Monodisperse Au Nanoparticles Research Articles

Monodispersed Au nanoparticles decorated MoS2 nanosheets with enhanced peroxidase-like activity based electrochemical H2O2 sensing for anticancer drug evaluations

BackgroundThe unique size, physical and chemical properties, and ultra-high stability of nanozymes have attracted extensive attentions in sensing, but improvement of catalytic activity of the nanozymes is still an urgent issue. Given the ultra-high simulated enzyme activity of metal nanoparticles and the advantage of multi-enzyme catalysis, an Au-decorated MoS2 nanosheets (MoS2/Au NS) integrating the double peroxidase-like (POD) activity is developed. ResultsBy optimizing and adjusting the density of AuNPs, as well as its morphology and other parameters, a monodisperse and high-density distribution of AuNPs on MoS2 nanosheets was obtained, which can greatly improve the POD-like activity of MoS2/Au NS. Nafion solution was applied to assist the modification of MoS2/Au NS on the electrode surface so as to improved its stability. An electrochemical H2O2 detection platform was constructed by modifying MoS2/Au NS nanozyme on the SPCE using the conductive Nafion solution. And the negatively charged sulfonic acid group can eliminate negatively charged electroactive substances to improve the specificity. Then ascorbic acid was used to stimulate tumor cells to produce H2O2 as therapeutic model, an ultrasensitive chronocoulometry detection for H2O2 in cell lysate was established. The logarithmically of ΔQ and the logarithmically of H2O2 concentration showed a good linear relationship between 1 μM and 500 mM, with a LOD value of 0.3 μM. SignificanceThe developed H2O2 sensor has excellent stability, reproducibility (RSD = 2.3 %, n = 6) and selectivity, realized the quantitative detection of H2O2 in cell lysate. Compared with commercial fluorescence detection kits for H2O2 in cell lysate, it is worth mentioning that the electrochemical H2O2 sensor developed in this study is simpler and faster, with higher sensitivity and lower cost. This provides a potential substitute for disease diagnosis and treatment evaluation based on accurate detection of H2O2.

Core‐shell TiO2@Au Nanofibers Derived from a Unique Physical Coating Strategy for Excellent Capacitive Energy Storage Nanocomposites

AbstractPolymer dielectrics have been widely employed in pulsed power systems, but their applications are severely restricted by the low energy density. Incorporating core‐shell nanofillers is one promising strategy to enhance the energy density of polymer dielectrics. Nowadays, core‐shell nanofillers are mainly prepared via chemical coating strategies, which always involve complex chemical synthesis procedures. Herein, a unique physical coating strategy is developed to prepare core‐shell TiO2@Au nanofibers consisting of monodispersed Au nanoparticles homogeneously anchored on the TiO2 nanofibers. Interestingly, the TiO2@Au nanofibers show outstanding dielectric energy storage boosting capability. Specifically, with merely introducing 0.1 wt.% TiO2@Au nanofillers, the TiO2@Au/PVDF composite exhibits a substantially enhanced breakdown strength of 749 MV m−1, which reaches 152.8% of PVDF. Meanwhile, a high dielectric constant of 10.2 (114.1% of PVDF) is obtained. Consequently, an ultrahigh energy density of 18.6 J cm−3, which is 250.1% of PVDF, is achieved. It is further revealed that the significant energy storage boosting effect is originated from the Coulomb blockade and micro‐capacitor effects of the TiO2@Au nanofibers. This work establishes a unique paradigm for the facile preparation of core‐shell nanomaterials, which have huge potential for both dielectric energy storage and other functional nanocomposites.

Highly sensitive label-free biomolecular detection using Au-WS2 nanohybrid based SERS substrates.

