Imperial College London

Professor Fang Xie

Faculty of EngineeringDepartment of Materials

Professor of Functional Materials
 
 
 
//

Contact

 

+44 (0)20 7594 9693f.xie Website

 
 
//

Location

 

1.03Royal School of MinesSouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

121 results found

Tabish TA, Xu J, Campbell CK, Abbas M, Myers WK, Didwal P, Carugo D, Xie F, Crabtree MJ, Stride E, Lygate CAet al., 2024, pH-sensitive release of nitric oxide gas using peptide-graphene co-assembled hybrid nanosheets, Nitric Oxide, Vol: 147, Pages: 42-50, ISSN: 1089-8603

Nitric oxide (NO) donating drugs such as organic nitrates have been used to treat cardiovascular diseases for more than a century. These donors primarily produce NO systemically. It is however sometimes desirable to control the amount, location, and time of NO delivery. We present the design of a novel pH-sensitive NO release system that is achieved by the synthesis of dipeptide diphenylalanine (FF) and graphene oxide (GO) co-assembled hybrid nanosheets (termed as FF@GO) through weak molecular interactions. These hybrid nanosheets were characterised by using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, zeta potential measurements, X-ray photoelectron spectroscopy, scanning and transmission electron microscopies. The weak molecular interactions, which include electrostatic, hydrogen bonding and π-π stacking, are pH sensitive due to the presence of carboxylic acid and amine functionalities on GO and the dipeptide building blocks. Herein, we demonstrate that this formulation can be loaded with NO gas with the dipeptide acting as an arresting agent to inhibit NO burst release at neutral pH; however, at acidic pH it is capable of releasing NO at the rate of up to 0.6 μM per minute, comparable to the amount of NO produced by healthy endothelium. In conclusion, the innovative conjugation of dipeptide with graphene can store and release NO gas under physiologically relevant concentrations in a pH-responsive manner. pH responsive NO-releasing organic-inorganic nanohybrids may prove useful for the treatment of cardiovascular diseases and other pathologies.

Journal article

Xie F, 2023, (Invited) Novel Plasmonic Materials as Fluorescence Enhancers for Biosensing and Bioimaging in Near Infrared Window, ECS Meeting Abstracts, Vol: MA2023-02, Pages: 2967-2967

<jats:p> Novel plasmonic nanostructures, which are near-IR active, has been developed in our group as powerful fluorescence enhancers. The technology is highly versatile for ultrasensitive diagnosis and deep tissue imaging-two key areas for future diagnostics. I will present some nanostructures we have designed and developed and then discuss their applications in biosensing and cell imaging in near infrared biological transparency window. </jats:p>

Journal article

Ji C, Zhou H, Tang S, Sharma P, Ryan MP, Jason Riley D, Xie Fet al., 2023, Advances in three-component plasmonic-assisted heterostructures for enhanced photocatalysis and photoelectrochemical catalysis, Materials Today, Vol: 70, Pages: 137-160, ISSN: 1369-7021

Traditional semiconductor materials such as metal-oxide-based photoelectrodes have been extensively explored for energy and environmental applications. However, their performance is hindered by poor light absorption, high charge recombination rates, and low surface kinetics. The incorporation of metal–organic framework (MOF) and plasmonic structures into semiconductors is one of the most promising strategies to achieve performances beyond those of bare MOF and/or conventional semiconductors. This review summarises the rational design of semiconductor-based photoelectrodes incorporating MOFs and plasmonic metals for hybrid photoelectrochemical catalysis and photocatalysis, with a wide variety of parameters including photoactivity, conductivity, catalytic property, surface morphology, porous architecture and bandgap alignment. Moreover, applications of this new generation of composite photoelectrodes in water splitting, CO2 reduction and pollution degradation are discussed in detail. The challenges and prospects of plasmonic MOF nanocomposites in eco-friendly and cost-efficient technologies for practical applications in water splitting, CO2 reduction and environmental remediation are also highlighted.

Journal article

Zhang H, Diao J, Liu Y, Zhao H, Ng BKY, Ding Z, Guo Z, Li H, Jia J, Yu C, Xie F, Henkelman G, Titirici M-M, Robertson J, Nellist P, Duan C, Guo Y, Riley DJ, Qiu Jet al., 2023, In-situ grown Cu dendrites plasmonically enhance electrocatalytic hydrogen evolution on facet-engineered Cu₂O, Advanced Materials, Vol: 35, ISSN: 0935-9648

