Absorption Bands Research Articles

Chemical evaluation and bioactivity of humic substances isolated from the mangrove ecosystem

Mangroves are an ecosystem that features dark colored sediment, rich in organic matter, with humic substances as its main component, which were the target of this work that aimed to characterize those humic substances chemically and spectroscopically and compare the biological activity of different humic materials isolated from mangrove areas with different levels of anthropic interference (Maria Ortiz high and Canal dos Escravos low). The chemical and spectroscopic characterization of the humic materials was performed through the analysis of elemental composition, E4/E6 ratio, fluorescence intensity and infrared and their biological activity was tested by evaluating changes in the root growth of corn seedlings in hydroponics. The humic materials, from the Maria Ortiz area, presented higher values in the C/N ratio, higher values in the fluorescence index and lower values in the E4/E6 ratio, when compared with the humic materials from the area of Canal dos Escravos. The absorption bands of the infrared spectrum indicated similarities with respect to the chemical functionality of the humic materials, however, it was possible to notice clear differences between the study areas. All humic materials promoted, in general, changes in the root architecture of corn seedlings when compared to the control treatment. This work shows that there are differences in the chemical and spectroscopic characteristics and in the biological activity of the studied humic materials, demonstrating that the anthropic activity alters the quality of the organic matter of the mangrove sediments, which may interfere in the survival and development of the mangrove forests.

Cationite synthesis using anthracene extracted from pyrolysis resin by-products: A sustainable approach for production of efficient metal adsorbent

Keeping sustainable waste management and sustainable economy in view, this study investigated the synthesis of a novel polymethyleneanthracene sulfoacid cationite, derived from anthracene extracted with high efficiency (97 % purity) from pyrolysis resin byproducts (a Ustyurt gas-chemical complex). The successful sulfonation of anthracene yielded a substantial amount of the desired product (22.96 g), with a notable reaction efficiency of 82 %. Infrared spectroscopy confirmed the structure of anthracene and its sulfonated derivative, revealing characteristic absorption bands consistent with those of aromatic compounds. Thermogravimetric analysis revealed the thermal stability of the material at temperatures up to 600 °C. The elemental composition, ascertained through EDS, quantified the elements as carbon (65.43 ± 0.05 %), oxygen (22.44 ± 0.05 %), sodium (4.13 ± 0.01 %), and sulfur (8.00 ± 0.01 %). SEM images revealed a highly porous material structure, which is advantageous for ion exchange applications, particularly metal adsorption. Compared to commercial KU-2–8 cationite, the synthesized material had a lower mass density (650–720 g/dm³), a higher humidity content (62.5 %), and a larger comparative size (4.8 cm³/g). The general static exchange capacitance was 475–490 mg-eqv/g, which is slightly lower than the commercial standard of 500–520 mg-eqv/g. These findings indicate that the synthesized cationite has promising potential for ion exchange applications because of its competitive physical and chemical properties.

Preparation and characterisation of fish skin collagen–chitosan–cinnamon essential oil composite film

SummaryThe composite film with collagen as the main component has been widely used due to its characteristics of non‐toxicity, environmental protection and health. Fish skin, a by‐product of fish, is an excellent source of collagen. Thus, collagen was extracted from an under‐utilised species, Atlantic cod (Gadus morhua) skin, and the composite film of fish skin collagen–chitosan–cinnamon essential oil was prepared by casting. The effects of the ratio of collagen to chitosan (2:8, 4:6, 5:5, 6:4, 8:2) and the concentration of essential oil (0%, 0.1%, 0.2%, 0.3%, and 0.4% (v/v)) on the composite film were studied. The structures of the composite films were analysed using scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and X‐ray diffractometry (XRD). The collagen content of Atlantic cod skin is approximately 50.12%, which is significantly higher than that found in basa fish and Nile tilapia (P < 0.05). The content of hydroxyproline was 4.51%. Analyses of tensile strength, elongation at break, water vapor permeability, and water solubility showed Co4Ch6 (Co:Ch = 4:6) had the optimal comprehensive performance, and Co4Ch6–0.2 (Co4Ch6 with 0.2% CEO) had high water resistance in the high‐humidity environment. As the CEO concentration rose, the composite films' infrared absorption bands were enhanced in amplitude, and the XRD peaks were gradually intensified, indicating the internal crystallinity and, thereby, the opacity of the composite films were improved. The bacteriostasis zones Co4Ch6–0.4 against Escherichia coli and Staphylococcus aureus were 2.02 cm and 1.73 cm, respectively. The DPPH radical scavenging rate of Co4Ch6 rose with the increase in CEO concentration, and the DPPH radical scavenging rate of C04Ch6–0.4 was up to 48.56%. Thus, the composite films prepared from fish skin collagen, chitosan, and cinnamon essential oils have outstanding mechanical properties, barrier ability, and antimicrobial activity and are promising for application in food packaging and storage. In addition, the composite films showed a potential antioxidation ability, which might be used as green bioactive films to preserve nutraceutical products.

