Photochemical Modification Research Articles

Protective role of carotenoids in the visual cycle.

Exposure to light and accumulation of aberrant visual cycle by-products causes stress in the retina. The physical and chemical properties of carotenoids may provide protection against such scenario. These pigments exist in retinas of many vertebrates, including humans. However, the absence of carotenoids in mice, the preferred ophthalmologic animal model, hindered molecular and biochemical examination of the pigments' role in vision. We established a mouse model that accumulates significant amounts of carotenoids in the retina due to inactivating mutations in the Isx and Bco2 genes. We introduced a robust light damage protocol for the mouse retina using green (532 nm) and blue (405 nm) low-energy lasers. We observed that blue but not green laser light treatment triggered the formation of aberrant retinaldehyde isomers in the retina. The production of these visual cycle by-products was accompanied by morphologic damage in inferior parts of the mouse retina. Zeaxanthin supplementation of mice shielded retinoids from these photochemical modifications. These pigments also reduced the extent of the damage to the retina after the blue laser light insult. Thus, our study discovered a novel role of carotenoids in the visual cycle and indicated that vertebrates accumulate carotenoids to shield photoreceptors from short-wavelength light-induced damage.-Widjaja-Adhi, M. A. K., Ramkumar, S., von Lintig, J. Protective role of carotenoids in the visual cycle.

Fiber Bragg grating as UVA sensor

The idea of this paper implies the possibility to exploit the properties of graphene oxide (GO) to fiber Bragg grating (FBG) UVA radiation sensor design. The idea assumes that a temperature change around the fiber can be induced by UVA radiation. UVA lighting will increase the internal energy of the GO and consequently locally raise the temperature on the surface of the optical fiber with FBG sensor and changing Bragg wavelength Full Text: PDF ReferencesZ. N. Azwa, B. F. Yousif, A. C. Manalo, W. Karunasena, " A review on the degradability of polymeric composites based on natural fibres", Materials & Design, Vol. 47, pp. 424-442, 2013 CrossRef B. R?nby, "Photochemical modification of polymers - photocrosslinking, surface photografting, and lamination", Polymer Ing. & Science, Vol. 38, Iss. 8, pp 1229-1243, 1998 CrossRef P. Lesiak, M. Szeląg, D. Budaszewski, R. Plaga, K. Mileńko, G. Rajan, Y. Semenova, G. Farrell, A. Boczkowska, A. Domański, T. Woliński, "Influence of lamination process on optical fiber sensors embedded in composite material", Measurement: Journal of the International Measurement Confederation, vol. 45, No. 9, pp. 2275-2280, 2012 CrossRef G. Eda et al., "Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material", Nature Nanotechnology 3, 270 (2008) CrossRef H. J. Kim et al., "Unoxidized Graphene/Alumina Nanocomposite: Fracture- and Wear-Resistance Effects of Graphene on Alumina Matrix", Scientific Reports 4, 5176 (2014) CrossRef A. Wróblewska et al., "Statistical analysis of the reduction process of graphene oxide probed by Raman spectroscopy mapping", Journal of Physics: Condensed Matter 29, 475201 (2017) CrossRef P. Lesiak, P. Sobotka, M. Bieda, A. Dużyńska, A. Wróblewska, M. Chychłowski and T. R. Woliński, "Innovative UV sensor based on highly birefringent fiber covered by graphene oxide", Photonics Letters of Poland Vol. 7, No 4, pp. 124-126, 2015 CrossRef B. Qi, M. Bannister, X. Liu, A. Michie, L. Rajasekera, B. Ashton, Response of an embedded fibre Bragg grating to thermal and mechanical loading in a composite laminate, IOME Australasia, Materials Forum 27 (2004) 93?100. DirectLink E. Chehura, C-C. Ye, S. Staines, S. James, R. Tatam, Characterisation of the response of fibre Bragg gratings fabricated in stress and geometrically induced high birefringence fibres to temperature and transverse load, Smart Materials and Structures 13 (2004) 888?895. CrossRef K. Schroeder et al., A fiber Bragg grating sensor system monitors operational load in a wind turbine rotor blade, Measurement Science & Technology 17 (2006) 1167?1172. CrossRef Z. Zhou, Q. Liu, Q. Ai, C. Xu, Intelligent monitoring and diagnosis for modern mechanical equipment based on the integration of embedded technology and FBGS technology, Measurement 44 (9) (2011) 1499?1511 CrossRef Z. C. Wu et al., Science 305, 1273 (2004) CrossRef A. Jorio, M. Dresselhaus, R. Saito, and G. F. Dresselhaus, Raman Spectroscopy in Graphene Related Systems (Wiley-VCH, 2011) CrossRef G. Sobon, J. Sotor, J. Jagiello, R. Kozinski, M. Zdrojek, M. Holdynski, P. Paletko, J. Boguslawski, L. Lipinska, and K. M. Abramski "Graphene Oxide vs. Reduced Graphene Oxide as saturable absorbers for Er-doped passively mode-locked fiber laser" Optics Express 20, 19463 (2012) CrossRef

