Although metal foams are not as commonly used as conventional catalyst supports such as carbonaceous materials, metal oxides, zeolites, and MOFs, they offer numerous advantages including a macroporous 3-D framework ensuring full coverage of the supported catalyst, intrinsic ease of handling, manipulation, high recyclability, and circumvention of additional steps typically required to pack, adhere, and deliver powder systems. Herein, a novel design of palladium nanocatalysts (NCs) on a polydopamine modified nickel foam is reported. NCs were created through a facile hydrothermal process, followed by atomic layer deposition (ALD) of a thin Al2O3 overcoat. The thin layer of polydopamine on Ni foam surface enhanced the uniform dispersion of NCs on Ni foam and Al2O3 ALD reduced the agglomeration of NCs and stabilized the material for multiple usage. The performance of the catalysts was evaluated by hydrogenation of nitrobenzene with H2. Even under mild conditions (3 bar H2, 50 °C), near quantitative conversions were observed (TON > 10000 based on %w Pd as active component). Most importantly, the catalysts proved to be highly recyclable. Quantitative conversions were found for hydrogenation of over thirty nitroaromatic, styrene, and phenylacetylene derivatives with H2 gas at low temprature, all with excellent selectivity. This promising framework can readily be extended to other noble-, and non-noble metal NCs.

Facile design for highly reactive, robust, and reusable precious-metal-based nanocatalysts secured on contiguous nickel foams

The global production of polystyrene (PS) has exceeded 15 million metric tons in 2019 because of its widespread use in packaging and non-packaging sectors. Therefore, the development of efficient and low-cost recycling strategies for PS are highly desirable. Herein, we present a PS depolymerization approach that can be performed in the presence of table salt and oxidized copper scrubber. The recovered styrene monomer was re-polymerized without further purification, and the thermal properties of the obtained PS were evaluated. This work has the potential to facilitate the chemical recycling of waste PS that is produced at a scale of 15 million tons/year using environmentally friendly catalysts and energy-efficient process; therefore, this study enables multiple green chemistry principles such as waste prevention, energy-efficient processes, and environmentally friendly catalysts.

Efficient depolymerization of polystyrene with table salt and oxidized copper

A novel chemical looping approach for direct propylene oxidation to propylene oxide and other oxygenated products was investigated. Supported Ag- and Au-based catalysts were prepared, using SrFeO3-δ perovskite as a catalyst support, and characterised using X-ray diffraction (XRD), electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Particles of the catalysts were used in experiments carried out in a packed bed reactor over the range 260–300OC, by passing 5vol% propylene over the material to generate oxygenated products, with oxygen provided via reduction of the catalyst support. The solid particles (AgCl/Au/SrFeO3-δ) were subsequently re-oxidised with air in a separate step, closing the chemical loop. Outlet gas was analysed using online Fourier-transform infrared spectroscopy (FTIR) and offline gas chromatography (GC). Gold-based catalysts displayed some activity towards propylene oxide production, as well as considerable selectivity towards formation of propan-1-ol, with 5wt%AgCl,5wt%Au/SrFeO3-δ giving stable c.55-60% selectivity towards propan-1-ol over the studied temperature range. Postulated mechanisms for propan-1-ol formation under chemical looping conditions are discussed, via propylene oxide or propanal intermediates.

Use of Ag and Au catalysts in chemical looping oxidation of propylene

Chloroform, as a widely used organic solvent, is persistent and can’t be effectively removed from the environment. Recent developments of persulfate activation with iron nanoparticles have attracted much attention. However, the removal efficiency of chloroform is suppressed because it is poorly reactive with iron-activated persulfate and the iron nanoparticles are easily inactive in real environment. In this study, a new system for the removal of chloroform from water was developed, in which the tannic acid was used to improve the activation of persulfate with Fe/Ni nanoparticles (Fe/Ni). The effects of molar ratio of tannic acid to Fe (mol% tannic acid-Fe), persulfate concentration, initial pH value, reaction temperature, inorganic anions and natural organic matters on chloroform removal were investigated. The tannic acid-Fe/Ni-persulfate system with 1.65 mol% of tannic acid-Fe and 3.2 mM of persulfate presented high removal percentage (86.6%-96.7%) in a wide range of pH (2.9-10.7). The results of electron paramagnetic resonance and radical quenching experiments indicated that sulfate radicals and hydroxyl radicals were primarily responsible for the removal of chloroform. In the presence of tannic acid, the Fe-tannic acid chelation could prevent the precipitation of iron hydroxide on Fe/Ni and therefore preserve their active sites. The tannic acid-Fe/Ni-persulfate system showed excellent removal performance for the recalcitrant chloroform, making it a very promising candidate for practical applications.

