Yejun Zhang

Ag2S Quantum Dot: A Bright and Biocompatible Fluorescent Nanoprobe in the Second Near-Infrared Window

Ag(2)S quantum dots (QDs) emitting in the second near-infrared region (NIR-II, 1.0-1.4 μm) are demonstrated as a promising fluorescent probe with both bright photoluminescence and high biocompatibility for the first time. Highly selective in vitro targeting and imaging of different cell lines are achieved using biocompatible NIR-II Ag(2)S QDs with different targeting ligands. The cytotoxicity study illustrates the Ag(2)S QDs with negligible effects in altering cell proliferation, triggering apoptosis and necrosis, generating reactive oxygen species, and causing DNA damage. Our results have opened up the possibilities of using these biocompatible Ag(2)S QDs for in vivo anatomical imaging and early stage tumor diagnosis with deep tissue penetration, high sensitivity, and elevated spatial and temporal resolution owing to their high emission efficiency in the unique NIR-II imaging window.

In Vivo Fluorescence Imaging with Ag2S Quantum Dots in the Second Near‐Infrared Region

Hits the dot: Ag(2)S quantum dots (QDs) with bright near-infrared-II fluorescence emission (around 1200 nm) and six-arm branched PEG surface coating were synthesized for in vivo small-animal imaging. The 6PEG-Ag(2)S QDs afforded a tumor uptake of approximately 10 % injected dose/gram, owing to a long circulation half-life of approximately 4 h. Clearance of the injected 6PEG-Ag(2)S QDs occurs mainly through the biliary pathway in mice.

Urchin-like CoP Nanocrystals as Hydrogen Evolution Reaction and Oxygen Reduction Reaction Dual-Electrocatalyst with Superior Stability

High-performance electrocatalysts with superior stability are critically important for their practical applications in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, we report a facile method to fabricate urchin-like CoP nanocrystals (NCs) as catalyst for both HER and ORR with desirable electrocatalytic activities and long-term stability. The urchin-like CoP NCs with a diameter of 5 μm were successfully prepared by a hydrothermal reaction following a phosphidation treatment in N2 atmosphere and present excellent HER catalytic performance with a low onset overpotential of 50 mV, a small Tafel slope of 46 mV/decade, and an exceptional low overpotential of ~180 mV at a current density of 100 mA cm(-2) with a mass loading density of 0.28 mg/cm(2). Meanwhile, a remarkable ORR catalytic activity was observed with a half-potential of 0.7 V and an onset potential of 0.8 V at 1600 rpm and a scan rate of 5 mV s(-1). More importantly, the urchin-like CoP NCs present superior stability and keep their catalytic activity for at least 10 000 CV cycles for HER in 0.5 M H2SO4 and over 30 000 s for ORR in 0.1 M KOH, which is ascribed to their robust three-dimensional structure. This urchin-like CoP NCs might be a promising replacement to the Pt-based electrocatalysts in water splitting and fuel cells.

In vivo real-time visualization of tissue blood flow and angiogenesis using Ag2S quantum dots in the NIR-II window

Improving the tissue penetration depth and spatial resolution of fluorescence-based optical nanoprobes remains a grand challenge for their practical applications in in vivo imaging, due to the scattering and absorption and endogenous autofluorescence of living tissues. Here, we present that Ag2S quantum dots (QDs), containing no toxic ions, exhibiting long circulation time and high stability, act as a new kind of fluorescent probes in the second near-infrared window (NIR-II, 1000-1350 nm) which enable in vivo monitoring of lymphatic drainage and vascular networks with deep tissue penetration and high spatial and temporal resolution. In addition, NIR-II fluorescence imaging with Ag2S QDs provide ultrahigh spatial resolution (~40 μm) that permits us to track angiogenesis mediated by a tiny tumor (2-3 mm in diameter) in vivo. Our results indicate that Ag2S QDs are promising NIR-II fluorescent nanoprobes that could be useful in surgical treatments such as sentinel lymph node (SLN) dissection as well in assessment of blood supply in tissues and organs and screening of anti-angiogenic drugs.

Matchstick‐Shaped Ag2S–ZnS Heteronanostructures Preserving both UV/Blue and Near‐Infrared Photoluminescence

