Universal Approach to Integrating Reduced Graphene Oxide into Polymer Electronics.

Flexible electronics have sparked significant interest in the development of electrically conductive polymer-based composite materials. While efforts are being made to fabricate these composites through laser integration techniques, a versatile methodology applicable to a broad range of thermoplastic polymers remains elusive. Moreover, the underlying mechanisms driving the formation of such composites are not thoroughly understood. Addressing this knowledge gap, our research focuses on the core processes determining the integration of reduced graphene oxide (rGO) with polymers to engineer coatings that are not only flexible and robust but also exhibit electrical conductivity. Notably, we have identified a particular range of laser power densities (between 0.8 and 1.83 kW/cm2), which enables obtaining graphene polymer composite coatings for a large set of thermoplastic polymers. These laser parameters are primarily defined by the thermal properties of the polymers as confirmed by thermal analysis as well as numerical simulations. Scanning electron microscopy with elemental analysis and X-ray photoelectron spectroscopy showed that conductivity can be achieved by two mechanisms-rGO integration and polymer carbonization. Additionally, high-speed videos allowed us to capture the graphene oxide (GO) modification and melt pool formation during laser processing. The cross-sectional analysis of the laser-processed samples showed that the convective flows are present in the polymer substrate explaining the observed behavior. Moreover, the practical application of our research is exemplified through the successful assembly of a conductive wristband for wearable devices. Our study not only fills a critical knowledge gap but also offers a tangible illustration of the potential impact of laser-induced rGO-polymer integration in materials science and engineering applications.

Fabrication of UV-Curable Polysiloxane Coating with Tunable Refractive Index Based on Controllable Hydrolysis.

In order to improve laser transmission efficiency at 1053 nm and 527 nm, a potassium deuterium phosphate (DKDP) crystal (a key component of high-power laser systems) needs a bi-layer antireflection coating system on its incident surface. UV-curable polysiloxane coatings with a refractive index varying from 1.500 to 1.485 were prepared through the polycondensation of a methacryloxy propyl trimethoxylsilane (MPS) monomer with a controllable degree of hydrolysis. Additionally, the influence rule of the coating structure on the refractive index was intensively studied, and the primary factors that dominate the hydrolysis process were discussed. Further refractive index adjustment was achieved using only a small amount of dopant based on the polysiloxane coating with refractive index of 1.485, allowing for high antireflection of the bi-layer coating system at desired wavelengths to be achieved. In addition, high laser damage resistance and remarkable mechanical properties of the coating were simultaneously realized through the incorporation of a minor quantity of dopants, which benefited from the successful modulation of the intrinsic refractive index of the polysiloxane coating.

Patterning GaSe by High-Powered Laser Beams.

We report the high-powered laser modification of the chemical, physical, and structural properties of the two-dimensional (2D) van der Waals material GaSe. Our results show that contrary to expectations and previous reports, GaSe at the periphery of a high-power laser beam does not entirely decompose into Se and Ga2O3. In contrast, we find unexpectedly that the Raman signal from GaSe gets amplified around regions where it was not expected to exist. Atomic force microscopy (AFM), dielectric force microscopy (DFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) results show that laser irradiation induces the formation of nanoparticles. Our analyses demonstrate that, except for a fraction of Ga2Se3, these nanoparticles still belong to the GaSe phase but possess different electrical and optical properties. These changes are evidenced in the increased Raman intensity attributed to the near-resonance conditions with the Raman excitation laser. The elemental analysis of nanoparticles shows that the relative selenium content increased to as much as 70% from a 50:50 value in stoichiometric GaSe. This elemental change is related to the formation of the Ga2Se3 phase identified by Raman spectroscopy at some locations near the edge. Further, we exploit the localized high-power laser processing of GaSe to induce the formation of Ag-GaSe nanostructures by exposure to a solution of AgNO3. The selective reaction of AgNO3 with laser-irradiated GaSe gives rise to composite nanostructures that display photocatalytic activity originally absent in the pristine 2D material. The photocatalytic activity was investigated by the transformation of 4-nitrobenzenethiol to its amino and dimer forms detected in situ by Raman spectroscopy. This work improves the understanding of light-matter interaction in layered systems, offering an approach to the formation of laser-induced composites with added functionality.

Internet-based intervention for postpartum depression in China ("Mommy go"): Protocol for a randomized controlled trial.

AIM: The purpose of this study is to design a research protocol for the clinical testing of the "Mommy go" for pregnant women with a risk of postpartum depression. DESIGN: A non-blinded randomized controlled trial. METHODS: A randomized controlled study will be performed from January 2018 to the completion of the study. The intervention group will follow the "Mommy go" protocol and the control group will receive traditional support. We will use the Edinburgh Postpartum Depression Scale and the Chinese version of the Postpartum Depression Predictors Inventory-Revised to measure the risk of postpartum depression in pregnant women. The outcomes are clinical data, postpartum depressive mood, self-efficacy, and infant temperament. Outcomes will be assessed using questionnaires and through data generated by digital technologies. DISCUSSION: The expected outcomes are increased self-efficacy and infant temperament, reduced postpartum depressive mood, and improvements to postpartum depression. We expect the study to have a clinical impact on future online interventions for postpartum depression in China. IMPACT: This study will provide an internet-based intervention for postpartum depression in China. It will be implemented in clinical practice if it can effectively improve postpartum depression. TRIAL REGISTRATION: Registered at the Chinese Clinical Trials.gov (ChiCTR1800018804).

