Real-time FTIR Research Articles

Enhanced photocatalytic oxidation of gaseous acetaldehyde using Fe-grafted ZnO nanocomposites in a continuous flow reactor

The purification of indoor air is a crucial application of photocatalysis, emphasizing the urgent need for more efficient photocatalytic systems. While photocatalytic oxidation of volatile organic compounds (VOCs) has been extensively studied in the liquid phase, effective removal of VOCs in the gaseous state in indoor air remains a significant challenge. This study focuses on the continuous gas-phase oxidation of gaseous acetaldehyde using ZnO and different weight percentage of Fe-grafted ZnO catalysts under light irradiation. The surface analysis using XPS and HR-TEM confirmed the presence of Fe(III) species, and UV–Vis-DRS analysis demonstrated a shift in the absorption edge towards the visible region. Real-time gas FTIR monitoring of acetaldehyde oxidation revealed that the 0.7% Fe(III)-grafted ZnO composite catalyst achieved a higher removal efficiency (74%) compared to bare ZnO and other Fe(III)-grafted ZnO ratios. The enhanced photocatalytic efficiency of acetaldehyde by Fe(III)-grafted ZnO supports indicated direct interfacial charge transfer (IFCT) from ZnO to Fe(III) species. Additionally, the Fe(III) cluster effectively improved the separation of electrons and holes, preventing their recombination and accelerating O₂ activation to generate O₂•⁻ radicals, which lead to high photocatalytic performance. The 0.7% Fe(III)-grafted ZnO also maintained its performance over a prolonged period of 360 min, showing excellent structural stability and durability across multiple cycles. This study highlights the possible synergistic effect of the ZnO and Fe systems, offering a new perspective on the photocatalytic decomposition of gaseous acetaldehyde in indoor environments.

Type I Photoinitiator Based on Sustainable Carbon Dots.

Sustainable carbon dots comprising surficial oxime ester groups following homolytic bond cleavage exhibit potential as photoinitiators for traditional free radical photopolymerization. Carbon dots were made following a solvothermal procedure from sustainable furfural available from lignocellulose. Surficial aldehyde moieties reacted with hydroxylamine to the respective oxime while reaction with benzoyl chloride resulted in a biobased Type I photoinitiator comprising sustainable carbon dot (CD-PI). Photoinitiating ability was compared with the traditional photoinitiator (PI) ethyl (2,4,6-trimethyl benzoyl) phenyl phosphinate (TPO-L) by real-time FTIR with UV exposure at 365 nm. Photopolymer composition based on a mixture of urethane dimethacrylate (UDMA) and tripropylene glycol diacrylate (TPGDA) resulted in a similar final conversion of about 70 % using either CD-PI or TPO-L. Nevertheless, it appeared homogeneous in the case of compositions processed with CD-PI, while those made with TPO-L were heterogeneous as shown by two glass transition temperatures. Moreover, the migration rate of CD-PI in the cured samples was lower in comparison with those samples using TPO-L as PI.

Synthesis of Cu-MOF-derived complex copper–chromium oxides and their catalytic study on the thermal decomposition of ammonium perchlorate

In this work, a series of complex copper-chromium oxides were prepared by adjusting the molar ratio of Cr3+/Cu2+ using MOF-199 as a template. X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure, microscopic morphology and valence information of the samples. The specific surface area of the sample was estimated by the Brunauer-Emmett-Teller method (BET), and the pore size parameters of the sample were obtained by using the Barrett-Joyner-Halenda (BJH) model. The effect of the samples on the thermal decomposition process of ammonium perchlorate (AP) was investigated by differential scanning calorimetry-thermogravimetric analysis. The results show that the copper and chromium oxides in the complex exhibit good catalytic effects. Among them, CuCr(0.8) had the best catalytic effect, reducing the peak pyrolysis temperature of AP by 95.7 °C, increasing the heat release by 817 J/g, and reducing the reaction activation energy by 62.4 kJ/mol. Real-time FTIR was used to characterize the gas products during the thermal decomposition of AP, and the gas products of AP with CuCr(0.8) catalyst were different from those of pure AP, which may also be the reason for the increase of AP heat release after adding CuCr(0.8) catalyst.

