A comparison of modifications induced by Li<Superscript>3+</Superscript> and Ag<Superscript>8+</Superscript> ion beams irradiation in poly(lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) films

Poly(lactide-co-glycolide) (PLGA) films were irradiated by 180 MeV/amu Ag⁸⁺ ions and 50 MeV/amu Li³⁺ ions at different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 1 × 10¹² ions/cm². Modifications of polymer films induced by the swift heavy ions (SHI) irradiation were studied by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The dominant effect of the SHI beam irradiation is proposed to be chain scission which leads to breakage of polymer chains, followed by hydrogen abstraction. The results from FTIR spectroscopy showed that the intensity of all peaks of the irradiated samples decreased at high fluence of SHI, suggesting PLGA samples significantly degraded at high SHI fluence. The variation in optical band gap energy and Urbach energy with increasing fluence was calculated from UV–Vis spectroscopy and explained in terms of changes occurring in the polymer matrix. X-ray diffraction patterns also show appreciable changes in PLGA at high fluence. FESEM results revealed that the hydrophilicity of the PLGA surface increased with an increase in ion fluence. In this paper the optical, chemical and structural changes with different fluence rates are discussed.     

Dielectric properties and surface morphology of swift heavy ion beam irradiated polycarbonate films

Swift heavy ion beam irradiation induces modification in the dielectric properties and surface morphologies of polycarbonate (PC) films. The PC films were irradiated by 55 MeV energy of C⁵⁺ beam at various ions fluences ranging from 1 × 10¹¹ to 1 × 10¹³ ions cm^?2. The dielectric properties (i.e., dielectric constant, dielectric loss, and AC conductivity) and surface morphologies of pristine and SHI beam irradiated PC films were investigated by dielectric measurements, atomic force microscopy (AFM), and optical microscopy. The dielectric measurements show that the dielectric constant, dielectric loss, and AC conductivity increase with ion fluences and temperature, however, the dielectric constant and AC conductivity decrease while dielectric loss increases with frequency. AFM shows the increase in average roughness values with ion fluences. The change of color in PC films has been observed from colorless to yellowish and then dark brown with increases of ion fluence by using optical microscopy.     

Swift heavy ion induced modification in dielectric and microhardness properties of polymer composites

Polymer composites with different concentrations of organometallics (ferric oxalate) dispersed PMMA were prepared. PMMA was synthesized by solution polymerization technique. These films were irradiated with 120 MeV Ni¹⁰⁺ ions in the fluence range 10¹¹-5 × 10¹² ions/cm². The radiation induced modifications in dielectric properties, microhardness, structural changes and surface morphology of polymer composite films have been investigated at different concentrations of filler and ion-fluences. It was observed that electrical conductivity and hardness of the films increase with the concentration of the filler and also with the fluence. The dielectric constant (?) obeys the Universal law given by ?αfⁿ⁻¹. The dielectric constant/loss is observed to change significantly due to irradiation. This suggests that ion beam irradiation promotes the metal to polymer bonding and convert polymeric structure into hydrogen depleted carbon network. This makes the composites more conductive and harder. Surface morphology of the films has been studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average surface roughness is observed to increase after irradiation as revealed by AFM studies. The SEM images show the blisters type of phenomenon on the surface due to ion beam irradiation.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrochemically exfoliated Ni-doped MoS2 nanosheets for highly efficient hydrogen evolution and Zn-H2O battery

