The influence of crystal structures on the performance of CoMoO4 battery-type supercapacitor electrodes

CoMoO4 is a promising battery-type supercapacitor electrode material that can offer relatively high storage capacity and cycle stability. In this work, we investigate the role of the crystalline phase of CoMoO4 in determining these performance parameters. The hydrate phase of CoMoO4 was synthesized on a nickel foam substrate via hydrothermal reaction with subsequent annealing under an inert atmosphere leading to the formation of the β-phase CoMoO4. Similar nanoplate morphologies were observed in all of the samples. The hydrate-phase CoMoO4 demonstrates larger specific capacity than the annealed β-phase CoMoO4. Besides, the samples synthesized at lower temperatures have better rate capability than the sample annealed at higher temperatures. However, the hydrate phase had worse long-term stability compared to the β-phase samples.

Electrochemical Polarization of Disparate Catalytic Sites Drives Thermochemical Rate Enhancement

Supported bimetallic catalysts commonly exhibit higher rates of reaction compared to their monometallic counterparts, but the origin of these enhancements is often poorly defined. The recent discovery that cooperative redox enhancement effects in Au-Pd systems promote bimetallic catalysis in thermochemical oxidation is an important development in this field. This effect aligns two important research fields, thermo- and electrocatalysis, but questions relating to the generality and origin of the effect remain. Here, we demonstrate that these effects can be observed in reactions over a range of bimetal combinations and reveal the origin using a combination of electrochemical and material characterization. We disclose that the observed activity enhancement in thermochemical systems is a result of the electrochemical polarization of two disparate catalytic sites. This forms an alternative operating potential for a given bimetallic system that increases the driving force of each of the composite half reactions in oxidative dehydrogenation. We therefore uncover the physicochemical descriptors that dictate whether these enhancement effects will be exhibited by a particular combination of supported metal catalysts and determine the magnitude of the effect.

Bioinspired, Non-Enzymatic, Aqueous Synthesis of Size-Tunable CdS Quantum Dots for Sustainable Optoelectronic Applications

The enzymatic production of hydrogen sulfide (H₂S) from cysteine in various metabolic processes has been exploited as an intrinsically "green" and sustainable mode for the aqueous biomineralization of functional metal sulfide quantum dots (QDs). Yet, the reliance on proteinaceous enzymes tends to limit the efficacy of the synthesis to physiological temperature and pH, with implications for QD functionality, stability, and tunability (i.e., particle size and composition). Inspired by a secondary non-enzymatic biochemical cycle that is responsible for basal H₂S production in mammalian systems, we establish how iron(III)- and vitamin B₆ (pyridoxal phosphate, PLP)-catalyzed decomposition of cysteine can be harnessed for the aqueous synthesis of size-tunable QDs, demonstrated here for CdS, within an expanded temperature, pH, and compositional space. Rates of H₂S production by this non-enzymatic biochemical process are sufficient for the nucleation and growth of CdS QDs within buffered solutions of cadmium acetate. Ultimately, the simplicity, demonstrated robustness, and tunability of the previously unexploited H₂S-producing biochemical cycle help establish its promise as a versatile platform for the benign, sustainable synthesis of an even wider range of functional metal sulfide nanomaterials for optoelectronic applications.

Insights into the Effect of Metal Ratio on Cooperative Redox Enhancement Effects over Au- and Pd-Mediated Alcohol Oxidation

The aerobic oxidation of alcohols and aldehydes over supported heterogeneous catalysts can be considered as comprising two complementary and linked processes: dehydrogenation and oxygen reduction. Significant rate enhancements can be observed when these processes are catalyzed by independent active sites, coupled by electron transport between the two catalysts. This effect, termed cooperative redox enhancement (CORE), could significantly influence how researchers approach catalyst design, but a greater understanding of the factors which influence it is required. Herein, we demonstrate that the Au/Pd ratio used in physical mixtures of monometallic catalysts and phase-separated Au and Pd bimetallic catalysts dramatically influences the degree to which CORE effects can promote alcohol oxidation. Perhaps more interestingly, the roles of Au and Pd in this coupled system are determined to be interchangeable. Preliminarily, we hypothesize that this is attributed to the relative rates of the coupled reactions and demonstrate how physical properties can influence this. This deeper understanding of the factors which influence CORE is an important development in bimetallic catalysis.