Influence of subphase temperature on Langmuir layers and thin films of A3B-type porphyrine derivative

The influence of aqueous subphase temperature on the formation and stability of floating layers of 5-(4-hydroxyphenyl)-10,15,20-tris(4-hexadecyloxyphenyl)porphyrin (P-OH) was investigated using the Langmuir technology. It was found that the increase in the subphase temperature from 1 to 40 °C leads to a loosening of floating layers (an increase in the area per molecule in the floating layer by ∼15% and a decrease in the surface compression modulus by more than two times). The stability of floating layers (i.e., the ability of a floating layer to maintain its area under the action of a constant compressive force) decreases with increasing subphase temperature. It has been shown that the most stable floating layers are formed at subphase temperatures lower than 30 °C. Monolayer films on solid substrates were obtained using the Langmuir-Schafer technique at subphase temperatures of 1, 10, 20, 30, and 40 °C. The surface relief of these films was studied by atomic force microscopy (AFM). The AFM analysis revealed that the films transferred from the aqueous subphase at a temperature of 20 °C had the highest continuity and the lowest roughness. The absorption spectra of the floating layers were obtained, in which a bathochromic shift of the Soret band and Q-bands were registered (by 19 nm at 20 °C) in comparison with chloroform solution spectrum. This shift is a consequence of the strong intermolecular π–π* interaction, resulting in the formation of J-type aggregates. The Soret band in the spectra of the floating layers shifted from 436 to 441 nm with an increase in subphase temperature from 1 to 40 °C. In the absorption spectra of thin films (8 transfers), the indicated shifts of absorption bands as well as a broadening of the Soret band are preserved. The results of this work can be used in the targeted creation of film samples with specific structure and properties.

Extraction, Purification, Sulfated Modification, and Biological Activities of Dandelion Root Polysaccharides.

In this study, polysaccharides were extracted at a rate of 87.5% ± 1.5% from native dandelion roots, and the dandelion root polysaccharides (DRPs) were then chemically modified to obtain sulfated polysaccharides (SDRPs) with a degree of substitution of 1.49 ± 0.07. The effects of modification conditions, physicochemical characterizations, structural characteristics, antioxidant properties, hypoglycemic activity, and proliferative effects on probiotics of DRP derivatives were further investigated. Results showed that the optimum conditions for sulfation of DRPs included esterification reagents (concentrated sulfuric acid: n-butanol) ratio of 3:1, a reaction temperature of 0 °C, a reaction time of 1.5 h, and the involvement of 0.154 g of ammonium sulfate. The DRPs and SDRPs were composed of six monosaccharides, including mannose, glucosamine, rhamnose, glucose, galactose, and arabinose. Based on infrared spectra, the peaks of the characteristic absorption bands of S=O and C-O-S appeared at 1263 cm-1 and 836 cm-1. Compared with DRPs, SDRPs had a significantly lower relative molecular mass and a three-stranded helical structure. NMR analysis showed that sulfated modification mainly occurred on the hydroxyl group at C6. SDRPs underwent a chemical shift to higher field strength, with their characteristic signal peaking in the region of 1.00-1.62 ppm. Scanning electron microscopy (SEM) analysis indicated that the surface morphology of SDRPs was significantly changed. The structure of SDRPs was finer and more fragmented than DRPs. Compared with DRPs, SDRPs showed better free radical scavenging ability, higher Fe2+chelating ability, and stronger inhibition of α-glucosidase and α-amylase. In addition, SDRPs had an excellent promotional effect on the growth of Lactobacillus plantarum 10665 and Lactobacillus acidophilus. Therefore, this study could provide a theoretical basis for the development and utilization of DRPs.