Recent advancements in nanotechnology have led to the development of surface-enhanced Raman spectroscopy (SERS) based rapid and low-cost technologies for ultra-sensitive label-free detection and identification of molecular analytes. Herein, we utilized the synergistic plasmonic and chemical enhancement effects of Au-WS2 nanohybrids to attain the high-intensity Raman signals of targeted analytes. To develop these nanohybrids, a series of monodispersed Au nanoparticles (NPs) of varying diameters from 20 to 80 nm was chemically synthesized and successively blended with liquid-phase exfoliated WS2 nano-flakes of average lateral size 90 nm. They provided a maximum enhancement factor (EF) of ∼1.80 × 109 corresponding to the characteristic peaks at 1364 cm-1 and 1512 cm-1 for R6G analyte molecules. Theoretical studies based on the finite-difference time-domain simulations on Au-WS2 nanohybrid systems revealed a huge field-intensity enhancement with an EF of more than 1000 at the plasmonic hotspots, which was induced by the strong coupling of individual plasmon oscillations of the adjacent Au NPs upon light interactions. These electromagnetic effects along with the chemical enhancement effects of WS2 nanoflakes were found to be mainly responsible for such huge enhancement in Raman signals. Furthermore, these hybrids were successfully employed for achieving highly sensitive detection of the E. coli ATCC 35218 bacterial strain with a concentration of 104 CFU mL-1 in phosphate-buffered saline media, indicating their real capabilities for practical scenarios. The findings of the present study will indeed provide vital information in the development of innovative nanomaterial-based biosensors, that will offer new possibilities for addressing critical public health concerns.

Interface and mechanical properties of graphene/copper composite with sonication induced Au decoration of graphene

The interfacial interaction between graphene and Cu restricts the efficacious properties' enhancement due to poor wettability between the reinforcement and matrix. Herein, we reported an interface modification strategy by Au decoration of graphene nanoplatelets (Au-GNPs) without carbide/oxide formation. Sonication was used to induce defects in GNPs, which were then decorated with Au nanoparticles and used to fabricate a composite material with Cu (Au-GNP/Cu) via low pressure cold pressing and sintering. Sonication parameters' optimization depicted higher exfoliation of GNPs with lower defects at lower sonication amplitude and higher sonication duration which resulted in relatively monodispersed Au nanoparticles attached to the GNPs' surface. The Au-GNP/Cu composite with 1 vol% showed highest sintered density, hardness and calculated tensile strength which decreased at higher Au-GNP content. The proposed interface design with noble metal nanoparticles acting as bridges between GNP and Cu, opens new horizons for superior mechanical properties of composites.

Interrelated Roles of Multiple Key Structure-Directing Agents in Seed-Mediated Growth of Monodisperse and Multibranched Au Nanoparticles.

Detailed mechanistic investigations of the interrelated roles of multiple key structure-directing agents in the growth solution of Au nanoparticles (AuNPs) is required for the optimization of synthetic protocols. Here, we report a robust seed-mediated growth strategy for synthesizing multibranched NPs (MB-AuNPs) with monodispersed size distribution, and investigate the roles of Ag ions and 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES) based on an overgrowth synthesis approach. The intertwining roles of Ag+, surface-capping stabilizers, and reducing agents were elucidated, and used to control the morphology of MB-AuNPs. The overgrowth of MB-AuNPs involves two distinct underlying pathways, namely, directional and anisotropic growth of Au branches on specific facets of Au seeds as well as an aggregation and growth mechanism governed by HEPES. In addition to Ag ions and HEPES, morphology tunability can also be achieved by pre-modification of the Au seeds with molecular probes. Optimized probe-containing MB-AuNPs prove to be excellent surface-enhanced Raman scattering (SERS) substrates and nanozymes. Taken together, the results of this work reveal the mechanistic evolution of nanocrystal growth which should stimulate the development of new synthetic strategies, improve the capabilities of tuning the optical, catalytic, and electronic properties of NPs, and further advance their applications in biolabeling, imaging, biosensing, and therapy.

