Light Absorption Research Articles

Construction of bilayer cellulose-based aerogel with salt-resistant design for efficient solar desalination and wastewater purification

Solar-driven interfacial evaporation (SDIE) technology, which utilizes green and renewable solar energy to produce clean water, has shown great potential in alleviating global water scarcity. However, practical applications still face numerous challenges, including salt crystallization precipitation and accumulation, low energy utilization, and complex preparation processes. Hence, We designed a vertically ordered porous bilayer aerogel based on nanofibrillated cellulose (NFC)/polyethyleneimine (PEI) with excellent salt resistance, light absorption and local thermal effects to achieve efficient solar steam generation. Specifically, the photothermal conversion layer (PCL) at the top had excellent light absorption and photothermal conversion efficiency by introducing graphene oxide (GO) as a highly efficient photothermal material. The water transport layer (WTL) at the bottom ensured a stable water supply to the evaporation layer by virtue of the vertical water transfer path and inherent hydrophilicity, and effectively prevented formation of salts in the evaporation area. In addition, the designed aerogel had a low thermal conductivity, which achieved effective thermal insulation and further enhanced the localized heating effect. This superhydrophilic bilayer aerogel achieved a high evaporation rate of 1.9596 kg m−2h−1 and an energy conversion efficiency of 92.28 % under one solar irradiation. It is noteworthy that evaporation process exhibited excellent stability during 8 h of continuous evaporation in 20 wt% brine and no salt accumulation was observed on the evaporated surface. In addition, the bilayer aerogel demonstrated excellent long-term stability and self-cleaning. Meanwhile, its excellent anti-contamination and wastewater treatment capabilities give SDIE technology a stable and continuous operation in practical applications, thus demonstrating significant application potential.

High light and nitrogen deficiency synergistically lead to biofuel and biomass accumulation in diatoms

As a clean energy source, the lipids from microalgae serve as alternatives to fossil oils. There are significant differences in the biofuel and biomass accumulation of microalgae under different environmental conditions. This study investigated the response of biofuel accumulation, photosynthetic capacity, and growth of diatom Thalassiosira pseudonana under stress conditions of high light and nitrogen deficiency, aiming to explore the features of biofuel and biomass accumulation in microalgae under special environmental conditions. The results indicated that the synthesis of chlorophyll was inhibited, leading to reduced light absorption and less damage to the photosynthetic system, with an improvement in electron transport efficiency. Lipid metabolism was more active during the dark cycle, with a 2.89-fold accumulation of fatty acids and a significant increase in the content of neutral lipids (2.39 times). The cell cycle progressed faster, resulting in a marked increase in biomass (1.41 times). These processes consumed a considerable amount of energy, affecting the synthesis of ribosomes. These findings suggest that increasing light exposure and reducing nitrogen supply can achieve the co-accumulation of biofuel and biomass in T. pseudonana.

Synergetic integration of photothermal and self-cleaning features in a composite phase change material based on layered double hydroxides and polypyrrole

Composite phase change materials (PCMs) with photothermal functionality play a crucial role in efficiently storing and utilizing solar energy. However, the challenge of effectively removing of contaminants on photothermal conversion coatings has long puzzled researchers. In this study, we propose a novel approach to enhancing both photothermal conversion performance and self-cleaning properties of wood-based composite phase change materials, ultimately facilitating the sustainable and effective utilization of solar energy. The method utilized metal-organic frameworks (MOFs) as a precursor to form rough layered double hydroxides (LDH) on the wood surface through hydrolysis-induced exchange. Subsequently, polypyrrole (PPy) was deposited through vapor phase onto the LDH, and paraffin wax (PW) is utilized as the phase change material to prepare a novel composite phase change material. This modified wood structure facilitates leak-proof PW encapsulation and effective heat storage (167.6 J/g). PPy acts as a proficient photothermal converter and improves the composite material's heat transfer efficiency by establishing thermal conduction pathways, resulting in an 87.4 % enhancement in thermal conductivity compared to pure PW. The rough surface of LDH promotes multiple light reflections and scattering within the material, leading to increased light absorption by the PPy coating and achieving a photothermal conversion efficiency of up to 96.4 %. Furthermore, the high roughness of the LDH layer combined with the low surface energy of PW imparts superhydrophobic self-cleaning properties to the material, ensuring sustained effectiveness of the photothermal conversion coating over time. This research presents a viable approach for maintaining the cleanliness and efficiency of solar energy systems.