Integrating colorimetry with surface sensitive transducers: Advancing molecular diagnostics in biofluids

Colorimetric sensors are preferred for visually detecting target analytes, but achieving ultra-low detection capabilities for food analysis, environmental samples, and molecular diagnostics is challenging. In this study, we interfaced a purpald-based formaldehyde color sensor (as a model probe reaction) with a surface plasmon gold microarray imaging chip. Such hyphenated surface-sensitive signal-amplifying techniques enabled ultra-low detection in biofluids with a linear range of 10−5 – 0.5 ppm compared to the spectrophotometric narrower linear range of 0.01–1 ppm. The detection limit of 86×10−6 ppm from the hyphenated sensing is 140-fold lower than the detection limit from the spectrophotometric method alone (12×10−3 ppm). The absorbance maximum of the purpald-formaldehyde adduct was 553 nm, with no notable tail overlap between the adduct absorbance band beyond 700 nm and the fixed angle source incident wavelength of 800 nm from the surface plasmon instrument. Hence, the possible adduct thiol-surface plasmon gold surface interaction, affinity, and the higher mass and refractive index changes of the adduct are likely causes of the observed signal amplification. We achieved a formaldehyde sample recovery of 92 % from a diluted serum (a minimally invasive assay method), which was comparable to the results in a buffer solution. Further, we extended to demonstrate in diluted urine sample matrices to be noninvasive bioanalysis and determined the interference from urea that could also form a purpald adduct like formaldehyde. In conclusion, coupling a surface-sensitive transducer with less sensitive colorimetric reactions is promising for molecular diagnostics in real samples and can be broadly extended to any other desired molecular targets and sample matrices.

Porphyrin Photosensitizers into Polysaccharide-Based Biopolymer Hydrogels for Topical Photodynamic Therapy: Physicochemical and Pharmacotechnical Assessments.

Photodynamic therapy (PDT) is an emerging treatment modality that utilizes light-sensitive compounds, known as photosensitizers, to produce reactive oxygen species (ROS) that can selectively destroy malignant or diseased tissues upon light activation. This study investigates the incorporation of two porphyrin structures, 5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.2.) and 5,10,15,20-tetrakis-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.1.), into hydroxypropyl cellulose (HPC) hydrogels for potential use in topical photodynamic therapy (PDT). The structural and compositional properties of the resulting hydrogels were characterized using advanced techniques such as Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic force microscopy (AFM), UV-Visible (UV-Vis) spectroscopy, and fluorescence spectroscopy. FTIR spectra revealed a slight shift of the main characteristic absorption bands corresponding to the porphyrins and their interactions with the HPC matrix, indicating successful incorporation and potential hydrogen bonding. XRD patterns revealed the presence of crystalline domains within the HPC matrix, indicating partial crystallization of the porphyrins dispersed within the amorphous polymer structure. TGA results indicated enhanced thermal stability of the HPC-porphyrin gels compared to 10% HPC gel, with additional weight loss stages corresponding to the thermal degradation of the porphyrins. Rheological analysis showed that the gels exhibited pseudoplastic behavior and thixotropic properties, with minimal impact on the flow properties of HPC by P2.1., but notable changes in viscosity and shear stress with P2.2. incorporation, indicating structural modifications. AFM imaging revealed a homogeneous distribution of porphyrins, and UV-Vis and fluorescence spectroscopy confirmed the retention of their photophysical properties. Pharmacotechnical evaluations showed that the hydrogels possessed suitable mechanical properties, optimal pH, high swelling ratios, and excellent spreadability, making them ideal for topical application. These findings suggest that the porphyrin-incorporated HPC hydrogels have significant potential as effective therapeutic agents for topical applications.

