Wei Bu

Wei Bu
University of Chicago | UC · Center for Advanced Radiation Sources

Doctor of Philosophy

About

113
Publications
6,281
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1,506
Citations
Citations since 2017
67 Research Items
998 Citations
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2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction
Wei Bu currently works at the Center for Advanced Radiation Sources, University of Chicago. Wei does research in Nanotechnology, Environmental Chemistry and Biochemistry.

Publications

Publications (113)
Article
Graphene oxide (GO) membranes are excellent candidates for a range of separation applications, including rare earth segregation and radionuclide decontamination. Understanding nanoscale water and ion behavior near interfacial GO is critical for groundbreaking membrane advances, including improved selectivity and permeability. We experimentally exam...
Article
Fundamental physical chemical properties of monolayers formed from a new anionic gemini surfactant with a minimal-length (single-bond) spacer unit have been investigated at the air-water interface and compared with those of monolayers formed from affiliated comparator surfactants. The minimal spacer surfactant, dubbed C18-0-C18, exhibited strikingl...
Article
Protein isoforms are structural variants with changes in the overall flexibility predominantly at the tertiary level. For membrane associated proteins, such structural flexibility or rigidity affects membrane stability by playing modulatory roles in lipid−protein interaction. Herein, we investigate the protein chain flexibility mediated changes in...
Preprint
Full-text available
During the solvent extraction of metal ions from an aqueous to an organic phase, organic-soluble extractants selectively target aqueous-soluble ions for transport into the organic phase. In the case of extractants that are also soluble in the aqueous phase, our recent studies of lanthanide ion-extractant complexes at the surface of aqueous solution...
Preprint
Full-text available
Graphene oxide (GO) membranes are excellent candidates for a range of applications, including rare earth separations and radionuclide decontamination. Membrane performance varies widely under different conditions, as water and ion interactions with the membrane are strongly affected by small system changes. Feed solution pH is one critical factor,...
Article
Full-text available
Protein adsorption on surfaces can result in loss of drug product stability and efficacy during the production, storage, and administration of protein-based therapeutics. Surface-active agents (excipients) are typically added in protein formulations to prevent undesired interactions of proteins on surfaces and protein particle formation/aggregation...
Article
Cholesterol induces faster collapse by compressed films of pulmonary surfactant. Because collapse prevents films from reaching the high surface pressures achieved in the alveolus, most therapeutic surfactants remove or omit cholesterol. The studies here determined the structural changes by which cholesterol causes faster collapse by films of dipalm...
Article
Graphene oxide is a promising, emerging separation material, as it is durable, dispersible in water, and has naturally forming functional groups. Bulk studies using graphene oxide flakes have demonstrated impressive metal adsorption. However, little interfacial information about water and metal organization near graphene oxide is available. A mecha...
Preprint
Full-text available
Graphene oxide is a promising, emerging separation material, as it is durable, dispersible in water, and has naturally forming functional groups. Bulk studies using graphene oxide flakes have demonstrated impressive metal adsorption. However, little interfacial information about water and metal organization near graphene oxide is available. A mecha...
Preprint
Full-text available
Graphene oxide is a promising, emerging separation material, as it is durable, dispersible in water, and has naturally forming functional groups. Bulk studies using graphene oxide flakes have demonstrated impressive metal adsorption. However, little interfacial information about water and metal organization near graphene oxide is available. A mecha...
Article
Full-text available
In polynuclear biological active sites, multiple electrons are needed for turnover, and the distribution of these electrons among the metal sites is affected by the structure of the active site. However, the study of the interplay between structure and redox distribution is difficult not only in biological systems but also in synthetic polynuclear...
Article
Full-text available
Solvent extraction is used widely for chemical separations and environmental remediation. Although the kinetics and efficiency of this process rely upon the formation of ion− extractant complexes, it has proven challenging to identify the location of ion−extractant complexation within the solution and its impact on the separation. Here, we use tens...
