Physicochemical Research Articles

Physicochemical attributes and bacteriome diversity of Lake Tunari, Taraba State, Nigeria

Physicochemical parameters of aquatic habitats can play an influential part in shaping the microbial communities of water bodies. In this study, water samples from Lake Tunari were analysed for its microbiome and physicochemical attributes, using spectrophotometric and culture-dependent methodologies respectively. The temperature of the lake ranged from 28.00 – 29.00 (°C), while the pH ranged from 6.50 – 7.20. Heavy metals such as Manganese (0.48 ppm), Lead (0.14 ppm) and Selenium (0.10 ppm) showed significantly high values in selected parts of the lake, surpassing limits set by the World Health Organisation. Microbiome analysis revealed the largest phylum across sample sites as Proteobacteria, Firmicutes, and Planctomycetota with peak relative abundance values of 64.13%, 45.29% and 16.11% respectively. Bacterial genera such as Exiguobacterium, Methylocystis and Rhodoferax were detected from designated sites. The presence of these genera capable of tolerating, utilizing or degrading metal ions in water samples of the Lake might be indicative of chemical and metal trickles into the water body. In addition, relatively new and understudied bacterial phyla such as Gemmatimonadota, as well as unknown bacterial clades were identified from water samples of the lake. This study has revealed that Lake Tunari is not impervious to pollution, caused by either anthropogenic activities or from adjoining water channels. Environmental health awareness programs can be introduced to enlighten the populace, while scheduled microbial and physicochemical surveillance can be adopted, to control microbial contamination and curtail toxic material inflow into the Lake.

Assessment of microbial properties, and heavy metals contents of surface water and ground water samples In Ureje and Ireje, Ekiti State, Nigeria.

Water is everywhere, · it is the most basic and necessary element of life, as well as the most important and abundant compound in the ecosystem. Standard methods were used to evaluate the physicochemical properties, microbial properties, and heavy metal content of river and well water samples in Ekiti State, South-West Nigeria. Important parameter like pH, electrical conductivity, total dissolved solids, DO, BOD, turbidity, total alkalinity, total hardness, heavy metals and microbial properties are determined. The research work indicated that temperature, odour, pH, alkalinity, TDS, biochemical oxygen demand, DO, chloride, nitrate and turbidity were within the range of WHO permissible limits for drinking water while color, Conductivity, iron and manganese were above the WHO permissible limits. The study also indicated that the microbial contents such as total viable count, yeast/mold and coliform were above the WHO permissible limits for drinking. These results show that the water sources were slightly contaminated and unsafe for human consumption. This water must be treated before it may be consumed or used for domestic application.

Formulation of colloidal astringent solution using green tea and neem oil

This thesis explores the formulation of a novel colloidal astringent solution utilizing the synergistic properties of green tea and neem oil in skincare applications. Astringents play a crucial role in skincare, offering benefits such as pore tightening, oil control, and skin texture refinement. Green tea and neem oil, renowned for their antioxidant, anti-inflammatory, and antimicrobial properties, present promising ingredients for enhancing skin health. The study begins with a comprehensive literature review, examining previous research on astringents, green tea, and neem oil. This review elucidates the individual properties and skincare benefits of these ingredients, providing a foundation for their integration into a colloidal solution. Relevant formulation techniques for colloidal solutions and astringents are also reviewed, informing the experimental approach. Experimental design focuses on formulating a colloidal astringent solution using green tea extract and neem oil, with the aim of harnessing their collective potency. Physicochemical properties of the solution, including pH, viscosity, particle size, and stability, are characterized to evaluate its suitability for skincare applications. Stability studies over time provide insights into the shelf-life and efficacy of the formulation. Results demonstrate the successful formulation of a colloidal astringent solution with optimized properties, showcasing the potential synergy between green tea and neem oil. Analysis of experimental findings highlights the formulation's efficacy in addressing common skincare concerns, such as pore refinement, oil control, and inflammation reduction. The study contributes to the growing body of knowledge in natural skincare formulations, offering insights into the development of innovative products that marry tradition with modern science. In conclusion, the formulation of a colloidal astringent solution using green tea and neem oil represents a promising approach to skincare, leveraging the therapeutic benefits of natural ingredients. Future research may explore clinical applications and further optimization of the formulation to maximize its efficacy and safety in diverse skincare routines.

