorescence intensity and photothermal effect. The cell viability evaluation in vitro demonstrates that Ag₂S QDs have low cytotoxicity to 293 T cells and Hela cells by methyl thiazolyl tetrazolium test. This paper proposes a convenient route to prepare unique Ag₂S QDs, which are capable to act as ideal theranostics probes for photothermal therapy and simultaneously monitoring the therapeutic effect for effective cancer treatment.     

Evolution of Ag3Sn compounds and microhardness of Sn3.5Ag0.5Cu nano-composite solders during different cooling rate and aging

This paper presents the microstructure and Vickers microhardness of Sn3.5Ag0.5Cu solder doped with trace amounts of TiO₂ nanopowders, obtained with different cooling rate and aging conditions. The experiment results that the coupling effect by cooling rate and TiO₂ nanopowders additions significantly affected primary β-Sn phase, Ag₃Sn grain size and spacing of the Ag₃Sn phase, as well as the morphology of Ag₃Sn. Ag₃Sn was relatively spherical at the water-cooling rate and had a needle-like morphology at the air-cooling rate. However, the Ag₃Sn IMC not obviously roughed after aging time at 125 °C for 7 days. Due to both nano-Ag₃Sn IMC and uniform microstructure of the nano-composite solders, the Vickers microhardness improved, in good agreement with the prediction of the classic theory of dispersion strengthening. It appears that adding trace TiO₂ nanopowders are an efficient way to develop novel high-performance solders.     

Effect of Ag content on the microstructure development of Sn-Ag-Cu interconnects

The impact of the Ag content on the microstructure development of the Sn-xAg-Cu (x= 0.0, 1.2, 2.6, 3.0, 3.5 and 3.9) interconnects was studied in detail by using surface microetching microscopy, cross section microscopy, differential scanning calorimetry and shear test. The thermal treatment was realized by conducting isothermal aging (150 ^∘C/1000 hrs). i) Ag content had a clear effect on the interconnect microstructure evolution. ii) Ag₃Sn intermetallic compound (IMC) plates were sophisticated microtextures with various morphologies and the basic microstructure of the Ag₃Sn plates had a morphology of a strengthened fan. iii) The Ag₃Sn plates grew in central symmetry. iv) The Cu-Sn IMC microstructures were also influenced by the Ag content, but to a lesser degree. iv) The occurrence of the Ag₃Sn plates did not exactly follow the trend of Ag content increase, but was governed more by the alloy undercooling. For the given Cu content, the undercooling of the alloy groups demonstrated a quasi-parabolic behavior with a minimum apex. vi) After aging, there were size recession and sharp edge smoothening for the Ag₃Sn plates after aging. These phenomena are explained by edge spheroidization and cylinderization of the Ag₃Sn plates during the aging. vii) The corresponding macro-mechanical performance of the LF interconnects did not degrade after the aging, independent to the Ag content.