Tannic acid promotes the activation of persulfate with Fe/Ni nanoparticles for highly efficient chloroform removal

Proper oxidation modeling is essential in developing useful tests performed in a reasonably short time. It is shown that one of the assuptions utilized in modeling, called the constant substrate concentration hypothesis (CSCH), is a weak, unrealistic proposition that is incompatible with the generally accepted basic autoxidation scheme. More reliable results can be achieved when the CSCH is replaced by the inherent, easily understandable relation between the substrate and hydroperoxide concentrations. Furthermore, utilization of the latter relationship plays a key role in the development of the chemiluminescence (CL) methodology for the experimental assessment of two major oxidation parameters - the induction time and the oxidation rate constant. The intrinsic connection between the former parameter and the commonly used in practice graphically acquired oxidation induction time is demonstrated. The procedures presented in the study are applicable to both unstabilized and stabilized systems. Conducting the isothermal CL experiment on a series of the phenolic-stabilized PP samples at somewhat higher temperature (1600C) than the standard oven temperature (1500C) and under pure oxygen allowed us to keep good correlation with the oven testing results and, at the same time, essentially shorten duration of the test. Comparative study of a great variety of the ABS formulations revealed CL superior sensitivity and permitted experiments at significantly lower temperatures than differential scanning calorimetry (DSC). Consequently, the DSC oxidative stability data can be related to resistance to oxidation during processing while the CL results are expected to be useful in evaluating durability at service conditions.

Oxidation modeling and evaluation of the thermal oxidative stability by means of chemiluminescence

G protein-coupled receptors (GPCRs) characterize the largest class of cell surface receptors in humans. Due to their major role in the regulation of various physiological processes, they represent the largest class of targets for approved drugs. However, lack of selectivity of ligands due to the intertwining of homologous ligand binding sites across diverse subfamilies still remains a challenge. The architectural organization of macrocycles allows them to compromise between structural pre-organization and sufficient adaptability to accommodate the facet of protein binding sites.Although not strictly following the "rule of five," macrocycles managed to obtain good cell permeability, enhanced metabolic steadiness, and address protein-protein interaction with low entropic cost. To create and visualize the interaction landscape between macrocycles and GPCRs, we created a fully automatized KNIME workflow capable of retrieving, interpreting, and visualizing the interaction landscape between macrocycles and GPCRs using data from ChEMBL v28. Out of 793.749 compound-target interaction data pairs, 19.046 comprise at least one macrocycle with a ring size of 9 to 30. Duplicate removal revealed 3.348 unique compounds interacting with 96 GPCRs (out of 411 GPCRs). The most diverse targets are Somatostatin receptors 1, 4, and 3, covering 25, 23, and 21 distinctive scaffolds, respectively. Only 2% of one-ring macrocycles are cyclopeptides, while 80% of IC50 values for one-ring macrocycles are &lt; 1µM. Structural and physicochemical examination of the compounds demonstrated notable contrasts in their profiles.