Efficient Photocatalytic H2 Evolution over CuCo2S4 Decorated ZnIn2S4 with S-scheme Charge Seperation Way

The construction of an S-scheme heterojunction can facilitate the separation and utilization of photogenerated charges, as well as reserve the reducing power of electrons to induce proton reduction for H2 evolution. In this study, CuCo2S4 nanoparticles and ZnIn2S4 nanoflowers were both synthesized via a hydrothermal method, and then CuCo2S4 was employed to decorate ZnIn2S4 to form CuCo2S4/ZnIn2S4 heterojunction through a simple physical solvent evaporation strategy. The experiment result shows that the rate of photocatalytic H2 evolution (rH2) over 10 wt.% CuCo2S4/ZnIn2S4 can reach up to 20421.3 μmol·g-1·h-1, which is 4.0 times that of ZnIn2S4 (5062.5 μmol·g-1·h-1) and 144.6 times that of CuCo2S4 (141.2 μmol·g-1·h-1). The improved activity results from the establishment of an S-scheme charge transfer way between CuCo2S4 and ZnIn2S4, which facilitates efficient charge separation while preserving active e- and h+. Besides, the formation of the heterojunction broadens the range of light absorption, promotes charge carrier generation, reduces charge transfer impedance, and increases electrochemically active surface area, these together lead to faster H2 evolution kinetics. The present study demonstrates the potential of bimetallic sulfides as a promising catalyst for construction ZnIn2S4-based photocatalysts for efficient solar conversion.

Lead-free Polymer Composite Film for Photon Energy Influenced Piezoelectric Nanogenerator based on Photoactive SnS2

Piezoelectric nanogenerators (PENGs) can power microelectronics, which convert weak mechanical vibrations to electrical impulses; however, low output voltage and poor mechanical durability limit PENG use. Thus, we provide photoactive SnS2 nanofillers in a PVDF matrix for piezoelectric nanogenerators (PPENGs). Raman spectroscopy demonstrates improvement of the electroactive β-phase of PVDF due to adding photoactive hexagonal SnS2 nanoparticles with a band gap of 2.4 eV. Sandwiching the PVDF-SnS2 composite between ITO-coated substrates with silver paste contacts fabricated the PPENG. The open-circuit voltage of PPENG is 24.4 V in the dark and 72.9 V under illumination with a short-circuit current of 0.75 μA, showing its outstanding photo responsiveness. The high light absorption of SnS2 and PVDF-SnS2 interfacial polarization caused the improved response. High-performance optoelectronic and energy harvesting applications may employ this photoactive piezoelectric nanogenerator development technique.

UV Aging Resistance Improvement of SBS Modified Asphalt Binder by Organic Layered Double Hydroxide and Naphthenic Oil: Its Preparation, Properties and Mechanism

To enhance the UV aging resistance of SBS modified asphalt, LDHs and naphthenic oil were selected to modify it compositely. Firstly, organic treatment for LDHs was carried out through the combination of surface modification method and intercalation modification method to improve its compatibility with asphalt, and effectiveness of organic treatment was evaluated through the microscopic testing methods. Then, the organic LDHs/SBS modified asphalt binders were developed by melt blending method, on this basis, appropriate naphthenic oil was added for composite modification. Subsequently, the conventional physical properties, storage stability and rheological properties tests were carried out to evaluate the comprehensive properties of the prepared modified asphalt containing LDHs and naphthenic oil. On this basis, TOPSIS method was conducted for multi-index optimization to determine the optimal dosages of LDHs and naphthenic oil. Finally, UV aging resistance of the developed modified asphalt was also evaluated, and reaction mechanism was explored with FTIR and FM. Test results show that stearic acid (SA) was successfully absorbed on the surface of LDHs, and -SO32- in ultraviolet light absorber (UVT) has successfully entered the interlayer galleries of LDHs, thus achieving the organic treatment for LDHs. Organic LDHs can significantly improve the high temperature properties and storage stability of SBS modified asphalt, and naphthenic oil can also improve the storage stability of SBS modified asphalt at the proper dosage. In addition, the two modifiers can both effectively improve the UV aging resistance of SBS modified asphalt. Based on the multi-index optimization results, it is recommended that the optimal dosages of LDHs and naphthenic oil are 2% and 2.5%, respectively, and at this conditions, comprehensive properties of the prepared modified asphalt can achieve the best. Microstructure characterization tests results reveal that LDHs and naphthenic oil are only simply dispersed in asphalt and do not cause the structural damage of SBS modified asphalt. Meanwhile, the special layered structure of LDHs can hinder the mobility of asphalt molecular chains, which enhances the interaction force between asphalt molecular chains and SBS modifier molecular chains, thus improving the road properties of SBS modified asphalt.