Simple Synthesis of Monodisperse Ultrasmall Au Icosahedral Nanoparticles

Ultrasmall metal nanoparticles (NPs) with a mean diameter below 2 nm are being intensively studied due to their unique structural and chemical properties. At such small sizes, metal particles can appear as various polyhedra with different atomic structures depending on whether electronic effects, surface energy, or the nucleation mechanism govern their crystallization. Therefore, the synthesis of monodisperse nanoparticles of a very small size and well-defined structure requires a good understanding of the different steps of the crystallization process, which can be achieved by conducting and coupling in situ studies at different length and time scales. In this article, we describe the synthesis of ultrasmall gold NPs by reduction of HAuCl4 in solution of oleylamine (OY) in hexane using trialkylsilanes as reducing agents. Thanks to time-resolved in situ small-angle X-ray scattering and X-ray absorption spectroscopy kinetic studies, a competition between nucleation of Au NPs from a solution containing Au(III) clusters and crystallization of a lamellar phase of composition OY-Au(I)-Cl was revealed. In situ X-ray diffraction and pair distribution function (PDF) analysis showed that the first chemical pathway leads to icosahedral NPs while the reduction of OY-Au(I)-Cl leads to fcc NPs. Increasing the reaction rate, achieved by adjusting the silane concentration, changing the nature of the silane (triethylsilane instead of triisopropylsilane), and/or increasing the temperature of reaction, avoided the formation of the Au(I) lamellar phase as the intermediate, leading to monodisperse Au NPs with an icosahedral structure. This fairly simple liquid-phase synthesis method yields highly concentrated suspensions of icosahedral gold NPs, paving the way for their future use in practical applications such as catalysis.

Raman spectroscopy of strained monolayer graphene modulated by monodispersed Au nanoparticles

Due to its inherent exceptional mechanical flexibility and strength, graphene provides an ideal platform for strain engineering, enabling versatile modulation and significant enhancement of their optical properties. Both uniaxial and biaxial strain have been achieved by transferring monolayer graphene onto monodispersed Au nanoparticles with negligible charge doping. We present a study on the phonon frequency and crystallographic orientation in graphene monolayer wrinkles under uniaxial and biaxial strain. The G and 2D peaks of graphene exhibit significant red shifts under tensile strain. The doubly degenerate G peak splits in two sub-peaks G− and G+ under larger uniaxial strain because of symmetry breaking, while this phenomenon does not occur in the 2D peak. But the 2D peak is much more sensitive to strain. Further, Raman spectra of the unsplit G and 2D peaks have been proved to show a distinctive polarization dependence. We proposed polarized Raman spectroscopy to determine the crystallographic orientation with respect to the strain of graphene by the unsplit G mode. The polarization dependence of 2D mode offers a unique opportunity to examine the anisotropic modifications of the phonon dispersion and changes in electronic structures. This result is of significant in strain engineering of graphene and other two-dimensional materials.

Recyclable fluorous gold nanoparticles as catalysts in the biphasic oxidation of 1-octene

A fluorous biphasic approach as a green strategy for the facile recycling of noble metal catalysts has been probed. A library of monodispersed fluorous-stabilized Au nanoparticles (NPs) were successfully synthesized using one of two synthetic methods i.e., a micelle-templated strategy, and a direct method employing two fluorous stabilizers. The fluorous-stabilized AuNPs were evaluated in the fluorous biphasic oxidation of 1-octene as the model substrate, in conjunction with O2, H2O2 and tertbutyl hydroperoxide (TBHP) as oxidants. All the fluorous-stabilized AuNPs which were evaluated were active in the oxidation of 1-octene achieving ± 50% conversions. Irrespective of the fluorous ligand or solvent employed in the oxidation reaction, the catalytic system exhibited an overwhelming degree of selectivity for epoxy-1,2-octane (> 60%) with a slight amount of the 1-octanal and 1-octanoic acid products being produced. More pertinently, the catalyst recycling presented auspicious results pertaining to a possible greener chemical approach to catalytic oxidation. The fluorous-stabilized AuNPs were recycled up to five times in the oxidation of 1-octene, with a negligible decrease in the catalytic conversion for each subsequent recycling run. Therefore, the fluorous biphasic method afforded a highly recyclable noble metal catalytic system, resulting in an increasingly cost-effective approach to catalysis. In an attempt to rationalize the products obtained from the oxidation process, a nanoparticle-assisted oxidation mechanism was proposed. The feasibility of the mechanism was probed through qualitative analysis by gas chromatography – mass spectrometry (GC-MS), which provided analytical evidence to consider the proposed mechanism as viable.