Electrocatalytic hydrogen evolution reaction (HER) is widely regarded as one of the most efficient and sustainable strategies for hydrogen production. Up to now, most electrocatalysis research related to HER mainly focuses on stand-alone electrocatalysis and fails to pay attention to the integration of other driving forces such as light. Herein, Cu2 O nanostructures with different exposed crystal facets were synthesized by wet chemical methods for electrocatalytic HER, and it was found that the octahedral Cu2 O nanostructures with exposed crystal planes of (111) (O-Cu2 O) had the best hydrogen evolution performance. Density functional theory (DFT) calculations found that the better HER performance on Cu2 O (111) facets was attributed to the lower energy barrier in the Heyrovsky step. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu2 O was reduced during HER, in which Cu dendrites were grown on the surface of the Cu2 O nanostructures, resulting in the better HER performance of O-Cu2 O after HER (O-Cu2 O-A) compared with that of the as-prepared O-Cu2 O. DFT calculations indicated that the charge transfer at the Cu2 O/Cu interface enhanced its surface electron concentration. Under illumination, the onset potential of O-Cu2 O-A is ca. 52 mV positive than that of O-Cu2 O, which is induced by the plasmon-activated electrochemical system consisting of Cu2 O and the in-situ generated Cu dendrites. Incident photon-to-current efficiency (IPCE) measurements, ultraviolet-visible (UV-Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) demonstrate the hot electron injection (HEI) from Cu dendrites to Cu2 O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed that the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu2 O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu2 O. These make t

Journal article

Xu J, Fu M, Ji C, Centeno A, Kim DK, Evers K, Heutz SEM, Oulton R, Ryan MP, Xie Fet al., 2023, Plasmonic‐enhanced NIR‐II downconversion fluorescence beyond 1500 nm from core–shell–shell lanthanide nanoparticles, Advanced Optical Materials, Vol: 11, ISSN: 2195-1071

This paper reports on the light amplification of NaGdF4:Yb,Er,Ce@NaGdF4:Yb,Nd@NaGdF4 core–shell–shell downconversion nanoparticles (CSS-DCNPs) in the near-infrared second biological window (NIR-II: 1000–1700 nm) by plasmonic nanostructures. Through a precisely controlled plasmonic metallic nanostructure, fluorescence from Yb3+ induced 1000 nm emission, Nd3+ induced 1060 nm emission, and Er3+ induced 1527 nm emission are enhanced 1.6-fold, 1.7-fold, and 2.2-fold, respectively, under an 808 nm laser excitation for the CSS-DCNPs coupled with a gold hole-cap nanoarray (Au-HCNA), while the Er3+ induced 1527 nm emission under a 980 nm laser excitation is enhanced up to 6-fold. To gain insight into the enhancement mechanism, the plasmonic modulation of Er3+ induced NIR-II emission at 1550 nm under 980 nm excitation is studied by FDTD simulation and lifetime measurements, showing the observed fluorescence enhancement can be attributed to a combination of enhanced excitation and an increased radiative decay rate.

Journal article

Ji C, Xu J, Jiang Q, Kerherve G, Zhou H, li X, Tang S, Sharma P, Riley DJ, Xie Fet al., 2023, Significantly boosted photoelectrochemical water splitting performance by plasmonic enhanced Hematite@MOF composite photoelectrodes, Materials Today Advances, Vol: 18, Pages: 1-13, ISSN: 2590-0498

Hematite as a catalyst for photoelectrochemical water splitting offers huge potential, due to its high chemical stability, great abundance, and low cost. However, the low water oxidation kinetics and poor charge transportation have hindered progress towards the manufacture of practical water splitting devices. To tackle these problems, a visible light responsive metal-organic framework (MOF) polyhedral zeolitic imidazolate (ZIF-67), and optimised plasmonic Ag nanorods were incorporated into hematite nanostructures to form a three-component heterojunction photoelectrode. The designed photoanode showed dramatically improved light harvesting in the visible range and enhanced charge transport. A mechanistic investigation allowed the deconvolution of the enhanced performance pathways. First, the Hematite@ZIF-67 core-shell p-n junction enables facile charge carrier transfer between ZIF-67 and hematite. In addition, ZIF-67 also provides active sites for water oxidation and boosts surface oxygen evolution reaction (OER) kinetics. Guided by finite-difference time-domain (FDTD) modelling, Ag nanorods with optimised aspect ratio were incorporated between ZIF-67 and hematite. The Ag nanorods facilitate broadband light absorption and surface charge injection, induced by near-field excitation enhancement and plasmonic resonance energy transfer (PRET) pathways. The design and addition of ZIF-67 and Ag nanorods result in superior performance for a hematite-based photoanode for photoelectrochemical (PEC) water oxidation.

Journal article

Morfill C, Pankratova S, Machado P, Fernando NK, Regoutz A, Talamona F, Pinna A, Klosowski M, Wilkinson RJ, Fleck RA, Xie F, Porter AE, Kiryushko Det al., 2023, Addition to "Nanostars carrying multifunctional neurotrophic dendrimers protect neurons in preclinical in vitro models of neurodegenerative disorders"., ACS Applied Materials and Interfaces, Vol: 15, Pages: 13824-13824, ISSN: 1944-8244

In the original version of this article (p. 47457), some acknowledgments were not included. In the revised Acknowledgments section provided below, we additionally provide The REC reference for the ethical approval of the human astrocyte isolation, an acknowledgment to Dr. Alize Proust at the Francis Crick Institute for establishing the triple coculture BBB model used in this study, and the reference and the grant number for the source of the human fetal material. This does not affect the results or conclusions of our work.