Uncovering Structure-Activity Relationships in Pt/CeO2 Catalysts for Hydrogen-Borrowing Amination

The hydrogen-borrowing amination of alcohols is a promising route to produce amines. In this study, experimental parameters involved in the preparation of Pt/CeO₂ catalysts were varied to assess how physicochemical properties influence their performance in such reactions. An amination reaction between cyclopentanol and cyclopentylamine was used as the model reaction for this study. The Pt precursor used in the catalyst synthesis and the properties of the CeO₂ support were both found to strongly influence catalytic performance. Aberration corrected scanning transmission electron microscopy revealed that the most active catalyst comprised linearly structured Pt species. The formation of these features, a function result of epitaxial Pt deposition along the CeO₂ [100] plane, appeared to be dependent on the properties of the CeO₂ support and the Pt precursor used. Density functional theory calculations subsequently confirmed that these sites were more effective for cyclopentanol dehydrogenation-considered to be the rate-determining step of the process-than Pt clusters and nanoparticles. This study provides insights into the desirable catalytic properties required for hydrogen-borrowing amination but has relevance to other related fields. We consider that this study will provide a foundation for further study in this atom-efficient area of chemistry.

Methane Oxidation to Methanol

The direct transformation of methane to methanol remains a significant challenge for operation at a larger scale. Central to this challenge is the low reactivity of methane at conditions that can facilitate product recovery. This review discusses the issue through examination of several promising routes to methanol and an evaluation of performance targets that are required to develop the process at scale. We explore the methods currently used, the emergence of active heterogeneous catalysts and their design and reaction mechanisms and provide a critical perspective on future operation. Initial experiments are discussed where identification of gas phase radical chemistry limited further development by this approach. Subsequently, a new class of catalytic materials based on natural systems such as iron or copper containing zeolites were explored at milder conditions. The key issues of these technologies are low methane conversion and often significant overoxidation of products. Despite this, interest remains high in this reaction and the wider appeal of an effective route to key products from C-H activation, particularly with the need to transition to net carbon zero with new routes from renewable methane sources is exciting.

Distinct pretreatment innate immune landscape and posttreatment T cell responses underlie immunotherapy-induced colitis

Immune-related adverse events represent a major hurdle to the success of immunotherapy. The immunological mechanisms underlying their development and relation to antitumor responses are poorly understood. By examining both systemic and tissue-specific immune changes induced by combination anti-CTLA-4 and anti-PD-1 immunotherapy, we found distinct repertoire changes in patients who developed moderate-severe colitis, irrespective of their antitumor response to therapy. The proportion of circulating monocytes were significantly increased at baseline in patients who subsequently developed colitis compared with patients who did not develop colitis, and biopsies from patients with colitis showed monocytic infiltration of both endoscopically and histopathologically normal and inflamed regions of colon. The magnitude of systemic expansion of T cells following commencement of immunotherapy was also greater in patients who developed colitis. Importantly, we show expansion of specific T cell subsets within inflamed regions of the colon, including tissue-resident memory CD8+ T cells and Th1 CD4+ T cells in patients who developed colitis. Our data also suggest that CD8+ T cell expansion was locally induced, while Th1 cell expansion was systemic. Together, our data show that exaggerated innate and T cell responses to combination immunotherapy synergize to propel colitis in susceptible patients.

Two microbiota subtypes identified in irritable bowel syndrome with distinct responses to the low FODMAP diet

OBJECTIVE

Reducing FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) can be clinically beneficial in IBS but the mechanism is incompletely understood. We aimed to detect microbial signatures that might predict response to the low FODMAP diet and assess whether microbiota compositional and functional shifts could provide insights into its mode of action.

DESIGN

We used metagenomics to determine high-resolution taxonomic and functional profiles of the stool microbiota from IBS cases and household controls (n=56 pairs) on their usual diet. Clinical response and microbiota changes were studied in 41 pairs after 4 weeks on a low FODMAP diet.

RESULTS

Unsupervised analysis of baseline IBS cases pre-diet identified two distinct microbiota profiles, which we refer to as IBSP (pathogenic-like) and IBSH (health-like) subtypes. IBSP microbiomes were enriched in Firmicutes and genes for amino acid and carbohydrate metabolism, but depleted in Bacteroidetes species. IBSH microbiomes were similar to controls. On the low FODMAP diet, IBSH and control microbiota were unaffected, but the IBSP signature shifted towards a health-associated microbiome with an increase in Bacteroidetes (p=0.009), a decrease in Firmicutes species (p=0.004) and normalisation of primary metabolic genes. The clinical response to the low FODMAP diet was greater in IBSP subjects compared with IBSH (p=0.02).