Fully automatized KNIME workflows for analyzing macrocyclic ligands of GPCRs

Functionalization of hexagonal boron nitride (hBN) by the hydroxyl group imparts enhanced dispersion properties and offers a wide range of applications. Thermal exfoliation and functionalization of hBN is an easy and efficient technique, where the pristine hBN is oxidized at 1000 degrees in an oxygen environment followed by hydrolyzation resulting in functionalized hBN (BNOH). Most of the studies reported assume that the oxidation of the hBN is uniform across the bulk material and lacks information about the crystalline and surface property at each step of the process. However, the oxidation does not take place uniformly on the surface due to possible sintering of the material at elevated temperature, which restricts the supply of oxygen to the inner layer of the bulk resulting in non-uniform oxidation of the bulk material. No work is reported, so far, to elaborate the separation of the BNOH based on the degree of oxidation. This research highlights the impact of dispersion and settling time on the phase separation/identification of the BNOH as a function of the degree of oxidation. This concept can be utilized for the large-scale production and targeted application of the material depending on the dispersion and BET surface area. The oxidized hBN showed a very low BET surface area ascribed to agglomeration or sintering. However, the hydrolyzation opens up the pores leading to a higher BET surface area of BNOH. BNOH-top, middle, and bottom are products collected based on decreasing oxygen content (Fig. 1a). Interestingly, the highly functionalized BN surface exhibits high dispersity and low BET area, and vice-versa. The functionalization has changed the surface morphology of the material as shown by SEM images (Fig.1b and c).

Phase identification of functionalized hexagonal boron nitride

Fungi are ubiquitous in the environment and are capable of producing highly deleterious chemical species as part their metabolic and respiratory pathways. These chemicals are potentially degrading to fabrics and organically coated metals used in the defense industry. The chemical structures and physical features of fabrics affect their propensity for microbiological decomposition. Aluminum alloys are predominantly used in aircraft for their low weight and comparatively high strength and toughness. These alloys are organically coated for corrosion protection. Defense aircraft operate around the world most frequently in hot, humid environments. In interior regions of the aircraft where sunlight cannot penetrate, fungal spores attach and proliferate leading to microbiologically influenced corrosion (MIC). This type of growth is unsightly, produces objectionable odors, and ultimately can compromise aircraft structural integrity. The presence of organic materials such as hydraulic fluid (HF), corrosion preventative compounds (CPCs) and the organic coatings themselves act as a feedstock for the fungi. Digesting the organic content, the fungi leave by-products such as organic acids, esterases, and lipases which are corrosive and destructive to protective coatings and structural metals, in addition to fabrics. A combination of field and laboratory exposures were used to challenge defense materials and assets to fungal growth.  Fabrics and organically coated metal coupons were exposed to deep tropical jungles in Panama and Suriname for up to 24 months. Coated aluminum panels, with and without HF and CPCs, were also exposed in a controlled elevated temperature and humidity chamber for 84 days with intentional inoculation with select fungal spores.  All samples were examined with environmental scanning microscopy. Additional analytical techniques were performed for the different materials including molecular microbial analysis, weight loss, mechanical property degradation and glucosamine concentration (a measure of biomass). The effectiveness of cleaning procedures were examined.

Fungal degradation of defense materials and assets

2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibrils (TOCNF) possess many attractive functional properties and exhibit remarkable application values. However, recycling of TEMPO is highly desirable because of the ecological and economic demands. In this study, a new strategy integrating direct reuse and extraction recovery of TEMPO was developed. 50% of filtrates after TEMPO oxidation were directly reused for next cycle and half of the fresh TEMPO was added to maintain a constant dosage. The obtained TOCNF within two cycles showed similar carboxylate content (~1.3 mmol g–1), crystallinity (~70%), and homogeneous width (~4 nm) compared to the original one. Furthermore, the TEMPO in the another 50% of filtrates was extracted by ethyl acetate followed by distillation. The TOCNF produced with the extracted TEMPO had almost the same properties compared to those of original one, suggesting a negligible loss of activity of the recovered catalyst. Compared to the traditional route without TEMPO recycling, the combined strategy for TEMPO recycling exhibited a 31.3% reduction in production cost. This new route enables clean and cost-effective production of TOCNF and shows a promising industrial feasibility.