A deep-curing UV-LED light photoinitiator based on diphenylpropanetrione

Benzophenone is a widely used type II photoinitiator, whose application is somewhat limited due to these shortcomings, such as short absorption wavelength, requirement for initiation with a co-initiator like tertiary amine and propensity to yellowing. In this study, 1,3-diphenylpropyltriacetone (DPPT) was synthesized and its photopolymerization was evaluated. Due to the adjacent conjugation of the tricarbonyl group, it has an absorption band at 400–500 nm. The photopolymeirzaition process of DPPT was tested by using real time FT-IR under 365 and 405 nm LED irradiation for various acrylate monomers. Interestingly, the results showed that the initiation efficiency of DPPT was improved by OH-containing monomers or alcohols. ESR-ST and steady-state photolysis experiments demonstrated that the benzoyl radicals were generated, but the photoreaction was expedited by the structure of the addition products of the central carbonyl group of DPPT and alcohol. Furthermore, the DPPT/alcohol initiator could be used for deep curing due to the light bleach property.

High-efficiency pentafluorostilbene-based photocatalysts dedicated to preparing fluorescent 3D printed polymer nanocomposites

ABSTRACT The following manuscript describes 10 newly synthesised pentafluorostilbene derivatives that are diverse in the character of the substituent attached to the second phenyl ring, as well as in the substitution site. The compounds were investigated for their applicability as iodonium salt photosensitisers for initiating cationic, radical and hybrid photopolymerisation. For this purpose, various spectroscopic studies were performed, such as absorbance and fluorescence quenching experiments. For kinetic research, Fourier transform infrared spectroscopy (real-time FT-IR) was utilised, which enabled analysis of the performance of the investigated two-component photoinitiating systems in real time. According to a variety of kinetic studies, the most effective initiator system was selected and applied for application studies in the subsequent stage, namely the preparation of photocurable polymer nanocomposites using light-initiated 3D printing technology (DLP – Digital Light Processing). The most effective two-component initiating system was tested in seven different photo-curable resins by thermogravimetry (TGA) and dynamic mechanical analysis (DMA) to demonstrate its applicability in 3D printing of nanocomposites.

A novel disulfide-containing monomer for photoinitiator-free self-healable photocured coatings

Disulfide-containing coatings are gaining importance due to the peculiar properties and responsiveness of SS bonds, which make them suitable for several applications, first among them self-healable materials. Herein, a novel UV-curable diacrylated polyurethane monomer containing disulfide bonds (DSPDA) was synthesized through a one-step process without the need for further purification, as assessed by NMR and HPLC analyses. The photopolymerization kinetics of the monomer was studied through real-time FTIR, highlighting a fast and complete conversion even in the absence of a photoinitiator, thus demonstrating the self-initiating capabilities of the synthesized monomer based on the disulfide cleavage upon UV light exposure. Clear coatings having a Tg = 72 °C were obtained. The self-healing ability of the films was assessed: thanks to the presence of disulfide bonds in the cured coating, a recovery of the damage was obtained in only 10 min by heating at 100 °C.

Low migration and high performance thioxanthone based photoinitiators

Photopolymerization technology has been limited in the application of the field of food packaging and biomedicine due to the high migration of the small molecule which are mostly from the photoinitiators. To improve migration stability of photoinitiators, polymerizable 2-vinyl thioxanthone (ETX) was synthesized by thiosalicylic acid and 4-fluorobenzaldehyde. Moreover, to further reduce the migration of photo- or co-photoinitiator, two macromolecular photoinitiators (PPI1, PPI2) were prepared by copolymerization of ETX with dimethylaminoethyl methacrylate (DMAEMA). The initiation activity of the prepared photoinitiators was studied by real-time FTIR spectroscopy. The results indicated ETX/triethanolamine (TEOA) system exhibited higher initiation performance than ITX/TEOA system by irradiation of 405 nm LED lamp, PPI2 as a one component photoinitiator displayed favorable initiation ability. In addition, the migration of ETX, PPI1 and PPI2 in the photocured film was declined obviously. ETX, PPI1 and PPI2 with low migration have potential application in the field of food package and biological materials.