Template-Free Fabrication of Refractive Index Tunable Polysiloxane Coating Using Homogeneous Embedding Strategy: Application in High-Power Laser System.

A refractive index (RI) tunable polysiloxane coating was fabricated based on the cross-linked network structure embedded with mesoporous silica nanoparticles (MSNs), in which the MSNs were utilized to modulate the RI as well as to support the interior structure of the polysiloxane coating. The Si-O-Si inorganic backbone structure in combination with characteristics from the photopolymerization of active bonds produced the main cross-linked network structure, and controllable embedding of MSNs constructed the network-sphere structure. This approach eliminated the high-temperature post-treatment that was needed to remove the template, which ensures the safe application for temperature-sensitive laser crystal substrates and avoids coating structure collapse. In addition, degradation of the resulting coating can be minimized due to the similar chemical formation between MSN and polysiloxane coating. Hereby, a polysiloxane coating with expected spectral and laser damage-resistant properties can be obtained. This will facilitate the fabrication and application of a laser component with both high-transmission and high-flux capability for a high-power laser system.

Ultra-Uniform and Very Thin Ag Nanowires Synthesized via the Synergy of Cl-, Br- and Fe3+ for Transparent Conductive Films.

The properties and applications of Ag nanowires (AgNWs) are closely related to their morphology and composition. Therefore, controlling the growth process of AgNWs is of great significance for technological applications and fundamental research. Here, silver nanowires (AgNWs) were synthesized via a typical polyol method with the synergistic effect of Cl-, Br-, and Fe3+ mediated agents. The synergistic impact of these mediated agents was investigated intensively, revealing that trace Fe3+ ions provided selective etching and hindered the strong etching effect from Cl- and Br- ions. Controlling this synergy allowed the obtainment of highly uniform AgNWs with sub-30 nm diameter and an aspect ratio of over 3000. Transparent conductive films (TCFs) based on these AgNWs without any post-treatment showed a very low sheet resistance of 4.7 Ω sq-1, a low haze of 1.08% at a high optical transmittance of 95.2% (at 550 nm), and a high figure of merit (FOM) of 1210. TCFs exhibited a robust electrical performance with almost unchanged resistance after 2500 bending cycles. These excellent high-performance characteristics demonstrate the enormous potential of our AgNWs in the field of flexible and transparent materials.

Preparation and characterization of flexible lithium iron phosphate/graphene/cellulose electrode for lithium ion batteries.

In this work, a free-standing flexible composite electrode was prepared by vacuum filtration method with LiFePO4, graphene and nanofibrillated cellulose (NFC). Compared with the pure LiFePO4 electrode, the resulting flexible composite (LiFePO4/graphene/NFC) electrode showed excellent mechanical flexibility, and possessed an enhanced initial discharge capacity of 151 mA h/g (0.1 C) and a good capacity retention rate with only 5% loss after 60 cycles due to suitable electrolyte wettability at the interface. Furthermore, the NFC and graphene formed a three-dimensional conductive framework, which provided high-speed electron conduction in the composite and reduced electrode polarization during charging-discharging processes. Moreover, the composite electrode could endure bending tests up to 1000 times, highlighting preferable mechanical strength and durability. These results demonstrated that the as-fabricated electrodes could be applied as flexible electrodes with an embedded power supply.

Easily fabricated and lightweight PPy/PDA/AgNW composites for excellent electromagnetic interference shielding.

Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm-1, and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm-3. In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.

Paper-Based Inkjet-Printed Flexible Electronic Circuits.

Printed flexible electronics have been widely studied for their potential use in various applications. In this paper, a simple, low-cost method of fabricating flexible electronic circuits with high conductivity of 4.0 × 107 S·m-1 (about 70% of the conductivity of bulk copper) is demonstrated. Teslin paper substrate is treated with stannous chloride (SnCl2) colloidal solution to reduce the high ink absorption rate, and then the catalyst ink is inkjet-printed on its surface, followed by electroless deposition of copper at low temperature. In spite of the decrease in conductance to some extent, electronic circuits fabricated by this method can maintain function even under various folding angles or after repeated folding. This developed technology has great potential in a variety of applications, such as three-dimensional devices and disposable RFID tags.

Defect effects on the physical and electrochemical properties of nanoscale LiFe0.92PO4 and LiFe0.92PO4/C/graphene composites.

Nanoscale LiFe0.92PO4 and LiFe0.92PO4/C/graphene composites including defects as performance-improved cathode materials for lithium-ion batteries were prepared by a carbothermal reduction method. The physical and electrochemical properties of samples were characterized by means of X-ray diffraction, inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and electrochemical testing techniques. The results confirmed that defects existed within the nanoscale LiFe0.92PO4 lattice and had significant effects on improving the electrochemical properties of samples. The excellent graphene sheets covered on nanoparticles and formed a three-dimensional conductive network in nanoscale LiFe0.92PO4/C/graphene composites. The composites exhibited a discharge capacity of 90 mA h g(-1) at 10 C and capacity retention ratios of 98% after 100 cycles at various rates, implying outstanding high-rate capability and cycling stability.