Modification of Polysulfide Surfaces with Low-Power Lasers.

The modification of polymer surfaces using laser light is important for many applications in the nano-, bio- and chemical sciences. Such capabilities have supported advances in biomedical devices, electronics, information storage, microfluidics, and other applications. In most cases, these modifications require high power lasers that are expensive and require specialized equipment and facilities to minimize risk of hazardous radiation. Additionally, polymer systems that can be easily modified by lasers are often complex and costly to prepare. In this report, these challenges are addressed with the discovery of low-cost sulfur copolymers that can be rapidly modified with lasers emitting low-power infrared and visible light. The featured copolymers are made from elemental sulfur and either cyclopentadiene or dicyclopentadiene. Using a suite of lasers with discreet wavelengths (532, 638 and 786 nm) and powers, a variety of surface modifications could be made on the polymers such as controlled swelling or etching via ablation. The facile synthesis and laser modification of these polymer systems were exploited in applications such as direct laser lithography and erasable information storage.

Electrochemical Synthesis of Gold-N-Heterocyclic Carbene Complexes.

An electrochemical synthesis of gold(I)-N-heterocyclic carbene (Au-NHC) complexes has been developed. The electrochemical methodology uses only imidazolium salts, gold metal electrodes, and electricity to produce these complexes with hydrogen gas as the only by-product. This high-yielding and operationally simple procedure has been used to produce eight mononuclear and three dinuclear Au-NHC complexes. The electrochemical procedure facilitates a clean reaction with no by-products. As such, Au-NHC complexes can be directly transferred to catalytic reactions without work-up or purification. The Au-NHC complexes were produced on-demand and tested as catalysts in a vinylcyclopropanation reaction. All mononuclear Au-NHC complexes performed similarly to or better than the isolated complexes.

Inactivation of human coronaviruses using an automated room disinfection device.

The emergence of more virulent and epidemic strains of viruses, especially in the context of COVID-19, makes it more important than ever to improve methods of decontamination. The objective of this study was to evaluate the potential of on-demand production of chlorine species to inactivate human coronaviruses. The commercial prototype disinfection unit was provided by Unipolar Water Technologies. The Unipolar device generates active chlorine species using an electrochemical reaction and dispenses the disinfectant vapour onto surfaces with an aspirator. The minimum effective concentration and exposure time of disinfectant were evaluated on human hepatoma (Huh7) cells using 50% tissue culture infectious dose (TCID50) assay and human coronavirus 229E (HCoV-229E), a surrogate for pathogenic human coronaviruses. We showed that chlorine species generated in the Unipolar device inactivate HCoV-229E on glass surfaces at ≥ 400 parts per million active chlorine concentration with a 5 min exposure time. Here, inactivation refers to the inability of the virus to infect the Huh7 cells. Importantly, no toxic effect was observed on Huh7 cells for any of the active chlorine concentrations and contact times tested.

Electrochemical Synthesis of Poly(trisulfides).

With increasing interest in high sulfur content polymers, there is a need to develop new methods for their synthesis that feature improved safety and control of structure. In this report, electrochemically initiated ring-opening polymerization of norbornene-based cyclic trisulfide monomers delivered well-defined, linear poly(trisulfides), which were solution processable. Electrochemistry provided a controlled initiation step that obviates the need for hazardous chemical initiators. The high temperatures required for inverse vulcanization are also avoided resulting in an improved safety profile. Density functional theory calculations revealed a reversible "self-correcting" mechanism that ensures trisulfide linkages between monomer units. This control over sulfur rank is a new benchmark for high sulfur content polymers and creates opportunities to better understand the effects of sulfur rank on polymer properties. Thermogravimetric analysis coupled with mass spectrometry revealed the ability to recycle the polymer to the cyclic trisulfide monomer by thermal depolymerization. The featured poly(trisulfide) is an effective gold sorbent, with potential applications in mining and electronic waste recycling. A water-soluble poly(trisulfide) containing a carboxylic acid group was also produced and found to be effective in the binding and recovery of copper from aqueous media.

Integration of the Exogenous Tuning of Thraustochytrid Fermentation and Sulfur Polymerization of Single-Cell Oil for Developing Plant-like Oils.