Integrating direct reuse and extraction recovery of TEMPO for production of cellulose nanofibrils

Birch tree barks are regarded as waste in the pulp and papermaking industry and used primarily as fuel. However, this material presents a source that contains many bio-derived molecules suitable for applications ranging from pharmaceuticals, plastics and composites, coatings, and antifeedants. Among the mixture of bio-derived molecules in birch barks, triterpenoids, such as betulin, betulinic acid, and lupeol, can be present up to 30% by weight of dry bark mass. They are highly valued for their anti-tumor, HIV, and inflammatory responses. Furthermore, birch barks also contain various other useful bio-derived molecules and derivative thereof, such as but not limited to, lignin, holocellulose, and suberin. In our presented work, birch bark extracts were produced from locally sourced river birch trees (Betula nigra) with an average yield of 10.6% (dry bark mass) and characterized via spectroscopy, chromatography, and hydroxyl number titration techniques. The extracts were directly used to synthesize bio-based thermoset polyesters with promising thermal and mechanical properties using minimal processing steps. Furthermore, thermoplastic polyesters containing betulin were synthesized using a melt polycondensation procedure with succinic acid, adipic acid, 1,12-dodecanedioic acid, 1,18-octadecanedioic acid, and itaconic acid. Additionally, glycerol was used for the formation of crosslinked betulin-based thermosets. All created bio-based polyesters were characterized via thermo-mechanical, mechanical, thermogravimetric, and chromatography (where appropriate) techniques to gain a fundamental understanding of the processing-structure-property relationships of these unique bio-based polymers. In addition to the lab-scale synthesis of these bio-based polyesters, we have also studied the economic viability and process scalability of value-added materials from birch bark. All-in-all, this work demonstrates the technical and commercial viability of utilizing birch bark derived molecules to prepare polyesters with potentially 100% bio-based content for a variety of applications.

Awesome polymers from birch bark

Satellite observations are the only means for humankind to probe our home planet’s health routinely at the global scale. This presentation provides a brief overview on what the satellite observations are telling us about the change of atmospheric composition in the past two decades and what insights we have gained from these observations for understanding and predicting air quality and climate. Advances in satellite remote sensing of wildfires are also presented in the context of public health and climate change.

Satellite observations of atmospheric composition and wildfires for air quality and climate change

Wastewater-based epidemiology (WBE) estimates collective consumption or exposure to chemicals or pathogens by tracking the substances excreted in the population's wastewater. Up till now he protein composition of wastewater was practically unknown until now. MS approaches based on HR-MS and MALDI–TOF-MS were used to detect the presence in urban sewage waters of proteins from diverse origins, including human proteins such as uromodulin, α-amylase, and S100A8, which have been proposed as health markers associated with renal function or stress-related changes . Wastewater protein composition in 10 WWTP in Catalonia which serve communities of different population and industrial profile will be shown. Up to 100 mL of water samples were filtered and the soluble part was concentrated in a SDS-PAGE gel. MALDI-TOF-MS (4800 TOF/TOF) and by HR-LC-MS/MS (Orbitrap-Velos) coupled to nanoLC separation) were used. Proteome Discoverer software and a semiquantitative analysis was performed based on the area of the unique peptides of each protein. We have been able to identify hundreds of proteins from different species including human. The molecules of human origin present in wastewater come mainly from feces and urine and are transported in the sewage system along with many other compounds. Thus, wastewater is part of a complex universe of biochemical signals that represent the population served by a specific water collection system. In addition, the analysis of the protein profile of other species (rat, mouse, cattle, pigs, poultry) has allowed us to find markers on industrial activity in the different areas studied (Fig.1). Monitoring large molecules that could serve as human biomarkers in wastewater is an important new contribution to the WBE field and as a useful complementary tool to the well-known small molecule approach globally used.

