Showing papers by "Richard D. Tilley published in 2022"
TL;DR: In this article , the authors demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts.
Abstract: Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. Here we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time. PtRu nanoparticles are the state-of-the-art catalysts for methanol electrooxidation—the anodic reaction in direct methanol fuel cells. Now, a method of dispersing single Pt atoms over Ru nanoparticles is presented and monitored in situ, thereby boosting the catalytic performance in the methanol oxidation reaction.
75 citations
TL;DR: In this article , the authors identify the systems containing different degrees of nanoconfinement and how they can affect the activity and selectivity of electrocatalytic reactions, and then they follow with a fundamental understanding of how electrochemistry and electrocatalysis are affected by nanocon finements, which is beginning to be uncovered, thanks to the development of new, atomically precise manufacturing and fabrication techniques as well as advances in theoretical modeling.
Abstract: Abstract The use of nanoparticles and nanostructured electrodes are abundant in electrocatalysis. These nanometric systems contain elements of nanoconfinement in different degrees, depending on the geometry, which can have a much greater effect on the activity and selectivity than often considered. In this Review, we firstly identify the systems containing different degrees of nanoconfinement and how they can affect the activity and selectivity of electrocatalytic reactions. Then we follow with a fundamental understanding of how electrochemistry and electrocatalysis are affected by nanoconfinement, which is beginning to be uncovered, thanks to the development of new, atomically precise manufacturing and fabrication techniques as well as advances in theoretical modeling. The aim of this Review is to help us look beyond using nanostructuring as just a way to increase surface area, but also as a way to break the scaling relations imposed on electrocatalysis by thermodynamics.
30 citations
TL;DR: In this paper , the authors investigated the microscopic carrier loss mechanisms in thin-film solar cells and found that the effective minority carrier lifetime of CZTSe is dominated by a large grain boundary recombination velocity, which is the major limiting factor of present device performance.
Abstract: Abstract Understanding carrier loss mechanisms at microscopic regions is imperative for the development of high-performance polycrystalline inorganic thin-film solar cells. Despite the progress achieved for kesterite, a promising environmentally benign and earth-abundant thin-film photovoltaic material, the microscopic carrier loss mechanisms and their impact on device performance remain largely unknown. Herein, we unveil these mechanisms in state-of-the-art Cu 2 ZnSnSe 4 (CZTSe) solar cells using a framework that integrates multiple microscopic and macroscopic characterizations with three-dimensional device simulations. The results indicate the CZTSe films have a relatively long intragrain electron lifetime of 10–30 ns and small recombination losses through bandgap and/or electrostatic potential fluctuations. We identify that the effective minority carrier lifetime of CZTSe is dominated by a large grain boundary recombination velocity (~10 4 cm s −1 ), which is the major limiting factor of present device performance. These findings and the framework can greatly advance the research of kesterite and other emerging photovoltaic materials.
28 citations
TL;DR: In this article , a method to anchor single atom catalysts (SACs) with ultra low mass loadings at the edges of edge-rich vertically aligned graphene (as low as 0.71 µg Pt cm-2) is developed.
Abstract: Graphene edges exhibit a highly localized density of states that result in increased reactivity compared to its basal plane. However, exploiting this increased reactivity to anchor and tune the electronic states of single atom catalysts (SACs) remains elusive. To investigate this, a method to anchor Pt SACs with ultra‐low mass loadings at the edges of edge‐rich vertically aligned graphene (as low as 0.71 µg Pt cm–2) is developed. Angle‐dependent X‐ray absorption spectroscopy and density‐functional theory calculations reveal that edge‐anchored Pt SACs has a robust coupling with the π‐electrons of graphene. This interaction results in a higher occupancy of the Pt 5d orbital, shifting the d‐band center toward the Fermi level, improving the adsorption of *H for the hydrogen evolution reaction (HER). Pt primarily coordinated to the graphene edge shows improved alkaline HER performance compared to Pt coordinated in mixed environments (turnover frequencies of 22.6 and 10.9 s–1 at an overpotential of 150 mV, respectively). This work demonstrates an effective route to engineering the coordination environment of Pt SACs by using the graphene edge for enhanced energy conversion reactions.