Improvement of fibre–matrix adhesion in cellulose/polyolefin composite materials by means of photo-chemical fibre surface modification

The mechanical performance of composites made from viscose fibre reinforcement fabrics and PP matrix polymers could be enhanced by photo-chemical surface modification of the viscose fibres. The surface modification was achieved by deposition of UV-polymerized organic thin layers using pentaerythritol triacrylate or diallylphthalate as monomers. The main effects of the photo-chemical modification refer to a decrease in wettability of the highly hydrophilic and water adsorbing viscose fibres and an increase in their affinity towards non-polar substances. Both effects were found to yield an increase in fibre–matrix adhesion and interfacial shear strength, resulting in better impact and tensile properties compared to untreated samples. The experimental composites were slightly inferior with regard to fibre–matrix adhesion and IFSS than established systems using modified matrix polymers such as the maleic anhydride modified PP, but exhibited similar or even improved properties in view of tensile strength and impact behaviour. The latter indicates superior energy transfer by the thin organic layers forming the fibre–matrix interface. Based on these observations, the studied concept of photo-polymerized inter-layers between fibre and matrix can be understood as a biomimetic concept mimicking the graded transitions of natural structures.

Surface photochemical modification of TiO2 nanotube/Ti plates for photocatalytic elimination of methylene orange dye

A facile strategy has been employed to fabricate efficient TiO2 nanotubes/Ti plate for photocatalyst application via photochemical modification with benzene. Microstructure studies show that benzene with formation of carbonaceous polymeric deposits has been uniformly grown on the walls of TiO2 nanotubes/Ti plates. The results of photocatalytic experiments demonstrate that the plates modified by benzene are more efficient than bare TiO2 nanotubes/Ti for the photocatalytic degradation of methylene orange (MO) dye. The new obtained plates can be recycled 4 times, while remaining at 89.25% MO degradation ratio. The enhanced photocatalytic performance was attributed to the increased separation rate of photogenerated charge carriers and adsorption efficiency of MO by modified electrode.

DNA's Encounter with Ultraviolet Light: An Instinct for Self-Preservation?

Photochemical modification is the major class of environmental damage suffered by DNA, the genetic material of all free-living organisms. Photolyases are enzymes that carry out direct photochemical repair (photoreactivation) of covalent pyrimidine dimers formed in DNA from exposure to ultraviolet light. The discovery of catalytic RNAs in the 1980s led to the "RNA world hypothesis", which posits that early in evolution RNA or a similar polymer served both genetic and catalytic functions. Intrigued by the RNA world hypothesis, we set out to test whether a catalytic RNA (or a surrogate, a catalytic DNA) with photolyase activity could be contemplated. In vitro selection from a random-sequence DNA pool yielded two DNA enzymes (DNAzymes): Sero1C, which requires serotonin as an obligate cofactor, and UV1C, which is cofactor-independent and optimally uses light of 300-310 nm wavelength to repair cyclobutane thymine dimers within a gapped DNA substrate. Both Sero1C and UV1C show multiple turnover kinetics, and UV1C repairs its substrate with a quantum yield of ∼0.05, on the same order as the quantum yields of certain classes of photolyase enzymes. Intensive study of UV1C has revealed that its catalytic core consists of a guanine quadruplex (G-quadruplex) positioned proximally to the bound substrate's thymine dimer. We hypothesize that electron transfer from photoexcited guanines within UV1C's G-quadruplex is responsible for substrate photoreactivation, analogous to electron transfer to pyrimidine dimers within a DNA substrate from photoexcited flavin cofactors located within natural photolyase enzymes. Though the analogy to evolution is necessarily limited, a comparison of the properties of UV1C and Sero1C, which arose out of the same in vitro selection experiment, reveals that although the two DNAzymes comparably accelerate the rate of thymine dimer repair, Sero1C has a substantially broader substrate repertoire, as it can repair many more kinds of pyrimidine dimers than UV1C. Therefore, the co-opting of an amino acid-like cofactor by a nucleic acid enzyme in this case contributes functional versatility rather than a greater rate enhancement. In recent work on UV1C, we have succeeded in shifting its action spectrum from the UVB into the blue region of the spectrum and determined that although it catalyzes both repair and de novo formation of thymine dimers, UV1C is primarily a catalyst for thymine dimer repair. Our work on photolyase DNAzymes has stimulated broader questions about whether analogous, purely nucleotide-based photoreactivation also occurs in double-helical DNA, the dominant form of DNA in living cells. Recently, a number of different groups have reported that this kind of repair is indeed operational in DNA duplexes, i.e., that there exist nucleotide sequences that actively protect, by way of photoreactivation (rather than by simply preventing their formation), pyrimidine dimers located proximal to them. Nucleotide-based photoreactivation thus appears to be a salient, if unanticipated, property of DNA and RNA. The phenomenon also offers pointers in the direction of how in primordial evolution-in an RNA world-early nucleic acids may have protected themselves from structural and functional damage wrought by ultraviolet light.

