Showing papers by "Xiong Gong published in 2020"

Highly stretchable, self-adhesive, biocompatible, conductive hydrogels as fully polymeric strain sensors

Abstract: Development of highly stretchable and sensitive soft strain sensors is of great importance for broad applications in artificial intelligence, wearable devices, and soft robotics, but it proved to be a profound challenge to integrate the two seemingly opposite properties of high stretchability and sensitivity into a single material. Herein, we designed and synthesized a new fully polymeric conductive hydrogel with an interpenetrating polymer network (IPN) structure made of conductive PEDOT:PSS polymers and zwitterionic poly(HEAA-co-SBAA) polymers to achieve a combination of high mechanical, biocompatible, and sensing properties. The presence of hydrogen bonding, electrostatic interactions, and IPN structures enabled poly(HEAA-co-SBAA)/PEDOT:PSS hydrogels to achieve an ultra-high stretchability of 4000–5000%, a tensile strength of ∼0.5 MPa, a rapid mechanical recovery of 70–80% within 5 min, fast self-healing in 3 min, and a strong surface adhesion of ∼1700 J m−2 on different hard and soft substrates. Moreover, the integration of zwitterionic polySBAA and conductive PEDOT:PSS facilitated charge transfer via optimal conductive pathways. Due to the unique combination of superior stretchable, self-adhesive, and conductive properties, the hydrogels were further designed into strain sensors with high sensing stability and robustness for rapidly and accurately detecting subtle strain- and pressure-induced deformation and human motions. Moreover, an in-house mechanosensing platform provides a new tool to real-time explore the changes and relationship between network structures, tensile stress, and electronic resistance. This new fully polymeric hydrogel strain sensor, without any conductive fillers, holds great promise for broad human-machine interface applications.

Recent Advancements and Challenges for Low-Toxicity Perovskite Materials

Abstract: Lead-based organic-inorganic hybrid perovskite materials have been developed for advanced optoelectronic applications. However, the toxicity of lead and the chemical instability of lead-based perovskite materials have so far been demonstrated to be an overwhelming challenge. The discovery of perovskite materials based on low-toxicity elements, such as Sn, Bi, Sb, Ge, and Cu, with superior optoelectronic properties provides alternative approaches to realize high-performance perovskite optoelectronics. In this review, recent advances in the aspects of low-toxicity perovskite solar cells, photodetectors, light-emitting diodes, and thermoelectric devices are highlighted. The antioxidation stability of metal cation and the crystallization process of the low-toxicity perovskite materials are discussed. In the last part, the outlook toward addressing various issues requiring further attention in the development of low-toxicity perovskite materials is outlined.

Molecular simulations and understanding of antifouling zwitterionic polymer brushes.

Abstract: Zwitterionic materials are an important class of antifouling biomaterials for various applications. Despite such desirable antifouling properties, molecular-level understanding of the structure–property relationship associated with surface chemistry/topology/hydration and antifouling performance still remains to be elucidated. In this work, we computationally studied the packing structure, surface hydration, and antifouling property of three zwitterionic polymer brushes of poly(carboxybetaine methacrylate) (pCBMA), poly(sulfobetaine methacrylate) (pSBMA), and poly((2-(methacryloyloxy)ethyl)phosporylcoline) (pMPC) brushes and a hydrophilic PEG brush using a combination of molecular mechanics (MM), Monte Carlo (MC), molecular dynamics (MD), and steered MD (SMD) simulations. We for the first time determined the optimal packing structures of all polymer brushes from a wide variety of unit cells and chain orientations in a complex energy landscape. Under the optimal packing structures, MD simulations were further conducted to study the structure, dynamics, and orientation of water molecules and protein adsorption on the four polymer brushes, while SMD simulations to study the surface resistance of the polymer brushes to a protein. The collective results consistently revealed that the three zwitterionic brushes exhibited stronger interactions with water molecules and higher surface resistance to a protein than the PEG brush. It was concluded that both the carbon space length between zwitterionic groups and the nature of the anionic groups have a distinct effect on the antifouling performance, leading to the following antifouling ranking of pCBMA > pMPC > pSBMA. This work hopefully provides some structural insights into the design of new antifouling materials beyond traditional PEG-based antifouling materials.

Multiple Physical Bonds to Realize Highly Tough and Self-Adhesive Double-Network Hydrogels

Abstract: Tough and adhesive hydrogels have shown great potential in wearable devices, flexible electronics, and human–machine interfaces. However, most existing tough hydrogels have weak surface adhesion, o...

Novel Quasi-2D Perovskites for Stable and Efficient Perovskite Solar Cells.

Abstract: Compared to three-dimensional (3D) organic–inorganic hybrid perovskites, two-dimensional (2D) ones possess great possibilities to realize stable cost-effective perovskite solar cells (PSCs). Howeve...

High-Performance Perovskite Solar Cells by One-Step Self-Assembled Perovskite-Polymer Thin Films

Abstract: Perovskite materials have drawn the greatest attention as alternatives for approaching cost-effective perovskite solar cells (PSCs) in the past decade. However, the desire for PSCs with photocurren...