15 citations
TL;DR: In this paper , an ultrasound sensitive and highly selective electrochemical biosensor was developed for the rapid detection of DNA methylation in blood, which is based on a network of probe DNA modified gold-coated magnetic nanoparticles (DNA-Au@MNPs) complementary to target DNA, and subsequently enzymatic cleavage to differentiate methylated DNA strand from corresponding unmethylated DNA strands.
11 citations
TL;DR: Optical nanopore sensing assays that have been developed to detect clinically relevant biomarkers, the potential for multiplexing such measurements, and techniques to fabricate high density arrays of nanopores with a view toward the use of these devices for clinical applications are discussed.
Abstract: Nanopore sensors have received significant interest for the detection of clinically important biomarkers with single-molecule resolution. These sensors typically operate by detecting changes in the ionic current through a nanopore due to the translocation of an analyte. Recently, there has been interest in developing optical readout strategies for nanopore sensors for quantitative analysis. This is because they can utilize wide-field microscopy to independently monitor many nanopores within a high-density array. This significantly increases the amount of statistics that can be obtained, thus enabling the analysis of analytes present at ultralow concentrations. Here, we review the use of optical nanopore sensing strategies for quantitative analysis. We discuss optical nanopore sensing assays that have been developed to detect clinically relevant biomarkers, the potential for multiplexing such measurements, and techniques to fabricate high density arrays of nanopores with a view toward the use of these devices for clinical applications.
10 citations
TL;DR: The importance of the physicochemical properties of nanoparticles on cellular uptake and how they can be adjusted to selectively target the dominated endocytosis pathway of cancer cells over healthy cells and to deliver anticancer drug to the target cells is highlighted.
Abstract: Targeted drug delivery in cancer typically focuses on maximising the endocytosis of drugs into the diseased cells. However, there has been less focus on exploiting the differences in the endocytosis pathways of cancer cells versus non-cancer cells. An understanding of the endocytosis pathways in both cancer and non-cancer cells allows for the design of nanoparticles to deliver drugs to cancer cells whilst restricting healthy cells from taking up anticancer drugs, thus efficiently killing the cancer cells. Herein we compare the differences in the endocytosis pathways of cancer and healthy cells. Second, we highlight the importance of the physicochemical properties of nanoparticles (size, shape, stiffness, and surface chemistry) on cellular uptake and how they can be adjusted to selectively target the dominated endocytosis pathway of cancer cells over healthy cells and to deliver anticancer drug to the target cells. The review generates new thought in the design of cancer-selective nanoparticles based on the endocytosis pathways.
9 citations
TL;DR: In this article , the authors demonstrate that varying the branch width by altering the size of the seed that the branch grows off is an effective method to precisely tune the stacking fault density in branched Ni nanoparticles.
Abstract: Creating high surface area nanocatalysts that contain stacking faults is a promising strategy to improve catalytic activity. Stacking faults can tune the reactivity of the active sites, leading to improved catalytic performance. The formation of branched metal nanoparticles with control of the stacking fault density is synthetically challenging. In this work, we demonstrate that varying the branch width by altering the size of the seed that the branch grows off is an effective method to precisely tune the stacking fault density in branched Ni nanoparticles. A high density of stacking faults across the Ni branches was found to lower the energy barrier for Ni2+/Ni3+ oxidation and result in enhanced activity for electrocatalytic oxidation of 5-hydroxylmethylfurfural. These results show the ability to synthetically control the stacking fault density in branched nanoparticles as a basis for enhanced catalytic activity.
9 citations
TL;DR: In this article , the atomic-scale structural features of exposed surface facets have been investigated for enhancing catalytic activity and stability of branched nanoparticles, and the role of branch dimensions and the number of branches has been discussed.
