Device Physics of Dye Solar Cells

Design of new materials for nanostructured dye solar cells (DSC) requires understanding the link between the material properties and cell efficiency. This paper gives an overview of the fundamental and practical aspects of the modeling and characterization of DSCs, and integrates the knowledge into a user‐friendly DSC device model. Starting from basic physical and electrochemical concepts, mathematical expressions for the IV curve and differential resistance of all resistive cell components are derived and their relation to electrochemical impedance spectroscopy (EIS) is explained. The current understanding of the associated physics is discussed in detail and clarified. It is shown how the model parameters can be determined from complete DSCs by current dependent EIS and incident‐photon‐to‐collected‐electron (IPCE) measurements, supplemented by optical characterization, and used to quantify performance losses in DSCs. The paper aims to give a necessary theoretical background and practical guidelines for establishing an effective feedback‐loop for DSC testing and development.     

Few‐Layer GeAs Field‐Effect Transistors and Infrared Photodetectors

The family of 2D semiconductors (2DSCs) has grown rapidly since the first isolation of graphene. The emergence of each 2DSC material brings considerable excitement for its unique electrical, optical, and mechanical properties, which are often highly distinct from their 3D counterparts. To date, studies of 2DSC are majorly focused on group IV (e.g., graphene, silicene), group V (e.g., phosphorene), or group VIB compounds (transition metal dichalcogenides, TMD), and have inspired considerable effort in searching for novel 2DSCs. Here, the first electrical characterization of group IV–V compounds is presented by investigating few‐layer GeAs field‐effect transistors. With back‐gate device geometry, p‐type behaviors are observed at room temperature. Importantly, the hole carrier mobility is found to approach 100 cm² V^?1 s^?1 with ON–OFF ratio over 10⁵, comparable well with state‐of‐the‐art TMD devices. With the unique crystal structure the few‐layer GeAs show highly anisotropic optical and electronic properties (anisotropic mobility ratio of 4.8). Furthermore, GeAs based transistor shows prominent and rapid photoresponse to 1.6 µm radiation with a photoresponsivity of 6 A W^?1 and a rise and fall time of ≈3 ms. This study of group IV–V 2DSC materials greatly expands the 2D family, and can enable new opportunities in functional electronics and optoelectronics based on 2DSCs.     

交联剂对PVP/PCL共聚凝胶性能的影响

研究了N,N-亚甲基双丙烯酰胺(NMBA)、戊二醛(GDA)两种交联剂对聚乙烯吡咯烷酮(PVP)/聚己内酯(PCL)共聚水凝胶性能的影响。交联剂含量低于NVP的0.7%时,GDA交联凝胶平衡溶胀率ESR较高,高于0.7%时,NMBA交联凝胶的ESR较高。DSC分析表明,GDA交联凝胶结合水含量较高。NMBA、GDA交联凝胶的Fick动力学参数n分别为0.462、0.267,说明GDA交联凝胶的溶胀过程偏离Fick模型。降解实验表明,GDA交联凝胶中PCL降解较慢。力学性能测试表明,GDA交联凝胶表现出较高的断裂强度和断裂伸长率。     

Preparation of decellularized and crosslinked artery patch for vascular tissue-engineering application

There is an urgent clinical need of tissue-engineering (TE) vascular grafts, so this study was for developing a fast and simple way of producing TE vascular scaffold. The TE vascular scaffold was prepared with pepsin, DNase and RNase enzymatic decellularization and crosslinked with 0.1, 1, 5% glutaraldehyde (GA), respectively. The samples were underwent analyses of burst pressure; suture strength; cytotoxicity; enzymatic degradation in vitro; degradation in vivo; rehydration; biocompatibilities detected with hematoxylin and eosin (H&E), scan electron microscope, immunohistochemistry both in vivo and in vitro; macrophage infiltration and calcification using Von Kossa staining. After being decellularized the scaffold had a complete removal of cellular components, an intact collagen structure. The burst pressure and suture strength were similar to native artery. 0.1% GA crosslinked scaffold showed less cytotoxicity than 1 and 5% GA groups (P?相似文献   

Selective Absorption of Hydrophobic Cations in Nanostructured Porous Materials from Crosslinked Hydrogen‐Bonded Columnar Liquid Crystals

A nanostructured porous material is obtained by crosslinking of a self‐assembled system consisting of columnar liquid crystals with polyamines and removal of the template. For this purpose, a columnar liquid crystal with liquid crystalline properties at room temperature is synthesized and fully characterized. The orthogonal self‐assembly of the columnar liquid crystal with polyamines (i.e., PPI dendrimers) results in the formation of nanosegregated structures. When crosslinked by photopolymerization a nanostructured crosslinked material is obtained. Partial removal of the polyamine template leads to a nanostructured porous material, which is characterized and the absorbent properties are investigated. The polarity of the porous material is probed and the porous material is used for the selective absorption of cationic dye molecules.     

