Efficient Photoelectrochemical Hydrogen Generation Based on Core Size Effect of Heterostructured Quantum Dots.

Colloidal quantum dots (QDs) are shown to be effective as light-harvesting sensitizers of metal oxide semiconductor (MOS) photoelectrodes for photoelectrochemical (PEC) hydrogen (H2) generation. The CdSe/CdS core/shell architecture is widely studied due to their tunable absorption range and band alignment via engineering the size of each composition, leading to efficient carrier separation/transfer with proper core/shell band types. However, until now the effect of core size on the PEC performance along with tailoring the core/shell band alignment is not well understood. Here, by regulating four types of CdSe/CdS core/shell QDs with different core sizes (diameter of 2.8, 3.1, 3.5, and 4.8 nm) while the thickness of CdS shell remains the same (thickness of 2.0 ± 0.1 nm), the Type II, Quasi-Type II, and Type I core/shell architecture are successfully formed. Among these, the optimized CdSe/CdS/TiO2 photoelectrode with core size of 3.5 nm can achieve the saturated photocurrent density (Jph) of 17.4 mA cm-2 under standard one sun irradiation. When such cores are further optimized by capping alloyed shells, the Jph can reach values of 22 mA cm2 which is among the best-performed electrodes based on colloidal QDs.

Quantifying Platinum and Palladium in Solid Ore Using Laser-Induced Breakdown Spectroscopy Assisted by the Laser-Induced Fluorescence (LIBS-LIF) Technique.

The laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF) in a two-step process was used to measure the concentration of platinum (Pt) and palladium (Pd) by surface analysis of a solid ore core from the Lac des Iles mine followed by analysis of the same core that was pulverized and compacted. This work focuses mainly on the measurement of Pt since the case of Pd has been extensively discussed in previous work. The excitation of Pt is performed at 235.71 nm with fluorescence emission observed near 269.84 nm. Calibration was performed with synthetic samples prepared from the same ore as the samples studied and the calibration curve shows good linearity in Pt content over several orders of magnitude. A limit of detection (LOD) of approximately 0.15 parts per million (ppm) over an average of 200 laser shots was demonstrated. In contrast, conventional LIBS provides a LOD of about 21 ppm over an average of 200 laser shots due to low signal-to-noise ratio and spectral interference from other elements and does not meet the requirements for estimating the average Pt concentration in the ore. The Pt concentrations obtained using LIBS-LIF on solid ore are generally in good agreement with those obtained in its pulverized and compacted form, as well as with laboratory measurements made by conventional chemical methods. However, the comparison of the results obtained for Pd using LIBS-LIF with the laboratory showed a less satisfactory agreement, probably due to its more inhomogeneous distribution in the ore.

Extending the Affinity Range of Weak Affinity Chromatography for the Identification of Weak Ligands Targeting Membrane Proteins.

The identification of weak-affinity ligands targeting membrane proteins is of great interest in Fragment-Based Drug Design (FBDD). Recently, miniaturized weak affinity chromatography (WAC) has been proposed as a valuable tool to study interactions between small ligands and wild-type membrane proteins embedded in so-called nanodisc biomimetic membranes immobilized on GMA-co-EDMA monoliths in situ-synthesized in capillary columns (less than one microliter in volume). In this proof-of-concept study, the achievable affinity range was limited to medium affinity (low micromolar range). The present work investigates different strategies to extend the affinity range towards low affinities, either by increasing the density of membrane proteins on the chromatographic support or by reducing non-specific interactions with the monolith. The combination of the use of a new and more hydrophilic monolithic support (poly(DHPMA-co-MBA)) and a multilayer nanodisc grafting process (up to three layers) allows a significant increase in the membrane protein density by a more than three-fold factor (up to 5.4 pmol cm-1). Such an increase in protein density associated with reduced non-specific interactions makes it possible to extend the range of detectable affinity, as demonstrated by the identification and characterization of affinities of very low-affinity ligands (Kd values of several hundred micromolar) for the adenosine receptor AA2AR used as a model protein, which was not possible before. The affinity was confirmed by competition experiments.

Engineering Fe-N4 Electronic Structure with Adjacent Co-N2C2 and Co Nanoclusters on Carbon Nanotubes for Efficient Oxygen Electrocatalysis.