Preparation, chemical characterization and determination of the antioxidant, cytotoxicity and therapeutic effects of gold nanoparticles green-synthesized by Calendula officinalis flower extract in diabetes-induced cardiac dysfunction in rat

• Preparation of mono-dispersed gold nanoparticles using the aqueous extract of Calendula officinalis. • Calendula officinalis acted as reducing and stabilizing agent. • COE@AuNPs shown good antioxidant properties. • The results shown therapeutic effects of COE@AuNPs on diabetes-induced cardiac dysfunction in rat. An ultrasound promoted bio-inspired synthesis of mono-dispersed Au nanoparticles (NPs) has been adopted in this article, templated over Calendula officinalis flower extract. The phytochemicals therein were explored as natural and green reducing as well as NP stabilizers. The as-synthesized bio-nanomaterial (COE@AuNPs) was characterized over FT-IR, UV–Vis spectroscopy, TEM, FE-SEM, EDX and XRD studies. Due to plant extract-based synthesis, the material was obtained as highly dispersed, semi-spherical particles of minuscule dimension (20–25 nm). In the in vivo condition, diabetes was induced by a fructose-enriched diet supplemented by streptozotocin. Half of the animals received COE@AuNPs by oral gavage. Compared to the animals receiving standard chow, serum fasting glucose level was increased and glucose tolerance was diminished in diabetic rats. COE@AuNPs affect significantly fasting hyperglycemia and glucose intolerance; also, it attenuated the diabetes-induced deterioration of cardiac output and cardiac work. Moreover, COE@AuNPs prevented the diabetes-induced increase in cardiac STAT3 phosphorylation. The results of this study indicated the therapeutic effects of COE@AuNPs the diabetes-induced cardiac dysfunction in rat.

Confining Gold Nanoparticles in Preformed Zeolites by Post-Synthetic Modification Enhances Stability and Catalytic Reactivity and Selectivity.

Confining Au nanoparticles (NPs) in a restricted space (e.g., zeolite micropores) is a promising way of overcoming their inherent thermal instability and susceptibility to aggregation, which limit catalytic applications. However, such approaches involve complex, multistep encapsulation processes. Here, we describe a successful strategy and its guiding principles for confining small (<2 nm) and monodisperse Au NPs within commercially available beta and MFI zeolites, which can oxidize CO at 40 °C and show size-selective catalysis. This protocol involves post-synthetic modification of the zeolite internal surface with thiol groups, which confines AuClx species inside microporous frameworks during the activation process whereby Au precursors are converted into Au nanoparticles. The resulting beta and MFI zeolites contain uniformly dispersed Au NPs throughout the void space, indicating that the intrinsic stability of the framework promotes resistance to sintering. By contrast, in situ scanning transmission electron microscopy (STEM) studies evidenced that Au precursors in bare zeolites migrate from the matrix to the external surface during activation, thereby forming large and poorly dispersed agglomerates. Furthermore, the resistance of confined Au NPs against sintering is likely relevant to the intrinsic stability of the framework, supported by extended X-ray absorption fine structure (EXAFS), H2 chemisorption, and CO Fourier transform infrared (FT-IR) studies. The Au NPs supported on commercial MFI maintain their uniform dispersity to a large extent after treatment at 700 °C that sinters Au clusters on mesoporous silicas or beta zeolites. Low-temperature CO oxidation and size-selective reactions highlight that most gold NPs are present inside the zeolite matrix with a diameter smaller than 2 nm. These findings illustrate how confinement favors small, uniquely stable, and monodisperse NPs, even for metals such as Au susceptible to cluster growth under conditions often required for catalytic use. Moreover, this strategy may be readily adapted to other zeolite frameworks that can be functionalized by thiol groups.