Formulation and evaluation of Dorzolamide hydrochloride microsponges loaded in situ gel for ocular administration

Due to the unique structure of the eye, which inhibits the entry of drug molecules into the desired site, the ophthalmic delivery of the drug has been one of the most challenging tasks for a pharmaceutical scientist. For this reason, in this investigation a novel microsponge for an anti-glaucoma drug, Dorzolamide hydrochloride, was formulated as in situ gel for ocular administration with an aim to improve its therapeutic efficacy and reduce the systemic adverse effects. The microsponges were prepared by the quasi emulsion solvent diffusion method and was incorporated into 20% pluronic F-127 which led to consistent in situ gel at 35°C. They were evaluated for physicochemical properties like pH, gelling capacity, gelation time, rheological properties and release profile and ocular irritancy test. The prepared Dorzolamide hydrochloride microsponges showed high entrapment efficiency of 85% and mean particle size of 2 μm with polydispersity index (PDI) of 0.77 which are ideal for ocular delivery. These microsponges is formulated into in situ gel which showed higher therapeutic efficacy compared to free drug in gel. It was found to be non-irritant to the rabbit’s eye. These results confirms that Dorzolamide hydrochloride microsponges in situ gels have promising features, benefits and advantages for a novel ophthalmic drug delivery to treat glaucoma.

Effect of Preharvest Treatment Using Jasmonic Acid and Methyl Jasmonate on the Physicochemical Properties and Antioxidant Activities of Red-fleshed Dragon Fruit (Hylocereus polyrhizus L.)

This study investigated the effect of exogenous plant growth regulators (PGR), namely jasmonic acid (JA) and methyl jasmonate (MeJA), on the physicochemical properties of flesh and peels of red-fleshed dragon fruit (Hylocereus polyrhizus). The fruit was sprayed with 100 and 1,000 ppm of JA and MeJA at 15 and 22 days of anthesis and harvested after 35 days. Then, the flesh and peels were analyzed for total soluble solids (TSS), total betacyanins, betanin, total phenolics (TP), total flavonoids (TF), and color characteristics. The fruit peels contained significantly higher (p<0.05) TP and antioxidant activities compared to flesh. No significant difference was detected between the variables in the peels, except for significantly higher (p<0.05) of total betacyanins (~295.6 and ~299.9 mg/100 g) and TP (~614.1 and 566.1 mg GAE/100 g) were recorded in control and 100 ppm MeJA, respectively. In the flesh, 1,000 ppm MeJA-treated fruit possessed the highest total betacyanins (~139.2 mg/100 g), betanin (~356.0 mg/g), TP (~244.9 mg GAE/100 g), TF (~329.0 mg CE/100 g), Trolox equivalent antioxidant capacity (TEAC) (63.2 µmol TE/g) and reducing power (~21.5 µmol TE/g). Overall, 1,000 ppm MeJA was more effective in enhancing the accumulation of bioactive compounds and antioxidant activities in the flesh of red-fleshed dragon fruit compared to other PGR treatments.

Metallacarboranes in Medicinal Chemistry: Current Advances and Future Perspectives.

Metallacarboranes, exemplified by cobalt bis(dicarbollide) ([COSAN]-), have excelled their historical metallocene analogue label to become promising in drug design, medical studies, and fundamental biological research. Serving as a unique platform for conjugation with biomolecules, they also constitute an auspicious building block for biologically active derivatives and a carrier for cellular transport of membrane-impermeable cargos. Modified [COSAN]- exhibits specific antimicrobial, antiviral, and anticancer actions showing promise for preclinical trials. Contributing to the ongoing development in medicinal chemistry, metallacarboranes offer desirable physicochemical properties and low acute toxicity. This article presents a critical look at metallacarboranes in the context of their application in medicinal chemistry, emphasizing [COSAN]- as a potential game-changer in drug design and biomedical sciences. As medicinal chemistry seeks innovative building blocks, metallacarboranes emerge as an important novelty with versatile solutions and promising implications.

Supramolecular cage-mediated cargo transport.

A steady stream of material transport based on carriers and channels in living systems plays an extremely important role in normal life activities. Inspired by nature, researchers have extensively applied supramolecular cages in cargo transport because of their unique three-dimensional structures and excellent physicochemical properties. In this review, we will focus on the development of supramolecular cages as carriers and channels for cargo transport in abiotic and biological systems over the past fifteen years. In addition, we will discuss future challenges and potential applications of supramolecular cages in substance transport.

Micronization induced gelatinization of tapioca starch and its effects on starch physicochemical and structural properties.