Regulating the local configuration of atomically dispersed transition-metal atom catalysts is the key to oxygen electrocatalysis performance enhancement. Unlike the previously reported single-atom or dual-atom configurations, we designed a new type of binary-atom catalyst, through engineering Fe-N4 electronic structure with adjacent Co-N2C2 and nitrogen-coordinated Co nanoclusters, as oxygen electrocatalysts. The resultant optimized electronic structure of the Fe-N4 active center favors the binding capability of intermediates and enhances oxygen reduction reaction (ORR) activity in both alkaline and acid conditions. In addition, anchoring M-N-C atomic sites on highly graphitized carbon supports guarantees of efficient charge- and mass-transports, and escorts the high bifunctional catalytic activity of the entire catalyst. Further, through the combination of electrochemical studies and in-situ X-ray absorption spectroscopy analyses, the ORR degradation mechanisms under highly oxidative conditions during oxygen evolution reaction processes were revealed. This work developed a new binary-atom catalyst and systematically investigates the effect of highly oxidative environments on ORR electrochemical behavior. It demonstrates the strategy for facilitating oxygen electrocatalytic activity and stability of the atomically dispersed M-N-C catalysts.

Prevalence of ultrasound and clinical findings suggestive of inflammatory arthritis in children with skin psoriasis.

OBJECTIVE: To evaluate the prevalence of clinical and ultrasound (grey-scale and Doppler) abnormalities in joints, periarticular structures and nails of children affected by skin psoriasis (PsO). METHODS: Cross-sectional study including consecutive children affected by PsO. A systematic clinical and ultrasound evaluation of joints, entheses, tendons and nails were performed by independent examiners blinded to each other assessment. RESULTS: 57 Children: 26 girls (46%), mean age of 9 ± 4 years, divided into two groups, asymptomatic (Asy, 42 children) and symptomatic (Sy, 15 children) according to musculoskeletal pain. Differences were observed between the two groups in relation to age (9 ± 3 in Asy vs 11 ± 4 yrs in Sy, p< 0.05), PsO duration (2.4 ± 2.4 vs 5.4 ± 3.9 yrs, p< 0.001), systemic treatment (23 [54.8%] vs 2 [13.3%], p< 0.01), tender joint count (0 vs 12 children [80%], p< 0.001), swollen joint count (0 vs 3 [20%], p< 0.01) and entheseal pain (0 vs 10 [66.7%], p< 0.001). Ultrasound evaluation showed statistically significant differences between Asy and Sy groups for the presence of ultrasound abnormalities (16/42 [38%] vs 12/15 [80%]), synovitis (1/42 [2%] vs 4/15 [25%]) and enthesitis (4/42 [9.5%] vs 5/15 [33%]). Three children in the Sy group were classified with juvenile psoriatic arthritis (JPsA). CONCLUSIONS: Ultrasound abnormalities were higher in the Sy group with synovitis and enthesitis as the most prevalent findings. Asy patients were more frequently under systemic treatment. Ultrasound and a systematic clinical evaluation are useful tools for detecting subclinical JPsA in children with PsO and musculoskeletal symptoms.

Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots.

InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.

Deciphering dynamic combinatorial libraries of glycoclusters with miniaturized weak affinity chromatography coupled with mass spectrometry (nano-FAC-MS).

We report an original methodology based on affinity chromatography coupled with mass spectrometry to decipher the complexity of dynamic combinatorial libraries (DCLs) of glycoclusters. Such libraries are intended to boost the design of potential therapeutic anti-infectious agents targeting Pseudomonas aeruginosa, which is responsible for numerous diseases, mostly found in hospitals as major a cause of nosocomial infections. Dynamic combinatorial chemistry provides a rapid access to an equilibrating mixture of glycocluster candidates through the formation of reversible covalent bonds under thermodynamic control. Identifying each molecule in the complex mixture overcomes challenges due to the dynamic process. Selection of glycoclusters candidates was first realized on a model lectin (Concanavalin A, ConA). Home-made affinity nanocolumns, containing covalently immobilized ConA and have volumes in the microliter range, were used to separate DCLs of glycoclusters with respect to their specific lectin binding properties under buffered aqueous conditions. Miniaturization facilitates the inline coupling with MS detection in such purely aqueous and buffered conditions and reduces target protein consumption. Monolithic lectin-affinity columns prepared by immobilization of ConA were first characterized using a known ligand. The amount of active binding immobilized lectin is 61 ± 5 pmol on 8.5-cm length column. We demonstrated the ability of our approach to evaluate individual dissociation constants of species directly in the complex mixture. The concept was then successfully applied to the screening of DCLs of more complex glycoclusters to identify (by mass spectrometry) and rank the ligands (by relative breakthrough curve delay) according to their affinity for the immobilized lectin in a single experiment.

