Preparation of hydrophobic porous Au-Ag alloy nanoparticle arrays and their SERS properties.

In this study, we prepared porous Au-Ag alloy nanoparticle arrays with hydrophobic surfaces through the polystyrene colloidal crystal template combined with the chemical etching method to realize rapid SERS detection for biochemical molecules. In the preparation process, the pore size of Au-Ag alloy nanoparticles could be adjusted by changing the deposition time of the Ag element. Furthermore, after depositing the Au film on the surface of the porous nanoparticle arrays, their surface changed from hydrophilic to hydrophobic. The hydrophobic surface can drive target molecules to locally aggregate. Meanwhile, the hydrophobic surface also possessed a large number of active "hot spots" due to the porous structure. For these reasons, the porous Au-Ag alloy nanoparticle arrays can enable rapid and trace SERS detection, which provide the material basis for the subsequent construction of the high-quality SERS substrate.

Facile Construction of 2D/2D ZnIn2S4-Based Bifunctional Photocatalysts for H2 Production and Simultaneous Degradation of Rhodamine B and Tetracycline.

A two-dimensional/two-dimensional (2D/2D) TiO2/ZnIn2S4 photocatalyst was reasonably proposed and constructed by a two-step oil bath-hydrothermal method. TiO2 nanosheets uniformly grown on the surface of ZnIn2S4 nanosheets and a synergetic effect between the TiO2 and ZnIn2S4 could highly contribute to improving the specific surface area and hydrophilicity of ZnIn2S4 as well as accelerating the separation and transfer of photon-generated e--h+ pairs, and thus enhancing the visible-light photocatalytic degradation and H2 evolution performance of ZnIn2S4. Rhodamine B (RhB) and tetracycline (TC) were simultaneously selected as the target pollutants for degradation in the work. The optimum photocatalytic RhB and TC degradation properties of TiO2/ZnIn2S4-10 wt% were almost 3.11- and 8.61-fold higher than that of pure ZnIn2S4, separately, while the highest photocatalytic hydrogen evolution rate was also observed in the presence of TiO2/ZnIn2S4-10wt% and 4.28-fold higher than that of ZnIn2S4. Moreover, the possible photocatalytic mechanisms for enhanced visible-light photocatalytic degradation and H2 evolution were investigated and proposed in detail. Our research results open an easy pathway for developing efficient bifunctional photocatalysts.

Coupling ZnIn2S4 Nanosheets with MoS2 Hollow Nanospheres as Visible-Light-Active Bifunctional Photocatalysts for Enhancing H2 Evolution and RhB Degradation.

In this study, Mo-glycerate was used as a precursor to create MoS2 hollow nanospheres (HNS), which were then used for the first time to modify ZnIn2S4 nanosheets to create MoS2 HNS/ZnIn2S4 photocatalysts. The findings demonstrate that MoS2 HNS/ZnIn2S4 heterojunctions exhibited remarkably boosted photocatalytic properties and excellent reusability for both RhB degradation and H2 evolution without the use of Pt as a co-catalyst. Among the heterojunctions, the RhB degradation and H2 evolution efficiencies of the optimized MoS2 HNS/ZnIn2S4-3 wt % composite were almost 5 and 34 times higher than those of ZnIn2S4, respectively. The excellent performance of MoS2 HNS/ZnIn2S4-3 wt % might be attributed to the expansion of the visible-light response range and the accelerated separation efficiency of photo-induced carriers, according to the findings of the optical property tests. Based on the established band gap position and characterization results, a potential mechanism for appealing photocatalytic activity over MoS2 HNS/ZnIn2S4 heterojunctions was also postulated.

Gold nanobipyramid@copper sulfide nanotheranostics for image-guided NIR-II photo/chemodynamic cancer therapy with enhanced immune response.

