Ultra-thin light-weight laser-induced-graphene (LIG) diffractive optics

The realization of hybrid optics could be one of the best ways to fulfill the technological requirements of compact, light-weight, and multi-functional optical systems for modern industries. Planar diffractive lens (PDL) such as diffractive lenses, photonsieves, and metasurfaces can be patterned on ultra-thin flexible and stretchable substrates and be conformally attached on top of arbitrarily shaped surfaces. In this review, we introduce recent research works addressed to the design and manufacturing of ultra-thin graphene optics, which will open new markets in compact and light-weight optics for next-generation endoscopic brain imaging, space internet, real-time surface profilometry, and multi-functional mobile phones. To provide higher design flexibility, lower process complexity, and chemical-free process with reasonable investment cost, direct laser writing (DLW) of laser-induced-graphene (LIG) is actively being applied to the patterning of PDL. For realizing the best optical performances in DLW, photon-material interactions have been studied in detail with respect to different laser parameters; the resulting optical characteristics have been evaluated in terms of amplitude and phase. A series of exemplary laser-written 1D and 2D PDL structures have been actively demonstrated with different base materials, and then, the cases are being expanded to plasmonic and holographic structures. The combination of these ultra-thin and light-weight PDL with conventional bulk refractive or reflective optical elements could bring together the advantages of each optical element. By integrating these suggestions, we suggest a way to realize the hybrid PDL to be used in the future micro-electronics surface inspection, biomedical, outer space, and extended reality (XR) industries.

Multifunctional oil-produced reduced graphene oxide - Silver oxide composites with photocatalytic, antioxidant, and antibacterial activities

Graphene-based nanomaterials that combine significant photocatalytic, antioxidant and antibacterial activity are very attractive candidates for biomedical and environmental applications. Conventional chemical synthesis routes may contaminate the resultant materials with toxic molecules, compromising their properties and limiting their use in biomedical applications. Ideally, to avoid any contamination, the nanomaterials should be synthesized from non-toxic precursors and reagents, e.g. foodstuff via a simple technology that does not rely on the use of hazardous chemicals yet produces materials of high quality. Here, we report an environmentally friendly, low cost reduced graphene oxide-silver-silver oxide nanocomposite with strong photocatalytic, antioxidant and antibacterial activity for environmental remediation. The reduced graphene oxide (FRGO) is synthesized from edible sunflower oil via a simple flame synthesis method. Next, silver nanoparticles (Ag/AgO/Ag₂O) are produced by phytochemical reduction of AgNO₃ using a reducing agent based on flavonoids from Coleus aromaticus (Mexican mint), also used in food industry. Thus-obtained FRGO-Ag/AgO/Ag₂O composite is characterized using X-ray diffraction spectroscopy, scanning electron microscopy, fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The degradation of anionic textile dye Methylene blue (MB) is used as a measure of photocatalytic activity of FRGO and FRGO/Ag/AgO/Ag₂O, with solution pH, initial dye concentration, and quantity of the catalyst considered as influencing factors. FRGO-Ag/AgO/Ag₂O composites show strong antioxidant activity, with improved radical inhibition as well as dye degradation properties when compared to pristine FRGO.

Silver doped reduced graphene oxide as a promising plasmonic photocatalyst for oxidative coupling of benzylamines under visible light irradiation

Visible light assisted photocatalytic reduction of nitro-compounds has been found as an efficient and sustainable approach for the production of amines.

Graphene Oxide-Mediated Protection from Photodamage

This Letter presents the unique properties of graphene oxide (GO) as a multitask material protecting from UVB-induced photodamage. Three mechanisms of GO action on fibroblast in vitro cultures are verified here: physical - a barrier blocking UV radiation; chemical - antioxidative activity; and biological - activation of cellular antioxidative defense. The changes in GO physicochemical properties appearing due to UVB exposure underpin the observed UV protection phenomena. The results reveal the simultaneous occurrence of two opposed processes, i.e., under small doses of UVB, the tested material undergoes oxidation and sp² network rebuilding. In the vicinity of the GO surface, the locally triggered high temperature is responsible for a reduction process, while strong oxidative agents such as OH radicals cause parallel GO oxidation. This phenomenon is enabled thanks to the exceptional properties of carbonaceous materials. As a consequence, GO turns out to be a multitask UV protector increasing fibroblast survival.

Statistical analysis of the reduction process of graphene oxide probed by Raman spectroscopy mapping

We propose a method for monitoring the large-scale homogeneity of the reduction process of graphene oxide. For this purpose, a Raman mapping technique is employed to probe the evolution of the phonon properties of two different graphene oxide (GO) thin films upon controllable thermal reduction. The reduction of GO is reflected by the upshift of the statistical distribution of the relative intensity ratio of the G and D peaks (I _D/I _G) of the Raman spectra and is consistent with the ratio obtained for chemically reduced GO. In addition, the shifts of the position distributions of the main Raman modes ([Formula: see text], [Formula: see text]) and their cross-correlation with the I _D/I _G ratio provides evidence of a change of the doping level, demonstrating the influence of reduction processes on GO films.

Application of Hole-Transporting Materials as the Interlayer in Graphene Oxide/Single-Wall Carbon Nanotube Silicon Heterojunction Solar Cells

Solid-state hole-transporting materials, including the traditional poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and recently developed 4,4′-(naphthalene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (NAP) and (E)-4′,4‴-(ethene-1,2-diyl)bis(N,N-bis(4-methoxyphenyl)-[1″,1‴-biphenyl]-4-amine) (BPV), have been applied as a hole-transporting interlayer (HTL) for graphene oxide/single-walled carbon nanotube–silicon (GOCNT/Si) heterojunction solar cells, forming a GOCNT/HTL/Si architecture. The influence of the thickness of the HTL has been studied. A new AuCl3 doping process based on bath immersion has been developed and proved to improve the efficiency. With the AuCl3-doped GOCNT electrodes, the efficiency of GOCNT/PEDOT:PSS/Si, GOCNT/NAP/Si, and GOCNT/BPV/Si devices was improved to 12.05 ± 0.21, 10.57 ± 0.37, and 10.68 ± 0.27 % respectively. This study reveals that the addition of an HTL is able to dramatically minimise recombination at the heterojunction interface.

Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity

The antibacterial activity and possible toxicity of graphene oxide and laser-irradiated graphene oxide (iGO) were investigated. Antibacterial activity was tested on Escherichia coli and shown to be higher for GO irradiated for at least three hours, which seems to be correlated to the resulting morphology of laser-treated GO and independent of the kind and amount of oxygen functionalities. X-ray photoelectron spectroscopy, Raman spectroscopy, dynamic light scattering and scanning electron microscopy (SEM) show a reduction of the GO flakes size after visible laser irradiation, preserving considerable oxygen content and degree of hydrophilicity. SEM images of the bacteria after the exposure to the iGO flakes confirm membrane damage after interaction with the laser-modified morphology of GO. In addition, a fish embryo toxicity test on zebrafish displayed that neither mortality nor sublethal effects were caused by the different iGO solutions, even when the concentration was increased up to four times higher than the one effective in reducing the bacteria survival. The antibacterial properties and the absence of toxicity make the visible laser irradiation of GO a promising option for water purification applications.

Super flexible, highly conductive electrical compositor hybridized from polyvinyl alcohol and silver nano wires

Super flexible, highly conductive electrical compositors were hybridized from polyvinyl alcohol and silver nanowires using a simple one-step blending method.