Towards Predicting the Sequential Appearance of Zeolitic Imidazolate Frameworks Synthesized by Mechanochemistry.

We use computational materials methods to study the sequential appearance of zinc-based zeolitic imidazolate frameworks (ZIFs) generated in the mechanochemical conversion process. We consider nine ZIF topologies, namely RHO, ANA, QTZ, SOD, KAT, DIA, NEB, CAG and GIS, combined with the two ligands 2-methylimidazolate and 2-ethylimidazolate. Of the 18 combinations obtained, only six (three for each ligand) were actually observed during the mechanosynthesis process. Energy and porosity calculations based on density functional theory, in combination with the Ostwald rule of stages, were found to be insufficient to distinguish the experimentally observed ZIFs. We then show, using classical molecular dynamics, that only ZIFs withstanding quasi-hydrostatic pressure P ≥ 0.3 GPa without being destroyed were observed in the laboratory. This finding, along with the requirement that successive ZIFs be generated with decreasing porosity and/or energy, provides heuristic rules for predicting the sequences of mechanically generated ZIFs for the two ligands considered.

Non-PGM Electrocatalysts for PEM Fuel Cells: A DFT Study on the Effects of Fluorination of FeNx-Doped and N-Doped Carbon Catalysts.

Fluorination is considered as a means of reducing the degradation of Fe/N/C, a highly active FeNx-doped disorganized carbon catalyst for the oxygen reduction reaction (ORR) in PEM fuel cells. Our recent experiments have, however, revealed that fluorination poisons the FeNx moiety of the Fe/N/C catalytic site, considerably reducing the activity of the resulting catalyst to that of carbon only doped with nitrogen. Using the density functional theory (DFT), we clarify in this work the mechanisms by which fluorine interacts with the catalyst. We studied 10 possible FeNx site configurations as well as 2 metal-free sites in the absence or presence of fluorine molecules and atoms. When the FeNx moiety is located on a single graphene layer accessible on both sides, we found that fluorine binds strongly to Fe but that two F atoms, one on each side of the FeNx plane, are necessary to completely inhibit the catalytic activity of the FeNx sites. When considering the more realistic model of a stack of graphene layers, only one F atom is needed to poison the FeNx moiety on the top layer since ORR hardly takes place between carbon layers. We also found that metal-free catalytic N-sites are immune to poisoning by fluorination, in accordance with our experiments. Finally, we explain how most of the catalytic activity can be recovered by heating to 900 °C after fluorination. This research helps to clarify the role of metallic sites compared to non-metallic ones upon the fluorination of FeNx-doped disorganized carbon catalysts.

High-sensitivity small-molecule detection of microcystin-LR cyano-toxin using a terahertz-aptamer biosensor.

We demonstrate the rapid and highly sensitive detection of a small molecule, microcystin-LR (MC-LR) toxin using an aptasensor based on a terahertz (THz) emission technique named the terahertz chemical microscope (TCM). The main component of the TCM is the sensing plate, which consists of a thin silicon layer deposited on a sapphire substrate, with a natural SiO2 layer formed on the top of the Si layer. The DNA aptamer is linked to the oxidized top surface of the silicon layer by a one-step reaction (click chemistry) between the DBCO-labeled aptamer and an azido group that binds to the surface. Using density functional theory (DFT) calculations, the number of active sites on the surface has been estimated to be 3.8 × 1013 cm-2. Aptamer immobilization and MC-LR binding have been optimized by adjusting the aptamer concentration and the binding buffer composition. When MC-LR binds with the DNA aptamer, it causes a change in the chemical potential at the surface of the sensing plate, which leads to a change in the amplitude of the THz signal. Compared with other bio-sensing methods such as surface plasmon resonance (SPR), TCM is a rapid assay that can be completed in 15 min (10 min incubation and 5 min data acquisition). Moreover, our results show that the aptamer-based TCM can detect MC-LR with an excellent detection limit of 50 ng L-1, which is 20 times more sensitive compared with SPR measurements of MC-LR.

N, P-Codoped Graphene Dots Supported on N-Doped 3D Graphene as Metal-Free Catalysts for Oxygen Reduction.

