Photochemical Modification Research Articles

Advanced one pot photochemical surface modification approach towards graphene materials and their application in dye removal

Carbonaceous materials have shown undisputable promise as adsorbents and catalysts in various applications. The ability to tune key features such as specific surface area and functionality to improve the activity, represents a key advantage. However, this requires the development of general and versatile synthetic methods to deliver these multifunctional materials. This work reports a convenient general approach to prepare a series of graphene-chromophore systems. Two photochemical methods involving a step-by-step procedure and a one-pot method were compared. It was found that the two-step procedure is limited by the stability of the diazonium salts and thus has a limited application. The one-pot method allows preparation of a wide range of different composites in an easy and inexpensive manner. Synthesised samples were characterised by a range of methods including electron microscopy, X-ray diffraction, infra-red spectroscopy and gas adsorption. Transmission electron microscopy analysis revealed an ordered array of chromophores on the surface of the graphene nanoplatelets. The samples were tested as potential materials for dye removal; these studies revealed that most graphene-chromophore materials can successfully remove organic pollutants such as methylene blue, rhodamine B and methyl orange from aqueous media.

Photodecoration of tungsten oxide nanoparticles onto eggshell as an ultra-fast adsorbent for removal of MB dye pollutant

Nowadays, the use of natural wastes and adsorbents along with their modification by simple and new methods based on metal oxides to remove dye pollutants has been the focus of many researchers. In this study, for the first time, simple and low-cost modification of eggshell (EGS) with tungsten oxide (WO3) based on the photochemical modification method as a green, ultra-fast, cost-effective, and biodegradable adsorbent is reported to remove of methylene blue (MB) dye pollutant. The EGS modified by WO3 was investigated by EDX, EDX mapping, XRD, FE-SEM, and UV–Vis Diffuse Reflectance (DRS) analyses. The obtained results show that the modified EGS by WO3 has more than ten times (78.5%) the ability to remove MB dye pollutant within 3 min compared to bare EGS (11%). Various parameters including dye pollutant pH, dye concentration, adsorbent dosage, and reusability of the WO3/EGS adsorbent for removal of MB dye pollutant were investigated and the result show that the adsorbent capacity of WO3/EGS is 1.64 mg g−1. EGS adsorbent The synthesis of WO3/EGS adsorbent with a novel photochemical method as a fast and very cheap adsorbent with excellent efficiency can be a promising alternative adsorbent for various purposes in removing dye pollutants from water environments.

Photochemical modification of a diamond surface using a pulsed UV laser as the energy source

The use of an excimer benchtop pulsed UV laser as the energy source for the photochemical modification of the surface of diamond films is reported. Boron-doped nanocrystalline diamond (NCD) films were deposited on Si wafers via plasma-enhanced chemical vapour deposition (PECVD). The as-deposited films were characterised by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Following characterisation, the surfaces of the films were subjected to a photochemical reaction with 2,2,2-trifluoroethyl undec-10-enoate using two different sources of radiation: a benchtop UV lamp (254 nm) and a KrF excimer pulsed UV laser (248 nm). The photochemically treated films were characterised by contact angle measurements and X-ray photoelectric spectroscopy (XPS) using non-treated films as a control. The use of a pulsed UV laser source was shown to reduce the photochemical reaction time from several hours to a few minutes.

Photochemical surface modification of amorphous carbon thin film to transparency in atmosphere of excited singlet oxygen atoms O(1D) under 157 nm F2 laser irradiation

Amorphous carbon (a-C) thin films have various useful properties; thus, their applications are wide-ranging. These properties are characterized by the ratio of sp3 to sp2 carbon in the thin film, and many studies have been reported on changing this ratio. In this paper, we used an F2 laser with a wavelength of 157 nm to photoexcite the surface of an a-C thin film, and simultaneously photodecompose atmospheric oxygen molecules O2 into excited singlet oxygen atoms O(1D). The results showed that O(1D) atoms can photochemically etch sp2 carbon in thin films significantly better than triplet oxygen atoms O(3P). Thus, we found that the surface layer of the a-C thin film was photochemically modified to be transparent. Raman spectroscopy revealed no change in the chemical bonding state of the transparently modified a-C thin film. On the other hand, in X-ray photoelectron spectroscopy, the intensity of the C 1s peak originated to sp2 carbon decreased. The refractive index was also slightly lowered, probably due to lowering film density. In addition, droplets mainly composed of sp2 carbon generated during thin film deposition were significantly removed after F2 laser irradiation. The electrical resistivity slightly decreased upon F2 laser irradiation and remarkably decreased as the substrate was heated, exhibiting low bandgap properties. Therefore, we succeeded in discovering a new method for changing the ratio of sp3 to sp2 carbon in a-C to be transparent thin film by preferentially generating O(1D) atoms using the F2 laser, as a new elemental technology for fabricating transparent flexible electronic devices.

