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Phase transformations that take place in nanocrystalline Ag2S silver sulfide have been systematically studied at temperatures from 298 to 893 K. The crystal structures of the polymorphic modifications α-Ag2S, β-Ag2S, and γ-Ag2S of nanocrystalline Ag2S have been found. It is established that the interstitial spacings between ions of silver in the superionic phases β-Ag2S and γ-Ag2S are noticeably smaller than diameter of the Ag+ ion. As a result of which, the probabilities of filling the sites of the metal sublattices of these phases with Ag atoms are very small. It was found that the “α-Ag2S—β-Ag2S” and “β-Ag2S—γ-Ag2S” transitions between polymorphic modifications of silver sulfide occur as phase transformations of the first order at temperatures of ~440–442 K and ~850–860 K. The structure of interface forming by nanostructured Ag2S and ZnS is considered, taking into account the anisotropy of elastic properties of these sulfides. It is established that a large amount of cubic zinc sulfide stabilizes the cubic structure of β-Ag2S argentite at 300 K during the co-deposition of Ag2S/ZnS heteronanostructures from colloid solutions. It is found that placing Ag atoms at four crystallographic positions located in one plane of the unit cell of cubic β-Ag2S argentite is most favorable for the appearance of Ag2S/ZnS heterostructures. The smallest strain distortions at the interface are observed at the minimum difference of shear moduli of the components forming heteronanostructure. The distributions of elastic characteristics, including the shear moduli of monocrystalline particles of cubic β-Ag2S argentite and ZnS sphalerite from the [hkl] direction, are found. The formation of Ag2S/ZnS heteronanostructures, in which the interface is formed by the (hk0) ≡ (110) plane of ZnS sphalerite and the (hk 0.4123) ≡ (1 1 0.4123) plane of β-Ag2S argentite, is the most energetically favorable.

Z-scheme Ag2S/BiFeO3 heterojunction composites were successfully prepared through a precipitation method. The morphology and microstructure characterization demonstrate that Ag2S nanoparticles (30–50 nm) are well-decorated on the surfaces of polyhedral BiFeO3 particles (500–800 nm) to form Ag2S/BiFeO3 heterojunctions. The photocatalytic and photo-Fenton catalytic activities of the as-derived Ag2S/BiFeO3 heterojunction composites were evaluated by the degradation of methyl orange (MO) under visible-light irradiation. The photocatalytic result indicates that the Ag2S/BiFeO3 composites exhibit much improved photocatalytic activities when compared with bare Ag2S and BiFeO3. The optimum composite sample was observed to be 15% Ag2S/BiFeO3 with an Ag2S mass fraction of 15%. Furthermore, the addition of H2O2 can further enhance the dye degradation efficiency, which is due to the synergistic effects of photo- and Fenton catalysis. The results of photoelectrochemical and photoluminescence measurements suggest a greater separation of the photoexcited electron/hole pairs in the Ag2S/BiFeO3 composites. According to the active species trapping experiments, the photocatalytic and photo-Fenton catalytic mechanisms of the Ag2S/BiFeO3 composites were proposed and discussed.

In this work, a series of carbon nanotubes (CNT)/Ag2S hybrid nanocomposites were successfully prepared by a facile precipitation method. Transmission electron microscope (TEM) observation indicates that Ag2S nanoparticles with an average particle size of ~25 nm are uniformly anchored on the surface of CNT. The photocatalytic activities of the CNT/Ag2S nanocomposites were investigated toward the degradation of rhodamine B (RhB) under visible and near-infrared (NIR) light irradiation. It is shown that the nanocomposites exhibit obviously enhanced visible and NIR light photocatalytic activities compared with bare Ag2S nanoparticles. Moreover, the recycling photocatalytic experiment demonstrates that the CNT/Ag2S nanocomposites possess excellent photocatalytic stability. The photoelectrochemical and photoluminescence measurements reveal the efficient separation of photogenerated charges in the CNT/Ag2S nanocomposites. This is the dominant reason behind the improvement of the photocatalytic activity. Based on active species trapping experiments, the possible photocatalytic mechanism of CNT/Ag2S nanocomposites for dye degradation under visible and NIR light irradiation was proposed.