CONCLUSION

50% of IBS cases manifested a 'pathogenic' gut microbial signature. This shifted towards the healthy profile on the low FODMAP diet; and IBSP cases showed an enhanced clinical responsiveness to the dietary therapy. The effectiveness of FODMAP reduction in IBSP may result from the alterations in gut microbiota and metabolites produced. Microbiota signatures could be useful as biomarkers to guide IBS treatment; and investigating IBSP species and metabolic pathways might yield insights regarding IBS pathogenic mechanisms.

Sequential, low-temperature aqueous synthesis of Ag-In-S/Zn quantum dots via staged cation exchange under biomineralization conditions

The development of high quality, non-toxic (i.e., heavy-metal-free), and functional quantum dots (QDs) via 'green' and scalable synthesis routes is critical for realizing truly sustainable QD-based solutions to diverse technological challenges. Herein, we demonstrate the low-temperature all-aqueous-phase synthesis of silver indium sulfide/zinc (AIS/Zn) QDs with a process initiated by the biomineralization of highly crystalline indium sulfide nanocrystals, and followed by the sequential staging of Ag⁺ cation exchange and Zn²⁺ addition directly within the biomineralization media without any intermediate product purification. Therein, we exploit solution phase cation concentration, the duration of incubation in the presence of In₂S₃ precursor nanocrystals, and the subsequent addition of Zn²⁺ as facile handles under biomineralization conditions for controlling QD composition, tuning optical properties, and improving the photoluminescence quantum yield of the AIS/Zn product. We demonstrate how engineering biomineralization for the synthesis of intrinsically hydrophilic and thus readily functionalizable AIS/Zn QDs with a quantum yield of 18% offers a 'green' and non-toxic materials platform for targeted bioimaging in sensitive cellular systems. Ultimately, the decoupling of synthetic steps helps unravel the complexities of ion exchange-based synthesis within the biomineralization platform, enabling its adaptation for the sustainable synthesis of 'green', compositionally diverse QDs.

Highly efficient catalytic production of oximes from ketones using in situ-generated H2O2

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H₂O₂) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H₂O₂ can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H₂O₂, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H₂O₂ and TS-1, while allowing for considerable process intensification.

Methane Oxidation to Methanol in Water

Methane represents one of the most abundant carbon sources for fuel or chemical production. However, remote geographical locations and high transportation costs result in a substantial proportion being flared at the source. The selective oxidation of methane to methanol remains a grand challenge for catalytic chemistry due to the large energy barrier for the initial C-H activation and prevention of overoxidation to CO₂. Indirect methods such as steam reforming produce CO and H₂ chemical building blocks, but they consume large amounts of energy over multistage processes. This makes the development of the low-temperature selective oxidation of methane to methanol highly desirable and explains why it has remained an active area of research over the last 50 years.The thermodynamically favorable oxidation of methane to methanol would ideally use only molecular oxygen. Nature effects this transformation with the enzyme methane monooxygenase (MMO) in aqueous solution at ambient temperature with the addition of 2 equiv of a reducing cofactor. MMO active sites are Fe and Cu oxoclusters, and the incorporation of these metals into zeolitic frameworks can result in biomimetic activity. Most approaches to methane oxidation using metal-doped zeolites use high temperature with oxygen or N₂O; however, demonstrations of catalytic cycles without catalyst regeneration cycles are limited. Over the last 10 years, we have developed Fe-Cu-ZSM-5 materials for the selective oxidation of methane to methanol under aqueous conditions at 50 °C using H₂O₂ as an oxidant (effectively O₂ + 2 reducing equiv), which compete with MMO in terms of activity. To date, these materials are among the most active and selective catalysts for methane oxidation under this mild condition, but industrially, H₂O₂ is an expensive oxidant to use in the production of methanol.This observation of activity under mild conditions led to new approaches to utilize O₂ as the oxidant. Supported precious metal nanoparticles have been shown to be active for a range of C-H activation reactions using O₂ and H₂O₂, but the rapid decomposition of H₂O₂ over metal surfaces limits efficiency. We identified that this decomposition could be minimized by removing the support material and carrying out the reaction with colloidal AuPd nanoparticles. The efficiency of methanol production with H₂O₂ consumption was increased by 4 orders of magnitude, and crucially it was demonstrated for the first time that molecular O₂ could be incorporated into the methanol produced with 91% selectivity. The understanding gained from these two approaches provides valuable insight into possible new routes to selective methane oxidation which will be presented here in the context of our own research in this area.