Nitrogen and phosphorus-codoped graphene dots supported on nitrogen-doped three-dimensional graphene (N, P-GDs/N-3DG) have been synthesized by a facile freeze-annealing process. On the surface of the 3D interconnected porous structure, the N, P-GDs are uniformly dispersed. The as-prepared N, P-GDs/N-3DG material served as a metal-free catalyst for oxygen reduction reaction (ORR) in an alkaline medium and evaluated by a rotating ring-disk electrode. The N, P-GDs/N-3DG catalyst exhibits excellent ORR activity, which is comparable to that of the commercial Pt/C catalyst. Furthermore, it exhibits a higher tolerance to methanol and better stability than the Pt/C. This enhanced electrochemical catalytic performance can be ascribed to the presence of abundant functional groups and edge defects. This study indicates that P-N bonded structures play a vital role as the active sites in ORR.

COVID-19 in French patients with chronic inflammatory rheumatic diseases: Clinical features, risk factors and treatment adherence.

OBJECTIVE: To explore how patients with chronic inflammatory rheumatic diseases (CIRDs) coped with their disease during the COVID-19 pandemic and to identify possible predictive factors of SARS-CoV-2 infection in this population. METHODS: Patients followed in a single rheumatology department in France or registered on the Spondy+ platform, a secure e-health platform for spondyloarthritis patients, were invited to complete a questionnaire focused on their experiences around COVID19 symptoms, testing and medications access during the lockdown period. Descriptive statistics were used to report questionnaire's results. Factors associated with COVID-19 or with treatment discontinuation were assessed by logistic regression. RESULTS: We obtained 655 answers from the 2,081 contacted patients: 474 with spondyloarthritis, 129 with rheumatoid arthritis and 52 with psoriatic arthritis. The population was predominantly female (61.8%) with a mean age of 51.0±13.4 years. Incidence of COVID-19 was 6.9% (95%CI: 5.1-9.2%), including 12 confirmed and 33 highly suspicious cases. No death was observed and five patients needed to be hospitalized. Factors independently associated with an increased risk of infection were SARS-CoV-2 exposure, younger age and non-smoking. More than 30% of the patients suspended or decreased the dosage of one of their drugs during the lockdown period. This was followed in 63.4% of them by increased disease activity. Modifications were mostly motivated by fear of contagion (79.3%). CONCLUSION: We did not observe any increase of incidence or severity of COVID-19 in patients suffering of the 3 most common CIRDs. This survey also adds evidence of the safety of anti-rheumatic drugs use regarding COVID-19.

18-FDG PSEUDOTUMORAL LESION WITH QUICK FLOWERING TO A TYPICAL LUNG CT COVID-19.

As coronavirus pandemic continues to spread over the world, physicians have to be aware of atypical features of COVID-19 pneumonia. We report the case of a 78-year-old man presenting with pseudo-tumoral focal lesion of the left lung which switched shortly to severe and diffuse COVID-19 induced pneumonia. Nuclear medicine physicians and radiologists should be careful of some misleading hypermetabolic aspects mostly in asymptomatic patients.

A colloidal heterostructured quantum dot sensitized carbon nanotube-TiO2 hybrid photoanode for high efficiency hydrogen generation.

Solar-driven photoelectrochemical (PEC) hydrogen (H2) generation is a promising approach to harvest solar energy for the production of a clean chemical fuel. However, the low photon-to-fuel conversion efficiency and long-term stability of PEC devices are major challenges to be addressed to enable large-scale commercialization. Here we report a simple, fast and cost-effective approach to fabricate high efficiency and stable PEC devices for H2 generation, by fabricating a hybrid photoanode obtained by incorporating small amounts of multiwall carbon nanotubes (MWCNTs) into a TiO2 mesoporous film and sensitizing with colloidal heterostructured CdSe/(CdSexS1-x)5/(CdS)2 quantum dots (QDs). The latter were specially designed to accelerate the exciton separation through a band engineering approach. The PEC devices based on the TiO2/QD-MWCNT (T/Q-M) hybrid photoanode with an optimized amount of MWCNTs (0.015 wt%) yield a saturated photocurrent density of 15.90 mA cm-2 (at 1.0 VRHE) under one sun illumination (AM 1.5G, 100 mW cm-2), which is 40% higher than that of the reference device based on TiO2/QD (T/Q) photoanodes. This is attributed to a synergistic effect of the promising optoelectronic properties of the colloidal heterostructured QDs and improved electron transport (reduced charge transfer resistance) within the TiO2-MWCNT hybrid anodes enabled by the directional path of MWCNTs for the photo-injected electrons towards FTO. Furthermore, the PEC device based on the T/Q-M hybrid photoanode is more stable (∼19% loss of its initial photocurrent density) when compared with the T/Q photoanode (∼35% loss) after two hours of continuous one sun illumination. Our results provide fundamental insights and a different approach to improve the efficiency and long-term stability of PEC devices and represent an essential step towards the commercialization of this emerging solar-to-fuel conversion technology.