Photochemical modification of tea waste by tungsten oxide nanoparticle as a novel, low-cost and green photocatalyst for degradation of dye pollutant

So far, many adsorbents and nanocomposites have been synthesized by different methods and used to remove or degradation of dye pollutants. Nowadays, the use of natural adsorbents and their modification with simple methods based on metal oxides are of interest to many researchers. In this study, for the first time, we report the simple and low-cost modification of tea pomace waste (TPW) with tungsten oxide (WO3) based on the photochemical method as a green, cost-effective, and biodegradable photocatalyst for the degradation of Rh B dye pollutant. The results obtained from FE-SEM, EDAX, XRD, XPS, PL, BET and UV–Vis Diffusive Reflectance (DRS) analyses confirmed the successful modification of the TPW surface with WO3 (WO3/TPW). The parameters affecting the photocatalytic behavior of WO3/TPW, including the time of photochemical modification and the type of radiation on its photocatalytic activity, were carefully optimized. WO3/TPW showed excellent photocatalytic activity compared to TPW for the degradation of Rh B dye pollutant under UV light for 30 min (94 %). Finally, the effective parameters on the value of Rh B dye degradation by WO3/TPW photocatalyst including pH, adsorbent dosage, the concentration of dye pollutant, and the kinetics of the degradation process were studied. It is expected that this type of photochemical modification method and natural WO3/TPW photocatalyst will be a promising path for the synthesis, modification, and increase of the photocatalytic performance of natural adsorbents.

Influence of production method on the structure and photocatalytic activity of CeO<sub>2</sub>/Au nanocomposite

Two methods for preparing mesoporous CeO2/Au nanocomposites were compared: template synthesis and photochemical modification of fibrous cerium(IV) oxide with gold nanoparticles. The composition, structure, morphology of the obtained nanocomposites, as well as the specific surface area and pore size distribution were studied by a complex of physicochemical methods: X-ray phase analysis, X-ray spectral microanalysis, scanning electron microscopy, low-temperature nitrogen adsorption, and electron spectroscopy. The catalytic properties of the obtained nanocomposites were studied in methyl orange photodegradation reactions. It is shown that the CeO2/Au catalyst obtained by the photochemical modification method has the highest photocatalytic activity both under the action of UV and visible light.

Photochemical Modification of the Extracellular Matrix to Alter the Vascular Remodeling Process.

Therapeutic interventions for vascular diseases aim at achieving long-term patency by controlling vascular remodeling. The extracellular matrix (ECM) of the vessel wall plays a crucial role in regulating this process. This study introduces a novel photochemical treatment known as Natural Vascular Scaffolding, utilizing a 4-amino substituted 1,8-naphthimide (10-8-10 Dimer) and 450 nm light. This treatment induces structural changes in the ECM by forming covalent bonds between amino acids in ECM fibers without harming vascular cell survival, as evidenced by our results. To further investigate the mechanism of this treatment, porcine carotid artery segments were exposed to 10-8-10 Dimer and light activation. Subsequent experiments subjected these segments to enzymatic degradation through elastase or collagenase treatment and were analyzed using digital image analysis software (MIPAR) after histological processing. The results demonstrated significant preservation of collagen and elastin structures in the photochemically treated vascular wall, compared to controls. This suggests that photochemical treatment can effectively modulate vascular remodeling by enhancing the resistance of the ECM scaffold to degradation. This approach shows promise in scenarios where vascular segments experience significant hemodynamic fluctuations as it reinforces vascular wall integrity and preserves lumen patency. This can be valuable in treating veins prior to fistula creation and grafting or managing arterial aneurysm expansion.

Postsynthetic Photochemical Modification and 2D Structuring of Zr-MOF Thin Films Containing Benzophenone Linker Molecules.

For the fabrication of next-generation MOF-based devices the availability of highly adaptable materials in suitable shapes is crucial. Here, we present thin films of a metal-organic framework (MOF) containing photoreactive benzophenone units. Crystalline, oriented and porous films of the zirconium-based bzpdc-MOF (bzpdc=benzophenone-4-4'-dicarboxylate) are prepared by direct growth on silicon or glass substrates. Via a subsequent photochemical modification of the Zr-bzpdc-MOF films, various properties can be tuned postsynthetically by covalent attachment of modifying agents. Apart from the modification with small molecules, also grafting-from polymerization reactions are possible. In a further extension, 2D structuring and photo-writing of defined structures is also possible, for example by using a photolithographic approach, paving the way towards micro-patterned MOF surfaces.