Poly(Ethylene Glycol) Diacrylate as the Passivation Layer for High-Performance Perovskite Solar Cells

Abstract: In the past decade, greatest effect has been paid on organic-inorganic halide perovskites for approaching high-performance perovskite solar cells (PSCs). It was found that severe surface-defect within the perovskite active layer restricted further boosting device performance of PSCs. Here, we report high-performance PSCs by utilization of an ultrathin solution-processed poly(ethylene glycol) diacrylate (PEGDA) layer to passivate the surface-defect within the perovskite thin film. Systematical studies demonstrate that the PEGDA-passivated perovskite thin film exhibit suppressed nonradiative recombination and trap density, as well as superior film morphology with a smoother surface, larger crystal size, and better crystallinity. Moreover, PSCs by the PEGDA-passivated perovskite thin film exhibit suppressed charge carrier recombination, reduced charge-transfer resistance, shorter charge carrier extraction time, and enlarged built-in potential. As a result, PSCs by the PEGDA-passivated perovskite thin film show a power conversion efficiency of over 21% and a photocurrent hysteresis index of 0.037. Moreover, unencapsulated PSCs by the PEGDA-passivated perovskite thin film possess over 10 day operational stability. All these results indicate that our approach provided a facile way to boost device performance of PSCs.

Enhanced thermoelectric performance of F4-TCNQ doped FASnI3 thin films

Abstract: In the past decade, great efforts have been devoted to the development of organic–inorganic hybrid perovskites for achieving efficient photovoltaics, but less attention has been paid to their thermoelectric applications. In this study, for the first time, we report the thermoelectric performance of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) doped NH2CHNH2SnI3 (FASnI3) thin films. It is found that the electrical conductivities of the F4-TCNQ doped FASnI3 thin films increase and then decrease along with increased doping levels of F4-TCNQ. Systematic studies indicate that enhanced electrical conductivities are attributed to the increased charge carrier concentrations and mobilities and superior film morphologies of the F4-TCNQ doped FASnI3 thin films, and decreased electrical conductivities originate from the cracks and poor film morphology of the F4-TCNQ doped FASnI3 thin films induced by excess F4-TCNQ dopants. The quantitative thermal conductivity scanning thermal microscopy studies reveal that the F4-TCNQ doped FASnI3 thin films exhibit ultralow thermal conductivities. Moreover, the thermoelectric performance of the F4-TCNQ doped FASnI3 thin films is investigated. It is found that the F4-TCNQ doped FASnI3 thin films exhibit a Seebeck coefficient of ∼310 μV K−1, a power factor of ∼130 μW m−1 K−2 and a ZT value of ∼0.19 at room temperature. All these results demonstrate that our studies open a door for exploring cost-effective less-toxic organic–inorganic hybrid perovskites in heat-to-electricity conversion applications at room temperature.

Computational Investigation of Antifouling Property of Polyacrylamide Brushes.

Abstract: Antifouling materials and coatings have broad fundamental and practical applications. Strong hydration at polymer surfaces has been proven to be responsible for their antifouling property, but molecular details of interfacial water behaviors and their functional roles in protein resistance remain elusive. Here, we computationally studied the packing structure, surface hydration, and protein resistance of four poly(N-hydroxyalkyl acrylamide) (PAMs) brushes with different carbon spacer lengths (CSLs) using a combination of molecular mechanics (MM), Monte Carlo (MC), and molecular dynamics (MD) simulations. The packing structure of different PAM brushes were first determined and served as a structural basis for further exploring the CSL-dependent dynamics and structure of water molecules on PAM brushes and their surface resistance ability to lysozyme protein. Upon determining an optimal packing structure of PAMs by MM and optimal protein orientation on PAMs by MC, MD simulations further revealed that poly(N-hydroxymethyl acrylamide) (pHMAA), poly(N-(2-hydroxyethyl)acrylamide) (pHEAA), and poly(N-(3-hydroxypropyl)acrylamide) (pHPAA) brushes with shorter CSLs = 1-3 possessed a much stronger binding ability to more water molecules than a poly(N-(5-hydroxypentyl)acrylamide) (pHPenAA) brush with CSL = 5. Consequently, CSL-induced strong surface hydration on pHMAA, pHEAA, and pHPAA brushes led to high surface resistance to lysozyme adsorption, in sharp contrast to lysozyme adsorption on the pHPenAA brush. Computational studies confirmed the experimental results of surface wettability and protein adsorption from surface plasmon resonance, contact angle, and sum frequency generation vibrational spectroscopy, highlighting that small structural variation of CSLs can greatly impact surface hydration and antifouling characteristics of antifouling surfaces, which may provide structural-based design guidelines for new and effective antifouling materials and surfaces.

Introduction and Fundamentals of Human Islet Amyloid Polypeptide Inhibitors

Abstract: Type 2 diabetes (T2D) is a common protein misfolding disease (PMD), and its pathogenesis is considered to be tightly associated with the aggregation of the disease-causative hIAPP (or amylin). Nume...