Sulfur Promotion in Au/C Catalyzed Acetylene Hydrochlorination

The formation of highly active and stable acetylene hydrochlorination catalysts is of great industrial importance. The successful replacement of the highly toxic mercuric chloride catalyst with gold has led to a flurry of research in this area. One key aspect, which led to the commercialization of the gold catalyst is the use of thiosulphate as a stabilizing ligand. This study investigates the use of a range of sulfur containing compounds as promoters for production of highly active Au/C catalysts. Promotion is observed across a range of metal sulfates, non-metal sulfates, and sulfuric acid treatments. This observed enhancement can be optimized by careful consideration of either pre- or post-treatments, concentration of dopants used, and modification of washing steps. Pre-treatment of the carbon support with sulfuric acid (0.76 m) resulted in the most active Au/C in this series with an acetylene conversion of ≈70% at 200 °C.

Clinicopathological characteristics and management of colitis with anti-PD1 immunotherapy alone or in combination with ipilimumab

Background

Colitis is one of the common immune-related adverse events that leads to morbidity and treatment discontinuation of immunotherapy. The clinical presentation, endoscopic and histopathological features and best management of this toxicity are not well defined.

Patients and methods

Patients with metastatic melanoma who received immunotherapy (programmed cell death protein 1 (PD1) antibodies, alone or in combination with a cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody (PD1 +CTLA-4)) and who developed clinically significant colitis (requiring systemic corticosteroids) were identified retrospectively from two academic centers. Clinical data were collected for all patients; endoscopic and histopathological data were examined in a subset.

Results

From May 2013 to May 2019, 118/1507 (7.8%) patients developed significant colitis; 80/553 (14.5%) after PD1+CTLA-4, 35/1000 (3.5%) PD1 alone, and three patients after Ipilimumab (IPI) alone. Combination therapy-induced colitis was more frequent (14.5% vs 3.5% in PD1 alone, p=<0.0001), had an earlier onset (6.3 weeks vs 25.7 weeks, p=<0.001), was more severe (grade 3/4 69% vs 31%, p=<0.001), and are more likely to require higher doses of steroids (91% vs 74%, p=0.01) than PD1 colitis. Among all patients treated with steroids (N=114), 54 (47%) responded and required no further therapy (steroid sensitive), 47 patients (41%) responded to infliximab (infliximab sensitive), and 13 (11%) were infliximab refractory and needed further immunosuppressive drugs. Infliximab-refractory patients all had onset within 4 weeks of immunotherapy commencement and were more likely to have an underlying autoimmune disease, have higher grade colitis, and require longer immunosuppression, yet had similar response and survival than other patients with colitis. Of 43 (37%) patients re-resumed treatment with PD1 monotherapy after colitis resolution, 16 (37%) of whom developed recurrent colitis. Endoscopic and histopathologic data were available for 64 patients. Most had left-sided colitis, with an increase in chronic inflammatory cells and neutrophils within the lamina propria, an increase in neutrophils in the surface epithelium, without increased lymphocytes or increased eosinophils. Infliximab-refractory colitis had a trend towards more confluent pancolitis with edema, erythema, ulceration, and absent vascularity with neutrophilic infiltration and erosion.

Conclusion

Clinically significant colitis varies in presentation, response to immunosuppression, and endoscopic/histologic features depending on the immunotherapy type. Infliximab-refractory colitis occurs early, is often high grade, and has adverse endoscopic and histopathologic features

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS^- in aqueous solutions of Cd-acetate and graphene oxide, respectively. Exchange of cysteamine for the native l-cysteine ligand capping the CdS QDs drives self-assembly of the now positively charged cysteamine-capped CdS (CdS/CA) onto negatively charged rGO. The use of this short linker molecule additionally enables efficient charge transfer from CdS to rGO, increasing exciton lifetime and, subsequently, photocatalytic activity. The visible-light hydrogen evolution rate of the resulting CdS/CA/rGO photocatalyst is 3300 μmol h^-1 g^-1. This represents, to our knowledge, one of the highest reported rates for a CdS/rGO nanocomposite photocatalyst, irrespective of the synthesis method.