Photoinitiators with low migration capability based on benzophenone

Due to the increasing safety concerns caused by migration of photoinitiators, the development of low migration photoinitiators has become a priority in the current stage. As a widely used Type II photoinitiator, benzophenone is known to cause the migration of residual small molecule initiators and co-initiators after photopolymerization, leading to safety issues and severely limiting its applications. In this work, a polymerizable photoinitiator (VBP) was synthesized by directly introducing an ethylene group into benzophenone, three different molecular weight single-component photoinitiators PVBN1-3 were synthesized based on VBP. The characterization was conducted by using spectroscopic techniques, revealing stronger absorption ability in the range of 200–330 nm compared to benzophenone. The initiation efficiency of the acrylic monomer by PVBN1-3 was evaluated by using real-time FT-IR technique. The migration stability of the cured system was investigated through immersion extraction. The results demonstrate that VBP and PVBN1-3 are a series of high-performance, low-migration photoinitiators.

Restorative Dental Resin Functionalized with Calcium Methacrylate with a Hydroxyapatite Remineralization Capacity.

The ability of dental materials to induce the mineralization of enamel like hydroxyapatite (HA) is of great importance. In this article, a novel kind of dental restorative material characterized by a mineralization ability was fabricated by photopolymerization. Calcium methacrylate (CMA) was introduced into the classical bisphenol A-glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) dental resin formulation. This functional dental resin (BTCM) was calcium-rich and can be prepared simply by one-step photopolymerization. The influence of CMA on the photopolymerization kinetics, the dental resin's mechanical properties, and its capacity to induce dynamic in situ HA mineralization were examined. Real-time FTIR, compression modulus, scanning electron microscopy, X-ray spectroscopy, MTT assay, and cell attachment test were carried out. The obtained data were analyzed for statistical significance using analysis of variance (ANOVA). Double bond conversion could be completed in less than 300 s, while the compression modulus of BTCM decreased with the increase in CMA content (30 wt%, 40 wt%, and 50 wt%). After being soaked in Ca(NO3)2 and Na2HPO4 solutions alternatively, dense HA crystals were found on the surface of the dental resin which contained CMA. The amount of HA increased with the increase in CMA content. The MTT results indicated that BTCM possesses good biocompatibility, while the cell adhesion and proliferation investigation demonstrated that L929 cells can adhere and proliferate well on the surface of BTM. Thus, our approach provides a straightforward, cost-effective, and environmentally friendly solution that has the potential for immediate clinical use.

Acrylate dendritic monomers for fabricating holographic data storage media with high performance

Photopolymer is well-recognized as an ideal holographic data storage medium. In order to improve the holographic performance of a two-stage photopolymer, five acrylate dendritic monomers (DM-1/2/3/4/5) with high refractive indices (1.590–1.634) are designed and synthesized in this study. Their structures are characterized by 1H NMR, 13C NMR, FTIR and HR-MS spectra, and their photopolymerization kinetics are investigated through real-time FTIR. Using these DMs as one recording monomer, a series of photopolymer samples with different formulations are fabricated. The influence of DM-1/2/3/4/5 on the holographic performances of these samples are explored under holographic exposure of a 532 nm laser. The results show that the photosensitivity and angle selectivity of these samples can be improved by adding these DMs. The most excellent holographic characteristics are obtained by a sample with 4% DM-1. Using it as a data storage medium, a volume holographic grating with high diffraction efficiency of 90% and narrow selection angle of 0.11° is recorded. Moreover, the sample achieves a high dynamic range of 13.7 and a low volume shrinkage of 0.36% after recording 60 holograms through angular-multiplexing with low record/read exposure dose, indicating its great application potential in holographic data storage.