Myoglobin (Mb), an important cardiac marker, plays a crucial role in diagnosing, monitoring, and evaluating the condition of patients with cardiovascular diseases. Here, we propose a label-free photoelectrochemical (PEC) sensor for the detection of Mb through target regulated the photoactivity of Ag 2 S/FeOOH heterojunction. The Ag 2 S/FeOOH nanospindles were synthesized and served as a sensing platform for the fabrication of bio-recognized process for Mb. Mb-aptamer was used as the responsive group to grasp the target Mb in a real sample due to its advantages of strong affinity, high stability, and ease of preparation. Mb-aptamer immunocomplex is formed in the presence of Mb, which hinders the interfacial electron transfer and then reduce the photocurrent. The proposed PEC aptasensor exhibited excellent analytical performance including wide linear range (1.0 pg mL −1  ~ 50 ng mL −1 ), low limit of detection (0.28 pg mL −1 ), and good selectivity and stability. This work introduces an innovative approach to PEC aptasensor, offering a promising method for precise determination of human biomarkers. Graphical Abstract

Due to their special features, quantum dots have recently attracted the attention of researchers in the fields of imaging, drug delivery, and cancer treatment. In this study, we prepared Ag 2 S quantum dots (QDs) intending to control the nucleus growth and reduce toxicity in Artemisia dracunculus (tarragon) extract substrate using the green synthesis method. Synthesized nanoparticles were analyzed using different characterization techniques. The DLS data analysis showed that Ag 2 S QDs prepared by the green synthesis method have a mean size of 56 nm, which is smaller compared to chemical synthesis. Additionally, the synthesis of Ag 2 S QDs with tarragon extract decreased the zeta potential from − 13 eV to -21 eV, which can be effective in enhancing colloidal stability and increasing their presence in the bloodstream. Examining the hemolysis data showed that the synthesis of Ag 2 S QDs with tarragon extract significantly reduces the lysis of red blood cells by modifying the surface chemistry. The cell culture data also confirmed the results of hemolysis, indicating increased cell viability with Ag 2 S QDs tarragon. These results indicated that the use of tarragon extract as a green synthesis material contributes to the biocompatibility and safety of Ag 2 S QDs.

Background Photothermal immunotherapy, as a promising technique in cancer treatment, offering precise eradication of tumor tissue, minimal adverse effects, and reduced risk of recurrence and metastasis. However, due to the instability of tracer function after photothermal immunotherapy, the long-term in vivo tracing is still a significant challenge, thereby greatly impeding the comprehensive assessment of immune response and drug delivery outcomes. Results Here, we successfully demonstrated the feasibility of stable long-term in vivo immune tracking of photothermal immunodiagnosis and immunotherapy for breast cancer. The biocompatible and stable Ag 2 S quantum dots, with an average size of 3.8 nm, were coated with ovalbumin (OVA) and loaded with immune adjuvant imiquimod (R837). This synthesized Ag 2 S@OVA-R837 nanovaccine exhibited an excellent photothermal response upon near-infrared irradiation at 808 nm and effectively activated dendritic cells. In an in vivo breast tumor mouse model, we demonstrated that this nanoplatform, in combination with laser treatment, significantly improved long-term survival rates, reduced tumor size, and elicited robust immune responses. Conclusions The results support that Ag 2 S@OVA-R837 is a promising photothermal immunotherapy (PIT) tracer nanoplatform to feedback immunoefficacy of therapeutics and holds great promise for precise treatment and diagnosis of malignant tumors, providing a novel avenue for visualizing the in vivo distribution and trafficking of functional therapeutics.