Downhill excitation energy flow in reaction centers of purple bacteria Rhodospirillum rubrum G9

Using femtosecond differential spectroscopy, excitation energy transfer in reaction centers (RCs) of the carotenoidless strain of purple bacteria Rhodospirillum rubrum G9 was studied at room temperature. Excitation and probing of the Qy, Qx and Soret absorption bands of the RCs were carried out by pulses with duration of 25–30 fs. Modeling of ΔA (light – dark) kinetics made it possible to estimate the characteristic time of various stages of excitation energy transformation. It is shown that the dynamics of the downhill energy flow in the RCs is determined both by the internal energy conversion Soret→ Qx → Qy in each cofactor and by the energy transfer H* → B* → P* (H – bacteriopheophytin, B – bacteriochlorophyll a, P – bacteriochlorophyll a dimer) between cofactors. The transfer of energy between the upper excited levels (Soret and Qx) of the cofactors accelerates its arrival to the lower exciton level of the P, from where charge separation begins. It turned out that all conversion and energy transfer processes occur within 40–160 fs: the conversion Soret → Qx occurs in 40–50 fs, the conversion Qx → Qy occurs in 100–140 fs, the transfer H* → B* has a time constant of 80–120 fs, and the transfer B* → P* has a time constant of 130–160 fs. The rate of energy transfer between the upper excited levels is close to the rate of transfer between Qy levels.

Thermotunable mid-infrared metamaterial absorption material based on combined hollow cylindrical VO2 structure

We have designed a metamaterial absorption material based on the VO2 phase transition effect. The aim is to realize thermally tunable broadband absorption in the mid-infrared band. The metamaterial absorption material is a three-layer structure. From top to bottom, the combined hollow cylindrical VO2 resonant layer, the SiO2 dielectric layer and the Ti substrate. In this work, we perform numerical simulations using the three-dimensional time-domain finite element difference method. The simulation shows that the absorption material's average absorption intensity is adjustable by temperature between 0.09 and 0.95. At a temperature of 342 K, the absorption material has an absorption bandwidth of 17.3 μm (6.43 μm to 23.73 μm) with an absorption rate above 90%. And the average absorption in this band range is 94.95%. And this band covers the wavelength of the atmospheric transparency window (8 μm∼14 μm), which suggests that our absorption material has great application prospects. In this work, we first analyze the electromagnetic field at the absorption material's resonant wavelength and explain the absorption material's absorption mechanism. Then, we investigated the absorption effect of the absorption material under the VO2 structure with different temperatures. And we explain temperature's effect on the absorption material's absorption effect by analyzing the electric field's change on the absorption material's surface at different temperatures for the same wavelength. The effect of the absorption material structural parameters on the absorption material absorption performance to determine the optimal structural parameters was then investigated. Finally, we investigate the absorption curves of the absorption material under different columnar VO2 layers and demonstrate the innovative and unique nature of the designed absorption material. The absorption material we designed has a simple structure and is easy to configure. And the absorption material has high average absorption rate and a wide absorption bandwidth. We therefore believe that the metamaterial absorption material has great application prospects in optoelectronic detection, infrared imaging and infrared stealth.

Mechanism of the Terahertz Wave-MXene Interaction and Surface/Interface Chemistry of MXene for Terahertz Absorption and Shielding.

ConspectusOver the past two decades, terahertz (THz) technology has undergone rapid development, driven by advancements and the growing demand for THz applications across various scientific and technological domains. As the cornerstone of THz technology, strong THz-matter interactions, especially realized as high THz intrinsic absorption in nanometer-thick materials, play a highly important role in various applications including but not limited to THz absorption/shielding, detection, etc. The rigorous electromagnetic theory has posited a maximum intrinsic absorption of 50% for electromagnetic waves by thin films, and the succinct impedance matching condition has also been formulated to guide the design of highly intrinsically absorbing materials. However, these theories face challenges when applied to the THz spectrum with an ultrabroad bandwidth. Existing thin films typically achieve a maximum intrinsic absorption within a narrow frequency range, significantly limiting the performance of THz absorbers and detectors. To date, both theoretical frameworks and experimental solutions are lacking in overcoming the challenge of achieving broadband maximum intrinsic absorption in the THz regime.In this Account, we describe how two-dimensional (2D) transition-metal carbide and/or nitride (MXene) films with nanometer thickness can realize the maximum intrinsic absorption in the ultrabroad THz band, which successfully addresses the forementioned longstanding issue. Surprisingly, traditional DC impedance matching theory fails to explain this phenomenon, while we instead propose a novel theory of AC impedance matching to provide a satisfactory explanation. By delving into the microscopic transport behavior of free electrons in MXene, we discover that intraflake transport dominates terahertz conductivity under THz wave excitation, while interflake transport primarily dictates DC conductivity. This not only elucidates the significant disparities between DC and AC impedance in MXenes but also underscores the suitability of AC impedance matching for achieving broadband THz absorption limits. Furthermore, we identify a high electron concentration and short relaxation time as crucial factors for achieving broadband maximum absorption in the THz regime. Although approaching the THz intrinsic absorbing limits, it still faces hurdles to the use of MXene in practical applications. First, diverse and uncontrollable terminations exist on the surface of MXene stemming from the synthesis process, which largely influence the electron structure and THz absorbing property of MXene. Second, MXene suffers from poor stability in the presence of oxygen and water. To address the above issues, we have undertaken distinctive works to precisely control the terminations and suppress the oxidation of MXene even at high temperature through surface and interface chemistry, such as low-temperature Lewis basic halide treatment and building a Ti3C2Tx/extracted bentonite (EB) interface. For practical application consideration, we proposed a copolymer-polyacrylic latex (PAL)-based MXene waterborne paint (MWP) with a strong intermolecular polar interaction between MWP and the substrate provided by the cyano group in PAL. This not only has strong THz EMI shielding/absorption efficiency but also can easily adhere to various substrates that are commonly used in the THz band. These studies may have significant implications for future applications of MXene nanofilms in THz optoelectronic devices.