Environmental proteomics in wastewater-based epidemiology (EP-WBE): Identification of large biomolecules as biomarkers of public health and industrial activities

Heteroanionic materials are inorganic compounds consisting of more than one type of anion. Layered heteroanionic materials with homoleptic polyhedra are particularly interesting. The interfacial interactions between these adjacent layers can lead to large lattice anharmonicity and consequently can promote ultralow intrinsic lattice thermal conductivity. As an analog of well-known ultralow thermal conductive BiCuOSe, BiAgOSe has been predicted to be a better ultralow thermal conductive material by DFT calculations. Utilizing thermodynamic calculations and Pourbaix diagrams, we discovered a high yield hydrothermal synthesis to make the BiAgOSe phase. The thermal conductivity of BiAgOSe, as predicted, is lower compared to BiCuOSe. To study the origin of the ultralow thermal conductivity of BiAgOSe, we combined lattice dynamic calculations and synchrotron X-ray diffraction measurements and found that the low lattice thermal conductivity results from both low phonon velocities and strong lattice anharmonicity which are associated with the anisotropic layered structure, the large distortion of AgSe4 tetrahedra and soft Ag−Se bonds.

Exploring hydrothermal synthesis of ultralow thermal conductive heteroanionic materials

Advanced nuclear reactors are well poised to replace the aging existing fleet of light water reactors. One design, the molten salt reactor (MSR), is of interest due to the thermodynamic advantages of using molten salts as the coolant and/or fuel. The objective of the MSR campaign, as part of the US Department of Energy’s Advanced Reactor Technologies Program, is to enable the deployment of future MSRs by performing fundamental research on various molten salts and material interaction and developing supporting technology. Laser-induced breakdown spectroscopy (LIBS) is proving a useful analytical tool for these efforts. LIBS is performed by focusing a high-energy laser pulse onto a sample surface where large energy density results in ablation followed by rapid thermal breakdown and formation of a plasma plume. As this plasma de-excites, unique electronic transitions occur, emitting photons at characteristic emissions. The collected spectrum provides an elemental fingerprint of the sample. LIBS is currently being deployed by the MSR campaign as an elemental sensor for off-gas streams and a posttest characterization tool for graphite salt exposures. Overviews of recent progress in these thrusts and future opportunities to employ LIBS for molten salts will be discussed.

Application of laser-induced breakdown spectroscopy for the molten salt reactor campaign

Quantum computational techniques have previously been explored for modeling molecular systems, typically on small problems. Modeling of complex material systems using these techniques remains relatively unexplored and more challenging than molecular systems. We showcase a complete workflow for modeling chemical reactions on surfaces with quantum algorithms. Using Density Functional Theory calculations as a classical pre-processing step, we develop local embedding methods for systematic determination of active spaces. Ground states of the active-space projected Hamiltonians are then obtained using Variational Quantum Eigensolver and Entanglement Forging algorithms, suitable for near-term quantum computers. Results demonstrate that active spaces capturing dominant correlations with a limited set of orbitals can be systematically constructed using these local embedding methods. Effects of k-point sampling and different ansatzes for quantum computing algorithms are investigated. Results are compared with quantum hardware experiments employing circuit reduction methods.

Quantum computing study of industrially relevant problems: Reactions on surfaces

A considerable interest in conductive hydrogels has led to many advances in responsive systems, drug delivery, batteries, and solar cells. Although there are numerous ways to make hydrogels conductive, this work focuses on the surface post-synthetic modification of the biopolymer-based hydrogel to photochemically initiate polymerization of conductive polymers (i.e., aniline, pyrrole, or thiophene). The photochemistry is dependent on the metal centers (i.e., V5+, Fe3+) implemented during this process. Different doping methods can be applied to improve the charge transfer abilities of the gel. Current-voltage sweeps (I-V) showed the efficiency of charge transfer within the system depending on the metal photoinitiator, the conductive polymer, as well as the dopant. More importantly, partitioning the synthesis steps of the hydrogels validates the role of the dopant on the electron transfer of the conductive polymers. It has also been shown that the Fe3+ system helps order the PANI in the alginate hydrogel but has little impact in the cellulose gels, whereas the V5+ system orders PANI more efficiently in the cellulose hydrogel. Initial results show that polypyrrole (PPy) induces more conductivity in the gels than polyaniline (PANI). The redox potentials of Fe and V in their respective systems can be studied using cyclic voltammetry. Potential applications to this work may include photo-patterning of the hydrogels via photoreduction, thus forming regions with varying conductive abilities.