In this study, we have demonstrated a bioprocessing approach encompassing the exogenous addition of low-molecular-weight compounds to tune the fatty acid (FA) profile in a novel thraustochytrid strain to produce desirable FAs. Maximum lipid recovery (38%, dry wt. biomass) was obtained at 1% Tween 80 and 0.25 mg/L of Vitamin B12. The transesterified lipid showed palmitic acid (C16, 35.7% TFA), stearic acid (C18, 2.1% TFA), and oleic acid (C18:1, 18.7% TFA) as the main components of total FAs, which are mainly present in plant oils. Strikingly, D-limonene addition in the fermentation medium repressed the production of polyunsaturated fatty acid (PUFAs). Sulfur-polymerization-guided lipid separation revealed the presence of saturated (SFAs, 53% TFA) and monounsaturated fatty acids (MUFAs, 46.6% TFA) in thraustochytrid oil that mimics plant-oil-like FA profiles. This work is industrially valuable and advocates the use of sulfur polymerization for preparation of plant-like oils through tuneable thraustochytrid lipids.

Modelling mercury sorption of a polysulfide coating made from sulfur and limonene.

A polymer made from sulfur and limonene was used to coat silica gel and then evaluated as a mercury sorbent. A kinetic model of mercury uptake was established for a range of pH values and concentrations of sodium chloride. Mercury uptake was generally rapid from pH = 3 to pH = 11. At neutral pH, the sorbent (500 mg with a 10 : 1 ratio of silica to polymer) could remove 90% of mercury within one minute from a 100 mL solution containing 5 ppm HgCl2 and 99% over 5 minutes. It was found that sodium chloride, at concentrations comparable to seawater, dramatically reduced mercury uptake rates and capacity. It was also found that the spent sorbent was stable in acidic and neutral media, but degraded at pH 11 which led to mercury leaching. These results help define the conditions under which the sorbent could be used, which is an important advance for using this material in remediation processes.

Vortex fluidic induced mass transfer across immiscible phases.

Mixing immiscible liquids typically requires the use of auxiliary substances including phase transfer catalysts, microgels, surfactants, complex polymers and nano-particles and/or micromixers. Centrifugally separated immiscible liquids of different densities in a 45° tilted rotating tube offer scope for avoiding their use. Micron to submicron size topological flow regimes in the thin films induce high inter-phase mass transfer depending on the nature of the two liquids. A hemispherical base tube creates a Coriolis force as a 'spinning top' (ST) topological fluid flow in the less dense liquid which penetrates the denser layer of liquid, delivering liquid from the upper layer through the lower layer to the surface of the tube with the thickness of the layers determined using neutron imaging. Similarly, double helical (DH) topological flow in the less dense liquid, arising from Faraday wave eddy currents twisted by Coriolis forces, impact through the less dense liquid onto the surface of the tube. The lateral dimensions of these topological flows have been determined using 'molecular drilling' impacting on a thin layer of polysulfone on the surface of the tube and self-assembly of nanoparticles at the interface of the two liquids. At high rotation speeds, DH flow also occurs in the denser layer, with a critical rotational speed reached resulting in rapid phase demixing of preformed emulsions of two immiscible liquids. ST flow is perturbed relative to double helical flow by changing the shape of the base of the tube while maintaining high mass transfer between phases as demonstrated by circumventing the need for phase transfer catalysts. The findings presented here have implications for overcoming mass transfer limitations at interfaces of liquids, and provide new methods for extractions and separation science, and avoiding the formation of emulsions.

Trace Amine-Associated Receptor 1 (TAAR1): Molecular and Clinical Insights for the Treatment of Schizophrenia and Related Comorbidities.

Schizophrenia is a complex and severe mental illness. Current treatments for schizophrenia typically modulate dopaminergic neurotransmission by D2-receptor blockade. While reducing positive symptoms of schizophrenia, current antipsychotic drugs have little clinical effect on negative symptoms and cognitive impairments. For the last few decades, discovery efforts have sought nondopaminergic compounds with the aim to effectively treat the broad symptoms of schizophrenia. In this viewpoint, we provide an overview on trace-amine associated receptor-1 (TAAR1), which presents a clinically validated nondopaminergic target for treating schizophrenia and related disorders, with significantly less overall side-effect burden. TAAR1 agonists may also be specifically beneficial for the substance abuse comorbidity and metabolic syndrome that is often present in patients with schizophrenia.

A fairer way to compare researchers at any career stage and in any discipline using open-access citation data.

The pursuit of simple, yet fair, unbiased, and objective measures of researcher performance has occupied bibliometricians and the research community as a whole for decades. However, despite the diversity of available metrics, most are either complex to calculate or not readily applied in the most common assessment exercises (e.g., grant assessment, job applications). The ubiquity of metrics like the h-index (h papers with at least h citations) and its time-corrected variant, the m-quotient (h-index ÷ number of years publishing) therefore reflect the ease of use rather than their capacity to differentiate researchers fairly among disciplines, career stage, or gender. We address this problem here by defining an easily calculated index based on publicly available citation data (Google Scholar) that corrects for most biases and allows assessors to compare researchers at any stage of their career and from any discipline on the same scale. Our ε'-index violates fewer statistical assumptions relative to other metrics when comparing groups of researchers, and can be easily modified to remove inherent gender biases in citation data. We demonstrate the utility of the ε'-index using a sample of 480 researchers with Google Scholar profiles, stratified evenly into eight disciplines (archaeology, chemistry, ecology, evolution and development, geology, microbiology, ophthalmology, palaeontology), three career stages (early, mid-, late-career), and two genders. We advocate the use of the ε'-index whenever assessors must compare research performance among researchers of different backgrounds, but emphasize that no single index should be used exclusively to rank researcher capability.

