Showing papers by "Qingbo Zhang published in 2022"

Light doping of tungsten into copper-platinum nanoalloys for boosting their electrocatalytic performance in methanol oxidation

Abstract: Coupling the bi-functional mechanism with compressive lattice strain might be an effective way to boost the electrocatalysis of platinum (Pt)-based nanoparticles for methanol oxidation reaction (MOR). This strategy weakens the chemisorption of poisoning CO-like intermediates generated during MOR on the active Pt sites by lowering their d-band center. In this context, we herein report the synthesis of ternary copper-tungsten-platinum (CuWPt) nanoalloys with light doping of W element by simply co-reducing their precursors at elevated temperature. In this ternary alloy system, the presence of only small amount of W element not only weakens the chemisorption of CO-like intermediates by lowering the Pt d-band center through compressive lattice strain, but also cleans the active Pt sites by "hydrogen spillover effect", endowing the as-prepared CuWPt nanoalloys at an appropriate Cu/W/Pt ratio with good activity for MOR. In specific, the ternary CuWPt alloy nanoparticles at a Cu/W/Pt molar ratio of 21/4/75 show a specific activity of 2.5 mA·cm⁻² and a mass activity of 2.11 A·mg⁻¹ with a better durability, outperforming those ternary CuWPt alloy nanoparticles at other Cu/W/Pt ratios, binary CuPt alloys and commercial Pt/C catalyst as well as a large number of reported Pt-based electrocatalysts. In addition, a single direct methanol fuel cell (DMFC) assembled using ternary CuWPt nanoalloys as anodic catalysts shows a power density of 24.3 mW·cm⁻² and an open-circle voltage of 0.6 V, also much higher than those of the single DMFC assembled from commercial Pt/C catalysts.

Multichannel power electronics and magnetic nanoparticles for selective thermal magnetogenetics

Abstract: Objective. We present a combination of a power electronics system and magnetic nanoparticles that enable frequency-multiplexed magnetothermal-neurostimulation with rapid channel switching between three independent channels spanning a wide frequency range. Approach. The electronics system generates alternating magnetic field spanning 50 kHz to 5 MHz in the same coil by combining silicon (Si) and gallium-nitride (GaN) transistors to resolve the high spread of coil impedance and current required throughout the wide bandwidth. The system drives a liquid-cooled field coil via capacitor banks, forming three series resonance channels which are multiplexed using high-voltage contactors. We characterized the system by the output channels’ frequencies, field strength, and switching time, as well as the system’s overall operation stability. Using different frequency–amplitude combinations of the magnetic field to target specific magnetic nanoparticles with different coercivity, we demonstrate actuation of iron oxide nanoparticles in all three channels, including a novel nanoparticle composition responding to magnetic fields in the megahertz range. Main results. The system achieved the desired target field strengths for three frequency channels, with switching speed between channels on the order of milliseconds. Specific absorption rate measurements and infrared thermal imaging performed with three types of magnetic nanoparticles demonstrated selective heating and validated the system’s intended use. Significance. The system uses a hybrid of Si and GaN transistors in bridge configuration instead of conventional amplifier circuit concepts to drive the magnetic field coil and contactors for fast switching between different capacitor banks. Series-resonance circuits ensure a high output quality while keeping the system efficient. This approach could significantly improve the speed and flexibility of frequency-multiplexed nanoparticle actuation, such as magnetogenetic neurostimulation, and thus provide the technical means for selective stimulation below the magnetic field’s fundamental spatial focality limits.

Increasing the antioxidant capacity of ceria nanoparticles with catechol-grafted poly(ethylene glycol).

Abstract: Ceria nanoparticles are remarkable antioxidants due to their large cerium(III) content and the possibility of recovering cerium(III) from cerium(IV) after reaction. Here we increase the cerium(III) content of colloidally stable nanoparticles (e.g., nanocrystals) using a reactive polymeric surface coating. Catechol-grafted poly(ethylene glycols) (PEG) polymers of varying lengths and architectures yield materials that are non-aggregating in a variety of aqueous media. Cerium(IV) on the ceria surface both binds and oxidizes the catechol functionality, generating a dark-red colour emblematic of surface-oxidized catechols with a concomitant increase in cerium(III) revealed by X-ray photoemission spectroscopy (XPS). The extent of ceria reduction depends sensitively on the architecture of the coating polymer; small and compact polymer chains pack with high density at the nanoparticle surface yielding the most cerium(III). Nanoparticles with increased surface reduction, quantified by the intensity of their optical absorption and thermogravimetric measures of polymer grafting densities, were more potent antioxidants as measured by a standard TEAC antioxidant assay. For the same core composition nanoparticle antioxidant capacities could be increased over an order of magnitude by tailoring the length and architecture of the reactive surface coatings.

Multifunctional Magnetic Nanoclusters Can Induce Immunogenic Cell Death and Suppress Tumor Recurrence and Metastasis.

Abstract: Metastasis is the predominant cause of cancer deaths due to solid organ malignancies; however, anticancer drugs are not effective in treating metastatic cancer. Here we report a nanotherapeutic approach that combines magnetic nanocluster-based hyperthermia and free radical generation with an immune checkpoint blockade (ICB) for effective suppression of both primary and secondary tumors. We attached 2,2'-azobis(2-midinopropane) dihydrochloride (AAPH) molecules to magnetic iron oxide nanoclusters (IONCs) to form an IONC-AAPH nanoplatform. The IONC can generate a high level of localized heat under an alternating magnetic field (AMF), which decomposes the AAPH on the cluster surface and produces a large number of carbon-centered free radicals. A combination of localized heating and free radicals can effectively kill tumor cells under both normoxic and hypoxic conditions. The tumor cell death caused by the combination of magnetic heating and free radicals led to the release or exposure of various damage-associated molecule patterns, which promoted the maturation of dendritic cells. Treating the tumor-bearing mice with IONC-AAPH under AMF not only eradicated the tumors but also generated systemic antitumor immune responses. The combination of IONC-AAPH under AMF with anti-PD-1 ICB dramatically suppressed the growth of untreated distant tumors and induced long-term immune memory. This IONC-AAPH based magneto-immunotherapy has the potential to effectively combat metastasis and control cancer recurrence.