Lactic Acid Aqueous Solution Research Articles

Bacterial inhibition and biofilm eradication ability of low-toxic deep eutectic solvents prepared from lactic acid and quaternary ammonium compounds

In the present communication, the preparation of deep eutectic solvents (DESs) based on an aqueous solution of lactic acid (LA) and two different quaternary ammonium compounds, choline chloride (ChCl) and tetraethylammonium chloride (TEAC), is proposed for the application as an antibacterial agent. The antibacterial and cytotoxic properties of the DESs obtained were studied and found to be highly effective in inhibiting both Gram-positive and Gram-negative bacteria and eradicating bacterial biofilms. Moreover, the DESs obtained exhibited reduced cytotoxicity towards soft tissue cells compared to the aqueous LA solution. The excellent antibacterial properties and low cytotoxicity of the DESs prepared make them a promising candidate for the development of novel antimicrobial agents or antibacterial eutectogels for delivery systems and tissue engineering applications.

CeO2-CuO composites prepared via supercritical antisolvent precipitation for photocatalytic hydrogen production from lactic acid aqueous solution

The global increase in energy demand requires a continuous search for renewable and clean alternative resources to fossil fuels. Hydrogen is emerging as a promising energy carrier for the future; its production via photocatalysis, driven by sunlight, can directly convert solar energy into a usable or storable energy resource. However, water splitting requires sacrificial agents or electron donors/hole scavengers, such as short-chain organic acids. This research explores the use of lactic acid as a source for photocatalytic hydrogen production, offering valuable alternatives for wastewater management and renewable energy production. This study employed the innovative supercritical antisolvent (SAS) technique to micronize the precursors of both the active phase (CeO2) and co-catalyst (CuO), ensuring rapid and complete solvent removal and size reduction of photocatalyst precursors. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). This study has shown that the micronization process resulted in a notable improvement in CeO2 photocatalytic activity, attributed to the reduction of the dimensions of the powders. Hydrogen production was equal to 3989 μmol L−1 for the SAS-produced photocatalyst while using a commercial CeO2 sample resulted in H2 production of 2519 μmol L−1. The enhanced photoactivity of CeO2-CuO composites was found to be related to the presence of CuO. The optimal CuO amount was equal to 0.5 wt%, determining a hydrogen production of 9313 μmol L−1 after 4 h of UV irradiation time. A photocatalytic test carried out with deuterated water (D2O) instead of distilled H2O demonstrated that hydrogen was preferentially produced from water splitting reaction, whereas lactic acid acted as a sacrificial agent being oxidized from positive holes photogenerated in the valence band of CuO.

Continuous co-digestion of sewage sludge and highly concentrated waste bioplastic hydrolyzate without shortening hydraulic retention time

Bioplastics have garnered substantial interest as alternatives to conventional petroleum-based plastics. However, their management and conversion to biogas continues to be significantly challenging. In this study, we evaluated the suitability of various plastics for hydrolysis at 160 °C for 12 h using different solvents. The biogas yield (BGY) of the monomers constituting these plastics and the obtained plastic hydrolyzates was comprehensively evaluated. When water was used as a solvent, 100 % hydrolysis of polylactic acid (PLA) and polybutylene succinate (PBS) was observed. When polybutylene adipate co-terephthalate (PBAT) and polyhydroxybutyrate (PHB) were hydrolyzed with water, the degradation ratio was approximately 30 %; however, using an aqueous lactic acid solution as a solvent improved the degradation ratio to 78 % and 100 %, respectively. In the BGY test of the plastic hydrolyzates, the biogas volumes derived from the hydrolyzates were 563, 461, 337, and 573 mL/g COD-added for PLA, PBS, PBAT, and PHB, respectively. With 1,160 gCOD/L waste PLA hydrolyzate, continuous co-digestion of sewage sludge and the hydrolyzate was conducted. Organic loading rates of sewage sludge and the hydrolyzate were 2.3 and 2.4 gCOD/L/d, respectively. The operation was stable and the methane production volume from the PLA hydrolyzate was 414 L/kgCOD-added. Using highly concentrated PLA hydrolyzate, the hydraulic retention time was 19.3 days, which was only 0.7 days shorter than that of anaerobic digestion of sewage sludge only (20 days). Therefore, highly concentrated PLA hydrolyzate maintains the retention time of normal sewage sludge digestion. Conclusively, the present study has crucial practical implications for plastic waste management.