Postsynthetische Photochemische Modifizierung und 2D Strukturierung von Zr‐MOF Dünnfilmen mit Benzophenon Linkermolekülen

AbstractFür die Herstellung von MOF‐basierten Bauteilen der nächsten Generation ist die Verfügbarkeit hochgradig anpassungsfähiger Materialien in geeigneten Formen entscheidend. In dieser Arbeit stellen wir Dünnfilme eines Metall‐organischen Gerüstes (MOF) mit photoreaktiven Benzophenon‐Brückenmolekülen vor. Kristalline, orientierte und poröse Filme des Zirkonium‐basierten bzpdc‐MOF (bzpdc=Benzophenon‐4‐4′‐dicarboxylat) können über direktes Wachstum auf Silizium‐ oder Glassubstraten hergestellt werden. Durch eine anschließende photochemische Modifizierung der Zr‐bzpdc‐MOF‐Filme lassen sich verschiedene Eigenschaften mittels kovalenter Anbindung von Modifizierungsreagenzien postsynthetisch einstellen. Neben der Modifizierung mit kleinen Molekülen sind auch grafting‐from Polymerisationsreaktionen möglich und in einer weiteren Ausbaustufe sogar die 2D‐Strukturierung und das Fotoschreiben definierter Strukturen; z.B. durch einen fotolithographischen Ansatz, der den Weg zu mikro‐strukturierten MOF‐Oberflächen ebnet.

High-Strength Epoxy Nanocomposites Reinforced with Photochemically Treated CNTs.

A carbon nanotube (CNT)/epoxy nanocomposite was prepared using a photochemical surface modification process of CNTs. The vacuum ultraviolet (VUV)-excimer lamp treatment created reactive sites on the CNT surface. Increasing the irradiation time increased the oxygen functional groups and changed the oxygen bonding state such as C=O, C-O, and -COOH. By the VUV-excimer irradiation on CNTs, the epoxy infiltrated well between the CNT bundles and formed a strong chemical bond between CNT and epoxy. The tensile strength and elastic modulus of the nanocomposites with VUV-excimer irradiated sample during 30 min (R30) were found to increase by 30 and 68% compared to using pristine CNT, respectively. R30 was not pulled out and remained embedded in the matrix until the fracture occurred. The VUV-excimer irradiation is an effective surface modification and functionalization method for improving the mechanical properties of CNT nanocomposite materials.

Tip Modification for Interaction Studies Between Polysaccharides and Dental Materials

Neutral polysaccharides, such as bacterial dextrans, are one of the main components of the oral conditioning film, which is the first step in the formation of microbial biofilms on dental materials in the oral cavity. Although they play an essential role alongside proteins, their adhesion mechanisms are still very unknown. Therefore, they are currently being studied using various analytical methods. In particular, by means of scanning force spectroscopy (SFS), the adhesion forces are to be measured as a function of multiple parameters such as pH value or surface material. Cantilever tips must therefore be modified with the polysaccharide of interest. A stable coupling of dextran, which serves as a model polysaccharide here, can be achieved by a photochemical modification method, which is verified by fluorescence microscopy, X‐ray photoelectron spectroscopy, scanning force microscopy, and SFS.

Photoanode with enhanced performance achieved by a novel charge modulation strategy without sacrificial agents

Although the catalytic effect can be enhanced by using sacrificial agents, it still faces numerous difficulties in large-scale production applications. Investigating the improvement of photocatalytic efficiency without sacrificial agents is therefore crucial. This study proposes a cost-effective and efficient photochemical modification system that utilizes a seed layer of BiVO4 to improve photoelectrochemical (PEC) performance, the result shows that the photocurrent density of BiVO4 with a seed layer thickness of 312 nm was improved by 40% to 0.99 mA cm−2 at 1.23 VRHE without any sacrificial agent. Meanwhile, Electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent spectroscopy (IMPS) demonstrated that the introduction of the seed layer effectively prevents the recombination of electron-hole pairs and improves the charge transfer efficiency, leading to a “slow” decrease in the current density of the composite photoanode (from 32% to 9.8%) in combination with the linear sweep voltammetry (LSV) results. We exhibit the scanning photoelectrochemical microscopy (SPECM) method to in-situ quantitatively study the hole transfer kinetics with different seed layer thicknesses using the feedback model and find those photoelectrodes with a thickness of 312 nm has the highest kinetic rate constant of 0.62 × 10−2 cm s−1 which is approximately 5 times higher than that of the pristine photoelectrode (0.11 × 10−2 cm s−1).