Journal article

Tian T, Xu J, Abdolazizi A, Ji C, Hou J, Riley DJ, Yan C, Ryan MP, Xie F, Petit Cet al., 2023, Occurrence, geochemical characteristics, enrichment, and ecological risks of rare earth elements in sediments of "the Yellow river- Estuary- bay" system*, MATERIALS TODAY NANO, Vol: 21, ISSN: 2588-8420

Journal article

Morton W, Joyce C, Taylor J, Ryan M, Angioletti-Uberti S, Xie Fet al., 2023, Modeling Au nanostar geometry in bulk solutions., The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 127, Pages: 1680-1686, ISSN: 1932-7447

The findings within make it possible to reference gold nanostars based on their geometric properties, similar to how a radius describes a nanosphere, rather than just the LSPR of the structure-the current practice. The average tip approximation presented reduces the complexity of nanostars in discrete dipole approximation simulations. By matching the projected area and LSPR of the modeled nanostars to synthesized nanostars, the volume, surface area, and number of tips can be approximated without a lengthy characterization process. Knowing the nanoparticle geometry can determine drug carrier capacity, an approximate number of hot spots for EM imaging, and how the particle will interact with cells. The geometric data obtained will drive the biological application and increase the usability of this particle class.

Journal article

Zhang H, Diao J, Ouyang M, Yadegari H, Mao M, Wang M, Henkelman G, Xie F, Riley DJet al., 2023, Heterostructured core-Shell Ni-Co@Fe-Co nanoboxes of prussian blue analogues for efficient electrocatalytic hydrogen evolution from alkaline seawater., ACS Catalysis, Vol: 13, Pages: 1349-1358, ISSN: 2155-5435

The rational construction of efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) is critical to seawater electrolysis. Herein, trimetallic heterostructured core-shell nanoboxes based on Prussian blue analogues (Ni-Co@Fe-Co PBA) were synthesized using an iterative coprecipitation strategy. The same coprecipitation procedure was used for the preparation of the PBA core and shell, with the synthesis of the shell involving chemical etching during the introduction of ferrous ions. Due to its unique structure and composition, the optimized trimetallic Ni-Co@Fe-Co PBA possesses more active interfacial sites and a high specific surface area. As a result, the developed Ni-Co@Fe-Co PBA electrocatalyst exhibits remarkable electrocatalytic HER performance with small overpotentials of 43 and 183 mV to drive a current density of 10 mA cm-2 in alkaline freshwater and simulated seawater, respectively. Operando Raman spectroscopy demonstrates the evolution of Co2+ from Co3+ in the catalyst during HER. Density functional theory simulations reveal that the H*-N adsorption sites lower the barrier energy of the rate-limiting step, and the introduced Fe species improve the electron mobility of Ni-Co@Fe-Co PBA. The charge transfer at the core-shell interface leads to the generation of H* intermediates, thereby enhancing the HER activity. By pairing this HER catalyst (Ni-Co@Fe-Co PBA) with another core-shell PBA OER catalyst (NiCo@A-NiCo-PBA-AA) reported by our group, the fabricated two-electrode electrolyzer was found to achieve high output current densities of 44 and 30 mA cm-2 at a low voltage of 1.6 V in alkaline freshwater and simulated seawater, respectively, exhibiting remarkable durability over a 100 h test.

Journal article

Morfill C, Pankratova S, Machado P, Fernando NK, Regoutz A, Talamona F, Pinna A, Klosowski M, Wilkinson RJ, Fleck RA, Xie F, Porter AE, Kiryushko Det al., 2022, Nanostars Carrying Multifunctional Neurotrophic Dendrimers Protect Neurons in Preclinical In Vitro Models of Neurodegenerative Disorders, ACS APPLIED MATERIALS & INTERFACES, Vol: 14, Pages: 47445-47460, ISSN: 1944-8244

Journal article

Tian T, Xu J, Xiong Y, Ramanan N, Ryan M, Xie F, Petit Cet al., 2022, Cu-functionalised porous boron nitride derived from a metal–organic framework, Journal of Materials Chemistry A, Vol: 10, Pages: 20580-20592, ISSN: 2050-7488