Cheap organocatalyst diphenyl phosphate for efficient chemical recycling of poly(lactic acid), other polyesters and polycarbonates

Bioplastics are regarded as a sustainable alternative to traditional petroleum-based plastics, particularly poly(lactic acid) (PLA). However, due to the slow biodegradation of PLA and the lack of an overall recycling strategy, its large-scale use could make it an acute source of future plastic pollution. Herein, we find that diphenyl phosphate (DPP), a cheap organocatalyst, can efficiently catalyze PLA hydrolysis into valuable oligomers/lactic acid. Without pressure and organic solvents, under mild conditions with 3.5 wt% DPP and a little water (160 °C, 1.5 h), commercial PLA pellets/products are rapidly converted into oligomers with molecular weight below 500 g/mol by random hydrolysis. DPP can catalyze at least 10 batches of PLA without compromising its catalytic performance, and kilogram-scale PLA degradation is facilely achieved. The DPP-containing oligomers can be used directly to synthesize lactide, and subsequently high-quality PLA is obtained using a well-established industrial route to achieve closed-loop recycling. Meanwhile, an aqueous lactic acid solution with comparable commercial quality and intact configuration retention is harvested. Moreover, DPP can also effectively catalyze the hydrolysis of other polyesters and polycarbonates. Overall, this study is expected to address the environmental and engineering challenges associated with plastic waste disposal, in particular fostering a PLA-based green circular bio-economy.

A novel ternary nano-photocatalyst (Ni/Ni3C/CdS) for HER and water purification with enhanced photocatalytic activity

CdS-based nanomaterials received much attention since it was synthesized and used as photocatalysts in HER reaction and degradations of organic pollutants. However, it is still an urgent issue to improve the stability and catalytic performance of these kinds of materials before they meet the requirements of the practical applications. Therefore, A novel nano-photocatalyst named as NC-15 was prepared in this paper by loading Ni3C nanosheets (NSs) and Ni nanoparticles (NPs) to the surface of CdS nanowires (NWs). Using a 300 W Xe-lamp (≥400 nm) as the illumination source, NC-15 could accelerate the H2-evolution reaction (HER) in aqueous solution of lacticacid (10 vol%) with the rates of 15247 μmol·g-1h−1 which is ca. 381-time higher than that of CdS NWs, and OTC (LEF) could be ca. 91 % (89 %) degenerated as its aqueous solution (40 ppm) were irradiated 60 mins. The electrochemical analysis indicates that NC-15 should be an n-type semiconductor with the overpotential of −1.08 V vs. Ag/AgCl, which is much lower than those of CdS NWs (-1.20 V), Ni3C/CdS (-1.18 V) and Ni/CdS (-1.13 V) and indicates a faster-photogenerated electrons transfer rate of NC-15. The theoretical simulations confirm that the Ni NPs should supply the active sites during the photocatalytic procedure and the internal electric field at the interfaces of CdS/Ni3C and Ni3C/Ni could accelerate the photogenerated carriers’ separation and migration. In a word, CdS-based ternary nano-photocatalysts possess great potential in the practical application of HER and photodegradation reactions.

Green extraction of berberine from Coscinium fenestratum (Gaertn.) Colebr. using ultrasound-assisted aqueous solutions of organic acids, polyalcohols, and deep eutectic solvents