Adsorption kinetics and thermodynamics of metal complex acid dyes on silk fabric

This study reports the adsorption phenomena of metal complex acid dyes onto silk fabric. Two commercial metal complex acid dyes namely Bestalan Yellow SF and Bestalan Navy SF were adsorbed onto degummed silk fabric. The functional properties and surface morphology of silk fabric were investigated with FT-IR spectroscopy and FE-SEM respectively. The typical absorption band of C = O stretching was found at 1620 cm−1 indicating amide I structure and C-N stretching as well as N-H bending vibrations were observed at 1510 cm−1 suggesting the β-sheet crystallites of amide I and amide II silk proteins. The effectiveness of degumming performance was confirmed by SEM images. The adsorption of dyes by silk fabric was investigated with respect to pH, initial dye bath concentration, and contact time. It was found that the adsorption of dye onto silk fabric was highly influenced by the dye bath pH, initial dye concentration, and contact time. The higher dye adsorption was observed at acidic dye bath condition (pH = 3.5). The adsorption of dye was also increased with the increase of the initial dye bath concentration. The dyes adsorption reached at equilibrium condition after 80 min. The adsorption isotherm and kinetics were also evaluated based on the experimental results. The adsorption pattern fitted well to the Langmuir adsorption isotherm with high correlation coefficient (R 2>0.97) for both dyes. The kinetic parameters suggested that the pseudo-second-order model is more suitable compare to the pseudo-first-order model considering the higher regression coefficients ( R 2 = ∼ 0.99 ) . The maximum adsorption of Bestalan Yellow SF and Bestalan Navy SF was found to be 232.5 and 222.2 mg/g respectively. The thermodynamic data were studied at 25, 40 and 60 °C. The change of Gibbs free energy of the system was positive indicating the spontaneous nature of the adsorption. The values of ΔH (-4.68 kJ/mole −3.65 kJ/mole) suggested the exothermic environment and the negative values of ΔS (-0.035 and −0.034 kJ/mole/k) advocated the good interaction between the metal complex acid dyes and silk fabric. The Langmuir adsorption model and pseudo-second-order kinetic suggested that the dyeing of metal complex acid dyes on silk fabric was controlled by ion-exchange chemical reaction.

Photoluminescence of polysiloxane-immobilized lignin-modified wood toward color-tunable and ultraviolet protective smart window