Thermal annealing-boosted photoinduced electron transfer efficiency of g-C3N4/Au NPs hybrids for promoting SERS detection of uric acids

As for the ultrasensitive diagnosis of biomolecules via surface-enhanced Raman scattering spectroscopy (SERS), the primary requirement is to effectively enhance the activity of nano-substrates. Herein, we report an interesting strategy for further boosting SERS activity by thermal annealing treatment of as-prepared hybrid substrates. Initially, highly dense and monodisperse plasmonic Au nanoparticles (NPs) were loaded on two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets. By adopting uric acids (UAs) as probe biomolecules, the g-C3N4/Au NPs with appropriate ~2.1% Au compositions exhibit much higher Raman signals than that of the hybrids with other Au contents. Besides the enhancement by routinely controlling hybrid components, the further maximizing SERS activity with a ~2.6-fold improvement than the original one can be obtained by thermal annealing of g-C3N4/Au NPs at 350 ℃ condition. It enables the thermal modified g-C3N4/Au NPs to be applied for highly sensitive monitoring of UAs in artificial urine. The corresponding detection limit is achieved at the ultralow level of 10−11 M, which is nearly two orders of magnitude better than that of the unannealed sample. It should be attributed to the stronger synergistic coupling effect by thermal annealing treatment that gives rise to the higher-efficiency photoinduced electron transfer (PIET) between g-C3N4 supports and plasmonic Au NPs. The present work provides a new opportunity for further promoting the SERS activity of prefabricating nano-substrates, holding great potential for practical monitoring of ultra-trace biomolecules in the near future.

Green and Facile Synthesis of Pullulan-Stabilized Silver and Gold Nanoparticles for the Inhibition of Quorum Sensing.

Pullulan (Pull) decorated with monodisperse Ag and Au nanoparticles (NPs) was synthesized by a simple and green method. Samples were characterized by FTIR, UV–vis, NMR, XRD, TGA, SEM, XPS, DLS, and TEM. SEM images showed highly oriented microforms reported for the first time for Pull, because of the supramolecular self-assembling behavior of Pull chains. Antimicrobial and quorum sensing (QS) inhibition activities were tested against six pathogen bacteria and reporter and biomonitor strain. Pull decorated with NPs, in particular, Ag-modified ones, outperformed pristine Pull. The cell proliferation was tested with an MTT assay. NPs-decorated Pull was studied for the first time as an inhibitory agent against bacterial signal molecules and found to be a good candidate. The promising performance of AgNPs@Pull compared to the commercial antibiotic gentamicin showed that it has great potential as a therapeutic approach to overcome the bacterial resistance that has developed against conventional antibiotics.

Raman Spectroscopy of Strained Monolayer Graphene Modulated by Monodispersed AU Nanoparticles

Raman Spectroscopy of Strained Monolayer Graphene Modulated by Monodispersed AU Nanoparticles

First principle and experimental investigations of monodispersed Au plasmonic nanoparticles on TiO2

Plasmonic nanostructures play an important part in improving the light absorption of semiconductors that are feasible for photovoltaic and other optical devices. In this context, we have synthesized TiO2 thin films with monodispersed Au nanoparticles. These metallic nanoparticles act as plasmonic structures over the smooth semiconductor surface thereby enhancing their properties. X-ray diffraction was done to confirm the formation of the rutile phase while electron microscope images reveal the presence of Au nanoparticles over the entire surface of TiO2 film. Electronic properties were performed to determine a direct bandgap of 2.8 eV which was reduced significantly to 0.3 eV. Thermoelectric calculations were performed to explore the various temeperature dependent physical properties. Optical properties were also enhanced as high values of optical absorption and refractive index were obtained for TiO2 thin film with monodispersed Au nanoparticles.