Highlights Wafer-scale integration of Ag 2 S-based memristive crossbar arrays was demonstrated using complementary metal–oxide–semiconductor (CMOS) compatible processes below 160 °C. A record-low threshold voltage for filament formation and an ultra-low switching-energy reaching that of biological synapses in wafer-scale CMOS-compatible memristive units were achieved. The energy-efficient resistance switching was enabled by self-supply of mobile Ag + ions in Ag 2 S electrolytes and low silver-nucleation barrier at Ag/Ag 2 S interface. Memristive crossbar arrays (MCAs) offer parallel data storage and processing for energy-efficient neuromorphic computing. However, most wafer-scale MCAs that are compatible with complementary metal-oxide-semiconductor (CMOS) technology still suffer from substantially larger energy consumption than biological synapses, due to the slow kinetics of forming conductive paths inside the memristive units. Here we report wafer-scale Ag 2 S-based MCAs realized using CMOS-compatible processes at temperatures below 160 °C. Ag 2 S electrolytes supply highly mobile Ag + ions, and provide the Ag/Ag 2 S interface with low silver nucleation barrier to form silver filaments at low energy costs. By further enhancing Ag + migration in Ag 2 S electrolytes via microstructure modulation, the integrated memristors exhibit a record low threshold of approximately − 0.1 V, and demonstrate ultra-low switching-energies reaching femtojoule values as observed in biological synapses. The low-temperature process also enables MCA integration on polyimide substrates for applications in flexible electronics. Moreover, the intrinsic nonidealities of the memristive units for deep learning can be compensated by employing an advanced training algorithm. An impressive accuracy of 92.6% in image recognition simulations is demonstrated with the MCAs after the compensation. The demonstrated MCAs provide a promising device option for neuromorphic computing with ultra-high energy-efficiency.

Due to its inherent ductility, Ag2S shows promise as a flexible thermoelectric material for harnessing waste heat from diverse sources. However, its thermoelectric performance remains subpar, and existing enhancement strategies often compromise its ductility. In this study, a novel Sn‐doping‐induced biphasic structuring approach is introduced to synergistically control electron and phonon transport. Specifically, Sn‐doping is incorporated into Ag2S0.7Se0.3 to form a biphasic composition comprising (Ag, Sn)2S0.7Se0.3 as the primary phase and Ag2S0.7Se0.3 as the secondary phase. This biphasic configuration achieves a competitive figure‐of‐merit ZT of 0.42 at 343 K while retaining exceptional ductility, exceeding 90%. The dominant (Ag, Sn)2S0.7Se0.3 phase bolsters the initially low carrier concentration, with interfacial boundaries between the phases effectively mitigating carrier scattering and promoting carrier mobility. Consequently, the optimized power factor reaches 5 µW cm−1 K−2 at 343 K. Additionally, the formation of the biphasic structure induces diverse micro/nano defects, suppressing lattice thermal conductivity to a commendable 0.18 W m−1 K−1, thereby achieving optimized thermoelectric performance. As a result, a four‐leg in‐plane flexible thermoelectric device is fabricated, exhibiting a maximum power density of ≈49 µW cm−2 under the temperature difference of 30 K, much higher than that of organic‐based flexible thermoelectric devices. Sn‐doping is proposed to design a biphasic structure, (Ag, Sn)2S0.7Se0.3 as the main phase and Ag2S0.7Se0.3 as the interstitial phase, realizing a ZT of 0.42 at 343 K with >90% ductility preserved. The main phase enhances carrier concentration, while interfaces restrain carrier scattering for high mobility. Micro/nanodefects induced by the biphasic structure effectively scatter phonons, leading to low thermal conductivity.