Nanobrass CuZn Nanoparticles as Foliar Spray Nonphytotoxic Fungicides.

Inorganic nanoparticles (NPs) have been proposed as alternative fertilizers to suppress plant disease and increase crop yield. However, phytotoxicity of NPs remains a key factor for their massive employment in agricultural applications. In order to investigate new effective, nonphytotoxic, and inexpensive fungicides, in the present study CuZn bimetallic nanoparticles (BNPs) have been synthesized as antifungals, while assessment of photosystem II (PSII) efficiency by chlorophyll fluorescence imaging analysis is utilized as an effective and noninvasive phytotoxicity evaluation method. Thus, biocompatible coated, nonoxide contaminated CuZn BNPs of 20 nm crystallite size and 250 nm hydrodynamic diameter have been prepared by a microwave-assisted synthesis. BNPs' antifungal activity against Saccharomyces cerevisiae was found to be enhanced compared to monometallic Cu NPs. Reactive oxygen species (ROS) formation and photosystem II (PSII) functionality at low light (LL) and high light (HL) intensity were determined on tomato plants sprayed with 15 and 30 mg L-1 of BNPs for the evaluation of their phytotoxicity. Tomato leaves sprayed with 15 mg L-1 of BNPs displayed no significant difference in PSII functionality at LL, while exposure to 30 mg L-1 of BNPs for up to 90 min resulted in a reduced plastoquinone (PQ) pool that gave rise to H2O2 accumulation, initiating signaling networks and regulating acclimation responses. After 3 h of exposure to 30 mg L-1 of BNPs, PSII functionality at LL was similar to control, indicating nonphytotoxic effects. Meanwhile, exposure of tomato leaves either enhanced (15 mg L-1) or did not have any significant effect (30 mg L-1) on PSII functionality at HL, attributed to the absence of semiconducting oxide phases and photochemical toxicity-reducing modifications. The use of chlorophyll fluorescence imaging analysis is recommended as a tool to monitor NPs behavior on plants.

Improvement of Abrasion Resistance of Automotive Resin Window Fabricated by Means of Photochemical Surface Modification

Improvement of Abrasion Resistance of Automotive Resin Window Fabricated by Means of Photochemical Surface Modification

Ultra-hardening of Hard-coat over Polycarbonate by Photochemical Surface Modification

Ultra-hardening of Hard-coat over Polycarbonate by Photochemical Surface Modification

How Performance and Fate of Biodegradable Mulch Films are Impacted by Field Ageing

Three black biodegradable films based on PBAT-blends (PBAT/PLA, PBAT/PPC and PBAT/Starch) were tested for vine mulching in real field conditions. The impact of field ageing on their morphology, mechanical performance and ultimate biodegradation was investigated on films exposed at the soil surface or buried into the soil in order to assess the respective contribution of the main related ageing factors i.e. UV radiations and microorganisms. The fact that the soil-facing surface of films exhibited holes 18 months after installation suggested that the biodegradation process could occur above-soil even without previous burying step. However, the early loss of integrity of the biodegradable materials was attributed to UV radiations since beyond a certain threshold the photochemical modifications undergone by the material were too high to sustain its integrity. Whatever the material tested the deterioration of mechanical properties was correlated with the crosslinking of polymer chains inducing the formation of a gel fraction. Considering that the major part of the three materials studied is made of PBAT, the nature of the other polymer constituting the blend would not have a significant impact on the ageing mechanism of the material. Biodegradation analyses conducted in compost medium indicated that field ageing had a low impact on the percentages of mineralization whether the materials had been previously aged or not.