The vibrating superfine mill (VSM) is a machine that belongs to the micronization technique. In this study, VSM was employed to produce micronized tapioca starch by varying micronization times (15, 30, 45, and 60min). The structural and physicochemical properties of the micronized starch were then examined. Scanning electron microscopy studies revealed that micronized starch was partially gelatinized, and the granule size dramatically increased when micronization time increased. X-ray diffraction patterns showed that the relative crystallinity was decreased from 24.67% (native) to 4.13% after micronization treatment for 15min and slightly decreased after that. The solubility of micronized starch significantly increased as the micronization time increased, which was associated with the destruction of the starch crystalline structure. Differential scanning calorimetry investigations confirmed that micronized starch was "partly gelatinized," and the degree of gelatinization increased to 81.27% when the micronization time was 60min. The weight-average molar mass was reduced by 15.0% (15min), 30.9% (30min), 55.7% (45min), and 70.5% (60min), respectively, indicating that the molecular structure was seriously degraded. The results demonstrated that the physicochemical changes of micronized starch granules were related to the destruction of the starch structure. These observations would provide details on micronized starch and its potential applications. PRACTICAL APPLICATION: These observations would provide details on micronized starch and its potential applications. Moreover, we believe that when the structures of starches were known, it is probable that the effect of VSM on the structural and physicochemical properties change of other starches might be predicted by adjusting the processing time.

Biomass-Derived Carbon Materials for Advanced Metal-Ion Hybrid Supercapacitors: A Step Towards More Sustainable Energy

Modern research has made the search for high-performance, sustainable, and efficient energy storage technologies a main focus, especially in light of the growing environmental and energy-demanding issues. This review paper focuses on the pivotal role of biomass-derived carbon (BDC) materials in the development of high-performance metal-ion hybrid supercapacitors (MIHSCs), specifically targeting sodium (Na)-, potassium (K)-, aluminium (Al)-, and zinc (Zn)-ion-based systems. Due to their widespread availability, renewable nature, and exceptional physicochemical properties, BDC materials are ideal for supercapacitor electrodes, which perfectly balance environmental sustainability and technological advancement. This paper delves into the synthesis, functionalization, and structural engineering of advanced biomass-based carbon materials, highlighting the strategies to enhance their electrochemical performance. It elaborates on the unique characteristics of these carbons, such as high specific surface area, tuneable porosity, and heteroatom doping, which are pivotal in achieving superior capacitance, energy density, and cycling stability in Na-, K-, Al-, and Zn-ion hybrid supercapacitors. Furthermore, the compatibility of BDCs with metal-ion electrolytes and their role in facilitating ion transport and charge storage mechanisms are critically analysed. Novelty arises from a comprehensive comparison of these carbon materials across metal-ion systems, unveiling the synergistic effects of BDCs’ structural attributes on the performance of each supercapacitor type. This review also casts light on the current challenges, such as scalability, cost-effectiveness, and performance consistency, offering insightful perspectives for future research. This review underscores the transformative potential of BDC materials in MIHSCs and paves the way for next-generation energy storage technologies that are both high-performing and ecologically friendly. It calls for continued innovation and interdisciplinary collaboration to explore these sustainable materials, thereby contributing to advancing green energy technologies.

Comparative Study of Chemical Activation and Physical Activation Approach to Optimize Biomass-Based Doped Carbons for Energy Applications

Abstract Two approaches have been utilized to optimize the energy storage characteristics of doped carbon materials derived from Lignosol, a biomass product, to address the rising energy demand issues. Herein, phosphorus and nitrogen co-doped carbon (PNDC) materials with varying doping agent volumes were synthesized by utilizing microwave irradiation. Chemical activation and physical activation were employed to enhance these materials’ characteristics. Chemical activation was performed in a one-pot, single-step process, rather than a traditional multi-step protocol, using small amounts of potassium hydroxide. Furthermore, the physical activation method required multiple steps: doped carbon was prepared via microwave, exposed to water, filtered, frozen and then dried. With this, the expansion properties of water at freezing temperatures were exploited to alter the materials’ surface characteristics. All materials were characterized and compared for their physicochemical properties. All defect ratios supported the presence of doping. Additional results revealed that both chemical and physical activation approaches effectively modify the topographical features as well as the electrochemical activity (charge storage) of the doped carbon materials. The chemically activated doped carbon exhibited the highest resulting surface area of 1352 m2/g and a specific capacitance value of 347 F g-1 with excellent cycling stability as compared to other similarly synthesized materials.