Thanks to tunable physical and chemical properties, two-dimensional (2D) materials have received intensive interest, endowing their excellent electrocatalytic performances for applications in energy conversion. However, their catalytic activities are largely determined by poor adsorption energy and limited active edge sites. Herein, a one-step electrochemical exfoliation strategy was developed to fabricate 2D Ni-doped MoS₂ nanosheets (Ni-EX-MoS₂) with a lateral size of ～500 nm and thickness of ～3.5 nm. Profiting from high electrical conductivity and abundant exposing active sites, Ni-EX-MoS₂ catalyst displayed an admirable performance for electrochemical hydrogen evolution reaction (HER) with a low overpotential of 145 mV at 10 mA/cm² as well as a small Tafel slope of 89 mV/dec in alkaline media, which are superior to those of the most reported MoS₂-based electrocatalysts. The formed Ni species with tuning electronic structure played a crucial role as primary active center of Ni-EX-MoS₂, as well as the forming stable 1T/2H phase MoS₂ interface demonstrated a synergistic effect on electrocatalytic HER performance. Further, Ni-EX-MoS₂ was employed as a cathode electrode for alkaline Zn-H₂O battery, which displayed a high power density of 3.3 mW/cm² with excellent stability. This work will provide a simple and effective guideline for design of electrochemically exfoliated transition metal-doped MoS₂ nanosheets to inspire their practical applications in energy catalytic and storage.     

Ag3PO4/MoS2纳米片复合催化剂制备及可见光催化性能

采用机械球磨法成功制备Ag₃PO₄/MoS₂纳米片复合催化剂。运用X射线衍射仪（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、紫外可见漫反射光谱（UV-Vis）和荧光发射光谱（PL）对复合催化剂的结构和形貌进行了表征。结果表明,Ag₃PO₄纳米粒子均匀地附着在MoS₂纳米片层结构上,两者形成紧密结合。以亚甲基蓝为模拟污染物,研究复合催化剂在可见光照射下的光催化特性;通过循环实验考察复合催化剂的稳定性。结果显示,含有1%的MoS₂纳米片与Ag₃PO₄形成的复合催化剂在30 min内对亚甲基蓝的降解率为95%,其降解动力学常数是纯相Ag₃PO₄的2倍。经过5次循环实验后复合催化剂对于亚甲基蓝的降解率为84%,而纯Ag₃PO₄对于亚甲基蓝的降解率仅为35%。Ag₃PO₄/MoS₂纳米片复合催化剂具有优良的光催化活性和高稳定性,主要归因于二硫化钼纳米片与磷酸银形成异质结,磷酸银激发的电子和二硫化钼纳米片产生的空穴直接复合,从而促使光生电子从磷酸银晶体表面快速分离,减轻了磷酸银的光电子腐蚀,同时也提高了复合物的光催化活性。     

Carbon ion beam induced modifications of optical,structural and chemical properties in PADC and PET polymers

We report a study on the carbon ion beam induced modifications on optical, structural and chemical properties of polyallyl diglycol carbonate (PADC) commercially named as CR-39 and Polyethyleneterepthalate (PET) polymer films. These films were then irradiated by 55 MeV C⁵⁺ ion beam at various fluences ranging from 1×10¹¹ to 1×10¹³ ions/cm². The pristine as well as irradiated samples were subjected to UV–Visible spectral study (UV–Vis), Photoluminescence (PL), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It has been found that ion irradiation may induce a sort of defects in the polymers due to chain scission and cross linking as observed from PL spectral study. It is revealed from UV–Vis spectra absorption edge shifted towards longer wavelength region after irradiation with increasing ion fluence. This shift clearly reflects decrease in optical band gap. The XRD study indicates the gradual decrease in intensity in case of PADC with increasing ion fluence. However, the intensity pattern increased in case of PET at fluence of 10¹¹ ion/cm² then decreased with further increase in fluence. Crystalline size of PADC was found to be decreasing gradually with increase of ion fluence. Whereas, the crystalline size of PET films found to increase with lower fluence and decreases with higher ion fluence. FTIR spectrum also shows the change in intensity of the typical bands after irradiation in the both the polymers. The results so obtained can be used successfully in heavy ions dosimetry using well reported techniques.     

