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Huntington's disease (HD) belongs to protein misfolding disorders associated with polyglutamine (polyQ)-rich mutant huntingtin (mHtt) protein inclusions. Currently, it is indicated that the aggregation of polyQ-rich mHtt participates in neuronal toxicity and dysfunction. Here, we designed and synthesized a polyglutamine-specific gold nanoparticle (AuNP) complex, which specifically targeted mHtt and alleviated its toxicity. The polyglutamine-specific AuNPs were prepared by decorating the surface of AuNPs with an amphiphilic peptide (JLD1) consisting of both polyglutamine-binding sequences and negatively charged sequences. By applying the polyQ aggregation model system, we demonstrated that AuNPs-JLD1 dissociated the fibrillary aggregates from the polyQ peptide and reduced its β-sheet content in a concentration-dependent manner. By further integrating polyethyleneimine (PEI) onto AuNPs-JLD1, we generated a complex (AuNPs-JLD1-PEI). We showed that this complex could penetrate cells, bind to cytosolic mHtt proteins, dissociate mHtt inclusions, reduce mHtt oligomers, and ameliorate mHtt-induced toxicity. AuNPs-JLD1-PEI was also able to be transported to the brain and improved the functional deterioration in the HD

Bismuth oxyhalides (BiOX, X = F, Cl, Br, I) are emerging energy materials because of their remarkable catalytic activity. The BiOX compounds usually have a tetragonal type crystal structure with unique layered morphology consisting of [X-Bi-O-Bi-X] sheets. Although the BiOX nanosheets exposed with {001} facets perform superior photoactivity, there is lack of understanding about their capability in the electrochemical CO2 reduction reaction (CO2RR). Herein, we adopt wet-chemical syntheses to make 2D BiOCl and Pd-doped BiOCl nanosheets for CO2RR. In the results, formic acid is the only one kind of product converted from CO2 along with H2 gas from water reduction over both BiOCl and Pd-doped BiOCl nanosheets. By thorough analyses with ex situ and in situ spectroscopy, the results reflect that (1) metallic Bi0 atoms generated by the applied negative potentials serve as the catalytic sites for the hydrogen evolution reaction (HER) and CO2RR and (2) the existence of doped Pd ions in the BiOCl structure reduces the barrier of charge transfer over the nanosheets, which enhances HER and CO2RR activities. We believe that the observations are important references for making catalysts toward CO2RR performance.

Professor Chia-Kuang (Frank) Tsung made his scientific impact primarily through the atomic-level design of nanoscale materials for application in heterogeneous catalysis. He approached this challenge from two directions: above and below the material surface. Below the surface, Prof. Tsung synthesized finely controlled nanoparticles, primarily of noble metals and metal oxides, tailoring their composition and surface structure for efficient catalysis. Above the surface, he was among the first to leverage the tunability and stability of metal-organic frameworks (MOFs) to improve heterogeneous, molecular, and biocatalysts. This article, written by his former students, seeks first to commemorate Prof. Tsung's scientific accomplishments in three parts: (1) rationally designing nanocrystal surfaces to promote catalytic activity; (2) encapsulating nanocrystals in MOFs to improve catalyst selectivity; and (3) tuning the host-guest interaction between MOFs and guest molecules to inhibit catalyst degradation. The subsequent discussion focuses on building on the foundation laid by Prof. Tsung and on his considerable influence on his former group members and collaborators, both inside and outside of the lab.

The global ammonia yield is critical to the fertilizer industry as the global food demand is highly dependent on it, whereas, NH3 is also a key chemical for pharmaceutical, textile, plastic, explosive, and dye-making industries. At present, the demand for NH3 is fulfilled by the Haber-Bosch method, which consumes 1-3% of global energy and causes 0.5-1% CO2 emission every year. To reduce emissions and improve energy efficiency, the electrochemical nitrogen gas reduction reaction (N2RR) has received much attention and support after the funding announcement by the U.S. Department of Energy. In this work, we have created hollow CuAu nanoboxes with Cu-rich inner walls to improve the NH3 Faradaic efficiency in N2RR. These beveled nanoboxes are produced in different degrees of corner and edge etching, which produces both polyhedral and concave structures. In N2RR, the binary CuAu nanoboxes enhanced NH3 production compared to individual Au and Cu nanocubes. The results of DFT calculations suggest the Cu-rich inner walls in the hollow beveled CuAu nanoboxes play a major role in their performance by reducing the free energy ΔG*NNH for the potential-determining step to form *NNH (* + N2(g) + H+ + e- → *NNH). Meanwhile, the results in 10-cycle and solar-illuminated N2RR indicate the beveled CuAu nanoboxes are not only robust electrocatalysts but show promise in photocatalysis as well.