Smart windows can benefit from the use of photochromic wooden materials. In the current study, we report the preparation of fluorescent wood that can switch color under visible and ultraviolet lighting conditions. In order to develop a transparent wood that is both fluorescent and photochromic, a mixture of europium and dysprosium activated strontium aluminum oxide (EDSA) nanoparticles (NPs; 8–13 nm) and room-temperature vulcanizing (RTV) silicone rubber (Polysiloxane) was integrated into a delignified wood. EDSA is known for its excellent photostability and thermal stability. The EDSA phosphor has to be efficiently dispersed in RTV to avoid the formation of aggregates, allowing for a better fabrication of colorless wood. The coloration findings from the CIE Lab parameters displayed that when illuminated with ultraviolet rays, this colorless wooden substrate turned green. Using a transmission electron microscope (TEM), the morphological properties of the synthesized EDSA NPs were examined. Various analysis techniques, including elemental mapping, energy-dispersive X-ray (EDX), X-ray fluorescence spectroscopic analyzer (WDXRF), scanning electron microscope (SEM), hardness testing, and photoluminescence spectra, were employed to study the photochromic woods. An absorption band (365 nm) and two emission bands (436 nm and 518 nm) were determined for the prepared photoluminescent woods. When increasing the EDSA content, the results showed that the produced EDSA-infiltrated wood was more water-resistant and highly protective against UV radiation. Reversible photochromic responsiveness to UV light was observed for the prepared transparent luminous wood without fatigue.

First principle insights on optoelectronic, mechanical, and thermoelectric properties of double perovskites Li2ScAu (Br/I)6 for energy harvesting applications

Li-based double perovskites (DPs) are extensively studied due to their potential applications for solar cells and thermoelectric devices. In the current paper, I have explored the electronic, optical, transport, and mechanical properties of Li2ScAu (Br/I)6 by density functional theory (DFT) based calculations. The tolerance factor and Born Criteria have been assumed for structural and mechanical stability. In contrast, energy and phonons band structures are examined for thermodynamic and dynamic (Lattice vibration) stabilities. The band gaps of 1.96 eV and 1.42 eV for Li2ScAuBr6 and Li2ScAuI6 fall the absorption bands in the visible zone. The optical characteristics are addressed in the energy range of 0–5.0 eV. The low lattice thermal conductivity, large Seebeck coefficient, and electrical conductivity enhance the figure of merit (ZT) scale that increasse their importance for thermoelectric generators.

An unusual CAr^CNHC- and bidentate NAr^CNHC-cyclometalated Re(I)-NHC complexes with quinoline-functionalized ligands: Syntheses, structures, and blue-luminescent properties

An unusual CAr^CNHC-cyclometalated rhenium(I) tetracarbonyl complexes fac- (CAr^CNHC)Re(CO)4 (13) (the first report) and six NAr^CNHC-cyclometalated rhenium(I) tricarbonyl iodide/chloride complexes with quinoline-functionalized N-heterocyclic carbenes (NHC), fac-Re(CO)3(LNHC)I / fac-Re(CO)3(LNHC)Cl (LNHC = 1-(quinolin-8-yl)-3-methyl-1H-imidazol-2-ylidene (4, 10); 1-(quinolin-8-yl)-4-methyl-1H-1,2,4-triazoline-5-ylidene (5, 11); 1-(quinolin-8-yl)-3-benzyl-1H-imidazol-2-ylidene (6, 12) have been synthesized under controllable reaction conditions and characterized by their 1H NMR, 13C NMR, ESI–MS, IR spectra, and single-crystal X-ray diffraction analysis. X-ray crystallography revealed that the Re(I)-NHC complex 13 is a rare five-member bidentate CAr^CNHC-cyclometalated structure containing the coplanar system of quinoline and imidazole ring with a dihedral angle of 7.6°. The density functional theory (DFT) calculations also indicated that the blue shift of 50 nm for the MLCT absorption band of 13 is in good agreement with the coplanar five-member cyclometalated structure and the Re(I)-NHC complex 10 is a thermodynamic product. Seven Re(I)-NHC complexes exhibit photoluminescence emission in the blue region (410–470 nm) with relatively short decay lifetime on the nanosecond time scale, and high quantum yields of the Re(I)-NHC complexes 5 (Φ = 0.558) and 6 (Φ = 0.629) based-triazole were calculated by using [Ru(bpy)3](PF6)2 in degassed acetonitrile solution (Φstd = 0.062) as standard, due to the coordination of quinoline rings, NHC ligands to Re(I) center.