Ag_3PO_4/MoS_2纳米片复合催化剂制备及可见光催化性能

采用机械球磨法成功制备Ag_3PO_4/MoS_2纳米片复合催化剂。运用X射线衍射仪(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis)和荧光发射光谱(PL)对复合催化剂的结构和形貌进行了表征。结果表明,Ag_3PO_4纳米粒子均匀地附着在MoS_2纳米片层结构上,两者形成紧密结合。以亚甲基蓝为模拟污染物,研究复合催化剂在可见光照射下的光催化特性;通过循环实验考察复合催化剂的稳定性。结果显示,含有1%的MoS_2纳米片与Ag_3PO_4形成的复合催化剂在30 min内对亚甲基蓝的降解率为95%,其降解动力学常数是纯相Ag_3PO_4的2倍。经过5次循环实验后复合催化剂对于亚甲基蓝的降解率为84%,而纯Ag_3PO_4对于亚甲基蓝的降解率仅为35%。Ag_3PO_4/MoS_2纳米片复合催化剂具有优良的光催化活性和高稳定性,主要归因于二硫化钼纳米片与磷酸银形成异质结,磷酸银激发的电子和二硫化钼纳米片产生的空穴直接复合,从而促使光生电子从磷酸银晶体表面快速分离,减轻了磷酸银的光电子腐蚀,同时也提高了复合物的光催化活性。     

100 keV H+ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

We report the influence of 100 keV H⁺ ion beam irradiation on the surface morphology, crystalline structure, and transport properties of as‐deposited Al‐doped ZnO (Al:ZnO) thin films. The films were deposited on silicon (Si) substrate by using DC sputtering technique. The ion irradiation was carried out at various fluences ranging from 1.0 × 10¹² to 3.0 × 10¹⁴ ions/cm². The virgin and ion‐irradiated films were characterized by X‐ray diffraction, Raman spectroscopy, atomic force microscopy, and Hall probe measurements. Using X‐ray diffraction spectra, 5 points Williamson‐Hall plots were drawn to deduce the crystallite site and strain in Al:ZnO films. The analysis of the measurements shows that the films are almost radiation resistant in the structural deformation under chosen irradiation conditions. With beam irradiation, the transport properties of the films are also preserved (do not vary orders of magnitude). However, the surface roughness and the crystallite size, which are crucial parameters of the ZnO film as a gas sensor, are at variation with the ion fluence. As ion fluence increases, the root‐mean‐square surface roughness oscillates and the surface undergoes for smoothening with irradiation at chosen highest fluence. The crystallite size decreases initially, increases for intermediate fluences, and drops almost to the value of the pristine film at highest fluence. In the paper, these interesting experimental results are discussed in correlations with ion‐matter interactions especially energy losses by the ion beam in the material.     

Improving the gas barrier,mechanical and thermal properties of poly(vinyl alcohol) with molybdenum disulfide nanosheets

New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS₂) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS₂ nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m³, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS₂ nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414     

Gold Nanoclusters Grown on MoS2 Nanosheets by Pulsed Laser Deposition: An Enhanced Hydrogen Evolution Reaction

Au nanoparticles were decorated on a 2H MoS₂ surface to form an Au/MoS₂ composite by pulse laser deposition. Improved HER activity of Au/MoS₂ is evidenced by a positively shifted overpotential (−77 mV) at a current density of −10 mA cm⁻² compared with pure MoS₂ nanosheets. Experimental evidence shows that the interface between Au and MoS₂ provides more sites to combine protons to form an active H atom. The density functional theory calculations found that new Au active sites on the Au and MoS₂ interface with improved conductivity of the whole system are essential for enhancing HER activity of Au/MoS₂.     

Ion‐beam‐induced morphology on the surface of thin polymer films at low current density and high ion fluence

The effect of Xe⁺ bombardment on the surface morphology of four different polymers, polystyrene (PS), poly(phenylene oxide), polyisobutylene, and polydimethylsiloxane, was investigated in ion energy and fluence ranges of interest for secondary ion mass spectrometry depth‐profiling analysis. Atomic force microscopy (AFM) was applied to analyze the surface topography of pristine and irradiated polymers. AFM analyses of nonirradiated polymer films showed a feature‐free surface with different smoothness. We studied the influence of different Xe⁺ beam parameters, including the incidence angle, ion energy (660–4000 eV), current density (0.5 × 10² to 8.7 × 10² nA/cm²), and ion fluence (4 × 10¹⁴ to 2 × 10¹⁷ ion/cm²). Xe⁺ bombardment of PS with 3–4 keV at a high current density did not induce any change in the surface morphology. Similarly, for ion irradiation with lower energy, no surface morphology change was found with a current density higher than 2.6 × 10² nA/cm² and an ion fluence up to 4 × 10¹⁶ ion/cm². However, Xe⁺ irradiation with a lower current density and a higher ion fluence led to topography development for all of the polymers. The roughness of the polymer surface increased, and well‐defined patterns appeared. The surface roughness increased with ion irradiation fluence and with the decrease of the current density. A pattern orientation along the beam direction was visible for inclined incidence between 15° and 45° with respect to the surface normal. Orientation was not seen at normal incidence. The surface topography development could be explained on the basis of the balance between surface damage and sputtering induced by the primary ion beam and redeposition–adsorption from the gas phase. Time‐of‐flight secondary ion mass spectrometry analyses of irradiated PS showed strong surface modifications of the molecular structure and the presence of new material. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 314–325, 2001     

