Laser modification of graphene oxide layers

The effect of linearly polarized laser irradiation with various energy densities was successfully used for reduction of graphene oxide (GO). The ion beam analytical methods (RBS, ERDA) were used to follow the elemental composition which is expected as the consequence of GO reduction. The chemical composition analysis was accompanied by structural study showing changed functionalities in the irradiated GO foils using spectroscopy techniques including XPS, FTIR and Raman spectroscopy. The AFM was employed to identify the surface morphology and electric properties evolution were subsequently studied using standard two point method measurement. The used analytical methods report on reduction of irradiated graphene oxide on the surface and the decrease of surface resistivity as a growing function of the laser beam energy density

The multi-energetic Au ion implantation of graphene oxide and polymers

The electric properties of polymers are increasingly important in a wide range of applications such as sensors, energy storages, microelectronics, and filtration membranes among others. In this work, the effect of multi-energetic Au ion implantation on the graphene oxide (GO), polyimide (PI), polyethylene terephthalate (PET) and polylactide (PLLA) elemental, chemical, structural end electric properties is presented with potential application in 3D metal-dielectric structure synthetization. The three energies, 3.2, 1.6, 0.8 MeV of Au ions with fluence 3.75×1014 cm-2 were used in ascending or descending order to create two sample sets, which were subsequently analysed by RBS, ERDA, EDS and AFM. RBS analysis was used for Au-depth profile characterization in the implanted samples, the profiles agree reasonably with those simulated by SRIM code. Electrical properties were investigated by standard two-point technique with respect to the used parameters of the ion irradiation. The sheet resistance decreases after ion irradiation and it is evident that the ascending order of ion implantation energies has more significant effect on the conductivity enhancement compare to the descending one

Synthesis of Porous Polydimethylsiloxane Gold Nanoparticles Composites by a Single Step Laser Ablation Process

Typically, polymeric composites containing nanoparticles are realized by incorporating pre-made nanoparticles into a polymer matrix by using blending solvent or by the reduction of metal salt dispersed in the polymeric matrix. Generally, the production of pre-made Au NPs occurs in liquids with two-step processes: producing the gold nanoparticles first and then adding them to the liquid polymer. A reproducible method to synthetize Au nanoparticles (NPs) into polydimethylsiloxane (PDMS) without any external reducing or stabilizing agent is a challenge. In this paper, a single-step method is proposed to synthetize nanoparticles (NPs) and at the same time to realize reproducible porous and bulk composites using laser ablation in liquid. With this single-step process, the gold nanoparticles are therefore produced directly in the liquid polymer. The optical properties of the suspensions of AuNPs in distilled water and in the curing agent have been analyzed by the UV-VIS spectroscopy, employed in the transmission mode, and compared with those of the pure curing agent. The electrical dc conductivity of the porous PDMS/Au NPs nanocomposites has been evaluated by the I–V characteristics. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis have monitored the composition and morphology of the so-obtained composites and the size of the fabricated Au nanoparticles. Atomic force microscopy (AFM) has been used to determine the roughness of the bulk PDMS and its Au NP composites

Pulsed Laser Deposition and Laser-Induced Backward Transfer to Modify Polydimethylsiloxane

Polydimethylsiloxane (PDMS) is a silicone-elastomer that owes its large application in the field of stretchable electronics to its chemical and thermal stability, transparency, flexibility, non-toxicity, compatibility, and low cost. PDMS is a versatile material because it can be used both as an elastic substrate and, after functionalization, as an active material for the design of stretchable electronics. One possible route for the functionalization of PDMS, thus becoming an active material together with numerous metals and semiconductors, is the embedding of conductive nanomaterials. Presently, pulsed laser deposition (PLD) and laser-induced backward transfer (LIBT) are used to deposit carbon- based material on polydimethylsiloxane. In this study, we explore and compare the surface treatments, advantages, and disadvantages of both different employed techniques in different environments. The modification of the wettability, elasticity, morphology, composition, and optical characteristics of polydimethylsiloxane will be evaluated by surface techniques such as scanning electron microscopy, Rutherford backscattering spectrometry, and the sessile drop method

Nanoparticles embedded in a sponge of polydimethylsiloxane by laser ablation in liquid