Surface texturing effect on crack suppression of SiO2 film formed by F2 laser-induced photochemical surface modification of silicone on polycarbonate under heat resistance test

A crack-free SiO2 film was successfully fabricated on silicone-coated polycarbonate (PC) even under heat resistance tests at 100 and 120 °C for 3 h by an additional rubbing treatment with steel wool for use as an automobile window material. The SiO2 film was formed by 157 nm F2 laser-induced photochemical surface modification of silicone on PC. The modified SiO2 layer was also zoned with a mesh mask during the laser irradiation. The zoned SiO2 layer was effective for suppressing cracks during laser irradiation. However, even the zoned layer caused cracks under heat resistance tests. A mechanism of the cracking was analyzed on the basis of observations of sample surfaces by confocal laser microscopy. The rubbed samples showed high heat resistance. By atomic force microscopy, the surface of the modified SiO2 layer was clearly observed to be textured, which reduced the large difference in the thermal expansion coefficient between SiO2 and silicone on PC, thus maintaining optical transparency.

Nonlinear imaging microscopy for assessing structural and photochemical modifications upon laser removal of dammar varnish on photosensitive substrates.

The nonlinear optical microscopy (NLM) modalities of Multi-Photon Excited Fluorescence (MPEF) and Third Harmonic Generation (THG) have been combined in this work to characterize as a function of depth with micrometric resolution the type and extent of morphological and photochemical modifications that take place upon ultraviolet (UV) pulsed laser removal of a dammar varnish layer applied on a photosensitive substrate. The latter consists on a layer of the synthetic polymer poly-methyl methacrylate doped with a photosensitizer, the aromatic compound 1,4-di[2-(5-phenyloxazolyl)] benzene, that strongly fluoresces upon UV light illumination. A number of laser conditions for partial or total elimination of the varnish coating were explored, namely different wavelengths (266, 248 and 213 nm) and pulse durations, in the nanosecond, picosecond and femtosecond ranges. Changes in the MPEF signals upon laser ablation of the outermost varnish layer successfully signpost photochemical modifications of the varnish or of the photosensitive under-layer, and their dependence with the laser ablation parameters, i.e., wavelength and pulse duration. In turn, THG signals mark the presence of layer boundaries and the reduction by laser ablation of the thickness of the varnish coating. The obtained MPEF and THG data are complemented by morphological observation by optical microscopy and measurements of laser induced fluorescence and micro-Raman spectra of the samples before and after laser ablation at the selected laser irradiation conditions. The results acquired through these non-destructive NLM imaging techniques serve to understand the phenomena that are induced upon laser ablation and to determine the best operating conditions that ensure controlled removal of the varnish with minimal morphological and chemical modifications to the under-layers. This research is of direct application to the UV pulsed laser cleaning of paintings and demonstrates the potential of NLM as a novel assessment tool for non-destructive, on line monitoring of the laser cleaning process.

Post-cycloaddition modification of a porous MOF for improved GC separation of ethanol and water.

An olefin-containing pyridinium derivative, 1-(4-carboxybenzyl)-4-[2-(4-pyridyl)-vinyl]-pyridinium chloride (HBCbpeCl) has been introduced into a novel 2D metal-organic framework with rare right- and left-handed spiral nanotubular channels arranged alternately in the structure. The 1D channel is modified by positively-charged pyridinium segments, which shows high affinities to Lewis basic molecules such as methanol, ethanol, and water vapor. Additionally, the BCbpe molecules in the structure have been directed through cation-π interactions to be aligned antiparallel to each other with the C[double bond, length as m-dash]C double bond arranged properly for [2 + 2] photocycloaddition, which can be triggered to undergo structural transformation from 2D to 3D. This post-cycloaddition modification strategy has been used to separate alcohols and water, which includes a successful adjustment of large tailor-made channels by the [2 + 2] cycloaddition reaction. The gas-chromatographic separation experiments show that ethanol can be better separated from water through a column filled with a post-cycloaddition modified sample than the as-synthesized one.