Ultrathin MoS2 Nanosheets Supported on N‐doped Carbon Nanoboxes with Enhanced Lithium Storage and Electrocatalytic Properties

Molybdenum disulfide (MoS₂) has received considerable interest for electrochemical energy storage and conversion. In this work, we have designed and synthesized a unique hybrid hollow structure by growing ultrathin MoS₂ nanosheets on N‐doped carbon shells (denoted as C@MoS₂ nanoboxes). The N‐doped carbon shells can greatly improve the conductivity of the hybrid structure and effectively prevent the aggregation of MoS₂ nanosheets. The ultrathin MoS₂ nanosheets could provide more active sites for electrochemical reactions. When evaluated as an anode material for lithium‐ion batteries, these C@MoS₂ nanoboxes show high specific capacity of around 1000 mAh g^?1, excellent cycling stability up to 200 cycles, and superior rate performance. Moreover, they also show enhanced electrocatalytic activity for the electrochemical hydrogen evolution.     

Ion implantation doping and electrical properties of high-temperature ladder polymers

We report the first ion implantation doping studies on high-temperature ladder polymers and show that insulting films of the benzimidazobenzophenanthroline-type ladder polymer (BBL) can be doped by boron, argon, and krypton implantation to conductivities as high as 224 S/cm at a dose of 4.0 × 10¹⁶/cm² while retaining the excellent mechanical properties of the pristine films. Effects of dose (ions/cm²) and beam current density (microamps/cm²) on electrical conductivity at fixed ion energies are reported. The temperature dependence of the conductivity indicates that the implanted ladder polymer films are semiconductors. Spatially selective implantation, creating regions of conducting lines in an insulating matrix, which suggests microelectronic device applications of the ladder polymers, is demonstrated.     

Excimer Laser Crystallization of SnO2:Sb Sol-Gel Films

Instead of classical or rapid thermal annealing, KrF excimer laser irradiation has been successfully applied to crystallize dried SnO₂:Sb films elaborated by a sol-gel process. The penetration of the crystallization front below the film surface, as imaged by transmission electron microscopy, is controlled by the laser fluence and the number of pulses and can thus be confined in the film itself without affecting sensitive substrates. All films laser irradiated at fluences higher than 40 mJ/cm² become conductive. At constant laser fluence, the electrical sheet resistance goes through a minimum with increasing number of pulses. The consequence of film's densification and morphology on electrical properties is discussed.     

Dielectric and conductivity studies of 90 MeV O7+ ion irradiated poly(ethylene oxide)/montmorillonite based ion conductor

In the present work effect of 90 MeV O⁷⁺ ions with five different fluences on poly(ethylene oxide) (PEO)/Na⁺-montmorillonite (MMT) nanocomposites has been investigated. PEO/MMT nanocomposites were synthesized by solution intercalation technique. With the increase in irradiation fluence, gallery spacing of MMT increases in the composite and an exfoliated nanostructure is obtained at the fluence of 5?×?10¹² ions/cm² as revealed by X-ray diffraction results. Highest room temperature ionic conductivity of 4.2?×?10^?6?S?cm^?1 was found for the fluence 5?×?10¹² ions/cm², while the conductivity for unirradiated polymer electrolyte was found to be 7.5?×?10^-8?S?cm^?1. The increase in intercalation of PEO chains inside the galleries of MMT results in the increase in interaction between Na⁺ cation and oxygen heteroatom leading to the increase in ionic conductivity of the composites. Surface morphology and interactions among the various constituents in the nanocomposites at different fluence have been examined by scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The appearance of peak for each fluence in the loss tangent suggests the presence of relaxing dipoles in the polymer nanocomposite electrolyte films. With the increase in ion fluence the peak shifts towards higher frequency side, suggesting decrease in the relaxation time.     