Berberine displays many potential bioactivities and is found in several medicinal herbs, such as Coscinium fenestratum. The extraction of berberine from biomass was carried out using volatile organic solvents, inorganic acid solutions, and more recently, ionic liquids and deep eutectic solvents. In order to develop more efficient and sustainable extraction processes, this study used inexpensive green solvents, such as carboxylic acid and polyalcohol aqueous solutions, to extract berberine from Coscinium fenestratum. Initial screening was performed to compare the berberine extraction performance of various solvents, including aqueous solutions of carboxylic acids, polyalcohols, and their deep eutectic solvents. The obtained results showed that lactic acid was a potential solvent for extracting berberine. After optimizing the process using response surface methodology (RSM), the optimal ultrasound-assisted extraction conditions were determined to be a lactic acid concentration of 60 % (w/w), a liquid-to-solid ratio of 17.25 mL/g, an extraction time of 20 min, and an extraction temperature of 66 °C. This resulted in an extraction efficiency of 38.23 ± 0.69 mg/g, corresponding to a berberine concentration of 2.22 ± 0.04 mg/mL. Additionally, the use of lactic acid as the extraction solvent yielded superior extraction efficiency and berberine purity compared to conventional volatile organic solvents, and inorganic acids, bases. The recovery of berberine was achieved using macroporous resins, allowing for the recovery of 99.52 ± 0.67 % of berberine from aqueous lactic acid solutions. The lactic acid solvent and the AB-8 resin were successfully recovered and reused for a minimum of three consecutive extraction cycles, maintaining their full effectiveness throughout the entire process. The recovered berberine from the lactic acid extract exhibited stronger antibacterial activity than the extracts obtained using ethanol, methanol, and acetone, as well as berberine recovered from the limewater and sulfuric acid extracts. Furthermore, the lactic acid solvent and its extracts demonstrated no cytotoxicity toward the human embryonic kidney cell line. The findings of this investigation establish a foundation for future studies utilizing eco-friendly solvents for alkaloid extraction from medicinal plants. This lays the groundwork for implementing a large-scale extraction process of natural active compounds in a safe and environmentally conscious manner.

Toward Thin Dielectric Films of Polyetherimide Electrodeposited from Aqueous Emulsions of the Polymer

Miniaturized, high power electronic devices are needed for a variety of applications. Although, the miniaturization of these devices is challenging. For instance, high power capacitors need to sustain high electric fields, with typically several hundred volts across micrometric dielectric layers. Among the most promising materials for this application, polyetherimide (PEI) has a number of desired characteristics such as adequate electrical properties, good chemical and mechanical resistance with thermal stability up to 170°C.Spin-coating is the conventional technique used in the microelectronics industry for polymer thin film deposition. However, this technique is not appropriate to form conformal deposits on 3D-structured substrates. To overcome this limitation, we investigate an electrochemical deposition process of PEI in which the electrolyte is an aqueous emulsion formed from organic droplets containing the polymer [1]. In this work, a pulsed voltage below 2 V/ECS, was applied for the deposition of PEI on Cu metal surfaces. The influence of deposition conditions on the thickness and surface smoothness of the deposit was thoroughly investigated, identifying the processing window.PEI aqueous emulsions were synthesized as follows, after the raw material dissolved in a mixture of N-methylpyrrolidone and acetophenone, N-methylpiperazine was added to be grafted on the imide groups of the polymeric chains. The PEI emulsions were subsequently produced by ultrasonic mixing [2] of the reaction crude with an aqueous solution of lactic acid. During mixing, nanoscale droplets were formed and electrostatically charged by protonation of ternary amine groups of N-methylpiperazine.Critical for the application are the droplet size and stability of the emulsion. These properties were modulated upon stoichiometry of both N-methylpiperazine for the degree of modified imide cycles and lactic acid for the degree of protonation of the amine [1,2]. FTIR and NMR were used to screen the quantity of modified imide groups, displaying that the PEI imide function attack by N-methylpiperazine is quantitative. The protonation was indirectly characterized by measuring the zeta potential of the emulsion [3]. As a result, in an optimized sequence, droplets with hydrodynamic diameters below 200 nm were repeatedly formed with zeta potentials greater than 50 mV. For emulsions containing 3.5 wt% PEI with 64 % modified imide groups and 50 % quaternisation, representing 32 % of the imide cycle initial population. The emulsions were stable for at least twenty-one days at 4°C. This is a significant improvement as compared to the stability reported in the literature [1].Deposition tests were conducted in a 3-electrode electrochemical cell, using a 10-time diluted emulsion, at relatively low voltage, below 2 V/ECS with pulsed DC waveform under mild conditions (room temperature, pH between 3 and 5). The pulses allowed the movement of droplets in the emulsion towards the cathode while minimizing H2 evolution. Under these conditions, a PEI coating was obtained with a thickness of a few micrometers within 600 s. The impact of deposition parameters on coverage and uniformity was also studied in detail.The last process step by removing the N-methylpiperazine and the residual solvents consists in recovering the initial unmodified structure of PEI grafted on the substrate. Curing conditions were chosen according to the previous literature [1] under vacuum. The FTIR spectra of the coated substrate were recorded after curing. From the FTIR spectra, the disappearance of the amide (I and II) peaks after curing and a good peak-for-peak correspondence between the spectrum of the cured polymer and the pristine polymer are observed.This work demonstrates that polymer films can be deposited by an electrochemical process under mild conditions, assuming that a stable emulsion of charged polymer droplets can be formed. The process is well suited to coat 3D structured substrates, in contrast with more conventional techniques for polymer deposition. This original electrodeposition process should allow the realization of integrated capacitors on silicon wafers for the next generation of power electronics devices.