Nanoscale grating-based perovskite solar cell with Improved efficiency

Abstract MAPbI3 perovskite-based solar cell (PSC) has received widespread attention in later years due to its high absorption. However, the top flat electrode affects badly the light received to the absorber layer with reduced efficiency. In this paper, the influence of texturing the top FTO electrode surface with a triangular saw-tooth grating on both the optical and electrical performance of the studied PSC is studied. Interference effects are considered by modeling the PSC structure as a Fabry–Perot resonator. In this regard, the finite difference time domain method is utilized to precisely simulate the optical characteristics of the nano-structural design. The geometrical parameters of the triangular grating (TG) are optically studied to maximize the light absorption. Furthermore, the effect of absorber thickness on the optoelectronic performance is investigated. To estimate the conversion efficiency (η) of the reported PSC structure, the bulk and Langevin recombination mechanisms are taking into account. The proposed grating enhances the light coupling and hence the light absorption and the generated current density are enlarged. At the absorber thickness of 350 nm, maximum η of 19.5 % is achieved for the proposed TG structure with an enhancement of 19.6% compared to the structure with flat FTO layer. Accordingly, the simulation results could be useful for further understanding and improving the physical behavior of MAPbI3 based PSC.

Enhancing photocatalytic activity via formation of heterojunctions introduced through postmetalation of metal organic frameworks with silver ions

The postmetalation of silver in zinc and manganese-based metal–organic frameworks (MOFs) represents a versatile and efficient approach for enhancing the degradation of methylene blue (MB) pollutant in aqueous environment. In the present study, zinc, manganese, and their bimetallic MOFs are synthesized using the solvothermal method. Subsequently, silver ions are incorporated into the synthesized MOFs. A suite of characterization techniques is employed to analyze the resulting material. Among the three silver loaded MOFs, Ag-mixed bimetallic MOF (Ag-BM) exhibits the least band gap of 2.28 eV, possessing a greater propensity for light absorption. The particle size of Ag-BM lies in the nanometer range, and it possesses the largest surface area. X-ray diffraction depicts the successful integration of Ag into MOF structure. The synthesized samples are used for degrading MB. Ag-BM outperforms the other MOFs in decomposing MB, with a degradation percentage of 91.8% in 120 min. The degradation process follows the first-order kinetics depicting that the rate of degradation positively correlates with the dye concentration remaining in the solution. Employing a reactive species quenching experiment with scavengers, hydroxyl radicals were identified as the principal active species responsible for MB degradation by Ag-BM.

Plasmonic effect of gold nanoparticles on rear side of flexible black silicon wafer fabricated by aluminum-assisted chemical etching

In this work, we investigate the effects of the different sizes of gold (Au) plasmonic nanoparticles (NPs) on the rear surface of flexible black silicon (b-Si) wafer. The flexible b-Si (65 μm thickness) is fabricated by aluminum-assisted chemical etching (AACE) process, utilizing aluminum (Al) as the catalyst. After the b-Si fabrication, nanopores are produced on the flexible wafer surface. Then, gold nanoparticles (Au NPs) are spin-coated on the rear side of the flexible b-Si, followed by surface morphological and optical characterizations. The Au NPs with sizes of 24–92 nm have been deposited on the rear surface of the b-Si wafer. Based on the optical characterization, light absorbance increases above wavelength 800 nm due to enhanced light scattering by the Au NPs at the back surface. The average reflectance (Rave) is calculated in the 300 nm–1100 nm wavelength range for flexible crystalline silicon (c-Si) reference and compared with flexible b-Si surface and flexible b-Si/Au NPs. The lowest Rave of 15.4% is achieved for Au NPs with average size of 92 nm.

Synthesis, Structure, and Light Absorption of Octanoyl Amino Acids

Amino acid lanthanide complexes are a promising class of environmentally friendly and non-toxic optical organic materials that find extensive applications in biomedicine, molecular probes, and optical devices. In this study, three amino acid lanthanide complexes, octanoyl glycine gadolinium (Gd(oct-ala)3×H2O), octanoyl serine gadolinium (Gd(oct-ser)3×H2O), and octanoyl phenylalanine gadolinium (Gd(oct-phe)3×H2O), were synthesized by reacting octanoyl amino acid ligands with gadolinium chloride. The coordination structure of the gadolinium complexes was determined by elemental analysis and infrared spectroscopy. XRD and polarized light microscopy confirmed the amorphous structure of the complexes. DSC and TG-DTA were used to investigate the thermodynamic stability of the gadolinium complexes, and their solubility and UV-visible light absorption properties were also evaluated. Our results demonstrate that all three gadolinium complexes exhibit excellent UV-visible light absorption performance, with the Gd(oct-phe)3×H2O containing a phenyl ring showing the highest light absorption efficiency.