Article
Full-text available
Immune surveillance cells such as T cells and phagocytes utilize integral plasma membrane receptors to recognize surface signatures on triggered and activated cells such as those in apoptosis. One such family of plasma membrane sensors, the transmembrane immunoglobulin and mucin domain (Tim) proteins, specifically recognize phosphatidylserine (PS)...
Preprint
Full-text available
Ion adsorption and transfer at charged interfaces play key roles in various industrial and environmental processes. Molecular scale details of ion-ion, ion-water, and ion-surface interactions and their dependence on the character of the ion (ion-specific effects) are still debated. Complex ions, such as SCN- and SeCN-, are particularly interesting...
Article
Full-text available
The interaction of monoclonal antibodies (mAbs) with air/water interfaces plays a crucial role in their overall stability in solution. We aim to understand this behavior using pendant bubble measurements to track the dynamic tension reduction and x-ray reflectivity to obtain the electron density profiles (EDPs) at the surface. Native immunoglobulin...
Preprint
Full-text available
During solvent extraction of rare earth ions, an aqueous electrolyte solution is placed in contact with an immiscible organic solution of extractants to enable extractant-facilitated transport of ions into the organic solvent. Although ex-perimental methodologies such as x-ray and neutron scattering have been applied to characterize ion-extractant...
Preprint
Full-text available
Ion adsorption and transfer at charged interfaces play key roles in various industrial and environmental processes. Molecular scale details of ion-ion, ion-water, and ion-surface interactions and their dependence on the character of the ion (ion-specific effects) are still debated. Complex ions, such as SCN- and SeCN-, are particularly interesting...
Article
Previous X-ray scattering measurements demonstrated the formation of a voltage-tunable 2-dimensional lattice of nanoparticles situated at the liquid-liquid interface between two immiscible electrolyte solutions (Nano Letters 2014, 14, 6816−6822). The nanoparticles had Au cores coated with trimethylammonium terminated ligands and the ITIES consisted...
Article
Electrochemistry at ITIES, which has been extensively studied for the oil (O)/water(W) interface, has been extended to the liquid/liquid interfaces of ionic liquids (ILs), namely, to the IL/W interface [1] and even to the IL/O interface [2,3]. One of several characteristics of ILs, compared with conventional molecular liquids like W and O, is the f...
Article
Full-text available
Phase-separated monolayers of 10,12-pentacosadiynoic acid and perfluorotetradecanoic acid can be photopolymerized to produce micrometer-sized, fluorescent polydiacetylene fibers at the air-solid interface. The photopolymer fibers were not uniformly fluorescent but rather showed a series of fluorescent spots along their lengths. The spots exhibited...
Article
The ability of Fe3+ to bind to Langmuir monolayers of an N, N, N′, N′‐dialkyl‐N, N′‐diacetate ethylenediamine gemini surfactant has been explored. Fe3+ in the subphase resulted in the formation of compacted, liquid‐phase monolayers with a mesh‐like morphology at the micron length scale in comparison with expanded, unstructured liquid‐phase monolaye...
Article
Full-text available
We report an experimental study of the structure of polymer-capped gold nanorods (AuNRs) binding to model phospholipid monolayers to elucidate the mechanism that drives the insertion of the AuNRs into phospholipid membranes. The experimental system consists of four different cases of AuNRs interacting with lipid monolayers: cationic and anionic pol...
Article
Thiol ligands bound to the metallic core of nanoparticles determine their interactions with the environment and self-assembly. Recent studies suggest that equilibrium between bound and free thiols alters the ligand coverage of the core. Here, X-ray scattering and MD simulations investigate water-supported monolayers of gold-core nanoparticles as a...
Cover Page
Full-text available
The cover art depicts the arrangement of surfactant components at the alveolar surface in lungs. Vesicles of pulmonary surfactant in the subphase prevent interfacial monolayers from collapse by expanding the ordered phase. The phospholipid‒cholesterol distribution displays a hexagonal unit cell revealed by X-ray diffraction. Cover design conceived...
Article
When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant in situ reduce surface tension to levels at which surfactant monolayers collapse from the surface in vitro. Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes induc...
