Fracture Toughness Characteristics of Stacked Bilayer Graphene via Far-Field Displacement Measurements.

Mechanical properties of graphene, e.g., strength, modulus, and fracture toughness are extremely sensitive to flaws. Here the fracture properties of stacked bilayer graphene sheets (SBLG) are reported, obtained via stacking two individually grown graphene sheets. The SBLG is presented here as a building block for flaw-resilient nanomaterials. The fracture properties of freestanding SBLG sheets, suspended on transmission electron microscope (TEM) grids, are characterized by stretching the TEM grid inside an scanning electron microscope (SEM) chamber and monitoring the local displacements in real-time. The fracture toughness is measured and expressed as a function of the critical displacement required to propagate existing cracks in the experiment via computational models. This approach decouples force and displacements measurements, and utilizes the known elastic modulus along with the known displacement boundary conditions at the onset of crack growth to estimate the far field force and stress. This strategy represents a breakthrough in nanoscale fracture mechanics for statistical analysis and high throughput experimens on multiple samples at a time. Results demonstrate that the SBLG is markedly tougher than as-grown single or multilayer graphene, with a mode I fracture toughness of ≈28.06 ± 7.5 MPa m $\sqrt m $ . The mechanisms leading to a higher toughness of SBLG are also analyzed and discussed.

Impact of educational and psychological interventions compared with standard care in college/university students with autism spectrum disorder: a systematic review protocol.

OBJECTIVE: This review will explore the impact of educational and psychological interventions on educational, social, behavioral, and mental health outcomes in students with autism spectrum disorder in tertiary education. INTRODUCTION: This systematic review will inform a new guideline on support for students with autism spectrum disorder in the tertiary education environment. These students face multiple educational, behavioral, social, and health-related problems that require effective interventions. INCLUSION CRITERIA: Participants are students with autism spectrum disorder in a tertiary education study program. Educational and psychological interventions will be included, such as accommodations, meta-cognitive and self-regulation training, psychological counseling, social skills training, and peer-mentoring/academic coaching. The comparator will be standard care. The study outcomes will include academic drop-out rates and evaluations, learning skills, social skills and social engagement, behavior, mental health (including anxiety, stress, and depression), and employment after graduation. This review will consider quantitative studies only. METHODS: A 3-step search strategy will be used to find both published and unpublished studies in MEDLINE, CINAHL, APA PsycINFO, SocINDEX, Web of Science, Clinical Trials, ProQuest Dissertations and Theses, Open Dissertations, ERIC, WHO ICRTP, and Google Scholar. There will be no date or language limitations. All stages of article screening, critical appraisal, and data extraction will be conducted by 2 independent reviewers with the resolution of any disagreements done via consensus or through a senior reviewer. If possible, the included studies will be pooled using meta-analysis. The degree of certainty of the evidence will be assessed according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO CRD42022323554.

Effect of low frequency sound vibration on acute stress response in university students-Pilot randomized controlled trial.

Background: Low frequency sound (LFS, combined with music listening) is applied by practitioners in vibroacoustic therapy who report a positive effect of this intervention on acute stress response. However, there is a lack of research on this topic and studies with mainly objective measurements are scarce. Materials and methods: In this pilot double-blinded Randomized Controlled Trial we used a multimodal approach to measurement of acute stress response in 54 international university students attending a university summer school in Olomouc, the Czech Republic who were individually randomized into a group receiving LFS vibration and a control group. In both groups, the acute stress response was measured by heart rate variability (HRV), visual analogue scales (VAS) for stress and muscle relaxation. Results: Differences were found in pre-test post-test measures, however, between groups differences occurred only for HRV, with statistically significant improvement in the experimental group (parameter LF/HF and pNN50). Conclusion: Vibroacoustic therapy has the potential to contribute to the stress management of university students. Further research is needed to explore the effect of LFS on stress response, especially when applied without additional music listening.

Carbazole-based polymers for organic photovoltaic devices.

Polymers based upon 2,7-disubstituted carbazole have recently become of great interest as electron-donating materials in organic photovoltaic devices. In this tutorial review the synthesis of such polymers and their relative performances in such devices are surveyed. In particular structure-property relationships are investigated and the potential for the rational design of materials for high efficiency solar cells is discussed. In the case of the 2,7-carbazole homopolymer it has been found that electron acceptors other than fullerenes produce higher energy conversion efficiencies. To get around possible problems with the build-up of charge density at the 3- and 6-positions and to improve the solar light harvesting ability of the polymers by reducing the bandgap, ladder- and step-ladder type 2,7-carbazole polymers have been synthesised. The fully ladderised polymers gave very poor results in devices, but efficiencies of over 1% have been obtained from a step-ladder polymer with a diindenocarbazole monomer unit. Donor-acceptor copolymers containing 2,7-carbazole donors and various electron-accepting comonomer units have been prepared. An efficiency of 6% has been reported from a device using such a copolymer and by suitable choice of the acceptor comonomer, polymers can be designed with potential theoretical power conversion efficiencies of 10%. While such efficiencies remain to be obtained, the results to date certainly suggest that carbazole-based polymers and copolymers are among the most promising materials yet proposed for obtaining high efficiency organic solar cells.

Supramolecular Organization and Photovoltaics of Triangle-shaped Discotic Graphenes with Swallow-tailed Alkyl Substituents.

Two novel triangle-shaped discotic graphenes with swallow-like alkyl tails are synthesized; these discotic graphenes allow facile purification, control over thermotropic properties, and solution fabrication into efficient photovoltaic devices. The unique molecular design results in an extremely broad liquid-crystalline range and the ability to self-heal at low processing temperatures, which improves the performance of photovoltaic cells.