Abstract: ConspectusBranched metal nanoparticles have unique catalytic properties because of their high surface area with multiple branches arranged in an open 3D structure that can interact with reacting species and tailorable branch surfaces that can maximize the exposure of desired catalytically active crystal facets. These exceptional properties have led to the exploration of the roles of branch structural features ranging from the number and dimensions of branches at the larger scales to the atomic-scale arrangement of atoms on precise crystal facets. The fundamental significance of how larger-scale branch structural features and atomic-scale surface faceting influence and control the catalytic properties has been at the forefront of the design of branched nanoparticles for catalysis. Current synthetic advances have enabled the formation of branched nanoparticles with an unprecedented degree of control over structural features down to the atomic scale, which have unlocked opportunities to make improved nanoparticle catalysts. These catalysts have high surface areas with controlled size and surface facets for achieving exceedingly high activity and stability. The synthetic advancement has recently led to the use of branched nanoparticles as ideal substrates that can be decorated with a second active metal in the form of islands and single atoms. These decorated branched nanoparticles have new and highly effective catalytic active sites where both branch metal and decorating metal play essential roles during catalysis.In the opening half of this Account, we critically assess the important structural features of branched nanoparticles that control catalytic properties. We first discuss the role of branch dimensions and the number of branches that can improve the surface area but can also trap gas bubbles. We then investigate the atomic-scale structural features of exposed surface facets, which are critical for enhancing catalytic activity and stability. Well-defined branched nanoparticles have led to a fundamental understanding of how the branch structural features influence the catalytic activity and stability, which we highlight for the oxygen evolution reaction (OER) and biomass oxidation. In discussing recent breakthroughs for branched nanoparticles, we explore the opportunities created by decorated branched nanoparticles and the unique bifunctional active sites that are exposed on the branched nanoparticle surfaces. This class of catalysts is of rapidly growing importance for reactions including the hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR), where two exposed metals are required for efficient catalysis. In the second half of this Account, we explore recent advances in the synthesis of branched nanoparticles and highlight the cubic-core hexagonal-branch growth mechanism that has achieved excellent control of all of the important structural features, including branch dimensions, number of branches, and surface facets. We discuss the slow precursor reduction as an effective strategy for decorating metal islands with controlled loadings on the branched nanoparticle surfaces and the spread of these metal islands to form single-atom active sites. We envisage that the key synthetic and structural advances identified in this Account will guide the development of the next-generation electrocatalysts.
8 citations
TL;DR: In this paper , the authors investigated the fluorescence and biocompatibility of hydrophilic silicon quantum dots (SiQDs) that are doped with scandium, copper, and zinc.
Abstract: This study investigated the fluorescence and biocompatibility of hydrophilic silicon quantum dots (SiQDs) that are doped with scandium (Sc-SiQDs), copper (Cu-SiQDs), and zinc (Zn-SiQDs), indicating their feasibility for the bioimaging of tear film. SiQDs were investigated for fluorescence emission by the in vitro imaging of artificial tears (TheraTears®), using an optical imaging system. A trypan blue exclusion test and MTT assay were used to evaluate the cytotoxicity of SiQDs to cultured human corneal epithelial cells. No difference was observed between the fluorescence emission of Sc-SiQDs and Cu-SiQDs at any concentration. On average, SiQDs showed stable fluorescence, while Sc-SiQDs and Cu-SiQDs showed brighter fluorescence emissions than Zn-SiQDs. Cu-SiQDs and Sc-SiQDs showed a broader safe concentration range than Zn-SiQDs. Cu-SiQDs and Zn-SiQDs tend to aggregate more substantially in TheraTears® than Sc-SiQDs. This study elucidates the feasibility of hydrophilic Sc-SiQDs in studying the tear film’s aqueous layer.
6 citations
TL;DR: In this article , a hyperbranched vertical array of defective graphene for enduring deep Li cycling at practical levels of areal capacity (>6 mAh cm−2) was proposed.