Article
Highly correlated positioning of ions underlies Coulomb interactions between ions and electrified interfaces within dense ionic fluids such as biological cells and ionic liquids. Recent work has shown that highly correlated ionic systems behave differently than dilute electrolyte solutions and interest is focused upon characterizing the electrical...
Article
Polyethylene glycol (PEG) coatings have been widely applied in pharmaceutical and biomedical systems to prevent non-specific protein absorption, increase vesicle blood circulation time, and sustain drug release. This study systematically investigated the planar interfacial organization of phospholipid monolayers containing various amounts of PEG co...
Article
Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple in situ surface sensitive experimental techniques, we show that surface affinity of SCN⁻ anions are so strong that they can adsorb at a negatively charged float...
Preprint
Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple in situ surface sensitive experimental techniques, we show that surface affinity of SCN<sup>-</sup> ions are so strong that they can adsorb at a negatively char...
Preprint
Full-text available
When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant in situ reduce surface tension to levels, at which surfactant monolayers collapse from the surface in vitro . Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes tha...
Article
The pharmaceutical industry uses surface active-agents (excipients) in protein drug formulations to prevent aggregation, denaturation, and unwanted immunological response of therapeutic drugs in solution as well as at the air/water interface. However, the mechanism of adsorption, desorption and aggregation of proteins at the interface in the presen...
Article
Full-text available
Although challenging, assembling and orienting non-spherical nanomaterials into two- and three-dimensional (2D and 3D) ordered arrays can facilitate versatile collective properties by virtue of their shape-dependent properties that cannot be realized with their spherical counterparts. Here, we report on the self-assembly of gold nanorods (AuNRs) in...
Article
Full-text available
We use synchrotron X-ray reflectivity and grazing incidence small-angle X-ray scattering to investigate the surface assembly of the polyethylene glycol (PEG) grafted gold nanoparticles (PEG-AuNPs) induced by different salts. We find that NaCl and CsCl behave as many other electrolytes, namely drive the PEG-AuNPs to the vapor/suspension interface to...
Article
Full-text available
The structure and dynamics of lipid membranes in the presence of extracellular macromolecules are critical for cell membrane functions and many pharmaceutical applications. The pathogen virulence-suppressing end-phosphorylated polyethylene glycol (PEG) triblock copolymer (Pi-ABAPEG) markedly changes the interactions with lipid vesicle membranes and...
Article
Selective transport of trivalent rare earth metals from aqueous into organic environments with the help of amphiphilic "extractants" is an industrially important process. When the amphiphilic extractant is positively charged or neutral, the co-extracted background anions are not only necessary for the charge balance but also have a large impact on...
Article
Ligands can endow unique physicochemical properties of nanomaterials and also mediate biological effects of nanomaterials. It is unclear whether the ligand density affects cytotoxicity and uptake. Herein, we studied the interaction between poly(diallyldimethylammonium chloride)-coated gold nanorods (PDC-Au) and endothelial cells, in which these PDC...
Article
We report the results of grazing incidence X-ray diffraction (GIXD) measurements from water supported Langmuir monolayers of gold nanoparticles ligated with dodecanethiol (12 carbons), tetradecanethiol (14 carbons), hexadecanethiol (16 carbons), and octadecanethiol (18 carbons). These monolayers are formed from solutions with varying concentrations...
Preprint
Selective transport of trivalent rare earth metals from aqueous into organic environments with the help of amphiphilic "extractants" is an industrially important process. When the amphiphilic extractant is positively charged or neutral, the co-extracted background anions are not only necessary for the charge balance but also have a large impact on...
Preprint
Full-text available
Although challenging, assembling and orienting non-spherical nanomaterials into two- and three-dimensional (2D and 3D) ordered arrays can facilitate versatile collective properties by virtue of their shape-dependent properties that cannot be realized with their spherical counterparts. Here, we report on the self-assembly of gold nanorods (AuNRs) in...