Anchoring highly-dispersed ZnCdS nanoparticles on NiCo Prussian blue Analogue-derived cubic-like NiCoP forms an S-scheme heterojunction for improved hydrogen evolution

This study used a facile hydrothermal technique to obtain a novel ZnCdS/NiCoP S-scheme heterojunction for highly photocatalytic H2 generation, Notably, phosphatization was used to derive the cubic NiCoP from a Prussian blue analog ZnCdS nanoparticles are simple to disperse on the surface because NiCoP has a cubic characteristic, which easily transfers interface charges, and consequently accelerates surface reaction kinetics. Furthermore, the ZnCdS/NiCoP-3% composite exhibited the highest photocatalytic H2 generation performance of 582.98 µmol with an apparent quantum yield (AQY) of 7.93% at 450 nm in the lactic acid aqueous solution, which is approximately 4.16 and 500-fold higher than that of the pure ZnCdS and NiCoP, respectively. Additionally, outstanding photostability was achieved after 20h of the four cycling experiments. Consequently, the peachy photocatalytic hydrogen evolution can be imputed for establishing S-scheme heterojunction, maintaining doughty redox capacity and achieving spatial separation of charges, thereby vastly restraining the fast recombination of photoexcitation. Furthermore, the photoluminescence (PL) spectroscopy and hydroxyl radical (OH) capture experiments further proved the S-scheme mechanism. Therefore, this study provides a neoteric perspective establishing S-scheme photocatalytic systems for solar energy conversion.

APPLICATION OF ORGANIC ACIDS FOR THE TREATMENT OF BEES AGAINST VARROATOSIS

The effectiveness of oxalic and lactic acids against varroatosis of honeybees was studied in laboratory and apiary conditions in the late autumn period. The studies were performed in the Tyumen Region apiaries in accordance with "Guidelines for the study of means and methods to control the varroa mite". The results of laboratory experiments showed that the maximum acaricidal activity was observed for 3.5% oxalic acid and 15% lactic acid and was 98.6±1.7% and 96.3±3.5%, respectively. In apiary conditions, the effectiveness was 87.1±2.2% (85.4–89.5%) for a single treatment of the broodless bee colonies with 3.5% oxalic acid by watering the bees in interframe spaces with 5 ml per beeway. In the control group, death of mites corresponded to 11.7±1.1%. The number of varroa mites was reduced by 90.0±2.1% (94.4–88.3%) by treating the broodless bee colonies twice in a 5 day interval with 15.0% aqueous lactic acid solution by spraying the frames with bees in a volume of 5 ml on each side of the comb. At the same time, the maximum death rate of mites was observed in the bee colonies during the first day after the treatment. The mite mortality was 10.7±1.10% in the control group during the follow-up. No death of queen-bees or bees was detected during the treatment in both experiments.

Black Phosphorus Quantum Dots Modified CdS Nanowires with Efficient Charge Separation for Enhanced Photocatalytic H2 Evolution

AbstractConstructing a high‐quality interface with strong coupling interaction is highly desirable in composite photocatalysts for the efficient interfacial charge transfer. Herein, we prepared black phosphorus quantum dots/CdS (BPQDs/CdS) binary composites with tight interfacial contact via a facile electrostatic self‐assembly approach for efficient photocatalytic H2 evolution. The optimized H2 evolution rate of 3 wt % BPQDs/CdS can reach up to 9.9 mmol g−1 h−1 in lactic acid aqueous solution, 99 and 5.5 times greater than that of pristine BPQDs and CdS, respectively. Benefiting from the strong interface interaction between CdS and BPQDs in well‐contacted BPQDs/CdS composites, efficient charge separation can be achieved, leading to enhanced photocatalytic H2 evolution activity. Notably, the rapid transfer of photogenerated electrons from CdS to BPQDs was unambiguously confirmed by time‐resolved transient absorption spectroscopy.