Effect of Cu/Bi ratio on the Photoelectrochemical Performance of CuBi2O4/CuO Nanocomposite Films for CO2 Reduction

Abstract Solar energy is free, clean, and virtually limitless; however, its conversion into a storable form presents technological challenges. One avenue towards solar energy utilization is the photoelectrochemical (PEC) reduction of CO2 to one- or two-carbon fuels, employing a semiconductor configured as an electrode. A potential material for this application is the p-type copper bismuth oxide (CuBi2O4) with a band gap capable of visible light absorption and a conduction band edge position suitable for CO2 reduction. In this study, CuBi2O4 nanocomposite films of varying Cu/Bi ratios (0.25, 0.51, 0.68, 0.94, 2.04) were prepared via an electrodeposition-spray deposition-annealing route. Where the Cu/Bi ratio exceeded the stoichiometric value of 0.5, a bilayered film composed of a copper (II) oxide (CuO) phase on top of CuBi2O4 was formed, creating a planar heterojunction between the two oxide layers. With increasing Cu/Bi ratio, the light absorption range of the films broadened due to the CuO phase. Analysis of the photocurrent-potential behavior of the films under visible-light illumination showed a 4–7-fold increase in the photocurrent from an inert electrolyte to a CO2-saturated electrolyte, confirming potential activity for CO2 reduction of the CuBi2O4/CuO films. A higher Cu/Bi ratio resulted to an improved charge separation efficiency, enhancing the photocurrent generation. However, the transient photocurrent response of the films showed a 70-80% decrease in the photocurrent after only 15 mins of testing. When tested in an electrolyte with an electron scavenger, the percent decrease was lowered to <10%, indicating that the instability of the films resulted from poor interfacial kinetics. While the CuBi2O4/CuO nanocomposite films can accomplish CO2 reduction, further strategies to improve their efficiency and stability are needed to realize practical application.

The Effect of the Number of Precursor Spin-Coating on the Properties of Sb<sub>2</sub>(S,Se)<sub>3</sub> Thin Film

Preparing of Sb2S3 precursor by sol gel method and the post selenization is a simple and low-cost method for preparing Sb2(S, Se)3. In the preparation process of this method, the number of spin-coating of Sb2S3 precursor determines the film thickness, structure, and S/Se ratio. In this work, the effects of different spin-coating times (1 to 5) on the structure, optical and electrical properties of the film were studied. The results showed that when the number of spin-coating increased from 1 to 5, the thickness of the film increased from 0.24 μm to 1.17 μm. When spin-coating twice, the strongest diffraction peak of the film changed from (120) to (230); as the spin-coating frequency continued to increase, the film gradually exhibited Sb2S3 characteristics, accompanied by a small amount of Sb2O3 impurities. In addition, excessive spin-coating cycles can cause large voids to appear on the surface of the film. From the UV-visible spectrum, it can be seen that as the thickness of the film increases, the light absorption also gradually improve, and the band gap increases from 1.34 eV to 1.66 eV. The Mott-Schottky test showed that the prepared thin films were all P-type semiconductor. When spin-coated twice, the carrier concentration of the thin film reached 5.8×1015cm-3.

Recent Developments in Immobilized Photocatalyst for Hydrogen Production

AbstractSolar‐driven water splitting for hydrogen production has emerged as one of the most promising methods for addressing environmental and energy crises. The utilization of immobilized photocatalyst for hydrogen production has attracted significant attention in recent years due to its excellent stability, high photocatalytic efficiency, and ease of recovery and reuse. Hence, a comprehensive review of the development of immobilized photocatalyst appears exceedingly significant. Herein, we initially analyze the advantages of the immobilized photocatalytic system in aspects such as light absorption, photon utilization, and charge separation. Subsequently, we introduce various assembly techniques for immobilized photocatalyst and elaborate on some representative characteristics of this immobilized system. Furthermore, we cite the examples of the application of immobilized photocatalyst in large‐scale hydrogen production to envision its future prospects. Finally, we discuss the remaining issues in this field and outline future directions of development and challenges therein. This review holds great promise for prompting the advancement of immobilized photocatalyst in the field of photocatalysis.