Article
To optimize the compositions of the lipid-based nanomedicine and to advance understanding of the roles of polyunsaturated phospholipids in biological membranes, this study examined the effects of polyunsaturated phospholipids on the degradation of giant unilamellar vesicles catalyzed by a secreted phospholipase A2 (sPLA2) using fluorescence microsc...
Article
When nanoparticles interact with cellular or organelle membranes, the coating ligands are known to affect the integrity of the membranes, which regulate cell death and inflammation. However, the molecular mechanisms of this modulation remain unresolved. Here, we use synchrotron X-ray liquid surface scattering and molecular dynamics simulations to s...
Article
In this report we examine a family of trinuclear iron complexes by multiple-wavelength, anomalous diffraction (MAD) to explore the redox load distribution within cluster materials by the free refinement of atomic scattering factors. Several effects were explored that can impact atomic scattering factors within clusters, including 1) metal atom prim...
Article
A new member of the N, N, N’, N’-dialkyl-N, N’-diacetate ethylenediamine family of anionic gemini surfactants has been synthesized and its miscibility with the model perfluorocarbon, perfluorotetradecanoic acid, has been investigated in monolayer films at the air-water interface. Thermodynamics of mixing and the accompanying changes in mixed film s...
Article
The intrinsic overexpression of secretory phospholipase A2 (sPLA2) in various pro-inflammatory diseases and cancers has the potential to be exploited as a therapeutic strategy for diagnostics and treatment. To explore this potential and advance our knowledge of the role of sPLA2 in related diseases, it is necessary to systematically investigate the...
Article
Rare earths, which are fundamental components of modern technologies, are often extracted from aqueous solutions using surfactants at oil-water interfaces. Heavier lanthanides are more easily extracted, even though all lanthanides are chemically very similar. Using x-ray fluorescence measurements and theoretical arguments, we show that there is a s...
Article
Full-text available
We report on the effect of interpolymer complexes (IPCs) of poly(acrylic acid) (PAA) with poly(ethylene glycol) functionalized Au nanoparticles (PEG-AuNPs) as they assemble at the vapor-liquid interface, using surface sensitive synchrotron X-ray scattering techniques. Depending on the suspension pH, PAA functions both as a weak polyelectrolyte and...
Article
Deconvoluting the atom‐specific electron density within polynuclear systems remains a challenge. We performed a multiple‐wavelength anomalous diffraction study on four clusters that share the same [Co6Se8] core. We designed two cluster types: one having a symmetric ligand sphere, and the other having an asymmetric ligand sphere. We find that in the...
Article
Deconvoluting the atom‐specific electron density within polynuclear systems remains a challenge. We performed a multiple‐wavelength anomalous diffraction study on four clusters that share the same [Co6Se8] core. We designed two cluster types: one having a symmetric ligand sphere, and the other having an asymmetric ligand sphere. We find that in the...
Article
Full-text available
Surface sensitive X-ray reflectivity (XR) and grazing incidence small angle X-ray scattering (GI-SAXS) reveal the structure of polymer-capped-gold nanoparticles (AuNPs that are grafted with Poly(N-isopropylacrylamide); PNIPAM-AuNPs) as they self-assemble and crystallize at the aqueous-suspension/vapor interface. Citrate stabilized AuNPs (5 and 10 n...
Article
Significance The selective separation of targeted metal ions is utilized for environmental remediation, mining of rare earth and base metals, as well as the separation and isolation of long-lived radionuclides from nuclear waste. During the process of solvent extraction, organic extractant molecules complex with metal ions to assist their transfer...
Article
A series of n-alkanes co-spread with alkanethiol stabilized gold nanoparticles (AuNP) were studied as Langmuir monolayers by synchrotron X-ray reflectivity and diffraction. Tetradecanethiol capped gold nanoparticles with core diameters close to 2 nm were used to make films at 20 C, below the ligand order-disorder temperature. A variety of n-alkane...
Article
Anion exchange at positively charged interfaces plays an important role in a variety of physical and chemical processes. However, the molecular scale details of these processes, especially with heavy and large anionic complexes, are not well-understood. We studied the adsorption of $PtCl_6^{2-}$ anionic complexes to floating DPTAP monolayers in the...