Extrusion-based bioprinting: considerations toward gelatin-alginate bioink

Purpose This study aims to develop a simplified bioink preparation method that can be applied to most hydrogel bioinks used in extrusion-based techniques. Design/methodology/approach The parameters of the bioprinting process significantly affect the printability of the bioink and the viability of cells. In turn, the bioink formulation and its physicochemical properties may influence the appropriate range of printing parameters. In extrusion-based bioprinting, the rheology of the bioink affects the printing pressure, cell survival and structural integrity. Three concentrations of alginate-gelatin hydrogel were prepared and printed at three different flow rates and nozzle gauges to investigate the print parameters. Other characterizations were performed to evaluate the hydrogel structure, printability, gelation time, swelling and degradation rates of the bioink and cell viability. An experimental design was used to determine optimal parameters. The analyses included live/dead assays, rheological measurements, swelling and degradation. Findings The experimental design results showed that the hydrogel flow rate substantially influenced printing accuracy and pressure. The best hydrogel flow rate in this study was 10 ml/h with a nozzle gauge of 18% and 4% alginate. Three different concentrations of alginate-gelatin hydrogels were found to exhibit shear-thinning behavior during printing. After seven days, 46% of the structure in the 4% alginate-5% gelatin sample remained intact. After printing, the viability of skin fibroblast cells for the optimized sample was 91%. Originality/value This methodology offers a straightforward bioink preparation method applicable to the majority of hydrogels used in extrusion-based procedures. This can also be considered a prerequisite for cell printing.

Gaussian processes modeling for the prediction of polymeric nanoparticle formulation design to enhance encapsulation efficiency and therapeutic efficacy.

Conventional drugs have been facing various drug delivery obstacles, including first-pass metabolism for oral medications, drug degradation by cellular enzymes, off-target effects, and cytotoxicity of healthy cells. Nanoparticles (NP) application in drug delivery can compensate for these drawbacks to a great extent. NPs can be fabricated using different materials and structures to achieve desired therapeutic effects. For each type of NP material, its physicochemical properties determine compatibility with specific drugs and other supplemental compositions. The optimized material selection becomes prominent in NP development to improve NP performances. Due to the nature of NP fabrication, the process is long and expensive. To accelerate NP composition optimization, machine learning (ML) techniques are among the most promising methods for efficient data predictions and optimizations.As a proof-of concept, we created Gaussian Process (GP) models to make predictions for drug encapsulation efficiency (EE%) and therapeutic efficacy of 32 poly (lactic-co-glycolic acid) (PLGA) NPs that are formed with materials with different physicochemical properties. Two model drugs, doxorubicin (DOX) and docetaxel (DTX) were loaded separately. The IC50 values for the various NPs formulations were evaluated using the OVCAR3 epithelial ovarian cancer cell line. EE% GP model has the highest prediction accuracy with the lowest normalized root-mean-squared-error (RMSE) of 0.187. The DOX and DTX IC50 GP models have normalized RMSEs of 0.296 and 0.206, respectively, which are higher than that of the EE% GP model.

Continuous Monoculture Alters the Fungal Community and Accumulates Potential Pathogenic Strains in the Rhizosphere of Codonopsis pilosula

Codonopsis pilosula (known as dangshen) is experiencing a serious replant disease caused by continuous monoculture in its main and endemic cultivation region in Dingxi, China. In this study, changes in physicochemical properties, fungal microbiomes, and isolated strains were investigated in the rhizosphere soil of 1-, 2-, 3-, and 5-year continuous monoculture natural fields. It was observed that wilted seedlings and a variety of root rot diseases occurred after the third year of continuous monoculture in the field. The soil-available potassium content and the pH value decreased significantly in the 3- and 5-year fields. Using Illumina sequencing, it was demonstrated that the 3- and 5-year fields had a higher diversity of fungal communities compared with the 1- and 2-year fields. At the genus level, abundance of some potentially pathogenic fungal taxa also increased. A total of 33 isolated strains belonging to the Fusarium species complexes Plectosphaerella cucumerina, Paraphoma ledniceana, Alternaria alstroemeriae, Mucor hiemalis, and Clonostachys rosea were obtained from the roots in 3- and 5-year fields. The correlation analysis revealed that the abundance of the fungal community at the genus level was positively correlated with the available phosphorus, total nitrogen, and soil organic matter. The results revealed that continuous monoculture has a negative impact on the fungal community and enriches potential pathogenic fungi in the rhizosphere of C. pilosula.