Crack suppression of silica glass formed by zoned F2 laser-induced photochemical surface modification of hard silicone thin film coating on polycarbonate

The surface layer of a hard silicone thin film coating on polycarbonate was modified to silica glass (SiO2) through F2-laser-induced photochemical reactions. To obtain samples with higher abrasion resistances, SiO2 films of 1 µm thickness and over were successfully formed without cracking, by zoning the laser-irradiated area of micrometer order. With the conversion of silicone to SiO2, the volumetric shrinkage of the sample was induced, which simply depended on the number of photons, by varying the single-pulse fluence and irradiation time of a F2 laser. The ratio of volumetric shrinkage to the original silicone was estimated to be approximately 0.85, generating tensile stress in SiO2. The stress could be suppressed to be lower than 48 MPa for typical SiO2 by reducing the laser-irradiated area to be of micrometer order. Also, when the length of one side of the irradiated area is 1 mm, the thickness of the SiO2 film is expected to increase to approximately 5 µm.

Photochemical Molecular Tailoring for Efficient Diffusion and Reorganization of Organic Nanocrystals for Ultra-Flexible Organic Semiconductor Arrays.

Solution-processed organic single crystals with high carrier mobility have been actively investigated for diverse applications such as displays, sensors, and next generation electronics on a flexible platform. However, the lack of precise alignment and growth control of organic single crystals impedes the widespread adoption of organic materials in an industrial perspective. Here, a photochemical modification approach is reported tailoring the solubility and molecular diffusivity of polymeric sacrificial layer and sequential batch-type vapor annealing to implement high-performance (average saturation mobility: 8.01 cm2 V-1 s-1 ) organic single-crystal thin film transistors with large channel width including multiple aligned single crystals. Additionally, the mechanical properties of the organic single crystals are systematically investigated with extreme strain conditions such as bending radius of 150 μm.

Crack Suppression of Transparent Protective Layer on Polycarbonate Formed by Fluorine Laser

SUMMARYA transparent, hard silica glass (SiO2) layer was formed on a conventional protective coat made of silicone ([SiO(CH3)2]n) on a polycarbonate plate by the 157 nm fluorine (F2) laser‐induced photochemical modification of silicone into SiO2. Long exposure of the F2 laser to the sample produced cracks on the surface; a metallic mesh mask was set on the sample during F2 laser irradiation to suppress the cracks successfully. As a result, the thickness of the formed SiO2 layer could increase to approximately 1.3 μm without any crack, and the hardness of the sample also increased to approximately 2.8 GPa.

Photochemical Modification of Single Crystalline GaN Film Using n-Alkene with Different Carbon Chain Lengths as Biolinker.

As a potential material for biosensing applications, gallium nitride (GaN) films have attracted remarkable attention. In order to construct GaN biosensors, a corresponding immobilization of biolinkers is of great importance in order to render a surface bioactive. In this work, two kinds of n-alkenes with different carbon chain lengths, namely allylamine protected with trifluoroacetamide (TFAAA) and 10-aminodec-1-ene protected with trifluoroacetamide (TFAAD), were used to photochemically functionalize single crystalline GaN films. The successful linkage of both TFAAA and TFAAD to the GaN films is confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurement. With increased UV illumination time, the intensity of the secondary ions corresponding to the linker molecules initially increases and subsequently decreases in both cases. Based on the SIMS measurements, the maximum coverage of TFAAA is achieved after 14 h of UV illumination, while only 2 h is required in the case of TFAAD to reach the situation of a fully covered GaN surface. This finding leads to the conclusion that the reaction rate of TFAAD is significantly higher compared to TFAAA. Measurements by atomic force microscopy (AFM) indicate that the coverage of GaN films by a TFAAA layer leads to an increased surface roughness. The atomic terraces, which are clearly observable for the pristine GaN films, disappear once the surface is fully covered by a TFAAA layer. Such TFAAA layers will feature a homogeneous surface topography even for reaction times of 24 h. In contrast to this, TFAAD shows strong cross-polymerization on the surface, this is confirmed by optical microscopy. These results demonstrate that TFAAA is a more suitable candidate as biolinker in context of the GaN surfaces due to its improved controllability.