Photo-cross-linkable hyaluronic acid bioinks for bone and cartilage tissue engineering applications

ABSTRACT Hyaluronic acid (HA) is of immense importance to biomaterials science and biomedical engineering. It is finding applications in diverse areas of bioengineering ranging from scaffolds for disease modelling to tissue culture for reconstruction. This review focuses on recent research on the role of HA as a photo-cross-linked bioink and its importance in combating bone and cartilage-related disease, injury and disorders. Photo chemical modifications and 3D fabrication technologies employed to produce HA-modified materials are analysed to provide a fundamental understanding of the structure–function-property relationships that influence printability, shape fidelity and biological performance both in-vitro and in-vivo. The article concludes with a future vision for HA-based bioinks and their deployment in light-based bioprinting technologies for bone and cartilage repair.

Photo-Initiated in situ synthesis of polypyrrole Fe-Coated porous silicon microspheres for High-performance Lithium-ion battery anodes

A simple and environmentally friendly photoinitiated fabrication approach based on the photoelectric effect of semiconductor silicon is designed to synthesize yolk-shell like polypyrrole-iron coated porous silicon microspheres (PSi@PPy-Fe) as anode materials for LIBs. The polymerization of pyrrole monomers only occurs on the interface of silicon matrix where the vacancies are available, which effectively avoids the production of free PPy-Fe particles. XPS and first-principles calculations reveal that both the hydrogen-bond interaction and the covalent linkage are formed between Si and PPy-Fe layer, which is of great significance for maintaining good contact and strengthening the structure stability. It is demonstrated that the PPy-Fe coating may accelerate charge transfer and ion diffusion as well as prevent the Si-based materials peeling off from Cu collector. More importantly, the PPy-Fe coating could alleviate the violent structural expansion of Si anode, thus ameliorating the mechanical strength of the electrode. Consequently, the as-prepared yolk-shell like polypyrrole-iron coated porous silicon microspheres present outstanding cycling ability (1853.7 mAh/g after 200 cycles at 1 A/g) and superior rate capability (1558.4 mAh/g at 4 A/g). This work indicates that the photochemical modification strategy for Si may have a bright prospect in a wide range of fields.

Synthesis and photochemical modification of monolayer thin MOF flakes for incorporation in defect free polymer composites.

Metal-organic frameworks (MOFs) with benzophenone linker molecules are characterized by their ability to undergo photochemical postsynthetic modification. While this approach opens up almost unlimited possibilities for tailoring materials to specific applications, the processability of the large particles is still lacking. In this work, we present a new approach to fabricate micro flakes of the stable Zr-bzpdc-MOF (bzpdc = benzophenone-4-4'-dicarboxylate) with a thickness of only a few monolayers. The crystalline and nanoporous flakes form dispersions in acetone that are stable for months. Embedding the flakes in polymer composites was investigated as one of many possible applications. Zr-bzpdc-MOF micro flakes were decorated with poly(dimethylsiloxane) (PDMS) via a photochemical postsynthetic modification and incorporated into silicon elastomers. The PDMS functionalization allows covalent cross-linking between the MOF and the polymer while maintaining the porosity of the MOF. The resulting hybrid materials provide defect-free interfaces and show preferential adsorption of CO2 over CH4, making them attractive for gas separation or sensing applications. The work should serve as a basis for bringing bzpdc-MOFs into real-world applications - in polymeric membranes, but also beyond.

Delicate and Fast Photochemical Surface Modification of 2D Photoresponsive Organosilicon Metal-Organic Frameworks.

Photoresponsive arylsilanes have been fascinating molecules for decades because of their unique photophysical characteristics and surface chemistry. Here we report the synthesis and fabrication of a crystalline two-dimensional trisilyl metal-organic framework (TSiMOF) orderly installed with the classical photoresponsive hexamethyltrisilane groups on the surface. Irradiated by UV light under air in minutes the fluorescence of the TSiMOF is turned on simultaneously with an intriguing surface transformation from superhydrophobic to hydrophilic. Thus, multifarious luminescent and hydrophilic patterns including logos, characters and Quick Response codes, etc. with good resolution are readily generated on the facilely fabricated TSiMOF film. The mechanism of this transformation is revealed by control experiments that the superficial trimethylsilyl groups suffering photochemical oxidation have been converted to hydroxyl groups.