We report the synthesis of α-Ag2S nanoparticles (NPs) by one-step laser ablation of a silver target in aqueous solution of thiourea (Tu, CH4N2S) mixed with cationic cetyltrimethylammonium bromide (CTAB) as surfactant. The effect of the CTAB surfactant on the structural, morphological, optical, and elemental composition of Ag2S NPs was evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and UV-vis spectroscopy. The optical absorption decreased and the optical energy gap of α-Ag2S increased from 1.5 to 2 eV after the CTAB surfactant was added to the Tu solution. XRD studies revealed that the synthesized Ag2S NPs were polycrystalline with a monoclinic structure and that crystallinity of the nanoparticles was improved after adding CTAB. Raman studies revealed the presence of peaks related to Ag-S bonds (Ag modes) and the longitudinal optical phonon 2LO mode. Scanning electron microscopy investigations confirmed the production of monodisperse Ag2S NPs when using the CTAB surfactant. The optoelectronic properties of α-Ag2S/p-Si photodetector, such as current-voltage characteristics and responsivity in the dark and under illumination, were also improved after using the CTAB surfactant. The responsivity of the photodetector increases from 0.64 to 1.85 A/W at 510 nm after adding CTAB. The energy band diagram of the α-Ag2S/p-Si photodetector under illumination was constructed. The fabricated photodetectors exhibited reasonable stability after three weeks of storage under ambient conditions with a responsivity of 70% of the initial value.We report the synthesis of α-Ag2S nanoparticles (NPs) by one-step laser ablation of a silver target in aqueous solution of thiourea (Tu, CH4N2S) mixed with cationic cetyltrimethylammonium bromide (CTAB) as surfactant. The effect of the CTAB surfactant on the structural, morphological, optical, and elemental composition of Ag2S NPs was evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and UV-vis spectroscopy. The optical absorption decreased and the optical energy gap of α-Ag2S increased from 1.5 to 2 eV after the CTAB surfactant was added to the Tu solution. XRD studies revealed that the synthesized Ag2S NPs were polycrystalline with a monoclinic structure and that crystallinity of the nanoparticles was improved after adding CTAB. Raman studies revealed the presence of peaks related to Ag-S bonds (Ag modes) and the longitudinal optical phonon 2LO mode. Scanning electron microscopy investigations confirmed the production of monodisperse Ag2S NPs when using the CTAB surfactant. The optoelectronic properties of α-Ag2S/p-Si photodetector, such as current-voltage characteristics and responsivity in the dark and under illumination, were also improved after using the CTAB surfactant. The responsivity of the photodetector increases from 0.64 to 1.85 A/W at 510 nm after adding CTAB. The energy band diagram of the α-Ag2S/p-Si photodetector under illumination was constructed. The fabricated photodetectors exhibited reasonable stability after three weeks of storage under ambient conditions with a responsivity of 70% of the initial value.

Silver sulfide (Ag 2 S) quantum dots hold tremendous potential as promising near-infrared (NIR) theranostic agents for cancer treatment owing to their exceptional photophysical properties and deep tissue penetration capabilities. However, their complex synthesis process under harsh reaction conditions and poor retention at the target site still restrict clinical applications. Herein, metalloprotein adhesive nanodots biomineralized using engineered silver-binding mussel protein (MAP-AgP35) are presented as biosafe, high-performance photosensitizers to enable NIR-triggered theranostics for local cancer treatments. By constructing donor-acceptor pairs within the nanostructures through interfacial adhesive bridging between the MAP-AgP35 and Ag 2 S minerals, the sticky proteinic Ag 2 S nanodots dramatically reduced the energy bandgap for enhanced light absorption; this enables remarkably efficient superoxide radical ( · O 2 − ) generation and photothermal conversion (η ~ 59%), in addition to effective fluorescence emission in the second NIR (NIR-II) region. The outstanding optochemical functionalities of these nanodots allow direct eradication of cancer cells via effective photodynamic and photothermal actions in the presence of an 808 nm NIR laser, with good biocompatibility toward normal cells. Importantly, these biomineralized nanodots overcome major limitations of conventional photosensitizers, offering a clinically translatable theranostic platform for realizing precise and complete ablation of cancer in a minimally invasive manner. Graphical abstract