Porous boron nitride (BN) displays promising properties for interfacial and bulk processes, e.g. molecular separation and storage, or (photo)catalysis. To maximise porous BN's potential in such applications, tuning and controlling its chemical and structural features is key. Functionalisation of porous BN with metal nanoparticle represents one possible route, albeit a hardly explored one. Metal–organic frameworks (MOFs) have been widely used as precursors to synthesise metal functionalised porous carbon-based materials, yet MOF-derived metal functionalised inorganic porous materials remain unexplored. Here, we hypothesise that MOFs could also serve as a platform to produce metal-functionalised porous BN. We have used a Cu-containing MOF, i.e. Cu/ZIF-8, as a precursor and successfully obtained porous BN functionalised with Cu nanoparticles (i.e. Cu/BN). While we have shown control of the Cu content, we have not yet demonstrated it for the nanoparticle size. The functionalisation has led to improved light harvesting and enhanced electron–hole separation, which have had a direct positive impact on the CO2 photoreduction activity (production formation rate 1.5 times higher than pristine BN and 12.5 times higher than g-C3N4). In addition, we have found that the metal in the MOF precursor impacts porous BN's purity. Unlike Cu/ZIF-8, a Co-containing ZIF-8 precursor led to porous C-BN (i.e. BN with a large amount of C in the structure). Overall, given the diversity of metals in MOFs, one could envision our approach as a method to produce a library of different metal functionalised porous BN samples.

Journal article

Xu J, Morton W, Jones D, Tabish TA, Ryan MP, Xie Fet al., 2022, Significant quantum yield enhancement for near infrared fluorescence dyes by silica templated silver nanorods, APPLIED PHYSICS REVIEWS, Vol: 9, ISSN: 1931-9401

Journal article

Yallop M, Wang Y, Masuda S, Daniels J, Ockenden A, Masani H, Scott TB, Xie F, Ryan M, Jones C, Porter AEet al., 2022, Quantifying impacts of titanium dioxide nanoparticles on natural assemblages of riverine phytobenthos and phytoplankton in an outdoor setting, SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 831, ISSN: 0048-9697

Journal article

Zhang H, Geng S, Ouyang M, Yadegari H, Xie F, Riley DJet al., 2022, A self-reconstructed bifunctional electrocatalyst of pseudo-amorphous nickel carbide @ iron oxide network for seawater splitting., Advanced Science, Vol: 9, Pages: 1-15, ISSN: 2198-3844

Here, a sol-gel method is used to prepare a Prussian blue analogue (NiFe-PBA) precursor with a 2D network, which is further annealed to an Fe3 O4 /NiCx composite (NiFe-PBA-gel-cal), inheriting the ultrahigh specific surface area of the parent structure. When the composite is used as both anode and cathode catalyst for overall water splitting, it requires low voltages of 1.57 and 1.66 V to provide a current density of 100 mA cm-2 in alkaline freshwater and simulated seawater, respectively, exhibiting no obvious attenuation over a 50 h test. Operando Raman spectroscopy and X-ray photoelectron spectroscopy indicate that NiOOH2-x active species containing high-valence Ni3+ /Ni4+ are in situ generated from NiCx during the water oxidation. Density functional theory calculations combined with ligand field theory reveal that the role of high valence states of Ni is to trigger the production of localized O 2p electron holes, acting as electrophilic centers for the activation of redox reactions for oxygen evolution reaction. After hydrogen evolution reaction, a series of ex situ and in situ investigations indicate the reduction from Fe3+ to Fe2+ and the evolution of Ni(OH)2 are the origin of the high activity.

Journal article

Zhang H, Li P, Zhou H, Xu J, Jiang Q, Hadden JHL, Wang Y, Wang M, Chen S, Xie F, Riley DJet al., 2022, Unravelling the synergy of oxygen vacancies and gold nanostars in hematite for the electrochemical and photoelectrochemical oxygen evolution reaction, Nano Energy, Vol: 94, Pages: 1-10, ISSN: 2211-2855

The development of hematite-based electrocatalysts (EC) and photoelectrocatalysts (PEC) for oxygen evolution reaction (OER) is highly promising on account of the low-cost and favorable chemical properties. Herein, we report a unique inverse opal framework hematite-based bi-functional catalyst for both EC and PEC water oxidation in alkaline media. Under the combined action of oxygen vacancies (Vo) and gold nanostars (AuNSs) on hematite, the catalyst exhibited excellent activity and stability on both EC and PEC. The composite showed superior electrocatalytic performance for OER with a low overpotential of 281 mV at 10 mA cm−2. Density functional theory (DFT) studies reveal that the coverage of Vo controls the d-band center of surface Fe sites, and the OER activity displays a volcano relationship with the Vo coverage. The addition of gold nanoparticles on the hematite with low Vo coverage improves the adsorption strength of oxygen-containing intermediates to the optimal point and increases the OER activity. Furthermore, the as-prepared photoanode exhibits a ∼3.13 fold increase in current (1.46 mA cm−2) at 1.23 V versus RHE. It is proposed that Vo promotes bulk conductivity and surface catalysis and exhibits reduced activation energy under high light intensity. AuNSs efficiently inhibits the bulk recombination and improves carrier concentration because of the Fermi level equilibration and plasmonic resonance, and the surface catalysis compensates the deterioration of interfacial recombination of carriers induced by Vo, playing a synergistic role.