Modulation of bimetallic nanocatalysts with atomic precision would allow for significant increases in catalyst activity through the optimization of heteroatomic interplay. In practice, this level o...

Efficient control of the perovskite crystallization and passivation of the defects at the surface and grain boundaries of perovskite films have turned into the most important strategies to restrain charge recombination toward high-performance and long-term stability of perovskite solar cells (PSCs). In this paper, we employed a small amount of natural vitamin B (carnitine) with dual functional groups in the MAPbI3 precursor solution to simultaneously passivate the positive- and negative-charged ionic defects, which would be beneficial for charge transport in the PSCs. In addition, such methodology can efficiently ameliorate crystallinity with texture, better film morphology, high surface coverage, and longer charge carrier lifetime, as well as induce preferable energy level alignment. Benefiting from these advantages, the power conversion efficiency of PSCs significantly increases from 16.43 to 20.12% along with not only a higher open-circuit voltage of 1.12 V but also an outstanding fill factor of 82.78%.

Copper is an earth-abundant element that can be used to reduce the high cost and unsatisfactory durability of pure Pt catalysts by the formation of bimetallic Pt–M nanocrystals. Among CuPt nanostru...

Advances in new systems of organic–inorganic hybrid nanocomposites are less prevalent, owing to a lack of facile strategies for precise control of their structures, compositions, and, hence, their properties. In this work, Au-BINOL hybrid nanocomposites with eccentric and concentric nanostructures were produced. The hybrid nanocomposites containing two distinct moieties of inorganic Au nanocrystals and organic BINOL nanospheres were applied to the catalytic hydrogenation of 4-nitrophenol with NaBH4 in the aqueous phase with and without the illumination of visible light. Here, we demonstrate that the existence of Au–BINOL interfaces offers benefits to their performance. The eccentric nanostructures made with CTAC show the superior activity from large Au–BINOL interfaces formed between the BINOL nanospheres and the faces of Au nanoplates. They further exhibit a high Au localized surface plasmon resonance (LSPR)-enhancement effect on the photoreduction of 4-nitrophenol, which is attributed to the strong LSPR...

The combined functionality of components in organic–inorganic hybrid nanomaterials render them efficient nanoreactors. However, the development in this field is limited due to a lack of synthetic avenues and systematic control of the growth kinetics of hybrid structures. In this work, we take advantage of an ionic switch for regio-control of Au-BINOL(1,1′-Bi-2-naphthol) hybrid nanostructures. Aromatic BINOL molecules assemble into nanospheres, concomitant with the growth of the Au nanocrystals. The morphological evolution of Au nanocrystals is solely controlled by the presence of halides in the synthetic system. Here we show that quaternary ammonium surfactants (CTAB or CTAC), not only bridging Au and BINOL, but also contributing to the formation of concentric or eccentric structures when their concentrations are tuned to the range of 10–5 to 10–3 M. This facile strategy offers the potential advantage of scalable production, with diverse functional organic–inorganic hybrid nanocomposites being produced ba...

Control of morphology in the synthesis of Rh nanocrystals can be used to precisely tailor the electronic surface structure; this in turn directly influences their performance in catalysis applications. Many works bring attention to the development of Rh nanostructures with low-index surfaces, but limited effort has been placed on the study of high-index and surface-defect-enriched nanocrystals as they are not favored by thermodynamics due to the involvement of high-energy surfaces and increased surface-to-volume ratios. In this work, we demonstrate an aqueous synthesis of concave Rh nanotetrahedra (CTDs) serving as efficient catalysts for energy conversion reactions. CTDs are surface-defect-rich structures that form through a slow growth rate and follow the four-step model of metallic nanoparticle growth. By tuning the surfactant concentration, the morphology of Rh CTDs evolved into highly excavated nanotetrahedra (HETDs) and twinned nanoparticles (TWs). Unlike the CTD surfaces with abundant adatoms and v...