Advanced 3D printing of graphene oxide nanocomposites: A new initiator system for improved dispersion and mechanical performance

The integration of nanoparticles, such as Graphene Oxide (GO), with photo-curable polymers in 3D printing has garnered significant interest in recent years due to the potential to create functional nanocomposite materials. This study explores the challenges of achieving optimal dispersion of GO nanoparticles within the polymer matrix and the crucial role of photoinitiators in overcoming these limitations. Traditional photoinitiators, like TPO, commonly used for GO/polymer resins, have raised concerns about high toxicity and limited sensitivity to visible light, prompting the need for alternative initiating systems. In this research, we propose a two-component initiator system based on bis-(4-t-butylphenyl)iodonium hexafluorophosphate and photosensitizer N-{4-[(E)-2-(pentafluorophenyl)ethenyl]phenyl}-2,1,3-benzothiadiazol-4-amine (IOD/PS1) as a promising solution. This new initiating system not only ensures a more environment-friendly resin but also exhibits enhanced polymerization kinetics and compatibility with GO nano fillers. This study investigated the effect of the addition of nano-GO on the kinetics of the radical photopolymerization process, 3D printing, and final mechanical and thermal properties of the received products. TPO and PEGDA/H2O were used as reference systems. In addition, a new two-component initiator system was synthesized, which is an interesting alternative to the commercial TPO initiator that is widely employed in additive techniques. This publication presents the research procedure involving various techniques: real-time FTIR and photoreology. In addition, the possibility of creating three-dimensional structures from the newly developed photo-curable resins was verified. Finally, the morphologies and mechanical properties of the resulting 3D structures were compared. Within the work, we demonstrate the advantages of the two-component initiator in achieving uniform distribution of GO and fabricating high-quality materials. By applying IOD/PS1 initiating system we facilitated a more controlled and efficient polymerization process, reducing shrinkage-induced stresses and enhancing interlayer bonding. The result was the fabrication of high-quality, well-dispersed materials with tailored properties suitable for various applications, particularly in the biomedical field.

High-performance photoinitiating systems for new generation dental fillings.

To obtain new generation dental composites with improved performance properties compared to currently available dental fillings on the market and to determine the influence of new initiating systems on final product parameters such as degree of cure, hardness, color, and shrinkage. In order to verify the effectiveness of the developed initiating systems, typical spectroscopic, electrochemical, and kinetic studies using the real-time FT-IR method were shown. Moreover, paste dental fillings were prepared, the compositions were irradiated with the dental lamp, and the degrees of cross-linking were measured by Raman spectroscopy. The polymerization shrinkage was also determined using the rheometer. In addition, their hardness was examined on the Shore scale. Finally, the color analysis of the composites in the L*a*b*color space was compared with the VITA CLASSIC colorant. It was shown that, due to their excellent spectroscopic and electrochemical properties, new quinazolin-2-one can act as co-initiators in cationic and radical photopolymerization. It was demonstrated that the most effective composite containing the initiator system in the form of 3-SCH3Ph-Q, IOD, MDEA, and an inorganic filler as nanometric silica and a bonding agent is cured more than 90% after just 1 cycle of dental lamp exposure (30s), the hardness of the composite after curing on the Shor Scale is 82±4, and the polymerization shrinkage is less than 2.8%. The article demonstrates effective new initiator systems as an alternative to CQ/amine for obtaining new-generation dental composites. The developed dental composites are a big competition to the currently used dental fillings on the market.

Synthesis and photochemistry of flavonol camphorsulfonates photoinitiator with different substituents

In this study, we synthesized five novel flavonol camphorsulfonates (HFSs) photoinitiators using a flavonol scaffold as the chromophore. These HFSs demonstrated photoinitiating properties in both one-component (Norrish Type I) and two-component photoinitiating systems, with high final reaction function conversion and excellent polymerization rates of acrylates in free radical photopolymerization. Additionally, HFSs exhibited thermal stability in thermogravimetric tests. To explain the photoinitiating mechanisms, we used various complementary approaches, including real-time FT-IR spectroscopy, UV–Vis absorption spectroscopy, fluorescence spectroscopy, analysis of photolysis products, cyclic voltammetry, free radical capture experiments and molecular modelling calculations.

Influence of the Type of Nanofillers on the Properties of Composites Used in Dentistry and 3D Printing.

Photopolymerization is a growing field with an extensive range of applications and is environmentally friendly owing to its energy-efficient nature. Such light-assisted curing methods were initially used to cure the coatings. However, it has become common to use photopolymerization to produce 3D objects, such as bridges or dental crowns, as well as to cure dental fillings. In this study, polymer nanocomposites containing inorganic nanofillers (such as zinc nano-oxide and zinc nano-oxide doped with two wt.% aluminum, titanium nano-oxide, kaolin nanoclay, zirconium nano-oxide, aluminum nano-oxide, and silicon nano-oxide) were fabricated and studied using Real Time FT-IR to investigate the effects of these nanoadditives on the final conversion rates of the obtained nanocomposites. The effects of the fillers on the viscosity of the produced nanocomposites were also investigated, and 3D prints of the selected nanocomposites were presented.