Journal article

Zhang H, Geng S, Ouyang M, Mao M, Xie F, Riley DJet al., 2022, Using metal cation to control the microstructure of cobalt oxide in energy conversion and storage applications, Small, Vol: 18, Pages: 1-13, ISSN: 1613-6810

Herein, a facile and efficient synthesis of microstructured Co3O4 for both supercapacitor and water-splitting applications is reported. Metal cations (Fe3+, Cu2+) serve as structure-directing agents regulating the structure of Co compounds, which are subsequently annealed to yield Co3O4. Detailed characterizations and density functional theory (DFT) calculations reveal that the in situ Cl-doping introduces oxygen defects and provides abundant electroactive sites, and narrows the bandgap, which enhances the electron excitation of the as-formed Co3O4. The as-prepared Cl-doped Co3O4 hierarchical nanospheres (Cl-Co3O4-h) display a high specific capacitance of 1629 F g−1 at 1 A g−1 as an electrode for supercapacitors, with excellent rate capability and cyclability. The Cl-Co3O4-h//activated carbon (AC) asymmetric supercapacitor (ASC) electrode achieves a specific capacitance of 237 F g−1 at 1 A g−1, with an energy density of 74 Wh kg−1 at a power density of 807 W kg−1 and even maintains 47 Wh kg−1 at the higher-power density of 24.2 kW kg−1. An integrated electrolyzer for water-splitting with Cl-Co3O4-h as both cathode and anode can be driven by Cl-Co3O4-h//AC ASC. The electrolyzer provides a high current density of 35 mA cm–2 at a cell voltage of 1.6 V, with good current density retention over 50 h.

Journal article

Sundaresan SM, Fothergill SM, Tabish TA, Ryan M, Xie Fet al., 2021, Aptamer biosensing based on metal enhanced fluorescence platform: A promising diagnostic tool, Applied Physics Reviews, Vol: 8, Pages: 1-14, ISSN: 1931-9401

Diagnosis of disease at an early, curable, and reversible stage allows more conservative treatment and better patient outcomes. Fluorescence biosensing is a widely used method to detect biomarkers, which are early indicators of disease. Importantly, biosensing requires a high level of sensitivity. Traditionally, these sensors use antibodies or enzymes as biorecognition molecules; however, these can lack the specificity required in a clinical setting, limiting their overall applicability. Aptamers are short, single stranded nucleotides that are receiving increasing attention over traditional recognition molecules. These exhibit many advantages, such as high specificity, making them promising for ultrasensitive biosensors. Metal enhanced fluorescence (MEF) utilizes plasmonic materials, which can increase the sensitivity of label-based fluorescent biosensors. The fluorescence enhancement achieved by placing metallic nanostructures in close proximity to fluorophores allows for detection of ultra-low biomarker concentrations. Plasmonic biosensors have been successfully implemented as diagnostic tools for a number of diseases, such as cancer, yet reproducible systems exhibiting high specificity and the ability to multiplex remain challenging. Similarly, while aptasensors have been extensively reported, few systems currently incorporate MEF, which could drastically improve biosensor sensitivity. Here, we review the latest advancements in the field of aptamer biosensing based on MEF that have been explored for the detection of a wide variety of biological molecules. While this emerging biosensing technology is still in its infant stage, we highlight the potential challenges and its clinical potential in early diagnosis of diseases.

Journal article

Primc D, Indrizzi L, Tervoort E, Xie F, Niederberger Met al., 2021, Synthesis of Cu3N and Cu3N-Cu2O multicomponent mesocrystals: non-classical crystallization and nanoscale Kirkendall effect, Nanoscale, Vol: 13, Pages: 17521-17529, ISSN: 2040-3364

Mesocrystals are superstructures of crystallographically aligned nanoparticles and are a rapidly emerging class of crystalline materials displaying sophisticated morphologies and properties, beyond those originating from size and shape of nanoparticles alone. This study reports the first synthesis of Cu3N mesocrystals employing structure-directing agents with a subtle tuning of the reaction parameters. Detailed structural characterizations carried out with a combination of transmission electron microscopy techniques (HRTEM, HAADF-STEM-EXDS) reveal that Cu3N mesocrystals form by non-classical crystallization, and variations in their sizes and morphologies are traced back to distinct attachment scenarios of corresponding mesocrystal subunits. In the presence of oleylamine, the mesocrystal subunits in the early reaction stages prealign in a crystallographic fashion and afterwards grow into the final mesocrystals, while in the presence of hexadecylamine the subunits come into contact through misaligned attachment, and subsequently, to some degree, realign in crystallographic register. Upon prolonged heating both types of mesocrystals undergo chemical conversion processes resulting in structural and morphological changes. A two-step mechanism of chemical conversion is proposed, involving Cu3N decomposition and anion exchange driven by the nanoscale Kirkendall effect, resulting first in multicomponent/heterostructured Cu3N–Cu2O mesocrystals, which subsequently convert into Cu2O nanocages. It is anticipated that combining nanostructured Cu3N and Cu2O in a mesocrystalline and hollow morphology will provide a platform to expand their application potential.