Solution-Processed Polymeric Thin Film as the Transparent Electrode for Flexible Perovskite Solar Cells

Abstract: In the past decade, perovskite solar cells (PSCs) were arising as a new generation of low-cost solar technology for renewable energy generation. More than 25% of power conversion efficiency (PCE) was reported from PSCs on the rigid indium tin oxide (ITO)/glass electrode. However, PSCs fabricated on flexible solution-processed transparent electrodes have still been a challenge to date. In this work, we report a solution-processed transparent polymeric thin film as the electrode for flexible solution-processed PSCs. The solution-processed polymeric thin film exhibits superior optical transparency and decent electrical conductivity. As compared with a PCE of 16.60% from PSCs on the ITO/glass substrate, PSCs on the solution-processed transparent polymeric electrode/glass substrate exhibit a PCE of 13.36% and PSCs on the solution-processed transparent polymeric thin-film/polyethylene terephthalate flexible substrate possess a PCE of 10.16%. Systematic studies demonstrate that poor electrical conductivity of the solution-processed transparent polymeric electrode and serious interfacial charge carrier recombination are responsible for low PCEs. Nevertheless, our results demonstrate that we provide a facile route to develop flexible PSCs by utilization of solution-processed polymeric thin films as the transparent electrodes.

All-Solid-State Asymmetric Supercapacitors with Novel Ionic Liquid Gel Electrolytes

Abstract: In the past years, all-solid-state supercapacitors, as energy storage devices, have drawn greatest attention in both academic and industrial sectors because of their potential applications, in part...

The compositional engineering of organic–inorganic hybrid perovskites for high-performance perovskite solar cells

Abstract: In the last decade, organic–inorganic perovskite materials have drawn great attentions in both academic and industrial sectors because of their remarkable optoelectronic and photovoltaic properties. Various perovskite materials have been investigated for high-performance perovskite solar cells. In this short review, we aim to illustrate optimized photovoltaic properties of perovskite materials through compositional engineering of organic–inorganic hybrid perovskite materials. We firstly elaborate the progresses of compositional engineering for each of three components in AMX3 perovskite materials, and then highlight the optoelectronic and photovoltaic properties of the resultant perovskite materials. It was found that the compositional engineering of organic–inorganic hybrid perovskites plays an important role in device performance of perovskite solar cells. Lastly, the outlook and prospects of compositional engineering of organic–inorganic hybrid perovskite materials are briefly discussed.

Ultrasensitive and high gain solution-processed perovskite photodetectors by CH3NH3PbI2.55Br0.45:Zn2SnO4 bulk heterojunction composite

Abstract: Hybrid perovskite photodetectors, the novel alternative devices transform incident light into electrical signal, have been rapidly developed in the past years. However, intrinsic unbalanced charge carrier transport within hybrid perovskite materials, restricting further boosting device performance of perovskite photodetectors, has rarely been addressed. In this study, we report room temperature–operated solution-processed bulk heterojunction perovskite photodetectors with ultrahigh sensitivity and great photo-gain. It is found that the introduction of Zn2SnO4 nanoparticles into CH3NH3PbI2.55Br0.45 perovskites results in enlarged photocurrent and suppressed dark current for bulk heterojunction perovskite photodetectors. As a result, a responsivity of over 1500 mAW−1 and projected detectivity of approximatively 1014 Jones (1 Jones = cm Hz1/2 W−1) from 380 to 760 nm are observed from bulk heterojunction perovskite photodetectors. In addition, bulk heterojunction perovskite photodetectors exhibit an excellent linear dynamic range of 124 dB and a great photo-gain of 535. All these results indicate that high-performance perovskite photodetectors could be realized through novel bulk heterojunction device structure.

High Performance Perovskite Solar Cells by Perovskites Co-Crystallized with Polymers

Abstract: Extensive interest has been raised by perovskite materials as emerging alternatives for low-cost and efficient perovskite solar cells (PSCs) in the past decade. However, achieving high-performance and stable PSCs with negligible photocurrent hysteresis behavior is still a challenging task due to the intrinsic foibles of perovskites. In this work, we report efficient and stable PSCs with dramatically suppressed photocurrent hysteresis by CH3NH3PbI3 co-crystallized with poly(ethylene oxide) (PEO). It is found that PEO-CH3NH3PbI3 thin film exhibit superior film morphology and significantly enlarged crystal grains as compared with CH3NH3PbI3 thin film. Systematical investigations reveal that the introduction of PEO in CH3NH3PbI3 could improve the charge transport and reduce the charge carrier recombination and promote the charge carrier extraction time within PSCs. As a result, PSCs by PEO-CH3NH3PbI3 thin film exhibit a power convention efficiency of 20.73%, which is over 20% enhancement as compared with that (17.42%) from PSCs by CH3NH3PbI3 thin film. Moreover, photocurrent hysteresis is dramatically suppressed in PSCs by PEO-CH3NH3PbI3 thin film. In addition, PSCs by PEO-CH3NH3PbI3 thin film exhibit boosted stability. All these results demonstrate that perovskites co-crystallized with polymers is an efficient approach towards high performance PSCs.