Aqueous dispersions of monodisperse Pt, Pd, and Au nanoparticles stabilized by thermosensitive polymer for the efficient reduction of nitroarenes

The reduction of nitroarenes is usually catalyzed by heterogeneous catalysts. In this work, highly stable aqueous dispersions of monodisperse Pt, Pd, and Au nanoparticles stabilized by thermosensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), are conveniently synthesized with the average sizes of 2.3, 3.1, and 2.3 nm, respectively. The modulation of the hydrophilic-hydrophobic nano-environments of the catalysts can be selectively provided by utilizing the temperature-responsive characteristics of PNIPAM. They are effective and thermosensitive pseudohomogeneous catalysts for nitroarenes reduction. The decreasing trend of catalytic activity is as follows: PNIPAM-Au > PNIPAM-Pd > PNIPAM-Pt. The catalytic reduction of nitrobenzene (NB), 4-nitrophenol (4-NP), and o-nitroaniline (o-NA) follow the pseudo-first-order kinetics, and the catalytic rates can be tuned by utilizing their temperature-responsive behavior. PNIPAM-Au nanocatalysts exhibit high turnover frequencies (TOF) up to 84, 12.9, and 40 min−1 for catalytic reduction of NB, 4-NP, and o-NA at 20 °C, respectively, which are one of the highest values ever reported.

A comparative study on the effect of monodisperse Au and Ag nanoparticles on the performance of organic photovoltaic devices

The monodisperse Au (~5 nm) and Ag (~3 nm) nanoparticles used in this study were obtained using surfactant-assistant solvothermal methods and characterized by XRD TEM and SEM. Then, these nanoparticles were embedded into the P3HT:PCBM photoactive layer at different ratios and the effects of the nanoparticles on the performance of the organic solar cells have been studied by varying the loading percent of the NPs in the range of 0.5–2 wt%. The best solar cell composition was determined to be 1 wt% for Au NPs and 0.5 wt% for Ag NPs. Optical absorption spectrum of P3HT:PCBM, P3HT:PCBM:AuNPs and P3HT:PCBM:AgNPs active layers were obtained using UV–visible spectroscopy. The J–V plots of ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al solar cells having 1.10−6 m2 OSC area and with different Au NPs and Ag NPs loading ratios in the P3HT:PCBM were obtained under air mass (AM) 1.5G illumination. Open circuit voltage, short-circuit current density, fill factor, and power conversion efficiency of the OSC were calculated. The highest PCE values were obtained as 3.35% for Au NPs and as 3.50% for Ag NPs doped devices. This increase in PCEs was explained by a plasmonic effect that stems from the metallic NPs.

Monodispersed gold nanoparticles entrapped in ordered mesoporous carbon/silica nanocomposites as xanthine oxidase mimic for electrochemical sensing of xanthine.

Monodispersed Au nanoparticles in ordered mesoporous carbon/silica (Au/OMCS) nanocomposites were prepared by the solvent evaporation induced self-assembly. Au/OMCS nanocomposites were characterized through XRD, BET, and TEM. The obtained nanocomposites exhibit uniform mesopores with the size of 18 ± 2nm. And ultrafine Au nanoparticles with the size of 3~7nm are well dispersed in the cavities. An ultrasensitive nanoenzyme sensor was fabricated based on aAu/OMCS-modified electrode. TheAu/OMCS-modified electrode displays high xanthine oxidase-like catalytic activity evaluated through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The DPV response currents are linearly dependent on concentrations of xanthine (Xa) in the range 0.10-20μM, along with a high sensitivity of 6.84μAμM-1cm-2 and very low detection limit of 0.006μM (S/N = 3) under the optimal working potential of 0.64V vs. SCE. Interference experiments show that thenanoenzyme sensor has no obvious responses to most potentially interfering species at apotential of 0.64V. The fabricated sensor has beenapplied to thedetermination of Xa in spiked urine samples with recoveries ranging from 98.26 to 101.4%. Graphical abstract.