Evaluation of physicochemical properties of Rohu fish noodles

Functional noodles are considered nutritious and healthy staple food products. This study aimed to develop value-added rohu fish noodles (Labeo rohita) and evaluate their physicochemical properties. Six noodle samples were prepared following several formulations. After a 2-day drying process, the noodles were stored in air-resistant plastic bags. The formulated noodles were investigated based on their physical (water absorption capacity, cooking loss, and volume increase) and chemical (moisture, ash, protein, fat, and fiber) properties. Statistical analysis revealed that the inclusion of rohu fish mince significantly increased moisture and protein content (p<0.01), while carbohydrate, energy, water absorption capacity, cooking loss, and volume decreased significantly (p<0.01). Noodles with the highest fish mince content (30%) demonstrated a higher amount of moisture (13.07%), ash (6.7%), fat (1.87%), protein (30.08%), sodium (0.64 mg), and calcium (0.26 mg), accompanied by reduced carbohydrate (48.3%) and energy (330.31 kcal). This formulation also exhibited lower water absorption capacity, cooking loss, and volume. Notably, no significant differences (p>0.05) were found in ash, fiber, fat, and mineral content among the various fish noodle samples. This study concludes that the incorporation of rohu fish mince can enhance the nutritional properties of traditional noodles.

Combined Aerobic Fermentation of Maricultural and Agricultural Solid Waste: Physicochemical Property and Bacterial Community Structure

The large-scale production of maricultural solid waste is not used effectively and has a significant impact on the environment. However, there is no report on the utilization of solid waste in mariculture of maricultural and agricultural solid waste. At present, aerobic composting is a simple and feasible means of waste resource utilization, but it also seriously pollutes the environment. This paper studied the change of physical and chemical properties (T1: solid waste + straw, T2: solid waste + cow dung + straw, T3: solid waste + cow dung + straw + 5% biochar, T4: solid waste + chicken dung + cow dung + straw + 5% biochar) and microbial succession in the composting process (T4: solid waste + chicken dung + cow dung + straw + 5% biochar) and the effect of decomposed products on seed growth. The results showed that the mixed compost of various materials had a good regulating effect on the physical and chemical indexes, and the highest temperature could reach 69.4 °C. Biochar could extend the high temperature period by 1–2 days. The germination indexes of seeds treated with T1–T4 were 75%, 80%, 81%, and 94%, respectively. Through the change of the seed germination index, it could be seen that the bacterial community structure changed significantly during composting. The Chao 1 index and Shannon index showed that the bacterial abundance and diversity index increased and then decreased. The analysis of the bacterial community structure showed that Proteobacteria and Acinetobacter were the main bacteria in composting, and the relative abundance of Proteobacteria was 81.9% at the phyla level. Acinetobacter and Pseudoxanthomonas were the main bacteria in the process of composting. Acinetobacter was the dominant bacteria in the heating stage, with an abundance of 67.2%.

Reclamation of coastal wetland to paddy soils alters the role of bacteria and fungi in nitrous oxide emissions: Evidence from a 53-year reclamation chronosequence study

Coastal wetlands are significant sources of nitrous oxide (N2O), a potent greenhouse gas and ozone depleting agent. Land reclamation is known to change N2O emissions from coastal wetlands, but the long-term impacts on N2O sources and emissions are not well-understood. Here, we performed respiration inhibition and molecular techniques to dissect the long-term effects of coastal reclamation on bacterial, fungal and overall N2O emissions across a 53-year chronosequence of paddy soils reclaimed from coastal wetlands. Our findings showed that reclamation of coastal wetlands to paddy soils generally promoted N2O emissions in the chronosequences, despite a significant reduction in uncultivated paddy soils. The observed increase in N2O emissions was primarily attributed to an imbalance between N2O production and consumption driven by bacterial denitrifiers. Additionally, reclamation of coastal wetlands to paddy soils shifted N2O emissions from fungal to bacterial predominance in the chronosequences, with denitrification mediated by bacterial denitrifiers dominating bacterial N2O emissions. By integrating the analysis of N2O emission rates with soil physicochemical and microbiological properties, we demonstrated that the reduced salinity following coastal reclamation diminished the relative abundance of key fungal denitrifiers (e.g., Paraconiothyrium, Penicillium and Trichoderma), thus lowering the fungal contribution to N2O emissions. This study provides novel insights into the long-term influences of coastal reclamation on the sources and emissions of N2O, and enhance our knowledge of the underlying mechanisms driving these impacts, thereby contributing to improving future models of N2O emissions from coastal ecosystems under global change.