Sulfur-doped Bi2O2CO3 nanosheet for enhanced visible-light-driven photocatalytic CO2 reduction to CO with ultra-high selectivity.

The photocatalytic reduction of carbon dioxide (CO2) has emerged as a compelling strategy for the conversion of renewable energy. However, the expeditious recombination of photogenerated charge carriers and the inadequate light absorption capabilities are currently predominant challenges. Herein, we developed a facile hydrothermal approach to synthesize a sulfur doped Bi2O2CO3 nanosheet with a tunable energy band structure designed to enhance visible light absorption. Our findings indicate that the incorporation of sulfur into the catalytic sites induces an electron sink effect, significantly improving the separation efficiency of photogenerated charge carriers. Consequently, this sulfur-doped Bi2O2CO3 catalyst exhibits a remarkable carbon monoxide (CO) yield of 16.64 μmol gcat-1 h-1 with nearly 100 % selectivity under illumination ranging from 420 to 780 nm. Through in-situ characterization techniques and theoretical calculations, it was revealed that sulfur-coordinated bismuth sites greatly enhance CO2 adsorption and decrease the energy barrier for critical intermediates formation (*COOH), thus selectively driving the reaction towards CO production. This work not only advances our understanding of mechanisms underlying photocatalytic reduction of CO2 on sulfur-doped bismuth-based catalysts but also sets a precedent for developing sophisticated photocatalytic systems for enhanced photoreduction reactions.

A photocatalysis-self-Fenton system based on NCDs@ZnIn2S4 composites at neutral pH and low amount of Fe2+ for the effective degradation of antibiotics

Photocatalysis-self-Fenton combining photocatalytic production of H2O2 with Fenton reaction has been a hotspot, but the pH limitation and iron sludge production problems remain unsolved. Herein, we proposed a self-fenton system based on N-doped carbon dots modified ZnIn2S4 (NCDs@ZnIn2S4) composites that exhibits effective degradation of antibiotics under neutral pH using low amounts of Fe2+. The decoration of ZnIn2S4 with NCDs significantly increased the surface area, visible light absorption, charge transfer ability and oxygen adsorption ability. NCDs@ZnIn2S4 composites exhibited a high H2O2 production rate (1528 μM g−1•h−1) under visible light, which was 1.9 and 5.3 times higher than ZnIn2S4 and NCDs, respectively. Meanwhile, the Fe2+/NCDs@ZnIn2S4 system with a low concentration of Fe2+(1 mg/L) could remove over 95% levofloxacin and oxytetracycline within 30 min. Interestingly, the highest degradation efficiency occurred under neutral pH. Quenching experiments and analytical measurements indicated that the high catalytic performance under pH = 7 with low amounts of Fe2+ stemmed from the higher amount of inner-generate H2O2 under neutral pH and easy regeneration of Fe2+ by photoinduced electrons for high •OH yields. Additionally, the Fe2+/NCDs@ZnIn2S4 system exhibited high degradation performance under different water matrix and ultrahigh degradation efficiency towards levofloxacin under real sunlight irradiation. The work shows the prospects of photocatalysis-self-Fenton systems for overcoming the pH limitation and the difficulty of iron sludge separation in the purification of effluents.

Boosted Near-Infrared Photothermal Conversion in Rare Earth Ions-Doped 2D SnSe Nanosheets for Solar-Powered Water Evaporation Systems.

Solar-powered water evaporation as a clean and abundant renewable energy-efficient desalination technology provides a promising strategy to solve the shortage of freshwater resources. However, the development and application of solar vapor technology are hindered by the relatively low near-infrared photothermal conversion efficiency of existing materials and the lack of effective improvement strategies. In this work, the conductivity characteristics of 2Dsemiconductors are capitalized on the high visible light absorption and ultra-low thermal. Specifically, rare-earth ion dopants into SnSe nanosheets, significantly boosting their near-infrared photothermal conversion efficiency and solar water evaporation performance are introduced. Remarkably, the photothermal conversion efficiency of the doped SnSe nanosheets surged from 51.56% to 82.11%, surpassing many previously reported photothermal materials. Furthermore, leveraging these nanosheets with enhanced photothermal conversion efficiency, a solar interfacial evaporation system is constructed. The evaporation rate of 2.17kgm-2h-1 and the efficiency of 96.5% can be achieved at one solar irradiance, and it also has good salt-resistance properties. The findings demonstrate the potential of rare earth ion-doped 2D semiconductor nanosheets in solar water evaporation, paving the way for future sustainable desalination solutions.