Reaction of [18F]Fluoride at Heteroatoms and Metals for Imaging of Peptides and Proteins by Positron Emission Tomography.

The ability to radiolabel proteins with [18F]fluoride enables the use of positron emission tomography (PET) for the early detection, staging and diagnosis of disease. The direct fluorination of native proteins through C-F bond formation is, however, a difficult task. The aqueous environments required by proteins severely hampers fluorination yields while the dry, organic solvents that promote nucleophilic fluorination can denature proteins. To circumvent these issues, indirect fluorination methods making use of prosthetic groups that are first fluorinated and then conjugated to a protein have become commonplace. But, when it comes to the radiofluorination of proteins, these indirect methods are not always suited to the short half-life of the fluorine-18 radionuclide (110 min). This review explores radiofluorination through bond formation with fluoride at boron, metal complexes, silicon, phosphorus and sulfur. The potential for these techniques to be used for the direct, aqueous radiolabeling of proteins with [18F]fluoride is discussed.

Carbonisation of a polymer made from sulfur and canola oil.

A polymer made from equal masses of sulfur and canola oil was carbonised at 600 °C for 30 minutes. The resulting material exhibited improved uptake of mercury from water compared to the polymer. The carbonisation could also be done after using the polymer to clean up oil spills, which suprisingly improved mercury uptake to levels rivaling commercial carbons.

Insulating Composites Made from Sulfur, Canola Oil, and Wool*.

An insulating composite was made from the sustainable building blocks wool, sulfur, and canola oil. In the first stage of the synthesis, inverse vulcanization was used to make a polysulfide polymer from the canola oil triglyceride and sulfur. This polymerization benefits from complete atom economy. In the second stage, the powdered polymer was mixed with wool, coating the fibers through electrostatic attraction. The polymer and wool mixture were then compressed with mild heating to provoke S-S metathesis in the polymer, which locks the wool in the polymer matrix. The wool fibers imparted tensile strength, insulating properties, and reduced the flammability of the composite. All building blocks are sustainable or derived from waste and the composite is a promising lead on next-generation insulation for energy conservation.

Sub-micron moulding topological mass transport regimes in angled vortex fluidic flow.

Shear stress in dynamic thin films, as in vortex fluidics, can be harnessed for generating non-equilibrium conditions, but the nature of the fluid flow is not understood. A rapidly rotating inclined tube in the vortex fluidic device (VFD) imparts shear stress (mechanical energy) into a thin film of liquid, depending on the physical characteristics of the liquid and rotational speed, ω, tilt angle, θ, and diameter of the tube. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as spinning top flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. The manifestation of mass transport patterns within the film have been observed by monitoring the mixing time, temperature profile, and film thickness against increasing rotational speed, ω. In addition, these flow patterns have unique signatures that enable the morphology of nanomaterials processed in the VFD to be predicted, for example in reversible scrolling and crumbling graphene oxide sheets. Shear-stress induced recrystallisation, crystallisation and polymerisation, at different rotational speeds, provide moulds of high-shear topologies, as 'positive' and 'negative' spicular flow behaviour. 'Molecular drilling' of holes in a thin film of polysulfone demonstrate spatial arrangement of double-helices. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45°, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter.

Azide-alkyne cycloadditions in a vortex fluidic device: enhanced "on water" effects and catalysis in flow.

The Vortex Fluidic Device is a flow reactor that processes reactions in thin films. Running the metal-free azide-alkyne cycloaddition in this reactor revealed a dramatic enhancement of the "on water" effect. For the copper-catalyzed azide-alkyne cycloaddition, stainless steel or copper jet feeds were effective reservoirs of active copper catalyst.

A critical evaluation of probes for cysteine sulfenic acid.

Cysteine oxidation is important in cellular redox regulation, signaling, and biocatalysis. To understand the biological relevance of cysteine oxidation, it is desirable to identify the proteins involved, the site of the oxidized cysteine, and the relevant oxidation states. Because the thiol of cysteine can be converted to a wide range of oxidation states, mapping these oxidative modifications is challenging. The dynamic and reversible nature of many cysteine oxidation states compounds the difficulty in such proteomic analyses. In this review, we examine methods to detect cysteine sulfenic acid - a particularly challenging functional group to analyze because of its reactive nature. We focus on the selectivity of recently reported probes and discuss some challenges and opportunities in this field.