Conventional gas sensors work upon changes in mechanical or conductive properties of sensing materials during a chemical process, which may limit availabilities of size miniaturization and design simplification. However, fabrication of miniaturized sensors with superior sensitivities in real-time and label-free probing of chemical reactions or catalytic processes remains highly challenging, in particular with regard to integration of materials into a desired smaller volume without losing the recyclability of sensing properties. Here, we demonstrate a unique bimetallic nanostructure, the Au–Pd–Au core–shell–frame nanobrick, as a promising archetype for fabrication of miniaturized sensors at nanoscale. Upon analysis of the aqueous synthesis, both ex situ and in situ, the formation of Au frames is consistent with selective deposition and aggregation of NaBH4-reduced Au nanoparticles at the corners and edges of cubic Pd shells, where the {100} surfaces, capped by iodide ions, are growth-limited. By virtue of ...

Platinum was coated on the surfaces of copper nanocubes to form Cu–CuPt core–alloy–frame nanocrystals with a rhombic dodecahedral (RD) shape. Co-reduction of Pt2+ ions and residual Cu+ ions in the supernatant of the Cu nanocube solution followed by the interdiffusion of Cu and Pt atoms over the core–shell interface allowed their formation. Growth in the ⟨100⟩ directions of the {100}-terminated Cu nanocubes resulted in the {110}-faceted rhombic dodecahedra. By the introduction of additional Pt precursor, the {100} vertices of the Cu–CuPt RD nanocrystals could be selectively extended to form spiny CuPt RD nanocrystals. After removing the Cu core template, both CuPt alloy RD and spiny CuPt alloy RD nanoframes (NFs) were obtained with Pt/Cu ratios of 26/74 and 41/59, respectively. Abundant surface defects render them highly active catalysts due to the open frame structure of both sets of NFs. The spiny RD NFs showed superior specific activity toward the oxygen reduction reaction, 1.3 and 3 times to those of t...

Au-Pd nanocrystals are an intriguing system to study the integrated functions of localized surface plasmon resonance (LSPR) and heterogeneous catalysis. Gold is both durable and can harness incident light energy to enhance the catalytic activity of another metal, such as Pd, via the SPR effect in bimetallic nanocrystals. Despite the superior catalytic performance of icosahedral (IH) nanocrystals compared to alternate morphologies, the controlled synthesis of alloy and core-shell IH is still greatly challenged by the disparate reduction rates of metal precursors and lack of continuous epigrowth on multiply twinned boundaries of such surfaces. Herein, we demonstrate a one-step strategy for the controlled growth of monodisperse Au-Pd alloy and core-shell IH with terraced shells by turning an ionic switch between [Br(-)]/[Cl(-)] in the coreduction process. The core-shell IH nanocrystals contain AuPd alloy cores and ultrathin Pd shells (2 nm). They not only display more than double the activity of the commercial Pd catalysts in ethanol electrooxidation attributed to monatomic step terraces but also show SPR-enhanced conversion of 4-nitrophenol. This strategy holds promise toward the development of alternate bimetallic IH nanocrystals for electrochemical and plasmon-enhanced catalysis.

Geometric modification of Au nanostructures is typically achieved in multistep reactions, where synthesis parameters need to be well-controlled. In this work, we report a facile method using IrCl3 to refine morphologically diverse Au nanostructures and trigger their morphological transformations. The synthesis is accomplished at room temperature by an iterative process of galvanic dissolution and recursive growth. Seeds retrieved after the dissolution of different Au nanostructure archetypes served in the structural recovery and morphological transformation via rapid and slow regrowth, respectively. The rapid regrowth was accomplished by adding ascorbic acid (AA), while the slow regrowth occurred spontaneously. In the structural recovery, the nanostructures regrew back to their original morphologies. Improvements in the shape quality and size distributions were observed for the rapid regrowth case. In the spontaneous slow regrowth transformation, the resulting nanostructures were encased by {111} facets, ...

Submicron-sized mesoporous nickel ferrite (NiFe2O4) spheres were prepared by an aerosol spray pyrolysis method using Pluronic F127 as a structure-directing agent, and their photocatalytic performance for hydrogen (H2) evolution was examined in an aqueous MeOH solution by visible light irradiation (λ > 420 nm). The structure of the spherical mesoporous nickel ferrites was studied by transmission electron microscopy, powder X-ray diffraction, and N2 adsorption–desorption isotherm measurements. Mesoporous NiFe2O4 spheres of high specific surface area (278 m2 g–1) with a highly crystalline framework were prepared by adjusting the amount of structure-directing agent and the calcining condition. High photocatalytic activity of mesoporous NiFe2O4 for H2 evolution from water with methanol was achieved due to the combination of high surface area and high crystallinity of the nickel ferrites.