Preparation and properties of visible light-cured strippable film for radioactive decontamination

In this research, solutions of styrene-butadiene-styrene block copolymer (SBS) in 2-ethoxyethyl methacrylate (EOEMA) were used to prepare strippable films via rapid visible-light curing, where the mixture of camphorquinone (CQ), diphenylsilane (DPS) and diphenyliodonium hexafluorophosphate (Iod) was employed as the photoinitiating system, LED@405 nm, sunlight or household LED panel light as the light source and no any solvent was involved. The double bond conversion for pure EOEMA under LED@405 nm was firstly monitored by real-time FTIR and it reached 72% within 300 s. The rapid-curing of SBS/EOEMA solutions were systematically investigated and it was found that the solution with 16 wt% SBS became completely dried at the presence of 2.16 mol% crosslinker and 3.6 wt% photoinitiating system after 240 s irradiation under LED@405 nm. The tensile strength, elongation at break and glass transition temperature of the resultant strippable film were determined to be about 4.4 ± 0.5 MPa, 130 ± 11.2% and 6.9 °C, respectively, by mechanical properties testing and DSC measurements. Also, the decontamination efficiencies (DE) of household LED panel light/sunlight cured-strippable film for uranium nitrate on stainless steel, glass, and ceramic surface were evaluated to be higher than 90%. These results indicate that this rapid-curing strippable films would be a good candidate material for large-scale radioactive decontamination.

A High-Phosphorus-Content Polyphosphonate with Combined Phosphorus Structures for Flame Retardant PET

A high-phosphorus-content polyphosphonate (PBDA), containing two phosphorus-based structures: phosphaphenanthrene (DOPO) and phenyl phosphonate groups, was synthesized and used in flame retardant polyethylene terephthalate (PET). Good self-extinguishing property (high UL 94 grade and LOI value), superior flame retardancy (lower heat/smoke release), and high quality retention (high carbon residue) were endowed to PET by PBDA. When 10 wt% PDBA was added, the peak heat release rate (pHRR), total heat release (THR), and total smoke rate (TSR) of PDBA/PET were found to be significantly reduced by 80%, 60.5%, and 21%, respectively, compared to the pure PET, and the LOI value jumped from 20.5% for pure PET to 28.7% with a UL-94 V-0 rating. The flame-retardant mode of action in PET was verified by thermogravimetric analysis-Fourier transform infrared (TGA-FTIR), pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), real-time FTIR, and scanning electron microscopy (SEM). Phosphaphenanthrene and phosphonate moieties in PDBA decomposed in sequence during heating, continuously releasing and keeping high-content PO· and PO2· radicals with a quenching effect and simultaneously promoting the formation of viscous crosslinked char layers causing a high barrier effect. PDBA mainly acted in the gas phase but the condensed-phase flame retardant function was also considerable.

A route to high-solid coatings: Hydrophobic polyurethane triazoles via bulk polymerization of azide-alkyne cycloaddition

In the present study, we showcase a series bulk polymerized siloxane-decorated polyurethane triazole coatings (Si-PUTs) achieved via azide-alkyne cycloaddition with excellent surface hydrophobicity and anti-corrosion properties. A simple functional modification converts aminopropyl trimethoxy silane to a dialkyne terminated monomer under mild conditions. Concurrently, a series of azide-terminated urethane monomers were synthesized by reacting azidoethanol with three common diisocyanates. Structural elucidation of the monomers was accomplished by FT-IR, 1H and 13C NMR along with ESI-MS. The azide-/alkyne- terminated monomer pairs undergo cycloaddition in absence of solvent and catalyst-free conditions to yield highly crosslinked siloxane-decorated polyurethane (Si-PUT) matrices post curing. FTIR and XPS analysis confirmed the successful formation of these Si-PUTs while the cure kinetics and reaction order was investigated by real-time FTIR. The physico-chemical properties of the polymers achieved were comprehensively assessed prior to evaluating their performance and feasibility as corrosion resistive coatings. The high contact angles in excess of 110°, transparency >85 % in the visible region, low Icorr, high polarization resistance, and corrosion rates in the order of 10−4 mm/year, all underscores the promise of Si-PUTs as excellent corrosion protection coatings. The encouraging results and ease of application demonstrate the potential to formulate environment friendly and multifunctional high-solid protective coatings.