Abstract: Lithium (Li) metal anode have shown exceptional potential for high-energy batteries. However, practical cell-level energy density of Li metal batteries is usually limited by the low areal capacity (<3 mAh cm−2) because of the accelerated degradation of high–areal capacity Li metal anodes upon cycling. Here, we report the design of hyperbranched vertical arrays of defective graphene for enduring deep Li cycling at practical levels of areal capacity (>6 mAh cm−2). Such atomic-to-macroscopic trans-scale design is rationalized by quantifying the degradation dynamics of Li metal anodes. High-energy Li metal cells are prototyped under realistic conditions with high cathode capacity (>4 mAh cm−2), low negative-to-positive electrode capacity ratio (1:1), and low electrolyte-to-capacity ratio (5 g Ah−1), which shed light on a promising move toward practical Li metal batteries.
TL;DR: In this paper , the authors present a review of the theoretical models used for the calculation of the resistance of the nanopore, and the corresponding change in nanopore resistance due to a translocation event.
Abstract: Nanopores are promising sensing devices that can be used for the detection of analytes at the single molecule level. It is of importance to understand and model the current response of a nanopore sensor for improving the sensitivity of the sensor, a better interpretation of the behaviours of different analytes in confined nanoscale spaces, and quantitative analysis of the properties of the targets. The current response of a nanopore sensor, usually called a resistive pulse, results from the change in nanopore resistance when an analyte translocates through the nanopore. This article reviews the theoretical models used for the calculation of the resistance of the nanopore, and the corresponding change in nanopore resistance due to a translocation event. Models focus on the resistance of the pore cavity region and the access region of the nanopore. The influence of the sizes, shapes and surface charges of the translocating species and the nanopore, as well as the trajectory that the analyte follows are also discussed. This review aims to give a general guidance to the audience for understanding the current response of a nanopore sensor and the application of this class of sensor to a broad range of species with the theoretical models.
TL;DR: A new photoelectrochemical surface based on a transparent electrode that is compatible with high-resolution fluorescence microscopy for isolating individual rare cells from complex biological samples and demonstrates the capture of cancer cells on an antibody-coated surface and selective release of single cancer cells with low expression of epithelial cell adhesion molecules.
Abstract: Selective isolation of individual target cells from a heterogeneous population is technically challenging; however, the ability to retrieve single cells can have high significance in various aspects of biological research. Here, we present a new photoelectrochemical surface based on a transparent electrode that is compatible with high-resolution fluorescence microscopy for isolating individual rare cells from complex biological samples. This is underpinned by two important factors: (i) careful design of the electrode by patterning discrete Au disks of micron dimension on amorphous silicon-indium tin oxide films and (ii) orthogonal surface chemistry, which modifies the patterned electrode with self-assembly layers of different functionalities, to selectively capture target cells on the Au disks and resist cell binding to the amorphous silicon surface. The co-stimulation of the surface using light from a microscope and an electric potential triggers the reductive desorption of the alkanethiol monolayer from the Au disks to release the single cells of interest from the illuminated regions only. Using circulating tumor cells as a model, we demonstrate the capture of cancer cells on an antibody-coated surface and selective release of single cancer cells with low expression of epithelial cell adhesion molecules.
TL;DR: Proof-of-concept evidence that HDX@YSN@CCM@cRGD could overcome the delivery barriers and achieve targeted treatment of glioblastoma is provided, as well as exceptional treatment efficacy of the NIR-triggered chemotherapy and photodynamic therapy.
Abstract: Glioblastoma is hard to be eradicated partly because of the obstructive blood-brain barrier (BBB) and the dynamic autophagy activities of glioblastoma. Here, hydroxychloroquine (HDX)-loaded yolk-shell upconversion nanoparticle (UCNP)@Zn0.5Cd0.5S nanoparticle coating with the cyclic Arg-Gly-Asp (cRGD)-grafted glioblastoma cell membrane for near-infrared (NIR)-triggered treatment of glioblastoma is prepared for the first time. UCNPs@Zn0.5Cd0.5S (abbreviated as YSN, yolk-shell nanoparticle) under NIR radiation will generate reactive oxygen species for imposing cytotoxicity. HDX, the only available autophagy inhibitor in clinical studies, can enhance cytotoxicity by preventing damaged organelles from being recycled. The cRGD-decorated cell membrane allowed the HDX-loaded nanoparticles to efficiently bypass the BBB and specifically target glioblastoma cells. Exceptional treatment efficacy of the NIR-triggered chemotherapy and photodynamic therapy was achieved in U87 cells and in the mouse glioblastoma model as well. Our results provided proof-of-concept evidence that HDX@YSN@CCM@cRGD could overcome the delivery barriers and achieve targeted treatment of glioblastoma.