In recent years, heterostructured nanomaterials have attracted intense research interest due to their integrated multifunctionality of disparate components. Such multifunctionality gives heterostructured nanomaterials great potential in different fields of diagnosis, sensors, catalysis, optoelectronic devices, and so on. In particular, enormous efforts have been devoted to synthesizing different heterodimer nanomaterials, including CoPt3–Au, [3] PbSe–Au, Fe3O4– Au, 5] PbS–Au, Fe3O4–Ag, [7,8] and Ag2S/Ag, [10] which combine optical and/or electrical, magnetic, catalytic properties. Matchstick-shaped heteronanostructures (HNSs) are an important kind of heterostructured nanomaterials which are very suitable for integrating into nanodevices for further applications. Metal-tipped semiconductor nanorod HNSs have been well studied in the last decade. Metal tips (Au, Pt, Co, etc.) were selectively grown on either top or side of CdS/CdSe nanorods, and the resulting metal–semiconductor interface facilitated charge separation, which favored their application in solar energy. Due to the flexibility of bandgap engineering, semiconductor–semiconductor HNSs have been considered to offer better opportunities for internal exciton separation and carrier transport and optoelectronic applications. Recently, we reported that Ag2S quantum dots (QDs) can be good candidates as near-infrared (NIR) emitters, and that ultrathin ZnS nanowires can emit in the UV/blue region. We therefore wondered how HNSs consisting of Ag2S QDs and ZnS nanowires would behave. Recently, Xu et al. prepared Ag2S–ZnS HNSs by a seeded-growth method in which Ag2S nanocrystals acted as catalyst for growth of ZnS nanorods. However, both Ag2S nanocrystals and ZnS nanorods of the as-prepared Ag2S–ZnS HNSs had large diameters of about 20 nm and their optical properties were not reported. Since the Bohr radius of ZnS is 2.4 nm (to the best of our knowledge, that of Ag2S is unknown), we expect that Ag2S–ZnS HNSs with smaller sizes will exhibit their intrinsic optical properties due to the quantum confinement effect. Therefore, the driving force for this work was to determine whether Ag2S–ZnS HNSs with smaller sizes preserve both the NIR and UV/blue emissions or not. Three merits of this work can be noted: 1) The as-prepared small Ag2S–ZnS HNSs exhibit both NIR and UV/blue emissions from Ag2S QDs and ZnS nanorods, respectively; 2) A facile one-pot method is utilized for Ag2S–ZnS HNSs synthesis by thermal co-decomposition of single-source precursors Ag(DDTC) and Zn(DDTC)2 (DDTC = diethyldithiocarbamate), which is much more convenient than the seededgrowth or catalyst-assisted growth method; 3) The size of the HNSs can be easily tuned by changing the reaction conditions, which is not possible for seeded-growth with given seeds. Figure 1a depicts a typical low-magnification TEM image of Ag2S–ZnS HNSs prepared with an Ag(DDTC)/Zn(DDTC)2 molar ratio of 2:1. The HNSs are of uniform matchstick shape with significant difference in the massthickness contrast between the spherical head (ca. 4.5 nm in diameter) and the stem (4 48 nm in diameter and length). The narrow size distribution of as-prepared Ag2S–ZnS HNSs facilitated their self-assembly into superlattice structures with hexagonal packing, which was supported by a selected-area fast Fourier transform (FFT) pattern (inset in Figure 1a). The Ag2S–ZnS HNS superlattices were perpendicular to the TEM grid, as was further confirmed by TEM tilting experiments (see Supporting Information), similar to a previously reported CoO nanorod superlattice. The mass-thickness contrast difference between the spherical head and stem indicated the various chemical compositions of the as-prepared HNSs. A high-resolution TEM (HRTEM) image of a typical Ag2S–ZnS HNS is shown in Figure 1b. The HNS is highly crystalline with a spherical head and a nanorodlike stem, and has a partially coherent interface between single-crystalline head and stem. Based on the analysis of the corresponding crystal lattices, the spherical head is composed of Ag2S and the stem of ZnS, and the conjunction interface consists of the ( 121) plane of the Ag2S head and the (008) plane of the ZnS stem with a lattice mismatch of 16% (Figure 1b). The (008) plane of ZnS was further confirmed by a higher quality HRTEM image (Figure 1c), in which hcp ABAB stacking of ZnS double layers along the [001] direction can be clearly observed. This is a strong evidence that d = 0.31 nm corresponds to the (008) plane of hexagonal ZnS. Detailed analysis of the local elemental composition of the Ag2S–ZnS HNSs was performed by line-scan energy-dispersive X-ray spec[*] Dr. S. Shen, Y. Zhang, L. Peng, Dr. Y. Du, Prof. Dr. Q. Wang Division of Nanobiomedicine andi-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences Suzhou, 215123 (China) Fax: (+ 86)512-6287-2620 E-mail: qbwang2008@sinano.ac.cn

Generalized synthesis of metal sulfide nanocrystals from single-source precursors: size, shape and chemical composition control and their properties

A general and facile method is reported for the synthesis of a wide range of metal sulfide nanocrystals including silver sulfide, zinc sulfide, cadmium sulfide, lead sulfide, bismuth sulfide, tin sulfide, iron sulfide and copper sulfide, etc. This method is based on the thermal decomposition of single-source precursors composed of metal-diethyldithiocarbamate in solution phase. By this method, not only the size and shape but also the chemical composition of the products can be easily controlled. Furthermore, these as-synthesized metal sulfides with different sizes, shapes and chemical compositions exhibit novel optical, electronic and magnetic properties, such as near-infrared (NIR) photoluminescence (PL), strong ferromagnetism and excellent electrochemical properties. We expect that this facile methodology for metal sulfides synthesis can be generalized to other nanocrystals synthesis, and be of high importance to explore the new properties.