Employing metal-polysaccharide coordination complexes for photoinitiated polymerization of conductive polymers intercalated in biomimetic composites

Ti3C2-Ag nanocomposites were synthesized, and their physical and electrochemical characteristics were investigated during the proposed study. This research aims at a new anode material for lithium-ion batteries (LIBs), Ag nanoparticle-decorated MXene (Ti3C2-Ag). The MXenes are resistant to oxidation, outstanding thermal and electrical conductivity, high electrochemical efficiency, composition flexibility, and a large specific surface area but because of the narrow gap between different MXene layers, coating the inner surface of MXene layers with metal oxide nanoparticles is difficult and time-consuming. SEM images revealed the growth of a nano-sized material with a well-homogeneous particle size distribution. Elemental mapping photos illustrate a uniform distribution of various elements throughout the material. The nanocomposite morphology developed consisted of Ag particles 50 nm in size, evenly dispersed in Ti3C2--MXene layers. For the electrochemical characteristics of Ti3C2--Ag nanocomposite, several electrochemical methods such as cyclic voltammetry, galvanostatic cycling, rates capability, and electrochemical impedance were comprehensively examined. When deployed as LIB anodes, Ti3C2--Ag nanocomposite outperformed pure Ti3C2-, providing greater performance and enhanced cycle efficiency. After 100 cycles at a current density of 0.1C, Ti3C2--Ag nanocomposite displayed good cyclic stability with a highly reversible potential of roughly 524 mAhg-1. In addition, the rate capability is exceptional (up to 180 mAhg-1 at a current density of 10C). These properties are obtained from the Ti3C2--Ag nanocomposite's unique composition. Furthermore, carefully coated Ti3C2- and Ti3+ layers produce high conductivity in MXene layers. Furthermore, Li+ ions can readily diffuse to the electrode through coated MXene layers.

Silver grafted TI3C2-MXene nanocomposite as novel anode materials for Lithium-ion batteries

Monitoring the viscosity in-situ of polymers in real-time remains a challenge as traditional rheological methods can’t be utilized in confined environments. In this study, [Cu(I)(diptmp)2]+ (diptmp = 2,9-diisopropyl-2,4,7,8-tetramethyl-1,10-phenanthroline) was used as an optical probe and incorporated into industrial adhesives. Real-time sensing of viscosity was monitored during the curing process (viscosity increases) via changes in the luminescence of the [Cu(I)(diptmp)2]+. [Cu(I)(diptmp)2] in epoxy glue showed increased emission lifetime of the triplet metal to ligand charge transfer (3MLCT) state in real-time as the glue was cured. To verify the absence of initiator chemical quenching, the real-time viscosity was also monitored reversibly by swelling (viscosity and lifetime decrease) and by unswelling (viscosity and lifetime increase) of the polymer film. Viscosity in opaque samples was also measured which showed a similar correlation of increased luminescence lifetime as the viscosity increased during curing of the adhesive. [Cu(I)(diptmp)2]+ optical probe had higher emission lifetimes and was more ubiquitous as a real-time viscosity sensor in a variety of systems compared to [Ru(II)(bpy)3]2+ (bpy = bipyridine) as a controlled study. These results highlight how the [Cu(I)(diptmp)2]+ optical probe can be used to sense small viscosity changes, including those that are unable to be detected using traditional polymer characterization methods such as rheology.

Real-time and in-situ micro-viscosity monitoring using luminescent Cu(I) phenanthroline complex.

This presentation describes experimental results aimed at identifying the atomic structure of the interface between liquid electrolytes and liquid metal electrodes while under electrochemical control. The motivation is to understand such platforms better for the purpose of materials synthesis. X-Ray reflectivity (XRR) was used to probe the local atomic detail of liquid water/liquid Hg interfaces used for crystalline Ge electrodeposition. XRR measurements of Hg immersed in 0.1 M Na2B4O7 (aq) both with and without 0.05 M GeO2 were explored at several different potentials where Hg either is net positively or net negatively charged. The data suggest a pristine water/Hg interface in the absence of dissolved GeO2. In solutions containing dissolved GeO2, a persistent increased in electron density at the interface was consistent with non-specific adsorption of H2GeO3. At the most positive potentials, the XRR and electrochemical data indicated a condensed phase forms at the Hg interface. The cumulative observables suggest the formation of a polygermanate film, driven by electrochemical deprotonation of adsorbed H2GeO3.