Photothermal therapy (PTT), photodynamic therapy (PDT), and chemodynamic therapy (CDT) can cause cancer cell death through an immunogenic process. However, the study of second near-infrared window (NIR-II)-triggered PTT and PDT combined with CDT to induce an immune response has not been recently reported. Here, we integrated gold nanobipyramids and copper sulfide in a core/shell architecture (AuNBP@CuS). The material displays both photodynamic and photothermal properties under irradiation with a NIR-II laser. The released Cu2+ from CuS under an acidic tumor microenvironment can be converted to Cu+ by glutathione following a Fenton-like reaction with hydrogen peroxide to generate highly toxic hydroxyl radicals in the tumor region. Both in vitro and in vivo results demonstrated that such multifunctional nanoplatforms could achieve enhanced efficiency for image-guided tumor suppression based on the NIR-II photo/chemodynamic therapy. We found that damage-associated molecular pattern molecules such as adenosine triphosphate, pre-apoptotic calreticulin, and high mobility group box-1 in dying cells induced by the NIR-II photo/chemodynamic therapy could simultaneously trigger adaptive immune responses. This is the first report revealing that NIR-II photo/chemodynamic therapy based on AuNBP@CuS had promising performance on tumor suppressor with an effective immunogenic cell death process. STATEMENT OF SIGNIFICANCE: 1. AuNBP@CuS displays both NIR-II photodynamic and photothermal properties. 2. Cu+ following a Fenton-like reaction to generate highly toxic hydroxyl radicals. 3. The NIR-II photo/chemodynamic therapy can trigger adaptive immune responses. 4. Such multifunctional nanoplatforms could achieve enhanced efficiency for tumor suppression.

In situ growing 3D-Cu coating to improve the reversibility and reaction kinetics of Zn metal anodes.

The zinc metal anode is the most promising metal anode material in aqueous battery systems due to its low cost and high theoretical capacity. However, it still undergoes irreversible reactions such as premature failure of the dendrites/dead Zn during Zn stripping/plating, resulting in the inferior cycling stability of the Zn-based full cell. Here, we demonstrate a facile 3D-Cu alloy coating to improve Zn reversibility by providing spatial voids to accommodate the plated Zn to form dendrite-free morphology. Combining the larger 3D surface and the alloying-dealloying process, the Zn anode reactions exhibit enhanced reaction kinetics to meet large operating current densities. The 3D-Cu-coated Zn anode can deliver improved cycling stability for 350 h under a large areal capacity of 3 mAh cm-2. It also enables MnO2-Zn at the full cell level to achieve a specific capacity of 205 mAh g-1 and longer cycling for 350 cycles with 87.4% retention of the initial capacity. This research provides a new pathway to achieve high reversible Zn metal chemistry.

Porous CoSe2@N-doped carbon nanowires: an ultra-high stable and large-current-density oxygen evolution electrocatalyst.

Nitrogen doped carbon functionalized CoSe2 nanowires (CoSe2@N-C NWs), which act as potential oxygen evolution reaction (OER) catalysts with a large current density and high stability have been reported. Owing to the collaborative optimization of electrical conductivity, free adsorption energy and binding strength of OER intermediates, the prepared CoSe2@N-C NWs exhibit an enhanced 6.61-fold catalytic activity compared to the pristine CoSe2 NW electrode in 1.0 M KOH solution at the overpotential of 340 mV.

Hollow FeP/Fe3O4 Hybrid Nanoparticles on Carbon Nanotubes as Efficient Electrocatalysts for the Oxygen Evolution Reaction.

We develop a method to prepare hollow FeP/Fe3O4 hybrid nanoparticles supported on carbon nanotubes (CNTs), which could be used as highly active and efficient electrocatalysts. The Fe@Fe3O4/CNT hybrids were first synthesized by annealing the CNTs adsorbed with Fe(NO3)3, followed by controlled phosphorization treatment. They exhibit an outstanding catalytic activity for oxygen evolution reaction (OER) with a low overpotential of 229 mV at a current density of 10 mA cm-2, a high turnover frequency value of 0.35 s-1 at an overpotential of 300 mV, and an ultralow Tafel slope of 27.6 mV dec-1, which is much better than that of FeP/Fe3O4, FeP/CNTs, Fe3O4/CNTs, and the commercial RuO2 electrocatalyst. More importantly, the Tafel slope is much lower than most non-noble metal-based OER electrocatalysts reported in the previous literature studies as far as we know. The excellent OER performance benefits from the electron transfer from Fe3O4 to FeP confirmed by X-ray photoelectron spectroscopy, together with good conductivity of CNTs. This hybrid structure supported on conductive CNTs may offer an efficient method to design earth-abundant and low-cost electrocatalysts for OER in practical applications.