Tailoring the interfacial structure of colloidal "giant" quantum dots for optoelectronic applications.

Colloidal semiconductor quantum dots (QDs) are promising building blocks for the realization of future optoelectronic technologies, thanks to their size-tunable electronic and optical properties. Among various types of QDs, colloidal "giant" QDs (g-QDs, core/thick-shell) have been widely used in different applications, such as solar cells, light emitting devices, luminescent solar concentrators and photoelectrochemical (PEC) hydrogen production. However, g-QDs have a thick-shell which serves as a physical barrier for electron and hole transfer, leading to a slow charge transfer rate. In this work, we synthesized CdSe/CdSexS1-x/CdS core/shell/shell g-QDs with an intermediate CdSexS1-x alloyed layer. The presence of this interfacial layer largely improves the absorption of CdSe/CdS QDs, particularly in the 300-650 nm range. By engineering the interfacial layer, the holes can leak more into the CdS shell region compared to that of CdSe/CdS QDs. PEC devices based on alloyed g-QDs exhibit a 20% higher saturated photocurrent density (11 ± 0.5 mA cm-2) compared to CdSe/CdS QDs. In addition, after one-hour illumination (100 mW cm-2), the PEC cell based on alloyed g-QDs still exhibits a photocurrent density of 7.5 mA cm-2, maintaining 70% of its initial value. Such alloyed g-QDs are very promising for several emerging optoelectronic applications, where charge separation, transfer and transport play a critical role for the realization of high performance devices.

Broadband and efficient adiabatic three-wave-mixing in a temperature-controlled bulk crystal.

Nonlinear interactions are commonly used to access to wavelengths not covered by standard laser systems. In particular, optical parametric amplification (OPA) is a powerful technique to produce broadly tunable light. However, common implementations of OPA suffer from a well-known trade-off, either achieving high efficiency for narrow spectra or inefficient conversion over a broad bandwidth. This shortcoming can be addressed using adiabatic processes. Here, we demonstrate a novel technique towards this direction, based on a temperature-controlled phase mismatch between the interacting waves. Using this approach, we demonstrate, by tailoring the temperature profile, an increase in conversion efficiency by 21%, reaching a maximum of 57%, while simultaneously expanding the bandwidth to over 300 nm. Our technique can readily enhance the performances of current OPA systems.

Alternatives to eye bank native tissue for corneal stromal replacement.

Corneal blindness is a major cause of blindness in the world and corneal transplantation is the only widely accepted treatment to restore sight in these eyes. However, it is becoming increasingly difficult for eye banks to meet the increasing demand for transplantable tissue, which is in part due to population aging. Donor tissue shortage is therefore a growing concern globally and there is a need for alternatives to human donor corneas. Biosynthetic corneal substitutes offer several significant advantages over native corneas: Large-scale production offers a powerful potential solution to the severe shortage of human donor corneas worldwide; Good manufacturing practices ensure sterility and quality control; Acellular corneal substitutes circumvent immune rejection induced by allogeneic cells; Optical and biomechanical properties of the implants can be adapted to the clinical need; and finally these corneal substitutes could benefit from new advances in biomaterials science, such as surface coating, functionalization and nanoparticles. This review highlights critical contributions from laboratories working on corneal stromal substitutes. It focuses on synthetic inert prostheses (keratoprostheses), acellular scaffolds with and without enhancement of endogenous regeneration, and cell-based replacements. Accent is put on the physical properties and biocompatibility of these biomaterials, on the functional and clinical outcome once transplanted in vivo in animal or human eyes, as well as on the main challenges of corneal stromal replacement. Regulatory and economic aspects are also discussed. All of these perspectives combined highlight the founding principles of the clinical application of corneal stromal replacement, a concept that has now become reality.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments.

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.