Journal article

Zhang H, Li P, Chen S, Xie F, Riley DJet al., 2021, Anodic transformation of a core-shell Prussian Blue analogue to a bifunctional electrocatalyst for water splitting, Advanced Functional Materials, Vol: 31, ISSN: 1616-301X

Developing low-cost oxygen evolution reaction (OER) catalysts with high efficiency and understanding the underlying reaction mechanism are critical for electrochemical conversion technologies. Here, an anodized Prussian blue analogue (PBA) containing Ni and Co is reported as a promising OER electrocatalyst in alkaline media. Detailed post-mortem characterizations indicate the transformation from PBA to Ni(OH)2 during the anodic process, with the amorphous shell of the PBA facilitating the transformation by promoting greater structural flexibility. Further study with operando Raman and X-ray photoelectron spectroscopy reveal the increase of anodic potential improves the degree of deprotonation of the transformed core-shell PBA, leading to an increase of Ni valence. Density functional theory calculations suggest that the increase of Ni valence results in a continuous increase in the adsorption strength of oxygen-containing species, exhibiting a volcano relationship against the OER activity. Based on the experiments and calculated results, an OER mechanism for the transformed product is proposed. The fully activated catalyst also works as the cathode and the anode for a water-splitting electrolysis cell with a high output current density of 13.7 mA cm−2 when a cell voltage of 1.6 V applied. No obvious performance attenuation is observed after 40 h of catalysis.

Journal article

Gomez-Gonzalez MA, Koronfel MA, Pullin H, Parker JE, Quinn PD, Inverno MD, Scott TB, Xie F, Voulvoulis N, Yallop ML, Ryan MP, Porter AEet al., 2021, Nanoscale chemical imaging of nanoparticles under real-world wastewater treatment conditions, Advanced Sustainable Systems, Vol: 5, ISSN: 2366-7486

Understanding nanomaterial transformations within wastewater treatment plants is an important step to better predict their potential impact on the environment. Here, spatially resolved, in situ nano-X-ray fluorescence microscopy is applied to directly observe nanometer-scale dissolution, morphological, and chemical evolution of individual and aggregated ZnO nanorods in complex “real-world” conditions: influent water and primary sludge collected from a municipal wastewater system. A complete transformation of isolated ZnO nanorods into ZnS occurs after only 1 hour in influent water, but larger aggregates of the ZnO nanorods transform only partially, with small contributions of ZnS and Zn-phosphate (Zn3(PO4)2) species, after 3 hours. Transformation of aggregates of the ZnO nanorods toward mixed ZnS, Zn adsorbed to Fe-oxyhydroxides, and a large contribution of Zn3(PO4)2 phases are observed during their incubation in primary sludge for 3 hours. Discrete, isolated ZnO regions are imaged with unprecedented spatial resolution, revealing their incipient transformation toward Zn3(PO4)2. Passivation by transformation(s) into mixtures of less soluble phases may influence the subsequent bioreactivity of these nanomaterials. This work emphasizes the importance of imaging the nanoscale chemistry of mixtures of nanoparticles in highly complex, heterogeneous semi-solid matrices for improved prediction of their impacts on treatment processes, and potential environmental toxicity following release.

Journal article

Xie F, 2021, (Invited) Nanoscale Engineering of Plasmonic Materials for Biosensing and Bioimaging, ECS Meeting Abstracts, Vol: MA2021-01, Pages: 1351-1351

<jats:p> Early diagnosis plays an increasingly significant role in current clinical drive. Detection, identification, and quantification of low abundance biomarker proteins form a promising basis for early clinical diagnosis and offer a range of important medical benefits. Amplification of light from NIR fluorophores by coupling to metal nanostructures, i.e. Metal Induced Fluorescence Enhancement (MIFE), represents a promising strategy for dramatically improving the detection and quantification of low abundance biomarker proteins, and potentially increase already sensitive fluorescence-based detection by up to three orders of magnitude. The amplification of the fluorescence system is based on interaction of the excited fluorophores with the surface plasmon resonance in metallic nanostructures. The enhanced fluorescence intensity due to the existence of metal nanostructures makes it possible to detect much lower levers of biomarkers tagged with fluorescence molecules either in sensing format or for tissue imaging. The first part of my talk will focus on some recent developments of plasmonic metal nanostructures by both "top-down" and "bottom up" methods. I will then discuss the prepared plasmonic nanostructures in the applications of biosensing and bioimaging, with the emphasis on plasmonic enhancement towards NIR I and NIR II regions. </jats:p>

Journal article

Zhang H, Jiang Q, Hadden JHL, Xie F, Riley DJet al., 2021, Pd ion-exchange and ammonia etching of a Prussian blue analogue to produce a high-performance water-splitting catalyst, Advanced Functional Materials, Vol: 31, Pages: 1-15, ISSN: 1616-301X