Dynamically Tunable Plasmonic Band for Reversible Colorimetric Sensors and Surface-Enhanced Raman Scattering Effect with Good Sensitivity and Stability.

A colorimetric sensor based on plasmonic nanoparticles (NPs) is a promising and convenient detection tool, but its reproducibility and adjustability remain a challenge because the NPs are mainly random and uncontrollable. Herein, a colorimetric sensor with good reversibility and reproducibility was prepared by embedding the two-dimensional (2D) Au NP arrays on the surface of the polyacrylamide hydrogel film to form 2D Au NP arrays attached a hydrogel composite. For this composite, with the change of the interspacing distance of Au NPs driven by the swelling-shrinking behavior of the hydrogel carrier, the diffraction peaks faded away and plasmonic coupling peaks appeared, accompanied by a series of obvious color changes (iridescence ↔ violet ↔ golden yellow ↔ red), which can be correlated to the applied water content. Importantly, the composite had good reproducibility as a result of a highly ordered array structure. Additionally, this colorimetric sensor with a dynamically tunable plasmonic band can be used as a high-quality surface-enhanced Raman scattering (SERS) substrate because the gap distance of the Au NPs can be uniformly controlled. We demonstrated that, as the active gap distance decreased, the SERS signals can be significantly intensified. When the water content reached 40%, this SERS substrate exhibited high sensitivity (10-10 M for 4-aminothiophenol and 10-9 M for thiram) and good reproducibility (relative standard deviation of <20%) using the excitation laser of 785 nm because of the small gap between two adjacent Au NPs and the highly ordered periodic structure. Such 2D Au NP arrays attached to a hydrogel composite could be a new strategy to obtain a high-quality colorimetric sensor and dynamic SERS substrate.

The effect of graphitized carbon on the adsorption and photocatalytic degradation of methylene blue over TiO2/C composites.

The TiO2/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO4)2 and flour. All TiO2/C composites displayed mesoporous structures with high BET surface areas (117-138 m2 g-1) and small crystal sizes of TiO2 (8-27 nm). The contents of graphitic carbon and rutile TiO2 increased, while the surface area and TiO2 crystal size decreased for the TiO2/C composite on increasing the calcination temperature from 650 to 800 °C; when calcinated at 800 °C, the anatase TiO2 completely changed into rutile TiO2 in the TiO2/C composite. The TiO2/C composite calcinated at higher temperatures exhibited better adsorptive and photocatalytic degradation performance in the removal of methylene blue (MB). For the entire rutile TiO2/C-800 composite, the adsorption process of MB can be well described by the pseudo-second-order kinetic model and is governed by chemical adsorption with the maximum adsorption capacity value equal to about 15 mg g-1. Under continuous illumination with a 254 nm UV lamp (15 W) for 3 h, the percentage of MB (14 mg l-1) photocatalytic degradation on 50 mg of TiO2/C-800 was 25.1% higher than that of the maximum adsorption removal. These results suggest that the graphitized carbon has a significant effect on the adsorptivity and photocatalytic activity of the TiO2/C composite.

In situ-generated NiCo@NiS nanoparticle anchored s-doped carbon nanotubes as dual electrocatalysts for oxygen reduction reaction and hydrogen evolution reaction.

Developing low cost and highly robust electrocatalysts for oxygen evolution reaction, hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) is of great importance for the efficient conversion of sustainable energy sources. Herein, we report a facile pyrolysis strategy for the controllable synthesis of NiCo@NiS/S-CNTs with NiCo@NiS nanoparticles anchored on sulfur-doped carbon nanotubes (CNTs). The obtained NiCo@NiS/S-CNT electrocatalyst exhibits excellent dual-functional catalytic activities under an alkaline condition, an ORR performance with an onset potential of -30 mV, and a half-wave potential of -150 mV (versus Ag/AgCl) while the overpotential for the HER is -1.16 V (versus Ag/AgCl) at a current density of 10 mA cm-2. It was found that the incorporation of sulfur can regulate the electronic structure of CNTs to accelerate the electron transfer performance and generate new catalytic sites, thus contributing to greatly enhancing both the activity and stability of the catalytic process. This work provides a promising way for the rational design of efficient and robust catalysts for sustainable energy conversion.