TL;DR: In this paper , a flow-based method for the synthesis of gold-coated magnetic nanoparticles via a flowbased manufacturing system that can easily be scaled up is presented, which can produce a complete, tunable gold shell with relatively uniform size and shape.
Abstract: Gold‐coated magnetic nanoparticles are key materials for the fast separation and ultrasensitive detection of analytes in magnetoplasmonic sensors. However, the synthesis of gold‐coated magnetic nanoparticles typically requires small‐scale, colloidal methods over hours or days and often results in incomplete shells with variable optical properties. A robust, rapid, and scalable synthesis method is still needed to reliably form a complete gold nanoshell around magnetic nanoparticles. Herein, a new methodology for the synthesis of gold‐coated magnetic nanoparticles via a flow‐based manufacturing system that can easily be scaled up is presented. The developed method first produces gold‐seeded silica coated magnetic nanoparticles and then a complete, tunable gold shell with relatively uniform size and shape. The flow‐based method can be performed in a total time of less than 2 min, enabling rapid and complete gold coating. The particles show both excellent magnetic and plasmonic properties, which facilitates application as biosensing agents in dark‐field microscopy and surface‐enhanced Raman scattering.
TL;DR: In this article , a calibration free approach for electrochemical aptamer-based sensors on bulk electrodes to microRNA (miR-21) detection with methylene blue terminated DNA modified Au@MNPs is presented.
Abstract: Gold coated magnetic nanoparticles (Au@MNPs), modified with DNA sequences give dispersible electrodes that can detect ultralow amounts of microRNAs and other nucleic acids but, as with most other sensors, they require calibration. Herein we show how to adapt a calibration free approach for electrochemical aptamer-based sensors on bulk electrodes to microRNA (miR-21) detection with methylene blue terminated DNA modified Au@MNPs. The electrochemical square wave voltammetry signal from the DNA-Au@MNPs when collected at a bulk electrode under magnetic control, decreases upon capture of miR-21. We show that the square wave voltammogram has concentration dependent and independent frequencies that can be used to give a calibration free signal.
TL;DR: In this article , the authors combine the best of both systems by developing a synthetic hydrogel with ionic cross-linking of block copolyelectrolytes to rapidly create hydrogels.
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TL;DR: In this paper , a spreading process was proposed to grow and spread Pt islands on faceted Ru branched nanoparticles to make single Pt atom on Ru catalysts. But the authors did not consider the formation of single Pt atoms from Pt islands.
Abstract: Single Pt atom catalysts on non-active carbon supports have been identified as key targets for electrochemical reactions because the high exposure of active Pt leads to record-high activities. For the methanol oxidation reaction (MOR) a PtRu allow materials is known as the most active catalyst, as the Ru atoms decrease CO poisoning of the active Pt. To combine the exceptional activity of single atom Pt catalysts with the benefits of an active metal support we must overcome the synthetic challenge of forming single Pt atoms on noble metal surfaces. Here, we have developed a process that grows and spreads Pt islands on faceted Ru branched nanoparticles to make single Pt atom on Ru catalysts [1]. Using high-speed atomic resolution in-situ environmental transmission electron microscopy (ETEM) studies, we reveal a spreading process as an effective concept for forming single Pt atom catalysts. The thermodynamically driven rearrangement of Pt islands on the Ru low index facets forms discrete Pt atoms on a Ru nanoparticle surface which display a very high resilience to CO-poisoning and generate record-high current density and mass activity. To understand the formation of single Pt atoms from Pt islands, changes in the Pt structure were observed over