Photoinitiator or photosensitizer? Dual behaviour of m-terphenyls in photopolymerization processes

A series of eight m-terphenyl-based compounds functionalized with amino, diethylamino, piperidine, and pyrrolidine moieties were synthesized and investigated for the first time as one-component free-radical photoinitiators for acrylate and methacrylate monomers. Developed compounds were also applied as photosensitizers of iodonium salt in two-component initiating systems for free radical and cationic photopolymerization. That is why they are excellent for hybrid polymerization e.g. synthesis of interpenetrating polymer networks (IPN). The mechanical properties of produced IPN samples were measured. We investigated the effect of the amine group modification and the presence of one or two bromine atoms on the photophysical and electrochemical properties of the m-terphenyls and their consequent efficiency in polymerization processes. Two bromine substituents in the molecule slightly shift the absorption spectrum towards longer wavelengths in comparison to a compound with one bromine atom. Functionalization of amine group by the introduction of alkyl moieties strongly affects absorption properties, the wavelength corresponding with the maximum absorption values increases in the following order: amine group > diethylamine group > piperidine group > pyrrolidine group. Investigated compounds were found to be efficient in photoinitiating systems for free-radical, cationic, and hybrid photopolymerization, kinetic of polymerization processes with the use of different monomers were followed using real-time FT IR methodology. Moreover, the chemical mechanism was investigated using photolysis and ESR experiments. Developed photoinitiators were also applied for laser writing experiments. In the next step, the key printing parameters were settled, the critical energy necessary to initiate polymerization (Ec) and penetration depth of curing light (Dp), and studied systems were applied for resin used for LCD-based 3d printing.

Sustainable approach for coating production: Room temperature curing of diglycidyl furfuryl amine and itaconic acid with UV-induced thiol-ene surface post-functionalization

In this work, diglycidyl furfuryl amine (DGFA) is synthesized towards the production of a functional coating. With the aim to reduce the energy consumption during processing, a room temperature (RT) curing of the epoxy monomer is performed in presence of bio-based itaconic acid (IA). The RT curing process was demonstrated by means of DSC, rheology, and real-time ATR FTIR and the thermo-mechanical properties were investigated by DMTA. As last step, the properties of the coating surface were modified via an UV-induced thiol-ene reaction between the CC double bonds from itaconic acid moieties and fluorine-based monomers. The surface functionalization was investigated by contact angle measurements and XPS analysis.

UV curing behavior of a liquid polyborosilazane and stereolithography to SiBCN ceramic components

The ultraviolet (UV) curing behavior and kinetics both in air and in nitrogen atmosphere of a liquid polyborosilazane were investigated by differential scanning photo calorimeter (DPC) measurement and real-time FTIR techniques. The results showed that the bifunctional acrylic reactive diluent tripropylene glycol diacrylate (TPGDA) content, photo-initiator concentration, and temperature had their optimal values to get the maximum ultimate reaction rate and conversion percentage. It's noteworthy that the addition of TPGDA will greatly enhance polymerization rate and conversion percentage within a very short time-frame. While the rate in air is higher than in nitrogen atmosphere, probably owing to the effect of oxidation curing, which is coordinated with the calculation results of activation energy.Based on the above experiment, we also report on the direct fabrication of SiBCN ceramic components from preceramic polyborosilazanes by stereolithography and subsequent pyrolysis at 900 ○C for 4 h. The TGA curve shows the ceramic yield is 51.1% after pyrolysis at 1200 ○C. A linear shrinkage of 27%, associated with the polymer-to-ceramic conversion, was observable and the density of pyrolyzed SiBCN is about 2 g cm−3 with slight residual porosity. The indentation hardness is 9.83 GPa and the modulus is 77.1 GPa after heat-treatment at 1400 ○C for 3 h.