(Invited) Nanotubes for DNA Conformation Sensing

The talk is focused on applying single-wall nanotubes (SWNT) as optical reporters of DNA structure. SWNT photoluminescence (PL) was used to explore photo-physics of pi-pi* transitions in the photoexcited DNA. The ssDNA wrapped CoMoCat SWNTs, water suspended, commonly produce a strong and stable PL under visible excitation[1]. Recently we demonstrated that under two-color excitation (visible plus UV) such a system shows rich behavior: normal double-band excitonic photogeneration resulting in UV-enhanced PL emission could be one type of response. The other behavior was found in a certain band of excitation wavelength: reversible PL quenching followed the cw-UV illumination, different from photobleaching or photochemical modification of pristine material. The explanation of this intriguing behavior was found and presented in Ref.[2]. By combination of optical spectroscopy, rate equation analysis for excited states, and semi-empirical quantum mechanical calculation the source of the PL quenching was identified to be free charge carriers introduced by the photoexcited DNA. It is known that the DNA in the course of biological evolution developed mechanisms of recovery after UV irradiation, as well as relaxation mechanisms for photoexcited states. One of those mechanisms, namely, the DNA autoionization (AI) mechanism has been detected experimentally using SWNT as a nanoscale reporter. Theoretical analysis of the effect showed existence of the AI rates shorter than 20 fs and dominated by a hole charge transfer from the ssDNA to the SWNT. The capability to detect a fundamental relaxation mechanism of UV-excited DNA by using two-color spectroscopy proves potential of a DNA-SWNT complex, as a model optical system, for detecting charge transfer from DNA. Furthermore, the model demonstrated that the AI rate is a function of the conformation of the DNA thus opening further avenues for biosensing of DNA architecture in these complexes. Significant contributions to this work by Dr. T. Ignatova (UC Irvine), Dr. A. Balaeff (University of Central Florida), Dr. M. Zheng (NIST), Mr. M. Blades (LU), and Mr. P. Stoeckl (University of Rochester) are kindly acknowledged; special thinks to Dr. J. Fagan (NIST) for help with instrumentation. Research was partially supported by National Science Foundation (ECCS-1509786).

Local Light-Induced Modification of the Inside of Microfluidic Glass Chips.

The ability to locally functionalize the surface of glass allows for myriad biomedical and chemical applications. This would be the case if the surface functionalization can be induced using light with wavelengths for which standard glass is almost transparent. To this aim, we present the first example of a photochemical modification of hydrogen-terminated glass (H-glass) with terminal alkenes. Both flat glass surfaces and the inside of glass microchannels were modified with a well-defined, covalently attached organic monolayer using a range of wavelengths, including sub-band-gap 302 nm ultraviolet light. A detailed characterization thereof was conducted by measurements of the static water contact angle, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and scanning Auger microscopy (SAM). Germanium attenuated total reflection Fourier transform infrared (GATR-FTIR) indicates that the mechanism of the surface modification proceeds via an anti-Markovnikov substitution. Reacting H-glass with 10-trifluoro-acetamide-1-decene (TFAAD) followed by basic hydrolysis affords the corresponding primary amine-terminated monolayer, enabling additional functionalization of the substrate. Furthermore, we show the successful formation of a photopatterned amine layer by the specific attachment of fluorescent nanoparticles in very discrete regions. Finally, a microchannel was photochemically patterned with a functional linker allowing for surface-directed liquid flow. These results demonstrate that H-glass can be modified with a functional tailor-made organic monolayer, has highly tunable wetting properties, and displays significant potential for further applications.

Photochemical functionalization of diamond films using a short carbon chain acid

Diamond is recognized as a promising semiconductor material for biological applications, because of its high chemical stability and biocompatibility. Here, we report an acid with only three carbon chain, acrylic acid (AA), for the functionalization of H-terminated diamond film via photochemical method. The successfully modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and contact angle analyzer. Our functionalization approach was proven to be simple and facile, which shows a new potential opportunity for the photochemical modification of diamond surface with short carbon chain acid.

Accelerated weathering and chemical resistance of polyurethane powder coatings

A study of the weathering mechanism of innovative polyurethane powder coatings has been performed. UV-B irradiation and condensation cycle accelerated tests were carried out on two different polyurethane powder coating formulations for outdoor applications. Using Fourier transform infrared spectroscopy and microscope observation, it was possible to analyze the photochemical and morphological modifications. In addition, the color and gloss changes were measured. Organic coatings are often in contact with solvents in particular during cleaning actions. The chemical resistance was then studied considering the evolution of the corrosion barrier property of the coating as a function of the solvent contact time. Electrochemical impedance spectroscopy measurements were carried out. Methylethylketone (polar) and xylene (apolar) were considered as representative solvents. Due to the strong polarity, the first solvent showed a strong interaction with the hydrogen bonds between the polyurethane chains causing the solvent uptake. The amount of solvent uptake depends on the coating chains rigidity caused by the different polyester resin monomers. The apolar xylene presented no significant interaction with the coatings.