铕杂EVA透明光转换膜的制备及交联动力学

将乙烯-乙酸乙烯酯共聚物（EVA）和乙酸乙烯酯-丙烯酸铕共聚物（VAA-Eu）的共混物（EVA/VAA-Eu）制成掺杂铕交联型透明光转换膜材料。紫外-可见吸收光谱和荧光光谱分析,表明此材料能将紫外线转换成蓝紫光和红光,作为农膜,可促进绿色植物的光合作用,提高阳光的利用效率。以硫化仪研究EVA/VAA-Eu的交联行为和动...     

纳米纤维素晶体和柠檬酸改性聚乙烯醇薄膜的制备及性能

以球形纳米纤维素晶体(NCC)作增强相、柠檬酸作交联剂对聚乙烯醇(PVA)进行改性,制备了PVA/NCC纳米复合薄膜和柠檬酸交联PVA/NCC纳米复合薄膜。通过热重分析、差热分析、吸水实验和拉伸实验考察了NCC的添加和柠檬酸的交联对薄膜热性能、耐水性和力学性能的影响。结果表明,与纯PVA薄膜相比,改性PVA薄膜的起始分解温度升高、熔融/结晶峰向高温方向移动、吸水率降低;只用NCC或柠檬酸对PVA改性时,所得PVA/NCC纳米复合薄膜、柠檬酸交联PVA薄膜的力学性能均对环境湿度敏感;同时用NCC(m(NCC)/m(PVA)=6/100)和柠檬酸(m(柠檬酸)/m(PVA)=3/100或m(柠檬酸)/m(PVA)=4.5/100)对PVA改性时,所得柠檬酸交联PVA/NCC纳米复合薄膜的力学性能不随环境湿度变化。     

HMDC crosslinking of bovine pericardial tissue: a potential role of the solvent environment in the design of bioprosthetic materials

The need for alternative crosslinking techniques in the processing of bioprosthetic materials is widely recognized. While glutaraldehyde remains the most commonly used crosslinking agent in biomaterial applications there is increasing concern as to its biocompatibility-principally due to its association with enhanced calcification, cytotoxicity, and undesirable changes in the mechanical properties of bioprosthetic materials. Hexamethylene diisocyanate (HMDC), like glutaraldehyde, is a bifunctional molecule which covalently bonds with amino groups of lysine residues to form covalent crosslinks. Evidence within the literature indicates HMDC-treated materials are less cytotoxic than glutaraldehyde-treated materials; however, there is limited characterization of the material properties of HMDC-treated tissue. This study uses a multi-disciplined approach to characterize the mechanical, thermal, and biochemical properties of HMDC-treated bovine pericardial tissue. Further, to facilitate stabilization of the HMDC reagent, non-aqueous solvent environments were investigated. HMDC treatment produced changes in mechanical properties, denaturation temperature, and enzymatic resistance consistent with crosslinking similar to that seen in glutaraldehyde treated tissue. The significantly lower extensibility and stiffness observed under low stresses may be attributed to the effect of the 2-propanol solvent environment during crosslinking. While the overall acceptability of HMDC as a crosslinking agent for biomaterial applications remains unclear, it appears to be an interesting alternative to glutaraldehyde with many similar features.     

Crosslinking of the electrospun polyethylene glycol/cellulose acetate composite fibers as shape-stabilized phase change materials

In a previous study, polyethylene glycol/cellulose acetate (PEG/CA) composite ultrafine fibers have been prepared by electrospinning. In order to improve their water-resistant ability and thermal stability for potential thermal storage applications, in this study, the electrospun PEG/CA fibers were crosslinked by using toluene-2, 4-diisocyanate (TDI). The morphology and thermal properties of the crosslinked fibers were investigated via SEM, DSC and TG, respectively. The results showed that the fibrous morphology of the crosslinked fibers was well preserved even after 24 h immersing in deionized water. Meanwhile, the crosslinking also led to an improvement on the thermal stability, but brought a decrease of the enthalpy compared with the original electrospun fibers.     