Delicate and Fast Photochemical Surface Modification of 2D Photoresponsive Organosilicon Metal–Organic Frameworks

AbstractPhotoresponsive arylsilanes have been fascinating molecules for decades because of their unique photophysical characteristics and surface chemistry. Here we report the synthesis and fabrication of a crystalline two‐dimensional trisilyl metal–organic framework (TSiMOF) orderly installed with the classical photoresponsive hexamethyltrisilane groups on the surface. Irradiated by UV light under air in minutes the fluorescence of the TSiMOF is turned on simultaneously with an intriguing surface transformation from superhydrophobic to hydrophilic. Thus, multifarious luminescent and hydrophilic patterns including logos, characters and Quick Response codes, etc. with good resolution are readily generated on the facilely fabricated TSiMOF film. The mechanism of this transformation is revealed by control experiments that the superficial trimethylsilyl groups suffering photochemical oxidation have been converted to hydroxyl groups.

Abstract 345: Natural Vascular Scaffolding Suppresses Experimental Abdominal Aortic Aneurysms

Objective: Proteolytic destruction of aortic extracellular matrix (ECM) is central to abdominal aortic aneurysm (AAA) pathogenesis. Matrix metalloproteinase inhibition with doxycycline failed to limit AAA progression. However, photochemical modification of collagen and elastin fibers may provide an alternative approach to ECM stabilization. We investigated the effectiveness of this treatment in limiting experimental AAA progression. Methods: AAAs were created in 8-10 weeks old male C57BL/6J mice via intra-aortic elastase infusion. Natural vascular scaffolding (NVS) (2 mg/ml, Alucent Biomedical) or vehicle solution was applied to the abluminal aortic wall immediately following elastase infusion and aortotomy closure and exposed to laser light activation. AAA progression was assessed via serial ultrasound aortic diameter measurements and histopathologic analysis at sacrifice. Results: Ultrasonography confirmed progressive aortic enlargement and AAA formation in all vehicle-treated mice within 14 days following elastase infusion. NVS treatment substantially attenuated AAA development and progression with reduced medial elastin degradation and smooth muscle cell depletion, as well as mural neovessel development. No difference was seen in aortic CD4 or CD8 T accumulation between the two treatment groups. Conclusion: Photochemical linking of extracellular matrix proteins attenuated experimental AAA progression, suggesting a potential translational application for this approach in clinical disease management.

Development of carbon sphere/ceria (CS/CeO2) heterostructured particles and their applications to functional abrasives toward photochemical mechanical polishing

Ceria (CeO2) possesses tribochemical ability and photochemical oxidation activity simultaneously. Herein, novel carbon-coupled CeO2 heterostructures were developed as functional abrasives toward photochemical mechanical polishing (PCMP) system. Polydispersed carbon spheres (CS) were uniformly grafted with pure and Y-doped CeO2 nanocrystals via an in-situ chemical precipitation approach. The resulting CS/CeO2 and CS/CeYO2 core/shell hybrids were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. As confirmed by atomic force microscope, the developed hybrid abrasives allowed the nearly non-damage surfaces with angstrom-level roughness (0.10–0.13 nm Ra, 0.14–0.16 nm RMS, within 5.0 × 5.0 μm2) in both CMP and PCMP experiments over oxide films. As expected, introduction of ultraviolet radiation and/or Y-doping modification were effective in enhancing removal rates (RR). The CS/CeYO2 abrasives offered a ca. 196% increment of RR-PCMP compared to the RR-CMP of undoped ones (139 nm/min vs 47 nm/min). The improved PCMP performance might be attributed to the cooperative effects of the CS/CeO2 heterostructures (overall modulus reduction, CS–CeO2 heterojunction construction, surface defect manipulation, etc.). The possible PCMP mechanism over CS/CeO2 was also discussed on the basis of the interfacial contact, the photochemical modification, and the tribochemical removal.

Controlled cationic curing of epoxy composites with photochemically modified silanol encapsulated carbon black

AbstractEpoxy resins have been an inspiration in adhesives and coatings, however, uneven photopolymerization kinetics result in wrinkled surface and filler segregation, causing aesthetic and mechanical damage. Hence a control over curing kinetics is required not only to dodge filler segregation but also to control composite surface smoothness. In this study, photochemical modification of carbon black with mercaptopropyltrimethoxysilane, has resulted in unique silanol dendrites exterior on carbon black. Kinetic investigation confirmed that Ea for cationic polymerization of modified CB composite is three folds less in comparison to neat matrix, and two folds less in comparison to unmodified CB composite. Silanol dendrites have contributed on epoxy curing kinetics, through activated monomer mechanism. Samples have been characterized through XPS, FTIR, SEM, TGA, DSC, Raman, and EDX.