Nanoplatforms with Remarkably Enhanced Absorption in the Second Biological Window for Effective Tumor Thermoradiotherapy.

Thermoradiotherapy acts as an important antitumor modality because heating can increase the blood flow and improve the oxygen level in tumor, thus remission of hypoxia-associated resistance for radiotherapy (RT). However, most agents for thermoradiotherapy are used either in the first near-infrared biological window or low photothermal conversion efficiency. Here, a facile method to prepare CuxS/Au nanocomposites via reduction methods from CuxS templates in mild synthetic conditions (i.e., aqueous solution and room temperature) is presented. After the growth of Au nanoparticles, the CuxS/Au nanocomposites have greater benefits for photothermal efficiency than that of CuxS nanoparticles due to the enhanced absorbance in the second near-infrared window. Moreover, biocompatibility and stability of these nanocomposites are greatly improved by lipoic acid poly(ethylene glycol). After the tumors were irradiated with a 1064 nm laser, their oxygenation status is subsequently improved, and the combination of photothermal therapy and RT achieves remarkable synergistic therapeutic effects. This work provides a novel idea to design a new-generation nanomedicine for tumor thermoradiotherapy.

Au@Prussian Blue Hybrid Nanomaterial Synergy with a Chemotherapeutic Drug for Tumor Diagnosis and Chemodynamic Therapy.

Recently, the chemodynamic therapy (CDT) has been widely reported and applied to tumor therapy. However, only low level hydroxyl radicals (•OH) generated by the endogenous hydrogen peroxide alone are insufficient to kill the cancer cells. To overcome the insufficient therapeutic effect, this study reports a novel CDT based on Fenton catalyst Au@Prussian blue nanocubes (Au@PB NCs), subsequently encapsulated with doxorubicin (Dox). The in vitro and in vivo results indicate that the Dox-Au@PB NCs can take synergistic effects on tumor suppressor by CDT. In addition, Au@PB NCs possess high X-ray computed tomography contrast enhanced efficiency about ∼27.13 HU·mL·mg-1. This study highlights a great potential of the Dox-Au@PB NCs for tumor diagnosis and CDT.

2D Au Nanosphere Arrays/PVA-PBA-Modified-Hydrogel Composite Film for Glucose Detection with Strong Diffraction Intensity and Linear Response.

A novel glucose sensor was reported that consisted of two-dimensional (2D) Au nanosphere arrays and glucose-responsive hydrogel film. This sensor exhibited an intense diffraction signal and an obvious diffraction color on a quartz slide due to the strong diffraction intensity of the Au nanosphere arrays. Thus, glucose was detected via the variation of diffraction wavelength and diffraction color, without a high reflective mirror. In addition, by introducing poly(vinyl alcohol) (PVA) to crosslink the phenylboronic acid (PBA)-modified hydrogel film, the diffraction wavelength of the 2D Au nanosphere arrays/hydrogel composite film shifted in the same direction in high ionic strength condition. In particular, it showed a nearly linear red-shift when the glucose concentration increased from 0 mM to 20 mM. Moreover, this glucose sensor displayed good reproducibility. The nearly linear response and good reproducibility were highly helpful for improving practical application of this glucose sensor.

Wafer-Scale Hierarchical Nanopillar Arrays Based on Au Masks and Reactive Ion Etching for Effective 3D SERS Substrate.

Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO2 nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO2 nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO2 nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO2 nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density "hotspots" derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods.

Physical process-aided fabrication of periodic Au-M (M = Ag, Cu, Ag-Cu) alloyed nanoparticle arrays with tunable localized surface plasmon resonance and diffraction peaks.