This work describes the preparation of polydimethylsiloxane (PDMS) sponge with pore sizes of about 50 and 900 µm. The sponges synthetized by the sugar template process were embedded with graphene oxide (GO) and gold nanoparticles (AuNPs) previously produced by laser ablation in liquid. The suspension containing graphene oxide and gold nanoparticles were optically characterized by UV-ViS spectroscopy. The dispersion of the nanoparticles in the PDMS sponges was observed by the Scanning Electron Microscopy (SEM). The biocompatibility of virgin PDMS, PDMS filled with graphene oxide, and with graphene oxide and gold nanoparticles was studied for different types of cell cultures. This study has allowed us to confirm that the PDMS sponge is a good matrix for embedding AuNPs and has highlighted as the presence of GO hinders the aggregation of AuNPs avoiding the use of surfactant and allowing their use in biological applications

Strain‐driven Switching Between Antiferromagnetic States in Frustrated Antiferromagnet UO2 Probed by Exchange Bias Effect

International audienceFrustrated antiferromagnets offer a captivating platform to study the intricate relationship of magnetic interactions, geometric constraints, and emergent phenomena. By controlling spin orientations, these materials can be tailored for applications in spintronics and quantum information processing. The research focuses on the interplay of magnetic and exchange anisotropy effects in artificial heterostructures based on a canonical frustrated antiferromagnet, UO 2 . The potential to manipulate the spin directions in this material and switch between distinct antiferromagnetic (AFM) states is investigated using substrate‐induced strain. The phenomenon is probed using exchange bias effects in stoichiometric UO 2 /Fe 3 O 4 bilayers. By employing many‐body first‐principles calculations magnetic configurations in the UO 2 layers are identified. Even a minor tetragonal distortion triggers a transition between AFM states of different symmetries, driven by a robust alteration of single‐ion anisotropy due to the distortion. Consequently, this change influences the arrangement of magnetic moments at the UO 2 /Fe 3 O 4 interface, affecting the magnitude of exchange bias. The findings showcase how epitaxial strain can effectively manipulate the AFM states in frustrated antiferromagnets by controlling single‐site anisotropy

Ion Lithography of Single Ions Irradiation for Spatially Regular Arrays of Pores in Membranes of Polyethylene Terephthalate

Routinely, in membrane technology, the decay from radioactive particles or the bombardment of ions with MeV energy per nucleon have been employed for the production of narrow and long pores in membranes. Presently, the ion lithography is proposed to make the fabrication cost more affordable. It is prospective for the use of medium capacity accelerators making more feasible the fabrication of customized membranes. Thin polyethylene terephthalate foils have been patterned using 12 MeV O5+ ions and then processed to obtain good aspect ratio ion track pores in membranes. Pores of micrometric diameter with the following profiles were fabricated in the membranes: truncated cone, double conical, ideal cone, and cylindrical. Monitoring of the shape and size of pores has been attempted with a combination of Scanning Transmission Ion Microscope and a newly designed simulation program. This study is focused on the use of low-energy ions, accomplished in all laboratories, for the fabrication of membranes where the pores are not randomly traced and exhibit higher surface density and negligible overlapping than in membranes commonly manufactured. The good reproducibility and the ordered pore locations can be potentially utilized in applications such as microfluidics and organ-on-chip microsystems, where cells growing over porous substrates are used in simulation of biological barriers and transport processes

THE EFFECT OF ZINC CONTENT ON THE ENHANCEMENT Er3+-Yb3+ LUMINESCENCE PROPERTIES IN THE SILICATE GLASS MATRIX

Glasses doped with Er and Yb show strong luminescence around 1530 nm, which makes them attractive luminophores for the preparation of multifunctional optical components. This article is focused on the influence of ZnO on the optical and luminescence properties of Er-Yb zinc-silicate glasses. The influence of silver doping on the resulting luminescence properties of the prepared glasses has also been investigated. Three types of silicate glasses containing different amounts of ZnO and RE ions (Er and Yb) were prepared. For all the glasses prepared, their density, glass-transformation temperature and refractive index were determined. Moreover, these glasses were doped with silver using two methods - ion implantation and ion exchange. The presence of silver metal nanoparticles was observed using optical absorption in the UV-VIS range. Photoluminescence spectroscopy was used to observe the effect of the presence silver or zinc oxide on the intensity of luminescence. The results have shown that the enhancement of ZnO content positively influenced erbium luminescence at 1530 nm without affecting the transparency or homogeneity of the glass matrix. Moreover, the presence Ag+ ions in this special type of glass matrix positively contributed to the enhancement of erbium photoluminescence