二硫化钼纳米片/碳纳米纤维杂化材料的制备及其析氢性能

以碳纳米纤维（CNFs）作为负载基体和反应器采用静电纺丝技术和碳化工艺生长和调控二硫化钼（MoS₂）纳米片。通过改变前驱体溶液浓度来调控纳米片的形貌和结构,利用MoS₂纳米片的高催化活性和CNFs高比表面积、良好的稳定性以及高电导率的协同作用,研究不同形貌和结构的杂化纳米材料在电催化析氢方面的应用,探索杂化材料形貌与性能之间的潜在规律。运用多种分析测试技术对制备得到的纳米杂化材料进行表征,并对所制备的MoS₂/CNFs杂化材料的电催化析氢性能（HER）进行研究,研究表明近似皮芯结构的MoS₂/CNFs-10杂化材料的电催化析氢性能最好,初始析氢过电位在220 mV,Tafel斜率为110 mV·dec^-1。     

二硫化钼纳米片/碳纳米纤维杂化材料的制备及其析氢性能

以碳纳米纤维(CNFs)作为负载基体和反应器采用静电纺丝技术和碳化工艺生长和调控二硫化钼(MoS_2)纳米片。通过改变前驱体溶液浓度来调控纳米片的形貌和结构,利用MoS_2纳米片的高催化活性和CNFs高比表面积、良好的稳定性以及高电导率的协同作用,研究不同形貌和结构的杂化纳米材料在电催化析氢方面的应用,探索杂化材料形貌与性能之间的潜在规律。运用多种分析测试技术对制备得到的纳米杂化材料进行表征,并对所制备的MoS_2/CNFs杂化材料的电催化析氢性能(HER)进行研究,研究表明近似皮芯结构的MoS_2/CNFs-10杂化材料的电催化析氢性能最好,初始析氢过电位在220 mV,Tafel斜率为110m V·dec~(-1)。     

Radiation Stability of Copper Films under Irradiation with He<Superscript>2+</Superscript> Ions

The effect of irradiation of copper films with low-energy He²⁺ ions on their structural properties has been studied. The surface morphology and structural properties of the samples before and after irradiation have been examined by scanning electron microscopy, energy dispersive analysis, and X-ray diffraction. Bombardment of the initial samples with He²⁺ ions at a fluence of 1 × 10¹⁶ion/cm² alters the surface morphology of copper films and leads to the formation of nanoscale inclusions of hexagonal shape. An increase in the fluence to 1 × 10¹⁷ ion/cm² and higher results in the formation of cracks and amorphous oxide inclusions on the sample surface.     

Free‐standing and Flexible MoS2/rGO Paper Electrode for Amperometric Detection of Folic Acid

The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact devices. We report a new type of flexible electrochemical sensor fabricated by integrating graphene and MoS₂ nanosheets. A highly flexible and free‐standing conductive MoS₂ nanosheets/reduced graphene oxide (MoS₂/rGO) paper was prepared by a two‐step process: vacuum filtration and chemical reduction treatment. The MoS₂/graphene oxide (MoS₂/GO) paper obtained by a simple filtration method was transformed into MoS₂/rGO paper after a chemical reduction process. The obtained MoS₂/rGO paper was characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy. The electrochemical behavior of folic acid (FA) on MoS₂/rGO paper electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that flexible MoS₂/rGO composite paper electrode exhibited excellent electrocatalytic activity toward the FA, which can be attributed to excellent electrical conductivity and high specific surface area of the MoS₂/rGO paper. The resulting biosensor showed highly sensitive amperometric response to FA with a wide linear range.