Real-time in vivo visualization of tumor therapy by a near-infrared-II Ag2S quantum dot-based theranostic nanoplatform

AbstractReal-time and objective feedback of therapeutic efficacies would be of great value for tumor treatment. Here, we report a smart Ag2S QD-based theranostic nanoplatform (DOX@PEG-Ag2S) obtained by loading the anti-cancer drug doxorubicin (DOX) into polyethylene glycol-coated silver sulfide quantum dots (PEG-Ag2S QDs) through hydrophobic-hydrophobic interactions, which exhibited high drug loading capability (93 wt.% of DOX to Ag2S QDs), long circulation in blood (t1/2 = 10.3 h), and high passive tumor-targeting efficiency (8.9% ID/gram) in living mice where % ID/gram reflects the probe concentration in terms of the percentage of the injected dose (ID) per gram of tissue. After targeting the tumor tissue, DOX from PEG-Ag2S cargoes was selectively and rapidly released into cancer cells, giving rise to a significant tumor inhibition. Owing to the deep tissue penetration and high spatio-temporal resolution of Ag2S QDs fluorescence in the second near-infrared window (NIR-II), the DOX@PEG-Ag2S enabled real-time in vivo reading of the drug targeting process and therapeutic efficacy. We expect that such a novel theranostic nanoplatform, DOX@PEG-Ag2S, with integrated drug delivery, therapy and assessment functionalities, will be highly useful for personalized treatments of tumors.

Diverse-shaped iron sulfide nanostructures synthesized from a single source precursor approach

Iron sulfide nanostructures with diverse shapes (nanoparticles, nanoribbons and nanoplates) have been synthesized via a single-source precursor of Fe(Ddtc)3 or Fe(Ddtc)2(Phen) (Phen = 1,10-phenanthroline; Ddtc = diethyldithiocarbamate) in the mixture solvents of oleic acid (OA)/oleylamine (OM)/1-octadecene (ODE). The chemical compositions of the as-formed iron sulfide nanostructures are found to be determined by the valencies of iron in the precursors. For phase-pure Fe3S4 and Fe7S8 nanostructures, their shape-selective syntheses could be realized mainly by modifying the ratio of reaction solvent compositions and the chemical composition of precursors. The growth of nanoparticles and nanoplates of iron sulfide is likely due to the selective adsorption of the capping ligands on specific crystal planes of the nanocrystals. Meanwhile, for FeSx nanoribbons, the growth of nanoribbons may come from the template-direction of micellar structures formed by self-assembly of capping ligands. Furthermore, the Fe3S4 and Fe7S8 nanostructures display strong ferromagnetic properties at room temperature.

MoSe2 porous microspheres comprising monolayer flakes with high electrocatalytic activity

A facile colloidal route to synthesize MoSe2 porous microspheres with diameters of 400–600 nm made up of MoSe2 monolayer flakes (∼0.7 nm in thickness) is reported. The solvents trioctylamine (TOA) and oleylamine (OAM) are found to play important roles in the formation of MoSe2 microspheres, whereby TOA determines the three-dimensional (3D) microspherical morphology and OAM directs the formation of MoSe2 monolayer flakes. The robust 3D MoSe2 microspheres exhibit remarkable activity and durability for the electrocatalytic hydrogen evolution reaction (HER) in acid, maintaining a small onset overpotential of ∼77 mV and keeping a small overpotential of 100 mV for a current density of 5 mA/cm2 after 1,000 cycles. In addition, similar 3D WSe2 microspheres can also be prepared by using this method. We expect this facile colloidal route could further be expanded to synthesize other porous structures which will find applications in fields such as in energy storage, catalysis, and sensing.

Real-Time Monitoring Surface Chemistry-Dependent In Vivo Behaviors of Protein Nanocages via Encapsulating an NIR-II Ag2S Quantum Dot.

Protein nanocages (PNCs) have been recognized as a promising platform for nanomedicine innovation. Real-time in vivo tracking of PNCs can provide critically important information for the development of PNC-based diagnostics and therapeutics. Here we demonstrate a general strategy for monitoring the behaviors of PNCs in vivo by encapsulating a Ag2S quantum dot (QD) with fluorescence in the second near-infrared window (NIR-II, 1000-1700 nm) inside the PNC, using simian virus 40 (SV40) PNC (PNCSV40) as a model. Benefiting from the high spatiotemporal resolution and deep tissue penetration of NIR-II fluorescence imaging, the dynamic distribution of the PNCSV40 in living mice was tracked in real time with high fidelity, and adopting the PEGylation strategy, surface chemistry-dependent in vivo behaviors of PNCSV40 were clearly revealed. This study represents the first evidence of real-time tracking of the intrinsic behaviors of PNCs in vivo without interference in PNC-host interactions by encapsulating nanoprobes inside. The as-described imaging strategy will facilitate the study of interactions between exogenously introduced PNCs and host body and prompt the development of future protein-based drugs, sensors, and high-efficacy targeted delivery systems.