The authors report an ammonia‐assisted in situ cation‐exchange method for the synthesis of dodecagon N‐doped PdCoNi carbon‐based nanosheets (Pd‐e‐NiCo‐PBA‐C) and explore the catalytic performance. Pd‐e‐NiCo‐PBA‐C exerts extremely low overpotential and Tafel slope for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) both in acidic and alkaline media, only 47 mV, 55 mV dec−1 (pH = 0, HER) and 147 mV, 67 mV dec−1 (pH = 14, HER), and 309 mV, 67 mV dec−1 (pH = 14, OER), outperforming commercial IrO2‐based and Pt‐based catalysts. In addition, after 5000 cycles, the linear sweep voltammetry curve shows a negligible shift, indicating excellent stability performance. To test its overall water‐splitting performance, Pd‐e‐NiCo‐PBA‐C is applied as both cathode and anode materials. A high current density of 33 mA cm−2 at a battery voltage of 1.6 V is obtained, with the catalytic activity maintained at 97.3% after over 50 h. To get a further insight into the superior OER and HER performance, theoretical calculations are carried out, the better performance originates from the affinity difference of Pd and Ni atoms for gas atoms, and the replacement of inert atoms can decrease the binding energy and enhance the electrocatalytic activity.

Journal article

Song W, Stein Scholtis E, sherrel P, deana T, Ngiam J, Lischner J, Fearn S, Bemmer V, Mattevi C, Klein N, Xie F, riley Jet al., 2020, Electronic Structure Influences on the Formation of the Solid Electrolyte Interphase, Energy and Environmental Science, ISSN: 1754-5692

Journal article

Joyce C, Fothergill SM, Xie F, 2020, Recent advances in gold-based metal enhanced fluorescence platforms for diagnosis and imaging in the near-infrared, Materials Today Advances, Vol: 7, ISSN: 2590-0498

This review examines metal enhanced fluorescence (MEF) using gold (Au) nanostructures, with a focus on biomedical applications of this phenomenon, namely fluorescence biosensing and imaging. The mechanism by which MEF occurs will be briefly discussed before a thorough review of recent investigations, particularly surrounding cancer detection and imaging. Work in this field has primarily focused on substrate-based MEF and more recently has explored solution-based enhancement. Therefore, this review will examine both the different nanostructured substrates as well as the colloidal nanomaterials that have been synthesized, along with their interactions with fluorescent molecules. The potential applications of plasmonic probes for optical imaging, particularly in the near-infrared II (NIR-II) window, are also discussed. By incorporating MEF into diagnostic and imaging techniques, it is expected that there will be dramatic improvements to patient survival rates via early diagnosis and efficient treatment.

Journal article

Jiang Q, xiangyu X, Riley DJ, Xie Fet al., 2020, Harvesting the lost photon by plasmonic enhanced hematite-upconversion nanocomposite for water splitting, Journal of Chemical Physics, Vol: 153, Pages: 011102-1-011102-6, ISSN: 0021-9606

Converting solar energy to chemical energy in the form of hydrogen via water splitting is one of the promising strategies to solve the global energy crisis. Hematite, a traditional semiconducting oxide photoelectrode, can only absorb UV and visible parts of the solar spectrum, losing 40% infrared energy. In this paper, we report a novel plasmonic enhanced water splitting photoanode based on hematite-lanthanide upconversion nanocomposites to harvest lost photons below the bandgap of hematite. NaYF4:Er, Yb upconversion nanoparticles can upconvert photons from 980 nm to 510 nm–570 nm within the bandgap of hematite. More importantly, a gold nanodisk array with a plasmonic peak centered ∼1000 nm can further boost the photocurrent by 93-fold. It is demonstrated that the excitation process of lanthanide upconversion nanoparticles can be significantly enhanced by plasmonic nanostructures and can thus improve the water oxidation activity via plasmonic enhanced upconversion and hot electron injection, respectively. This new promising strategy will pave the way for plasmonic enhanced lost photon harvesting for applications in solar energy conversion.

Journal article

Xie F, 2020, (Invited) Nanoscale Engineering of Plasmonic Materials for Biosensing and Bioimaging, ECS Meeting Abstracts, Vol: MA2020-01, Pages: 2002-2002

<jats:p> Early diagnosis plays an increasingly significant role in current clinical drive. Detection, identification, and quantification of low abundance biomarker proteins form a promising basis for early clinical diagnosis and offer a range of important medical benefits. Amplification of light from NIR fluorophores by coupling to metal nanostructures, i.e. Metal Induced Fluorescence Enhancement (MIFE), represents a promising strategy for dramatically improving the detection and quantification of low abundance biomarker proteins, and potentially increase already sensitive fluorescence-based detection by up to three orders of magnitude. The amplification of the fluorescence system is based on interaction of the excited fluorophores with the surface plasmon resonance in metallic nanostructures. The enhanced fluorescence intensity due to the existence of metal nanostructures makes it possible to detect much lower levers of biomarkers tagged with fluorescence molecules either in sensing format or for tissue imaging. The first part of my talk will focus on some recent developments of plasmonic metal nanostructures by both “top-down” and “bottom up” methods. I will then discuss the prepared plasmonic nanostructures in the applications of biosensing and bioimaging, with the emphasis on plasmonic enhancement towards NIR I and NIR II regions. </jats:p>