A study on the surface responses and degradation mechanisms of epoxy-amine coating subjected to UV accelerated weathering and hygrothermal ageing using ToF-SIMS and FTIR analysis

Epoxy amine coatings were subjected to hygrothermal ageing and accelerated weathering conditions that is comprised of neutral salt spray test and UV accelerated degradation condition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to study the surface responses and spectral variation of epoxy amine coatings subjected to different ageing conditions. As a result, principal component analysis (PCA) of ToF-SIMS positive ion spectra illustrated that principal component 1 (PC1) has collected information on a variation of surface responses caused by accelerated weathering and hygrothermal ageing conditions as compared to fresh epoxy amine coatings. On the other hand, principal component 2 (PC2) has distinguished the different surface responses generated on epoxy amine coatings that were subjected to UV accelerated degradation conditions and those that were not. FTIR analysis has demonstrated the hydrolysis and photooxidation of epoxy amine coatings from the growth of two absorption bands at 1709 cm−1 and 1650 cm−1, indicating the formation of carbonyl-containing groups such as ketones, aldehydes, phenyl formates, imine or tertiary amides. This comprehensive analysis provides significant insights into the degradation mechanisms of epoxy amine coatings subjected to corrosion under insulation (CUI) and/or artificial weathering (AW) environment. Understanding these mechanisms is pivotal for industries reliant on epoxy coatings, such as oil and gas, ensuring enhanced performance and extended lifespan of their products under varying environmental conditions. The findings also contribute to the broader field of materials science by offering methodologies and analytical approaches that can be applied to other polymeric coatings and materials.

Regulating the luminescence properties of Eu2W3O12 red-emitting phosphor via rare-earth ions doping for optical thermometry, white light-emitting diode and plant growth applications

To fulfil various applications, series of rare-earth (RE) ions (i.e., La3+, Gd3+, Sm3+) doped Eu2W3O12 (EWO) phosphors were synthesized. All the designed phosphors can emit glaring visible lights from Eu3+ and their fluorescence intensities were significantly enhanced through RE ions doping. To explore the impact of RE ions doping on the symmetric properties of Eu3+ in studied samples, theoretical calculation based on Judd-Ofelt theory was performed. Moreover, through utilizing temperature-related emission spectra, the thermal quenching behaviors of resultant phosphors were studied and found that their thermal stability had been improved by adding RE ions. Furthermore, the thermometric properties of designed phosphors were examined through adopting the single-band ratiometric technique to analyzing the temperature-dependent fluorescence intensity ratio of the emission band arising from 5D0 → 7F2 transition of Eu3+. It is found that maximum absolute and relative sensitivities of resulting phosphors were 0.197 and 1.202 % K−1, respectively. Additionally, two types of devices, i.e., white light-emitting diode (white-LED) and red-emitting LED, where the prepared phosphors play as red-emitting components, were fabricated. The packaged white-LEDs can emit warm white light with high color rendering index and low correlated color temperature, which are insensitive to operating current. Considering the red-emitting LEDs, their emission bands overlap with the absorption bands of plant pigments, which can promote plant growth and it was verified by peppermint growth experiments. These results verify that the introduction of RE ions is a feasible approach to modify the luminescence performances of phosphors to realize diversified applications.

BF2‐Bridged Azafulvene Dimer‐Based 1064 nm Laser‐Driven Superior Photothermal Agent for Deep‐Seated Tumor Therapy

AbstractSmall organic photothermal agents (PTAs) with absorption bands located in the second near‐infrared (NIR‐II, 1000–1700 nm) window are highly desirable for effectively combating deep‐seated tumors. However, the rarely reported NIR‐II absorbing PTAs still suffer from a low molar extinction coefficient (MEC, ϵ), inadequate chemostability and photostability, as well as the high light power density required during the therapeutic process. Herein, we developed a series of boron difluoride bridged azafulvene dimer acceptor‐integrated small organic PTAs. The B‐N coordination bonds in the π‐conjugated azafulvene dimer backbone endow it the strong electron‐withdrawing ability, facilitating the vigorous donor‐acceptor‐donor (D‐A‐D) structure PTAs with NIR‐II absorption. Notably, the PTA namely OTTBF shows high MEC (7.21×104 M−1 cm−1), ultrahigh chemo‐ and photo‐stability. After encapsulated into water‐dispersible nanoparticles, OTTBF NPs can achieve remarkable photothermal conversion effect under 1064 nm irradiation with a light density as low as 0.7 W cm−2, which is the lowest reported NIR‐II light power used in PTT process as we know. Furthermore, OTTBF NPs have been successfully applied for in vitro and in vivo deep‐seated cancer treatments under 1064 nm laser. This study provides an insight into the future exploration of versatile D‐A‐D structured NIR‐II absorption organic PTAs for biomedical applications.