Role of the Support in Gold-Containing Nanoparticles as Heterogeneous Catalysts

In this review, we discuss selected examples from recent literature on the role of the support on directing the nanostructures of Au-based monometallic and bimetallic nanoparticles. The role of support is then discussed in relation to the catalytic properties of Au-based monometallic and bimetallic nanoparticles using different gas phase and liquid phase reactions. The reactions discussed include CO oxidation, aerobic oxidation of monohydric and polyhydric alcohols, selective hydrogenation of alkynes, hydrogenation of nitroaromatics, CO₂ hydrogenation, C–C coupling, and methane oxidation. Only studies where the role of support has been explicitly studied in detail have been selected for discussion. However, the role of support is also examined using examples of reactions involving unsupported metal nanoparticles (i.e., colloidal nanoparticles). It is clear that the support functionality can play a crucial role in tuning the catalytic activity that is observed and that advanced theory and characterization add greatly to our understanding of these fascinating catalysts.

Enhanced catalyst selectivity in the direct synthesis of H2O2 through Pt incorporation into TiO2 supported AuPd catalysts

The introduction of low levels of Pt dopant into AuPd nanoparticles supported on TiO₂ significantly enhances their catalytic performance for the direct synthesis of H₂O₂.

Gold–palladium colloids as catalysts for hydrogen peroxide synthesis, degradation and methane oxidation: effect of the PVP stabiliser

PVP polymer stabilisers effect the reactivity of AuPd nanoparticles towards H₂O₂ synthesis/decomposition and methane oxidation.

In Situ Biomineralization of CuxZnySnzS4 Nanocrystals within TiO2-Based Quantum Dot Sensitized Solar Cell Anodes

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO₂ anode template where the formed nanocrystals bind to the TiO₂ surface. This in situ biomineralization approach facilitates enhanced distribution of the nanocrystals in the anode and, through this, enhanced QDSSC performance.

Benzyl alcohol oxidation with Pd-Zn/TiO2: computational and experimental studies

Pd-Zn/TiO2 catalysts containing 1 wt% total metal loading, but with different Pd to Zn ratios, were prepared using a modified impregnation method and tested in the solvent-free aerobic oxidation of benzyl alcohol. The catalyst with the higher Pd content exhibited an enhanced activity for benzyl alcohol oxidation. However, the selectivity to benzaldehyde was significantly improved with increasing presence of Zn. The effect of reduction temperature on catalyst activity was investigated for the catalyst having a Pd to Zn metal molar ratio of 9:1. It was found that lower reduction temperature leads to the formation of PdZn nanoparticles with a wide particle size distribution. In contrast, smaller PdZn particles were formed upon catalyst reduction at higher temperatures. Computational studies were performed to compare the adsorption energies of benzyl alcohol and the reaction products (benzaldehyde and toluene) on PdZn surfaces to understand the oxidation mechanism and further explain the correlation between the catalyst composition and its activity.

Synthesis of highly uniform and composition-controlled gold-palladium supported nanoparticles in continuous flow

The synthesis of supported bimetallic nanoparticles with well-defined size and compositional parameters has long been a challenge. Although batch colloidal methods are commonly used to pre-form metal nanoparticles with the desired size-range in solution, inhomogeneous mixing of the reactant solutions often leads to variations in size, structure and composition from batch-to-batch and even particle-to-particle. Here we describe a millifluidic approach for the production of oxide supported monometallic Au and bimetallic AuPd nanoparticles in a continuous fashion. This optimised method enables the production of nanoparticles with smaller mean sizes, tighter particle size distributions and a more uniform particle-to-particle chemical composition as compared to the conventional batch procedure. In addition, we describe a facile procedure to prepare bimetallic Au@Pd core-shell nanoparticles in continuous flow starting from solutions of the metal precursors. Moreover, the relative ease of scalability of this technique makes the proposed methodology appealing not only for small-scale laboratory purposes, but also for the industrial-scale production of supported metal nanoparticles.