Chemically induced repair, adhesion, and recycling of polymers made by inverse vulcanization.

Inverse vulcanization is a copolymerization of elemental sulfur and alkenes that provides unique materials with high sulfur content (typically ≥50% sulfur by mass). These polymers contain a dynamic and reactive polysulfide network that creates many opportunities for processing, assembly, and repair that are not possible with traditional plastics, rubbers and thermosets. In this study, we demonstrate that two surfaces of these sulfur polymers can be chemically joined at room temperature through a phosphine or amine-catalyzed exchange of the S-S bonds in the polymer. When the nucleophile is pyridine or triethylamine, we show that S-S metathesis only occurs at room temperature for a sulfur rank > 2-an important discovery for the design of polymers made by inverse vulcanization. This mechanistic understanding of the S-S metathesis was further supported with small molecule crossover experiments in addition to computational studies. Applications of this chemistry in latent adhesives, additive manufacturing, polymer repair, and recycling are also presented.

Reactive Compression Molding Post-Inverse Vulcanization: A Method to Assemble, Recycle, and Repurpose Sulfur Polymers and Composites.

Inverse vulcanization provides dynamic and responsive materials made from elemental sulfur and unsaturated cross-linkers. These polymers have been used in a variety of applications such as energy storage, infrared optics, repairable materials, environmental remediation, and precision fertilizers. In spite of these advances, there is a need for methods to recycle and reprocess these polymers. In this study, polymers prepared by inverse vulcanization are shown to undergo reactive compression molding. In this process, the reactive interfaces of sulfur polymers are brought into contact by mechanical compression. Upon heating these molds at relatively low temperatures (≈100 °C), chemical bonding occurs at the polymer interfaces by S-S metathesis. This method of processing is distinct from previous studies on inverse vulcanization because the polymers examined in this study do not form a liquid phase when heated. Neither compression nor heating alone was sufficient to mold these polymers into new architectures, so this is a new concept in the manipulation of sulfur polymers. Additionally, high-level ab initio calculations revealed that the weakest S-S bond in organic polysulfides decreases linearly in strength from a sulfur rank of 2 to 4, but then remains constant at about 100 kJ mol-1 for higher sulfur rank. This is critical information in engineering these polymers for S-S metathesis. Guided by this insight, polymer repair, recycling, and repurposing into new composites was demonstrated.

Proteome-Wide Survey of Cysteine Oxidation by Using a Norbornene Probe.

Rapid detection of cysteine oxidation in living cells is critical in advancing our understanding of responses to reactive oxygen species (ROS) and oxidative stress. Accordingly, there is a need to develop chemical probes that facilitate proteome-wide detection of cysteine's many oxidation states. Herein, we report the first whole-cell proteomics analysis using a norbornene probe to detect the initial product of cysteine oxidation: cysteine sulfenic acid. The oxidised proteins identified in the HeLa cell model represent the first targets of the ROS hydrogen peroxide. The panel of protein hits provides new and important information about the targets of oxidative stress, including 148 new protein members of the sulfenome. These findings provide new leads for the study and understanding of redox signalling and diseases associated with oxidative stress.

Synthesis and Applications of Polymers Made by Inverse Vulcanization.

Elemental sulfur is an abundant and inexpensive chemical feedstock, yet it is underused as a starting material in chemical synthesis. Recently, a process coined inverse vulcanization was introduced in which elemental sulfur is converted into polymers by ring-opening polymerization, followed by cross-linking with an unsaturated organic molecule such as a polyene. The resulting materials have high sulfur content (typically 50-90% sulfur by mass) and display a range of interesting properties such as dynamic S-S bonds, redox activity, high refractive indices, mid-wave IR transparency, and heavy metal affinity. These properties have led to a swell of applications of these polymers in repairable materials, energy generation and storage, optical devices, and environmental remediation. This article will discuss the synthesis of polymers by inverse vulcanization and review case studies on their diverse applications. An outlook is also presented to discuss future opportunities and challenges for further advancement of polymers made by inverse vulcanization.

Crosslinker Copolymerization for Property Control in Inverse Vulcanization.

Sulfur is an underused by-product of the petrochemicals industry. Recent research into inverse vulcanization has shown how this excess sulfur can be transformed into functional polymers, by stabilization with organic crosslinkers. For these interesting new materials to realize their potential for applications, more understanding and control of their physical properties is needed. Here we report four new terpolymers prepared from sulfur and two distinct alkene monomers that can be predictively tuned in glass transition, molecular weight, solubility, mechanical properties, and color.