Janus nanodisc of diblock copolymers.

Janus nanodiscs of diblock copolymers are prepared by stepwise disassembly of PS-b-P4VP disc-stacked particles. The Janus nanodiscs are uniform in thickness and regular in contour. By preferential growth of functional materials at the positively charged P4VP side, the composition, microstructure, and performance of the Janus nanodiscs are tunable.

Ionic liquid functionalized Janus nanosheets.

Ionic liquid functionalized Janus nanosheets are synthesized by selective treatment of the imidazolin terminated side of Janus nanosheets while the other side is preserved. The Janus performance of the nanosheets and thus emulsion stability are reversibly triggered by anion exchange.

Janus micro-reactors.

Janus hollow spheres, with different compositions compartmentalized onto both interior and exterior surfaces of the same shell and P25 nanoparticles encapsulated in the cavities, are synthesized by the ultrasonic spray method to selectively enrich desired reagents in a confined environment for further reaction.

Photoluminescent poly(ether ether ketone)-quantum dot composite films.

A fluoropoly(ether ether ketone) (FPEEK) demonstrating blue fluorescence was developed as a flexible, transparent membranous matrix for the incorporation of quantum dots (QDs) to fabricate a composite photoluminescent film which is promising as a self-referenced temperature sensor.

Janus hollow spheres by emulsion interfacial self-assembled sol-gel process.

Janus hollow silica spheres with an asymmetric shell are synthesized by self-assembled sol-gel process at an emulsion interface, and desired materials can be preferentially laden inside the cavities from their surroundings.

Polymer nanotubes toward gelating organic chemicals.

Crosslinked polymer nanotubes are large scale synthesized. The method is based on fast cationic polymerization using immiscible initiator nanodroplets. Nanoporous network processed from the nanotubes is superhydrophobic, which can absorb all the tested organic chemicals forming robust gels. The nanotubes are promising in the collection of spilled organic chemicals, detoxification and water treatment.

pH triggered injectable amphiphilic hydrogel containing doxorubicin and paclitaxel.

Injectable hydrogel with hydrophobic microdomains for incorporating both hydrophilic and hydrophobic drugs, herein doxorubicin hydrochloride (DOX) and paclitaxel (PTX), was synthesized through dynamic bonding of glycol chitosan and benzaldehyde capped poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) via Schiff's reaction triggered by environmental pH. Rheology tests show that the inclusion of hydrophilic drug decreases the gelation time and gains more robust gel, while the addition of hydrophobic drug has opposite influences. Dual-drug release from the DOX+PTX loaded gels was observed and the release rate can be accelerated by decreasing the environmental pH from physiological (7.4) to weak acidic pH (6.8). In vivo investigation proved that the gels were able to diminish the amount of DOX in blood circulation and limit the DOX-induced cardiotoxicity. By intratumoral administration, the hydrogel-drug formulations resulted in efficient growth inhibition of subcutaneous tumor (B16F10) on C57LB/6 mouse model. The advantage of the current system for DOX+PTX combination therapy was demonstrated by a prolongation of survival time in comparison with the single drug therapy.

Large scale synthesis of Janus submicron sized colloids by wet etching anisotropic ones.

Janus colloids have inspired growing interests due to their diverse potential applications. Herein, we present a facile approach to fabricate Janus submicron sized colloids by the selective etching of anisotropic colloids. Size ratio, microstructure and composition are tunable. The method can be scaled up, which is the key to further exploit practical applications.

A simple and efficient method using polymer dispersion to prepare controllable nanoporous TiO2 anodes for dye-sensitized solar cells.

An efficient method using a polymer dispersion (PD) based on a copolymer of styrene and butyl acrylate to prepare TiO2 electrodes for dye-sensitized solar cells (DSCs) was introduced. The obtained TiO2 nanoporous film was investigated by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. A porous structure with pore size distribution from tens of nanometers to several hundred nanometers or even micrometers was characterized. This offered the film a feature of high haze factor and porosity. When using the film as photoanode, a quasi-solid-state DSC was successfully fabricated. The device showed an improved per-weight-efficiency by a factor of 2.7, resulting from the reduced interfacial resistance and the enhanced light scattering effect revealed by electrochemical impedance spectroscopy and transmittance spectroscopy, respectively. The developed PD-based colloid is promising to be applied in production on a large scale as a result of its simple prescription and stability during storage. A proposal to further improve the porous film is also introduced at the end of the paper.

Exciton diffusion controlled quantum efficiency in hybrid dye sensitized solar cells.

Well-ordered and uniform titania nanoparticle arrays were synthesized using diblock copolymers as structure directing agents. High molecular weight copolymers of polystyrene-b-polyethylene oxide and poly(methylmethacrylate)-b-polyethylene oxide were used to control the distance between titania nanoparticles in the range of 20-60 nm. Using these titania nanoparticle arrays and regioregular poly(3-hexylthiophene), models for a dye sensitized photovoltaic cell were assembled, in which the interparticle spacing was systematically varied. In these simplified solar cells, the titania nanocrystals were surrounded by a continuous regioregular poly(3-hexylthiophene) phase. The spacing between the titania nanoparticles was chosen as to provide enough space for the hole transfer material-regioregular poly(3-hexylthiophene)-to assemble as pi stacks. The external quantum efficiency showed a clear dependence on the distance between titania nanoparticles and reached 12% at an excitation wavelength of 515 nm in the best case. This demonstrates that the regioregular poly(3-hexylthiophene) phase acts as the locus of excition generation while the dye layer prevents charge recombination at the heterointerface. Thus control of the exciton diffusion is a key issue for present solid-state dye sensitized solar cells.