Bimetallic nanoparticle catalysts provide enhanced activity, as combining metals allows tuning of electronic and geometric structure, but the enhancement may vary during the reaction because the nanoparticles can undergo metal migration under catalytic reaction conditions. Using cyclic voltammetry to track the surface composition over time, we carried out a detailed study of metal migration in a well-defined model Au-Pd core-shell nanocatalyst. When subjected to electrochemical conditions, Au migration from the core to the shell was observed. The effect of Pd shell thickness and electrolyte identity on the extent of migration was studied. Migration of metals during catalytic ethanol oxidation was found to alter the particle's surface composition and electronic structure, enhancing the core-shell particles' activity. We show that metal migration in core-shell nanoparticles is a phenomenon common to numerous electrochemical systems and must be considered when studying electrochemical catalysis.

Developing syntheses of more sophisticated nanostructures comprising late transition metals broadens the tools to rationally design suitable heterogeneous catalysts for chemical transformations. Herein, we report a synthesis of Pd-Rh nanoboxes by controlling the migration of metals in a core-shell nanoparticle. The Pd-Rh nanobox structure is a grid-like arrangement of two distinct metal phases, and the surfaces of these boxes are {100} dominant Pd and Rh. The catalytic behaviors of the particles were examined in electrochemistry to investigate strain effects arising from this structure. It was found that the trends in activity of model fuel cell reactions cannot be explained solely by the surface composition. The lattice strain emerging from the nanoscale separation of metal phases at the surface also plays an important role.

Colloidal techniques were used to synthesize monodisperse Pt nanoparticles of four distinct sizes between 2 and 7 nm before immobilization onto silica. Ethylene hydrogenation demonstrated structure-insensitive behavior with TOFs of ∼12 s–1 before poisoning. With thiophene being a strong binding adsorbate, TOFs decreased by orders of magnitude, and the poisoning-induced antipathetic structure sensitivity because thiophene adsorbed more strongly to the coordinatively unsaturated, as compared with coordinatively saturated, surfaces, and the degree of saturation increased with decreasing Pt size. This effort is part of a broader study in which structure sensitivity is analyzed for adsorbates in complex reaction networks.

We have systematically explored how plasmonic effects influence the characteristics of polymer photovoltaic devices (OPVs) incorporating a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). We blended gold nanoparticles (Au NPs) into the anodic buffer layer to trigger localized surface plasmon resonance (LSPR), which enhanced the performance of the OPVs without dramatically sacrificing their electrical properties. Steady state photoluminescence (PL) measurements revealed a significant increase in fluorescence intensity, which we attribute to the increased light absorption in P3HT induced by the LSPR. As a result, the rate of generation of excitons was enhanced significantly. Furthermore, dynamic PL measurements revealed that the LSPR notably reduced the lifetime of photogenerated excitons in the active blend, suggesting that interplay between the surface plasmons and excitons facilitated the charge transfer process. This phenomenon reduced the recombination level of geminate excitons and, thereby, increased the probability of exciton dissociation. Accordingly, both the photocurrents and fill factors of the OPV devices were enhanced significantly. The primary origin of this improved performance was local enhancement of the electromagnetic field surrounding the Au NPs. The power conversion efficiency of the OPV device incorporating the Au NPs improved to 4.24% from a value of 3.57% for the device fabricated without Au NPs.