Article
The miscibility and film structure of mixed Langmuir monolayer films comprised of an anionic gemini N, N, N’, N’dialkyl-N,N’-diacetate ethylenediamine surfactant (Ace(12)-2-Ace(12)) with perfluorotetradecanoic acid (C13F27COOH; PF) has been investigated using a variety of thermodynamic and structural characterization methods. The two film component...
Article
Glassy Langmuir polymer films exhibit a rapid increase in surface pressure at high compression. High relative humidity typically mitigates this increase in surface pressure. In an attempt to understand the origin of this phenomenon, we investigated the effects of relative humidity on surface pressure–area isotherm properties for four different type...
Article
Total reflection x-ray fluorescence (TXRF) is a widely applicable experimental technique for studying chemical element distributions across finely layered structures at extremely high sensitivity. To promote and facilitate scientific discovery using TXRF, we developed a MATLAB-based software package with a graphical user interface, named XeRay, for...
Article
Numerous applications of liquid crystals (LC) rely on control of molecular orientation at an interface. However, little is known about the precise molecular structure of such interfaces. In this work, synchrotron X-ray reflectivity measurements, accompanied by large-scale atomistic molecular dynamics simulations, are used for the first time to reco...
Article
When lanthanide ions are present in the aqueous subphase of a floating monolayer (Langmuir film), the ions attracted to the interface will in many cases form commensurate and/or incommensurate two-dimensional structures. These lattices depend not only on the molecules forming the monolayer, but also on the atomic number of the lanthanide, with a su...
Article
Achieving structurally well-defined catalytic species requires fundamental understanding of surface chemistry. Detailed, structural characterization of the catalyst binding sites in situ, such as single site catalysts on silica supports, is technically challenging or even unattainable. Octadecyltrioxysilane (OTOS) monolayers formed from octadecyltr...
Article
X-ray surface scattering is the most powerful probe of near-atomic-level structure at liquid-vapor and liquid-liquid interfaces. Synchrotron X-ray sources throughout the world have specialized instruments available for the study of these interfaces. Since 2002, the ChemMatCARS facility at Sector 15 of the Advanced Photon Source near Chicago, IL, US...
Article
Amphiphilic phospholipids and nanoparticles functionalized with hydrophobic capping ligands have previously been extensively investigated for their capacity to self-assemble into Langmuir monolayers at the air/water interface. However, understanding of composite films consisting of both nanoparticles and phospholipids, and by extension, the complex...
Article
Full-text available
T cell/transmembrane immunoglobulin mucin protein 1, 3, and 4 (TIM1, TIM3, and TIM4) are vital regulators in the innate immune system. Their activation involves specifically binding phosphatidylserine (PS) exposed cell membranes. Elucidation of the detailed mechanism of this TIMs/lipid interaction is key to understanding their immunological functio...
Chapter
Synchrotron X-ray scattering studies have transformed our understanding of liquid surfaces and interfaces, which play an important role in many biological, environmental, and technological processes. During the past several decades, these studies have begun to explore the relationship between the nanoscale interfacial structure and interfacial prop...
Chapter
Synchrotron X-ray scattering studies have transformed our understanding of liquid surfaces and interfaces, which play an important role in many biological, environmental, and technological processes. During the past several decades, these studies have begun to explore the relationship between the nanoscale interfacial structure and interfacial prop...
Article
The interface between two immiscible electrolyte solutions consisting of alkali chlorides in water and the organic electrolyte BTPPATPFB in 1,2-dichloroethane is characterized with X-ray reflectivity, interfacial tension and impedance spectroscopy measurements over a range of applied voltage between the bulk solutions. X-ray reflectivity probes the...
Article
Experiments and computer simulations provide a new perspective that strong correlations of counterions with charged nanoparticles can influence the localization of nanoparticles at liquid-liquid interfaces and support the formation of voltage-tunable nanoparticle arrays. We show that ion condensation onto charged nanoparticles facilitates their tra...