Heterogeneously catalysed crosslinking of polycarbosilane with divinylbenzene

Crosslinking of polycarbosilane (PCS) with divinylbenzene (DVB) is readily accomplished using heterogeneous catalysis with platinum chloride in heptane to provide a silicon carbide precursor that produces a ceramic with significantly reduced oxygen content. The ceramic yield after crosslinking increased from 47% to between 72% and 78%; however, crosslinking may be influenced by dehydrogenative silylation of hydroxyl groups. Solid-state ¹³C NMR spectroscopy of the crosslinked PCS showed peaks assignable to the aromatic group at 144 and 126.7 ppm. Monitoring of the crosslinking reaction by ¹H NMR spectroscopy indicated 40% consumption of the vinyl bonds of DVB within 10 min and complete consumption within 16 h. Infrared spectroscopy showed no increase in the peak at 3,650 cm⁻¹ due to O–H stretching in Si–OH, demonstrating that hydrosilylation crosslinking is a highly effective non-oxidative crosslinking technique. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of the molecular weight of a polyethylene glycol on the photoluminescence spectra of porous TiO2 films for dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) are expected to be used for future clean energy. In general, when the titania porous electrode in DSCs is made, a polyethylene glycol (PEG) is added to obtain the porous structure. Although the conversion efficiency of the DSC became high when the high molecular weight of PEG was used, its reason was not clear. In the present study, the photoluminescence spectrum of titania films with the different molecular weight of PEG was measured at room temperature, and we discussed the relation between molecular weight and the conversion efficiency of the DSC.     

ZnO Nanostructures for Dye‐Sensitized Solar Cells

This Review focuses on recent developments in the use of ZnO nanostructures for dye‐sensitized solar cell (DSC) applications. It is shown that carefully designed and fabricated nanostructured ZnO films are advantageous for use as a DSC photoelectrode as they offer larger surface areas than bulk film material, direct electron pathways, or effective light‐scattering centers, and, when combined with TiO₂, produce a core–shell structure that reduces the combination rate. The limitations of ZnO‐based DSCs are also discussed and several possible methods are proposed so as to expand the knowledge of ZnO to TiO₂, motivating further improvement in the power‐conversion efficiency of DSCs.     

聚合物共混体系辐射交联研究进展

综述了近年来聚合物共混体系辐射交联研究的新进展,主要包括三个方面:1.聚合物共混体系辐射交联行为及表征;2.辐射交联聚合物共混体系的性能;3.辐射交联聚合物共混体系的应用领域。     

Glutaraldehyde as a crosslinking agent for collagen-based biomaterials

The formation of Schiff bases during crosslinking of dermal sheep collagen (DSC) with glutaraldehyde (GA), their stability and their reactivity towards GA was studied. All available free amine groups had reacted with GA to form a Schiff base within 5 min after the start of the reaction under the conditions studied (0.5% (w/w) GA). Before crosslinks are formed the hydrolysable Schiff bases initially present were stabilized by further reaction with GA molecules. An increase in shrinkage temperature (T _s) from 56°C for non-crosslinked DSC (N-DSC) to 78°C for GA crosslinked DSC (G-DSC) was achieved after crosslinking for 1 h. From the relationship between the free amine group content and the T _s during crosslinking it was concluded that higher GA concentrations and longer reaction times will result in the introduction of pendant-GA-related molecules rather than crosslinks. After 24 h crosslinking an average uptake of 3 GA molecules per reacted amine group was found. No increase in the tensile strength of the materials was observed after crosslinking, which may be a result of formation of crosslinks within the fibres rather than in between fibres. Aligning of the fibres by applying a pre-strain to the samples and subsequent crosslinking yielded materials with an increased tensile strength.     

Fabrication and characterization of biodegradable composites based on microfibrillated cellulose and polyvinyl alcohol

Microfibrillated cellulose (MFC) based thin membrane-like fully biodegradable composites were produced by blending MFC suspension with polyvinyl alcohol (PVA). Desired MFC content in the composites could be easily obtained by varying the PVA solution concentration. Chemical crosslinking of PVA was carried out using glyoxal to increase the mechanical and thermal properties of the composites as well as to make the PVA partially water-insoluble. Examination of composite surfaces and fracture topographies indicated that the MFC fibrils were well bonded to PVA and uniformly distributed. Infrared spectroscopy showed that acetal linkages could be formed in the MFC–PVA composites by a glyoxal crosslinking reaction. Sol–gel and swelling results indicated that crosslinking reaction made PVA partially insoluble and reduced its swelling ability. The MFC–PVA composites had excellent tensile properties which were further enhanced by crosslinking. Thermogravimetric analysis (TGA) showed higher thermal stability for MFC–PVA composites compared to PVA. The crosslinked MFC–PVA composites showed even higher thermal stability. Differential scanning calorimetry (DSC) indicated that crosslinking increased the glass transition temperature and reduced melting temperature and crystallinity of PVA in MFC–PVA composites. Results also indicated that nano- and micro-fibrils in MFC inhibit the crystallization of PVA. These composites could be good candidates for replacing today’s traditional non-biodegradable plastics.     