Physicochemical Properties of Lithium Bis(trifluoromethanesulfonyl)imide Solutions in Sulfolane

Abstract A study is performed of the physicochemical properties (ionic conductivity, viscosity, and density in the 30–50°C range of temperatures) and the electrochemical and thermal stability of lithium bis(trifluoromethanesulfonyl)imide solutions in sulfolane in the 0.001–1.89 M range of concentrations. It is shown that lithium bis(trifluoromethanesulfonyl)imide solutions in sulfolane exhibit high electrochemical stability (5.75 V vs. Li/Li+) and moderate ionic conductivity (2.75 × 10−3 Ω−1 cm−1 at 30°C for a 1 M solution), which are comparable to the respective parameters of sulfolane solutions of lithium hexafluorophosphate. The structure and transport properties of sulfolane solutions of lithium bis(trifluoromethanesulfonyl)imide are determined by their concentrations. In dilute solutions, lithium bis(trifluoromethanesulfonyl)imide is weakly associated. The degree of electrolytic dissociation of LiN(SO2CF3)2 initially falls and then rises upon an increase in its concentration. The electrolytic dissociation of lithium bis(trifluoromethanesulfonyl)imide rises along with its concentration, due to the formation of ion triplets and more complex ion associates. The constant of association and limit equivalent conductivity of LiN(SO2CF3)2 in sulfolane rise along with temperature, due to a drop in the degree of self-association and the degradation of the solvent’s structure. A specific feature of sulfolane solutions of lithium bis(trifluoromethanesulfonyl)imide is their tendency to form stable supercooled solutions.

Modeling Specific Capacitance of Carbon Nanotube-Based Supercapacitor Electrodes by Machine Learning Algorithms

Abstract Carbon nanotubes (CNTs) have emerged as promising materials for supercapacitors (SCs) due to their unique properties and exceptional electrical conductivity. These cylindrical structures composed of carbon atoms offer several advantages for SC electrode applications. The electrochemical performance of CNT-based electrodes is strongly influenced by factors such as surface area, pore structure, and ID/IG ratio. However, the lack of a credible physical model capable of accurately predicting the performance of SCs based on these physicochemical properties of CNTs poses a challenge. In this study, we propose the utilization of a data-driven approach employing various models including a gradient boosting regression (GBR), Bayesian regression (BR), ridge regression (RR), and stochastic gradient descent (SGD) model to predict the performance of SCs with CNT electrodes based on the microstructural properties of the electrode material and electrochemical operational parameters. The developed GBR model demonstrates its feasibility by achieving a low root mean square error (RMSE) value of approximately 36.31 for the prediction of specific capacitance for test split. Additionally, a sensitivity analysis was conducted to investigate the influence of independent input parameters on a single output parameter, specifically the specific capacitance. This analysis provides insights into the relative importance and impact of various input parameters on the specific capacitance of CNT-based SCs.&amp;#xD;

Broadband and ascendant nonlinear optical properties of the wide bandgap material GaN nanowires

Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10−4 cm3/GW2. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm2, 5.58 GW/cm2 and 14.13 GW/cm2. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.

Probing Chemical Equilibrium in Frozen Sodium Phosphate Buffer Solution by 31P Solid-State NMR.

Phosphate buffers are crucial for cryopreservative stability in pharmaceuticals, food processing, biomedical sciences, and biology. However, their freeze concentrates lack quantitative characterization, especially regarding the physicochemical properties of phosphate salt species in equilibrium at subzero temperatures. This study employs 31P solid-state NMR (ssNMR) to analyze frozen sodium phosphate (NaP) solutions, providing insights into phase composition, ionic strength, and pH. For the first time, we have directly quantified phosphate species in frozen NaP buffer, including crystallized disodium phosphate dodecahydrate (Na2HPO4·12H2O) content and the concentrations of H2PO4- and HPO42- in the freeze concentrate. This enabled the calculation of the pH as well as the ionic strength in the freeze concentrate. Trehalose effectively mitigated pH shifts in buffer solutions by preventing the selective crystallization of salt, a spectroscopic phenomenon not previously observed experimentally.