Journal article

Rodrigues RL, Xie F, Porter AE, Ryan MPet al., 2020, Geometry-induced protein reorientation on the spikes of plasmonic gold nanostars, Nanoscale Advances, Vol: 2, Pages: 1144-1151, ISSN: 2516-0230

Functionalized gold nanostars (AuStrs) are remarkable candidates for drug delivery, photothermal therapy and imaging due to their large surface area to volume ratio and plasmonic properties. In this study, we address the challenge of achieving therapeutically controlled dosing using these high aspect ratio nanoparticle vectors by tailoring the nanostar loading area and protein conformation. We synthesized a library of different Au nanostars with varied geometries for potential biomedical applications. The Au nanostars were subsequently coated with different amounts of transferrin (Tf) and a novel depletion method was devised to measure the amount of Tf bound to the surface of the nanostructures. This methodology allowed us to show that coating thickness could be controllably varied and moulded onto the nanoparticle's high index features, whilst simultaneously preserving the key properties of the particle. The orientation of the Tf was measured on nanostars and spheres using transmission electron microscopy by negatively staining the Tf. The Tf was conformal on the nanostars, and protein packing efficiency increased on the AuStrs by 14-fold due to a geometry-induced protein reorientation at the nanoparticle surface. Interestingly, the reorientation of the transferrin observed at the AuStrs spikes did not occur at the AuStrs tips thus highlighting surface energy effects associated with surface curvature.

Journal article

Song W, Jiang Q, Xie X, Brookfield A, McInnes EJL, Shearing PR, Brett DJL, Xie F, Riley DJet al., 2019, Synergistic storage of lithium ions in defective anatase/rutile TiO2 for high-rate batteries, Energy Storage Materials, Vol: 22, Pages: 441-449, ISSN: 2405-8297

Fabrication of heterostructured materials is a strategy to boost the charge-transfer kinetics and the performance of high-rate lithium storage. Here, a facile, low-temperature method for the synthesis of high-area TiO2 nanospheres containing both anatase and rutile phases is described. The as-prepared materials contain a high concentration of oxygen vacancies facilitating electron conduction in the anatase phase and theoretical calculations provide evidence of a low energy barrier for Li+ transport in the rutile phase. The synergy between the two phases renders the shared conduction of electrons through anatase and Li+ ions via rutile at high-current rates, leading to the anodes that outperform the alternate TiO2 systems when the combination of capacity at high current densities and cycle stability are considered, displaying a capacity of 95.4 mAh g−1 at 10 A g−1 and a 97.2% retention of capacity over 500 cycles at 1 A g−1.

Journal article

Gomez-Gonzalez MA, Koronfel MA, Goode AE, Al-Ejji M, Voulvoulis N, Parker JE, Quinn PD, Scott TB, Xie F, Yallop ML, Porter AE, Ryan MPet al., 2019, Spatially resolved dissolution and speciation changes of ZnO nanorods during short-term in situ incubation in a simulated wastewater environment, ACS Nano, Vol: 13, Pages: 11049-11061, ISSN: 1936-0851

Zinc oxide engineered nanomaterials (ZnO ENMs) are used in a variety of applications worldwide due to their optoelectronic and antibacterial properties with potential contaminant risk to the environment following their disposal. One of the main potential pathways for ZnO nanomaterials to reach the environment is via urban wastewater treatment plants. So far there is no technique that can provide spatiotemporal nanoscale information about the rates and mechanisms by which the individual nanoparticles transform. Fundamental knowledge of how the surface chemistry of individual particles change, and the heterogeneity of transformations within the system, will reveal the critical physicochemical properties determining environmental damage and deactivation. We applied a methodology based on spatially resolved in situ X-ray fluorescence microscopy (XFM), allowing observation of real-time dissolution and morphological and chemical evolution of synthetic template-grown ZnO nanorods (∼725 nm length, ∼140 nm diameter). Core-shell ZnO-ZnS nanostructures were formed rapidly within 1 h, and significant amounts of ZnS species were generated, with a corresponding depletion of ZnO after 3 h. Diffuse nanoparticles of ZnS, Zn3(PO4)2, and Zn adsorbed to Fe-oxyhydroxides were also imaged in some nonsterically impeded regions after 3 h. The formation of diffuse nanoparticles was affected by ongoing ZnO dissolution (quantified by inductively coupled plasma mass spectrometry) and the humic acid content in the simulated sludge. Complementary ex situ X-ray absorption spectroscopy and scanning electron microscopy confirmed a significant decrease in the ZnO contribution over time. Application of time-resolved XFM enables predictions about the rates at which ZnO nanomaterials transform during their first stages of the wastewater treatment process.

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00600833&limit=30&person=true