Piezo-photocatalysis synergy in γ-GeSe for highly efficient oxygen evolution reaction

Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers.

Eminent Red Sea water hydrogen generation via a Pb(ii)-iodide/poly(1H-pyrrole) nanocomposite photocathode

Abstract The development of a photocathode based on a Pb(ii)-iodide/poly(1H-pyrrole) porous spherical (PbI2/P1HP PS) nanocomposite has been successfully achieved in the efficient production of H2 gas from Red Sea water. The distinguishable spherical and porous shapes of these nanocomposites are characterized by a minimum surface measuring approximately 25 nm. This structural configuration, coupled with the nanocomposite’s substantial light absorbance, results in a modest bandgap of 2.4 eV. This turns the nanocomposite into a highly promising candidate for renewable energy applications, particularly for H2 gas generation from natural sources like Red Sea water. The economic viability of the PbI2/P1HP PS nanocomposite, relying on a glass substrate, mass production, and straightforward fabrication techniques, adds to its promising profile for H2 gas evolution. The photocathode exhibits significant potential for H2 gas production, with a notable current density (J ph) value of 1.0 mA·cm−2 in a three-electrode cell configuration. The IPCE reaches 3.1%, reflecting the successful evolution of 24 µmol·h−1 10 cm2 of the photocathode. Importantly, the use of natural Red Sea water as an electrolyte underscores a key feature for H2 gas production: utilizing freely available natural resources. This aspect holds considerable promise for industrial applications, emphasizing the environmentally sustainable nature of the photocathode.

Assessing the Aesthetic Performance of CAD/CAM Provisional Restorative Materials: A Spectrophotometric Analysis

Achieving color match between natural teeth and restorative materials is crucial in dentistry. Factors such as the light source, brightness, and opacity influence tooth color, determined by light absorption and scattering within the material. Advances in CAD/CAM systems have enhanced prosthodontic treatments, particularly with new temporary materials, but data on their color stability and masking ability remains limited. However, data on the color stability and masking ability of these CAD/CAM materials is limited. Telio® CAD-Temp and VITA CAD-Temp® blocks were cut into slices and polished. Composite resin specimens were prepared using a custom-designed metal resin former and light-cured. Samples were paired randomly and assigned to experimental groups based on base type and thickness (n = 30). Samples were stored in a controlled environment for 24 h before color evaluation using an EasyShade® V spectrophotometer. Color difference (ΔE) was calculated using L*, a*, and b* values. Statistical analyses included the Shapiro–Wilk test, Levene’s test, and three-way ANOVA, with post-hoc comparisons using the Bonferroni method (α = 0.05). ΔE was classified according to perceptibility (PT = 1.2) and acceptability (AT = 2.7) values.

Photoinduced Evolutions of Permafrost-Derived Carbon in Subarctic Thermokarst Pond Surface Waters.

In subarctic regions, rising temperature and permafrost thaw lead to the formation of thermokarst ponds, where organics from eroding permafrost accumulate. Despite its environmental significance, limited knowledge exists regarding the photosensitivity of permafrost-derived carbon in these ponds. In this study, laboratory experiments were conducted to explore the photochemical transformations of organic matter in surface water samples from thermokarst ponds from different environments in northern Quebec, Canada. One pond near Kuujjuarapik is characterized by the presence of a collapsing palsa and is therefore organically rich, while the other pond near Umiujaq is adjacent to a collapsing lithalsa and thus contains fewer organic matters. Photobleaching occurred in the Umiujaq sample upon irradiation, whereas the Kuujjuarapik sample exhibited an increase in light absorbance at wavelength related to aromatic functionalities, indicating different photochemical aging processes. Ultrahigh-resolution mass spectrometry analysis reveals that the Kuujjuarapik sample preferentially photoproduced highly unsaturated CHO compounds with great aromaticity, while the irradiated Umiujaq sample produced a higher proportion of CHON aromatics with reduced nitrogen functionalities. Overall, this study illustrates that the photochemical reactivity of thermokarst pond water varies with the source of organic matter. The observed differences in reactivity contribute to an improved understanding of the photochemical emission of volatile organic compounds discovered earlier. Further insights into the photoinduced evolutions in thermokarst ponds may require the classification of permafrost-derived carbon therein.