We report highly facet-dependent electrical properties of Cu(2)O nanocubes and octahedra and significant enhancement of gold nanocrystal cores to the electrical conductivity of Au-Cu(2)O core-shell octahedra. Cu(2)O nanocubes and octahedra and Au-Cu(2)O core-shell cubes and octahedra were synthesized by following our reported facile procedures at room temperature. Two oxide-free tungsten probes attached to a nanomanipulator installed inside a scanning electron microscope made contacts to a single Cu(2)O nanocrystal for the I-V measurements. Pristine Cu(2)O octahedra bounded by {111} facets are 1100 times more conductive than pristine Cu(2)O cubes enclosed by {100} faces, which are barely conductive. Core-shell cubes are only slightly more conductive than pristine cubes. A 10,000-fold increase in conductivity over a cube has been recorded for an octahedron. Remarkably, core-shell octahedra are far more conductive than pristine octahedra. The same facet-dependent electrical behavior can still be observed on a single nanocrystal exposing both {111} and {100} facets. This new fundamental property may be observable in other semiconductor nanocrystals. We also have shown that both core-shell cubes and octahedra outperform pristine cubes and octahedra in the photodegradation of methyl orange. Efficient photoinduced charge separation is attributed to this enhanced photocatalytic activity. Interestingly, facet-selective etching occurred over the {100} corners of some octahedra and core-shell octahedra during photocatalysis. The successful preparation of Au-Cu(2)O core-shell heterostructures with precise shape control has offered opportunities to discover new and exciting physical and chemical properties of nanocrystals.

We report the growth of core−shell Ga−GaN nanostructures by simple refluxing of a mixture of GaCl3 and lithium bis(trimethylsilyl)amide (LiHMDS) in trioctylamine at 380 °C for 24 h under nitrogen flow. The resulting spherical Ga−GaN nanostructures had diameters of ∼550 nm. By immersing the nanostructures in aqua regia, the gallium cores could be removed, and hollow GaN spheres with thicknesses of 15−25 nm were produced. The shells consisted of connected GaN nanocrystals of both cubic and hexagonal phases. Infrared spectroscopy confirmed the presence of silica or silicate in the GaN shells. The silicon source likely comes from the pyrolysis of LiHMDS. The growth process was studied by examining the intermediate products formed. Gallium metal cores appeared below 380 °C, followed by the slow formation of GaN nanocrystals on the core surfaces. The slow growth of the GaN shells is related to the gradual supply of the nitrogen source from the thermal decomposition of LiHMDS. Thinner shells with a thickness of ...

Here we report the hydrothermal synthesis of octahedral gold nanocrystals from an aqueous solution of HAuCl4, trisodium citrate, and cetyltrimethylammonium bromide (CTAB) surfactant. By heating the mixture at 110 °C for 6, 12, 24, 48, and 72 h, gold octahedra with approximate average sizes of 30, 60, 90, 120, and 150 nm can be obtained. The percent yield of octahedral nanocrystals is more than 90% for all the samples. Products formed at shorter reaction times were also examined. Structural characterization confirmed that the octahedra are bounded by entirely {111} faces. As particle size increases, the surface plasmon resonance (SPR) absorption band red-shifts from 543 to 635 nm. These monodisperse gold octahedra can spontaneously self-assemble into long-range ordered packing structures upon water evaporation. Three types of self-assembled structures with faces, edges, or corners of the octahedra contacting the substrates have been identified. Particle size can affect the type of packing structure they ad...

We report a facile method for the synthesis of cuprous oxide nanocrystals with systematic shape evolution. Monodisperse truncated cubic, cuboctahedral, truncated octahedral, and octahedral nanocrystals can be synthesized directly in an aqueous solution of CuCl2, sodium dodecyl sulfate (SDS) surfactant, hydroxylamine (NH2OH·HCl) reductant, and NaOH by simply varying the volume of hydroxylamine added to the reaction mixture. SDS surfactant was found to be necessary for a precise control of the nanocrystal morphology. Adjustment of the volume of NaOH added provides a means to vary the particle size. In the case of octahedral nanocrystals, particles with sizes of 160−460 nm can be prepared. By examining the intermediate products formed, which resemble the final nanocrystal structures, a growth mechanism is proposed. Optical characterization of these Cu2O nanocrystals showed band gap absorption at 470−490 nm and strong light scattering bands extending from the visible to the near-infrared light region. All fou...

We report the synthesis of pentagonal- and hexagonal-shaped gold nanoparticles with controlled diameters ranging from 5 to 50 nm. These nanoparticles were prepared by a seeding growth approach. Sodium dodecyl sulfate (SDS) molecules served as the capping agent to restrict the particle size. In addition, the formation of highly faceted gold nanoparticles may be facilitated by the possibly ineffective capping interactions between the lamellar micellar structures formed by the SDS molecules and the gold nanoparticles. The crystal structure of the highly faceted particles was found to consist of mostly [111] surfaces as particle size increases, as revealed by both TEM and XRD results.