Periodic alloyed (Au-Ag, Au-Cu, Au-Ag-Cu) nanoparticle (NP) arrays with uniform size, controllable composition and center-to-center spacing were fabricated by a novel and facile strategy based on physical vapor deposition on a monolayer colloidal crystal template and further heat treatment. The composition and center-to-center spacing were manipulated by adjusting the sputtering target in the deposition process and the size of colloidal spheres of the template, respectively. The shadow effect and a dewetting model were employed to analyze the whole process of evolution from a metallic thin film to spherical nanoparticles with uniform size. The localized surface plasmon resonance (LSPR) and diffraction peaks of these alloyed arrays were systematically measured. The dielectric constant has an important influence on LSPR peaks and diffraction peaks. Both the LSPR and diffraction peaks of Au-Ag alloyed NPs arrays exhibit a blue shift due to their lower dielectric constant than that of pure Au NPs. However, compared with Au, Cu possesses a higher dielectric constant, leading to a red shift of the LSPR and diffraction peaks of Au-Cu alloyed NPs arrays. With the increase of NP size, the diffraction peaks of both binary alloyed NPs exhibit a slight red shift. Moreover, the LSPR absorption peaks were more sensitive to the composition of the NPs than the diffraction peaks. This work would open up a novel strategy in the production of alloyed NP arrays with tunable LSPR peaks and diffraction peaks, which would be very helpful to improve their practical applications in various fields.

Optical sensing properties of Au nanoparticle/hydrogel composite microbeads using droplet microfluidics.

Uniform Au nanoparticle (NP)/poly (acrylamide-co-acrylic acid) [P(AAm-co-AA)] hydrogel microbeads were successfully prepared using droplet microfluidics technology. The microbeads exhibited a good stimuli-responsive behavior to pH value. Particularly in the pH value ranging from pH 2-pH 9, the composite microbead sizes gradually increased along with the increase of pH value. The homogeneous Au NPs, which were encapsulated in the P(AAm-co-AA) hydrogel microbeads, could transform the volume changes of hydrogel into optical signals by a tested single microbead with a microspectrometre system. The glucose was translated into gluconic acid by glucose oxidase. Thus, the Au NP/P(AAm-co-AA) hydrogel microbeads were used for detecting glucose based on pH effects on the composite microbeads. For this, the single Au NP/P(AAm-co-AA) hydrogel microbead could act as a good pH- or glucose-visualizing sensor.

Rapid and Efficient Self-Assembly of Au@ZnO Core-Shell Nanoparticle Arrays with an Enhanced and Tunable Plasmonic Absorption for Photoelectrochemical Hydrogen Generation.

High-quality Au@ZnO core-shell nanoparticle (NP) array films were easily and efficiently fabricated through an air/water interfacial self-assembly. These materials have remarkable visible light absorption capacity and fascinating performance in photoelectrochemical (PEC) water splitting with a photocurrent density of ∼3.08 mA/cm2 at 0.4 V, which is superior to most ZnO-based photoelectrodes in studies. Additionally, the interesting PEC performance could be effectively adjusted by altering the thickness of the ZnO shell and/or the layer number of the array films. Results indicated that the bilayer film based on Au@ZnO NPs with 25 nm shell thickness displayed optimal behavior. The remarkable PEC capability could be ascribed to the enhanced light-harvesting ability of the Au@ZnO structured NPs by the SPR effect and the optimum film thickness. This work demonstrates a desirable paradigm for preparing photoelectrodes based on the synergistic effect of plasmatic NPs as the core and a visible optical absorbent and semiconductor as the shell. Moreover, this work provides a new approach for fabricating optoelectronic anode thin film devices through a self-assembly method.

Surface enhanced Raman scattering properties of dynamically tunable nanogaps between Au nanoparticles self-assembled on hydrogel microspheres controlled by pH.

We developed an interesting route for preparing a poly (acrylamide-co-acrylic acid) (P(AAm-co-AA)) hydrogel microsphere with a coating of Au nanospheres (hydrogel microsphere @ Au nanospheres) through self-assembly based on electrostatic interaction. The fabricated composites could be used as highly sensitive enhanced Raman scattering substrates. The nanogaps between adjacent Au nanospheres were dynamically tuned by volume changes in the hydrogel microspheres in the semiwet state under different pH conditions. At pH 6, the hydrogel microsphere @ Au nanospheres demonstrated highly sensitive SERS with an enhancement factor of 109. The product could detect very low concentrations of analytes up to 10-12M 4-aminothiophenol (4-ATP) molecules. This paper proposes a new method for detecting trace amounts of environmental organic pollutants by dynamically tuning the SERS enhancement in the semiwet testing state.