Evaluation of Injectable Composite Material Comprising Biphasic Bone Substitutes and Crosslinked Collagen

Bone tissue engineering has emerged as a promising approach to regenerate bone tissue, and injectable biomaterials have shown potential for bone regeneration applications due to their ease of administration and ability to fill irregularly shaped defects. This study aims to develop and characterize an injectable composite material comprising biphasic bone substitutes (BBS) and crosslinked porcine collagen type I for bone regeneration applications. The collagen is crosslinked via a UVA-riboflavin crosslinking strategy and evaluated by testing the physicochemical properties, including the rheological behavior, dynamic storage modulus (G′) and loss modulus (G″), and in vitro degradation process. The results show that the crosslinked collagen (xCol) exhibits suitable physicochemical properties for injectability and improved viscoelasticity and degradation resistance. Furthermore, xCol is then combined with BBS in a predetermined ratio, obtaining the injectable composite material. The biocompatibility of the materials is evaluated in vitro by XTT and BrdU assays on fibroblasts and preosteoblasts. The results demonstrate that the composite material is biocompatible and supporting pre-osteoblasts proliferation. In conclusion, the injectable composite material BBS-xCol has promising physiochemical and biological properties for bone regeneration applications. Further studies are warranted to evaluate its efficacy in vivo and optimize its composition for clinical translation.     

环氧化合物和碳化二亚胺交联pADM的性能比较

采用丙三醇缩水甘油醚(GPE)和碳化二亚胺(EDC)对脱细胞真皮基质(pADM)分别进行交联改性,通过对交联后材料EC(GPE)-pADM、EDC-pADM的交联效率、XPS分析、KM鼠经口急毒、浸提液细胞毒性的表征和比较,探寻改性方法与材料性能之间的基本关系.研究结果表明,EDC比EC具有更高的交联效率;EC-pADM的亲水性能比EDC-pADM更好;EDC-pADM漫提液对KM鼠表现出一定经口毒性,而EC-pADM的毒性相对较低;两者浸出液细胞毒性检测均合格.综合而言,EC-pADM的性能优于EDC-pADM.     

辐射与硫磺交联丁二烯－苯乙烯共聚物的性能比较

考察了各种多官能团单体对丁二烯－苯乙烯共聚物（ＳＢＲ）辐射交联的强化效应，发现Ａ－ＴＭＭＴ四羟甲基甲烷四丙烯酸酯）在降低ＳＢＲ辐射交联必要剂量方面效果显著。对辐射交联ＳＢＲ的应力－应变、动态力学及其它性能进行了分析，并与典型硫磺交联产物进行了比较。通过使用Ａ－ＴＭＭＴ作为ＳＢＲ辐射交联的强化剂，成功地获得了与硫磺交联产物性能相当的辐射交联ＳＤＲ。     

Durability of crosslinked polydimethylsyloxanes: the case of composite insulators

Abstract

Most applications of silicones are linked to their hydrophobic properties and (or) their high resistance to ageing (e.g. thermal ageing and photoageing). However, when placed in extreme environments, these materials can fail as in the case of epoxy/fiber glass composite powerlines insulators, where crosslinked polymethylsyloxanes (PDMSs) are used as the protective envelope (housing) of the insulator. We report on the behavior of both pure/noncrosslinked PDMSs and typical formulations used in industrial insulators, i.e. containing peroxide crosslinked PDMS, alumina trioxide hydrated (ATH) and silica. Special attention is paid on both (i) the sources of potential degradation and (ii) the best analytical methods that can be applied to the study of very complex formulations. (i) Aside from conventional types of ageing such as photo-ageing and thermal, hydrolytic, and service life ageings, treatments with acidic vapors, plasma and ozone possibly generating species from the reaction of a high electric field with air were also performed, which allowed to accelerate electrical and out-door ageings and to obtain differently aged materials. (ii) Aside from conventional analytical methods of polymer degradation such as FTIR/ATR spectroscopy and SEC, TG, hardness measurements, more specific methods like photo/DSC, TG/IR, thermoporosimetry, resistivity and density measurements were also performed to characterize the chemical and physical evolutions of polymer materials. In particular, it was found that treatment with nitric acid vapor has detrimental effects on the properties of both fire retardants (e.g. ATH) and PDMSs, affecting the hardness and resistivity of the formulated material.     

新型壳聚糖/PBLG-co-PGA复合膜的研究

采用壳聚糖和聚谷氨酸苄酯-co-聚谷氨酸(PBLG-co-PGA)通过1-乙基-3-(3-二甲基氨基丙基)碳化二亚胺(EDC)与N-羟基琥珀酰亚胺(NHS)交联得到复合膜.采用FTIR和XRD对复合膜的结构进行了表征,同时对复合膜的吸水率进行了研究.研究结果表明,复合膜中壳聚糖和PBLG-co-PGA分子之间成功地发生了交联反应,二者之间的交联与氢键作用改变了二者原有的结晶结构,这对复合膜的性能有着重要的影响.以复合膜为载体培养软骨细胞发现,复合膜与壳聚糖膜相比,具有更高的细胞粘附率,预示着该复合膜是一种具有良好应用前景的生物医用材料.