Hydrated Electron Generation by Excitation of Copper Localized Surface Plasmon Resonance

Hydrated electrons are important in radiation chemistry and charge-transfer reactions, with applications that include chemical damage of DNA, catalysis, and signaling. Conventionally, hydrated electrons are produced by pulsed radiolysis, sonolysis, two-ultraviolet-photon laser excitation of liquid water, or photodetachment of suitable electron donors. Here we report a method for the generation of hydrated electrons via single-visible-photon excitation of localized surface plasmon resonances (LSPRs) of supported sub-3 nm copper nanoparticles in contact with water. Only excitations at the LSPR maximum resulted in the formation of hydrated electrons, suggesting that plasmon excitation plays a crucial role in promoting electron transfer from the nanoparticle into the solution. The reactivity of the hydrated electrons was confirmed via proton reduction and concomitant H₂ evolution in the presence of a Ru/TiO₂ catalyst.

Low temperature aqueous synthesis of size-controlled nanocrystals through size focusing: a quantum dot biomineralization case study

Traditional quantum dot synthesis techniques rely on the separation of nucleation and growth to control nanocrystal size. However, the same goal can be achieved through slow and continuous introduction of reactive precursors to keep the growth mechanism in the size focusing regime throughout synthesis. In this work, we demonstrate the efficacy of this approach within the framework of functional material biomineralization where, despite simultaneous nucleation and growth of particles, this growth mechanism enables size-controlled nanocrystal synthesis. Herein, the single enzyme cystathionine γ-lyase (CSE) is utilized to biomineralize CdS nanocrystals via the slow, but continuous turnover of the amino acid l-cysteine to produce H2S. Nanocrystal nucleation and growth theories confirm that consistent addition of monomers will result in a high supersaturation term, driving the nanocrystal growth mechanism into the size focusing regime. We further confirm this theory by mimicking biomineralization via chemical routes and demonstrate the influence of varying supersaturation, to further control the average nanocrystal size. Finally, altering the chelation strength of the capping agent l-cysteine is found to play a key role in balancing nanocrystal growth in solution and long-term stability.

Highly selective PdZn/ZnO catalysts for the methanol steam reforming reaction

Catalysts were prepared by impregnation-based method involving excess Cl⁻ anion addition to the metal chloride precursors which resulted in improved mixing of metals and led to formation of highly ordered PdZn alloys responsible for high catalytic selectivity.

Acetarsol Suppositories: Effective Treatment for Refractory Proctitis in a Cohort of Patients with Inflammatory Bowel Disease

BACKGROUND

Management of proctitis refractory to conventional therapies presents a common clinical problem. The use of acetarsol suppositories, which are derived from organic arsenic, was first described in 1965. Data concerning clinical efficacy and tolerability are very limited.

AIM

To examine the efficacy of acetarsol suppositories for the treatment of refractory proctitis.

METHODS

A retrospective analysis was performed on patients with inflammatory bowel disease treated with acetarsol suppositories between 2008 and 2014 at Addenbrooke's Hospital, Cambridge, United Kingdom. Clinical response was defined as resolution of symptoms back to baseline at the time of next clinic review.

RESULTS

Thirty-nine patients were prescribed acetarsol suppositories between March 2008 and July 2014 (29 patients with ulcerative colitis, nine with Crohn's disease, and one with indeterminate colitis). Thirty-eight were included for analysis. The standard dose of acetarsol was 250 mg twice daily per rectum for 4 weeks. Clinical response was observed in 26 patients (68%). Of the 11 patients who had endoscopic assessment before and after treatment, nine (82%) showed endoscopic improvement and five (45%) were in complete remission (Wilcoxon signed-rank test p = 0.006). One patient developed a macular skin rash 1 week after commencing acetarsol, which resolved within 4 weeks of drug cessation.

CONCLUSION

Acetarsol was effective for two out of every three patients with refractory proctitis. This cohort had failed a broad range of topical and systemic treatments, including anti-TNFα therapy. Clinical efficacy was reflected in significant endoscopic improvement. Adverse effects of acetarsol were rare.

Activation and Deactivation of Gold/Ceria-Zirconia in the Low-Temperature Water-Gas Shift Reaction

Gold (Au) on ceria-zirconia is one of the most active catalysts for the low-temperature water-gas shift reaction (LTS), a key stage of upgrading H₂ reformate streams for fuel cells. However, this catalyst rapidly deactivates on-stream and the deactivation mechanism remains unclear. Using stop-start scanning transmission electron microscopy to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X-ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (NPs; 1-2 nm) from subnanometer Au species. These NPs were then seen to agglomerate further over 48 h on-stream, and most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au NPs.