In-Situ electrochemical X-Ray reflectivity of liquid metal-electrolyte interfaces

Lead halide perovskites (HaPs) have been intensively reinvestigated over the past decade. Their attractive device-level properties are partially attributed to the purported tolerance of the electronic structure against structural and chemical defects. However, challenges remain in verifying the existence of defect tolerance and, if present, precisely defining what it is and elucidating its origin(s). Theory and computation have led experiment thus far, though the calculation of quantities such as defect energetics depends critically on parameters such as which exchange-correlation functional is used in DFT calculations. Hence, experimental support is urgently required but progress has been hindered by variations in sample quality, material susceptiblity to beam damage, the lack of suitable atomic-level probes and more. Here we use bulk-sensitive, element-/orbital-/symmetry-selective high-resolution X-ray spectroscopy of the PbBr6 octahedra, in prototypical APbBr3 perovskites in single crystal form, to show which portions of the electronic structure are or are not defect tolerant to photodegradation. The organic perovskites show gradual photoinduced changes to the bromine 4p σ-π energy separation and lead 6d crystal field splitting in the conduction band, which is not observed with CsPbBr3. We find evidence for photoinduced self-n-doping in CsPbBr3, not observed with the organic perovskites. Changes to the crystal field splitting are mostly reversed with self-healing in MAPbBr3. Our work reveals the pivotal role of the A-cation in defect formation and self-healing, in a regime that does not involve degradation into the precursors. While photodegradation of the organic perovskites leads to internal structural distortion of the PbBr6 octahedra and changes to the conduction band electronic structure, band edge electron dynamics may not be affected significantly as the bromine K-edge absorption onsets, associated with the band edge states, are relatively unaffected. Bromine valence-to-core X-ray emission spectroscopy reveals that the distribution of bromine 4p states near the valence band edge are unaffected by photodegradation, supporting the existence of A-cation-independent defect tolerance in the valence band electronic structure. Our findings clarify the underpinnings of defect tolerance in halide perovskites and has implications for all beam-based measurements of HaPs, electron dynamics, energy level alignment at device interfaces and defect calculations.

Partial defect tolerance in the electronic structure of lead bromide perovskites

The phosphorylated cellulose nanofibrils (PCNF) made from woody biomass have aroused immense interest because of its promising applications in various fields including flame retardancy, adsorption, and separation. However, traditional production methods generally show adverse environmental impacts and the obtained PCNF has lower charge. In this study, PCNF with varied charge contents (2.09−3.79 mmol g–1) was produced by heat soaking pretreatment of cellulose fibers in phosphate salt and urea solutions, followed by curing and nanofibrillation. An optimized pretreatments can be achieved by heat-assistant soaking at 80 °C for 25 min, which was effective to produce PCNF with better performance (e.g., higher charge and crystallinity and fewer kinks) compared to those of traditional methods. Furthermore, the optimized route is more environmentally friendly and cost-effective, with substantial decreases in energy consumption and costs by over 70%, which exhibits great potential for scale-up production of PCNF.

Heat soaking pretreatments for clean and cost-effective production of phosphorylated cellulose nanofibrils with high charge

Incorporation of V(V) clusters into polymer hydrogels has been used to impart photoresponsive behavior and to tune materials properties during light irradiation. We have developed cellulose-agarose hydrogels that incorporate light responsive vanadium(V) moieties that are able to change the mechanical properties of the gels after light irradiation. The photoreaction was evidenced when the hydrogel turned from yellow to blue through a green intermediate. This color change was attributed to the reduction of V(V) to V(IV) as described in our previous work. A concomitant oxidative breakdown of the polysaccharide chain was noticeable upon the reduction of V(V). Just by controlling the exposure to light, mechanical properties of the matrix as well as the viscosity of the polysaccharide can be manipulated. Light can be used to create discrete patterns on these materials as gradients in elasticity. Scanning electron microscopy studies show the increase in pore sizes and guest cavity formation during irradiation. The gels are also able to encapsulate cargo, and deliver the cargo during light irradiation. By photo patterning, we can create distinct areas for controlled delivery and diverse mechanical properties within the same hydrogel. We now expect to develop and tune conductivity in these polysaccharide-based material with light responsive properties of vanadium at the molecular level.