BF2-Bridged Azafulvene Dimer-Based 1064 nm Laser-Driven Superior Photothermal Agent for Deep-Seated Tumor Therapy.

Small organic photothermal agents (PTAs) with absorption bands located in the second near-infrared (NIR-II, 1000-1700 nm) window are highly desirable for effectively combating deep-seated tumors. However, the rarely reported NIR-II absorbing PTAs still suffer from a low molar extinction coefficient (MEC, ϵ), inadequate chemostability and photostability, as well as the high light power density required during the therapeutic process. Herein, we developed a series of boron difluoride bridged azafulvene dimer acceptor-integrated small organic PTAs. The B-N coordination bonds in the π-conjugated azafulvene dimer backbone endow it the strong electron-withdrawing ability, facilitating the vigorous donor-acceptor-donor (D-A-D) structure PTAs with NIR-II absorption. Notably, the PTA namely OTTBF shows high MEC (7.21×104 M-1 cm-1), ultrahigh chemo- and photo-stability. After encapsulated into water-dispersible nanoparticles, OTTBF NPs can achieve remarkable photothermal conversion effect under 1064 nm irradiation with a light density as low as 0.7 W cm-2, which is the lowest reported NIR-II light power used in PTT process as we know. Furthermore, OTTBF NPs have been successfully applied for in vitro and in vivo deep-seated cancer treatments under 1064 nm laser. This study provides an insight into the future exploration of versatile D-A-D structured NIR-II absorption organic PTAs for biomedical applications.

A highly emissive near infrared thiophene-benzoindolium ligand binding to mitochondrial G-quadruplexes triggers triple-negative breast cancer cell death

Small-molecule fluorescent ligands targeting mitochondrial G-quadruplexes (mtG4s) are considered as a promising direction in tumor therapy, especially those with dual roles of both detecting the mtG4 structures and interfering with the mtG4 functions. Herein, based on our previous studies, two novel thiophene-benzoindolium ligands (YS-1 and YS-2) were designed and synthesized. One of them, YS-2, may be a potential NIR fluorescent probe, with an absorption band centered at 595 nm and an emission band centered at 685 nm, as well as a good quantum yield upon binding G4s. YS-2 was further proved to selectively bind to mtG4s in MDA-MB-231 cells, and then induce mitochondrial dysfunction, showing suppressive effects on the proliferation of tumor cells in both 2D and 3D cell models. To sum up, a novel highly emissive NIR ligand binding to mtG4s was successfully discovered, giving insights into the future development of novel G4 fluorescent ligands targeting mtG4s with therapeutic possibilities against tumors.

Enhanced photocatalytic degradation of methylene blue dye using CuO nanoparticles from the fruit extracts of Diplocyclos palmatus (L) C. Jeffrey for wastewater remediation

ABSTRACT The degradation of synthetic organic dyes through photocatalysis requires structured nanoparticles (NPs). Copper oxide (CuO) NPs were used as the newest developed catalyst for the organic dye degradation under the irradiation of sunlight: The metal oxide NPs were synthesized using the fruit extract of Diplocyclos palmatus (L) C. Jeffrey. UV–visible light spectra showed an absorption band for CuO NPs at 277 nm. X-ray diffraction confirmed the monoclinic phase of CuO NPs. Scanning electron microscopy confirmed rod-shaped stacked particles. Energy-dispersive X-ray spectra indicating the presence of Cu in oxide form. For the degradation of methylene blue dye (MB), CuO NPs were used as photocatalyst for dye degradation under sunlight irradiation. This study confirmed the effects, such as irradiation time, concentration, pH, and catalyst dosage. The CuO NPs showed high photocatalytic degradation, degrading 90% of the dye in 120 min. The increased degradation of dye was observed on exposure to longer irradiation time. The increased concentration of dye resulted in a decreased rate of photodegradation. 95% degradation achieved at pH 9 showing that the pH medium also enhances the degradation. A higher dye degradation percentage was achieved by increasing the higher catalyst dosage of 0.013 g degraded 93% of dye. Thus in the treatment of wastewater containing pollutants, the synthesized CuO NPs acted as an efficient photocatalyst.