Enzymatic biomineralization of biocompatible CuInS2, (CuInZn)S2 and CuInS2/ZnS core/shell nanocrystals for bioimaging

This work demonstrates a bioenabled fully aqueous phase and room temperature route to the synthesis of CuInS₂/ZnS core/shell quantum confined nanocrystals conjugated to IgG antibodies and used for fluorescent tagging of THP-1 leukemia cells. This elegant, straightforward and green approach avoids the use of solvents, high temperatures and the necessity to phase transfer the nanocrystals prior to application. Non-toxic CuInS₂, (CuInZn)S₂, and CuInS₂/ZnS core/shell quantum confined nanocrystals are synthesized via a biomineralization process based on a single recombinant cystathionine γ-lyase (CSE) enzyme. First, soluble In-S complexes are formed from indium acetate and H₂S generated by CSE, which are then stabilized by l-cysteine in solution. The subsequent addition of copper, or both copper and zinc, precursors then results in the immediate formation of CuInS₂ or (CuInZn)S₂ quantum dots. Shell growth is realized through subsequent introduction of Zn acetate to the preformed core nanocrystals. The size and optical properties of the nanocrystals are tuned by adjusting the indium precursor concentration and initial incubation period. CuInS₂/ZnS core/shell particles are conjugated to IgG antibodies using EDC/NHS cross-linkers and then applied in the bioimaging of THP-1 cells. Cytotoxicity tests confirm that CuInS₂/ZnS core/shell quantum dots do not cause cell death during bioimaging. Thus, this biomineralization enabled approach provides a facile, low temperature route for the fully aqueous synthesis of non-toxic CuInS₂/ZnS quantum dots, which are ideal for use in bioimaging applications.

Template-Induced Structuring and Tunable Polymorphism of Three-Dimensionally Ordered Mesoporous (3DOm) Metal Oxides

Convectively assembled colloidal crystal templates, composed of size-tunable (ca. 15-50 nm) silica (SiO₂) nanoparticles, enable versatile sacrificial templating of three-dimensionally ordered mesoporous (3DOm) metal oxides (MO_x) at both mesoscopic and microscopic size scales. Specifically, we show for titania (TiO₂) and zirconia (ZrO₂) how this approach not only enables the engineering of the mesopore size, pore volume, and surface area but can also be leveraged to tune the crystallite polymorphism of the resulting 3DOm metal oxides. Template-mediated volumetric (i.e., interstitial) effects and interfacial factors are shown to preserve the metastable crystalline polymorphs of each corresponding 3DOm oxide (i.e., anatase TiO₂ (A-TiO₂) and tetragonal ZrO₂ (t-ZrO₂)) during high-temperature calcination. Mechanistic investigations suggest that this polymorph stabilization is derived from the combined effects of the template-replica (MO_x/SiO₂) interface and simultaneous interstitial confinement that limit the degree of coarsening during high-temperature calcination of the template-replica composite. The result is the identification of a facile yet versatile templating strategy for realizing 3DOm oxides with (i) surface areas that are more than an order of magnitude larger than untemplated control samples, (ii) pore diameters and volumes that can be tuned across a continuum of size scales, and (iii) selectable polymorphism.

Single Enzyme Direct Biomineralization of CdSe and CdSe-CdS Core-Shell Quantum Dots

Biomineralization is the process by which biological systems synthesize inorganic materials. Herein, we demonstrate an engineered cystathionine γ-lyase enzyme, smCSE that is active for the direct aqueous phase biomineralization of CdSe and CdSe-CdS core-shell nanocrystals. The nanocrystals are formed in an otherwise unreactive buffered solution of Cd acetate and selenocystine through enzymatic turnover of the selenocystine to form a reactive precursor, likely H₂Se. The particle size of the CdSe core nanocrystals can be tuned by varying the incubation time to generated particle sizes between 2.74 ± 0.63 nm and 4.78 ± 1.16 nm formed after 20 min and 24 h of incubation, respectively. Subsequent purification and introduction of l-cysteine as a sulfur source facilitates the biomineralization of a CdS shell onto the CdSe cores. The quantum yield of the resulting CdSe-CdS core-shell particles is up to 12% in the aqueous phase; comparable to that reported for more traditional chemical synthesis routes for core-shell particles of similar size with similar shell coverage. This single-enzyme route to functional nanocrystals synthesis reveals the powerful potential of biomineralization processes.