Photofabricating the mechanical properties of vanadium(V)-polysaccharide coordination hydrogels for controlled delivery

Crystal structure engineering in metallic nanoparticles represents an important strategy in catalyst design, as the composition, shape, exposed facets, crystal structure, and atom distribution dictate activity. While techniques have been developed to control each of these parameters, there is no general method that allows one to optimize all parameters in polyelemental systems. In this work we combine a solid-state, Bi-influenced, high-index facet shape regulation strategy with thermal annealing, to achieve control over crystal structure in high-index facet nanoparticles. Indeed, this results in an unprecedentedly diverse library of chemically disordered and ordered multimetallic (Pt, Co, Ni, Cu, Fe, and Mn) tetrahexahedral (THH) nanoparticles. By employing density functional theory calculations we show that surface Bi modification stabilizes the {210} high-index facets of the nanoparticles, regardless of their internal atomic ordering. Moreover, we find that the ordering transition temperatures for the nanoparticles are dependent on their composition, which can be seen in the case of Pt3Fe1 THH nanoparticles. Finally, we have discovered that ordered intermetallic THH Pt1Co1 nanocatalysts exhibit a catalytic performance superior to disordered THH Pt1Co1 nanoparticles and commercial Pt/C catalysts toward methanol electrooxidation, highlighting the importance of crystal structure and atom distribution control on high-index facets in nanoscale catalysts. This approach broadens the synthetic scope and accessibility of new nanocatalysts for use in a diverse range of chemical processes.-

Crystal structure engineering in multimetallic high-index facet nanocatalysts

Binding of organic molecules on oxide mineral surfaces is a key process in soil preservation due to its ability to protect soil organic carbon from microbial degradation. To understand the nature and strength of sorption of organic carbon in soil, we investigated the binding of small organic molecules and larger polysaccharide biomolecules (typical building blocks of soil organic carbon) on α-Al2O3, a common soil mineral which is known to strongly bind organic matter. The calculations of adsorption on the α-Al2O3 (0001) surface were carried out using density functional theory (DFT) with empirical dispersion correction. First, adsorption of small organic molecules containing of a variety of functional groups was investigated and compared to the binding of water. Amine, amide and carboxylic acid functional groups were found to bind to this surface more strongly than water. Alcohol, ether, ester and thiol groups' binding energies were very similar to water, while hydrocarbons were found to bind less strongly. Carboxylic acids were the most strongly bound adsorbates in this study. Dissociated adsorption configurations were usually more favourable than molecular adsorption; hydrogen bonding was also found to make a significant contribution to the strength of adsorption. Thus, a number of organic functional groups were identified, such as amine, amide and carboxylic acids, which are able to bind to the α-Al2O3 (0001) surface more strongly than water and are likely to adsorb on this mineral surface under ambient conditions. Informed by these insights into adsorption of small molecules, we modelled adsorption of biomolecules - fragments of polysaccharides which naturally occur in soil: cellulose, chitin, chitosan and pectin. Pectin, which contains hydroxyl and carboxylic groups, and chitosan, which contains hydroxyl, amine and amide groups, were found to bind strongly, consistent with the strong binding of the functional groups present in these molecules. Cellulose, which contains only ether and hydroxyl groups, showed the least strong adsorption among the biomolecules studied. Our results show that biomolecules containing acid, amine and amide groups, such as pectin and chitosan, bind strongly to soil minerals and therefore are likely to be stable in soil.

Modelling mineral-organic interactions: Adsorption of organic molecules and biomolecules on the α-Al2O3 (0001) surface

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.