Quantifying Electrocatalytic Reduction of CO2 on Twin Boundaries

Summary A protocol relying on the use of silver nanostructures with well-defined dimensions and morphologies (e.g., nanocubes and nanowires) has been developed to differentiate and quantitatively determine the atom-specific activities of different surface atoms toward catalyzing electrochemical CO2 reduction reaction (CO2RR). The atom-specific activity of the twin-boundary edges (TBEs) is comparable to (or slightly higher than) that of the single-crystal edges (SCEs) formed from the crossing of two {100} surfaces, and it is on the order of ∼16 attoampere/atom (aA/atom) toward electrochemical CO2RR. This value is more than two orders higher than the atom-specific activity of the {100} surface atoms, i.e., ∼0.1 aA/atom. The high catalytic activity of the TBEs, which represent a class of commonly existing surface defects in stable metal nanostructures with face-centered cubic lattices, is consistent with the DFT calculations, in which the bridge-type binding configuration of COOH∗ at the TBEs stabilizes this intermediate to promote overall CO2RR.

Photothermal Antibacterial and Antibiofilm Activity of Black Phosphorus/Gold Nanocomposites against Pathogenic Bacteria

Black phosphorus (BP) as a layered two-dimensional (2D) semiconductor material with a tunable band gap has attracted growing attention for promising applications in diverse fields including biotechnology owing to its excellent physical and chemical properties. In this study, BP crystals were synthesized using a chemical vapor transport method and exfoliated into BP nanosheets in deoxygenated water or hexane. Next, monodisperse Au nanoparticles that were synthesized using a surfactant-assisted chemical reduction method were assembled on exfoliated BP nanosheets hexane to yield BP/Au nanocomposites. The photothermal antibacterial and antibiofilm activities of BP nanosheets and BP/Au nanocomposites were investigated against Enterococcus faecalis, a pathogenic biofilm-forming bacterium, by studying the photothermal effect and bacterial growth curve and using colony counting and live/dead fluorescence staining methods under near-infrared (NIR) light irradiation. Thanks to the higher photothermal conversion efficiency of BP/Au nanocomposites than that of bare BP nanosheets under NIR light irradiation, they destructed the bacterial cell membrane more efficiently than bare BP with the biofilm inhibition rate of 58%. It should be noted that this is the first study on the antibacterial and antibiofilm activity of BP/Au nanocomposites via a photothermal process under NIR light irradiation. This work shows the potential of BP/Au nanocomposites in fighting against pathogenic bacteria and paves the way for the exploration of antibacterial platforms based on the biocompatible 2D semiconductor BP.

Optical Sorting at the Single-Particle Level with Single-Nanometer Precision Using Coordinated Intensity and Phase Gradient Forces.

Position-controlled sorting of colloidal nanoparticles (NPs) at the single-particle level is a challenge in nanoscience. Optofluidic potential wells can partially address this challenge, but they have limited flexibility, reconfigurability, and precision. Here we introduce a strategy by feedback-controlled manipulation of NPs using reconfigurable optical traps with designed intensity and phase gradient. Spatiotemporal patterns of these optical traps coordinatively manipulate the NPs based on machine vision of their positions and differentiated scattering intensities. The NPs are always kept inside the optical field during the manipulation and stably trapped once the sorting is accomplished. To substantiate the key advantages of our approach, we present position-controlled optical sorting of single Ag and Au NPs of the same size (150 nm diameter) and ordering of monodisperse Au NPs (80 ± 9 nm diameter) according to their sub-10 nm radius variation, which can hardly be done via other approaches.