The important role of non-covalent interactions for the vibrational circular dichroism of lactic acid in aqueous solution

We present a computational study of vibrational circular dichroism (VCD) in solutions of (S)-lactic acid, relying on ab initio molecular dynamics (AIMD) and full solvation with bulk water.

Removal of paracetamol in the presence of iron(III) complexes of glutamic and lactic acid in aqueous solution under NUV irradiation

Low concentrations of drugs and their metabolites occurring on the aquatic environment are of significant concern due to their potential effects. This work reports on the removal from aqueous solution, of paracetamol or acetaminophen (APAP) as a model pharmaceutical pollutant, promoted by the photo-Fenton system generated by the photolysis of two organic iron(III) complexes, FeIII-Glutamate & FeIII-Lactate, under 365 nm irradiation (2 < pH < 4). UVA photolysis of these complexes is relatively fast: ca.73% of the FeIII-Glu complex decomposed after 1 h of irradiation (t½=6.4 min, pH = 3.40), 91% in the case of FeIII-Lact complex (t½=6.4 min, pH = 3.0). FeIII + Lact system showed a maximum pseudo-first order rate constant at pH ca. 3, while for FeIII + Glu system it increases with pH.NUV irradiation of FeIII-carboxylic acid complexes promotes APAP photodegradation, that is faster with lactate. The maximum pseudo-first order rate constant was observed at pH = 3 for FeIII + Lact + APAP, while it slightly increased with pH for FeIII + Glu + APAP. The rate constant decreases for both systems as APAP concentration increases, likely due to the formation of FeIII-APAP complexes. At t > 180 min, a second, slower, process is observed.Addition of 1% of t-BuOH and anaerobic conditions inhibit APAP photodegradation, which indicates APAP photodegradation in the presence of FeIII-Glu and FeIII-Lact complexes is limited by formation of H2O2, the source of HO. Seven transformation photoproducts were identified by HPLC-MS, mainly hydroxylated derivatives. Reaction pathways are identified, highlighting the role of the photoformed FeIII-carboxylate long-lived radicals, dissolved O2 and HO in the abatement of pollution due to emerging organic contaminants such as APAP.

Study of effectiveness of lactic acid at varroatosis in the apiaries of Tyumen Region, Russia

The study objective is to study the effectiveness of lactic acid in varroatosis and its impact on the development of bee colonies under conditions of the South of Tyumen region. The acaricidal effectiveness of lactic acid was studied in October 2019 using one method in two experiments in 30 broodless bee colonies kept in two apiaries, where bee colonies were divided into 2 groups (experimental - 10 colonies and control groups of 5 colonies each). For treatment of bee colonies from the experimental group, frames with bees were removed from the hives in turn, which were sprayed with a 15.0% aqueous solution of lactic acid in the volume of 5 ml on each side of the honeycomb. Bee colonies were treated twice with an interval of 5 days. The bees in the control group were not treated. Dead mites were registered on a daily basis in all groups within 5 days after each treatment, for these reasons laminated cardboard sheets were placed on the bottom of the hives, which then were taken out and the number of fallen ectoparasites was recorded. Studies on the impact of lactic acid on the development of bee colonies were conducted in 20 brood bee colonies in the period from May to July 2020. It has been found that the effectiveness of treatment of experimental bee colonies with the drug was 90.0 ± 2.1% (apiary No 1) and 7.8 ± 1.9% (apiary No 2). At the same time, the maximum death of mites in colonies was observed during the first day after treatment. In the control groups, the number of mites decreased by 10.9 ± 0.8% and 11.6 ± 1.0%, respectively. It has been established that the treatment of bees with an aqueous solution of lactic acid in the above concentration, dose and multiplicity did not have a negative impact on the development of bee colonies, their strength and food supply, and no deaths of bees and queens were detected during the observation period.

Effects of lactic acid and mixed acid aqueous solutions on the preparation, structure and properties of thermoplastic chitosan

In this paper, a lactic acid (LA) aqueous solution and a mixed acid (MA) aqueous solution, composed of lactic acid and hydrochloric acid (HCl), were used as plasticizers to plasticize thermoplastic chitosan. The plasticizing behavior of chitosan under melt processing with different concentrations of the LA and MA solutions and different ratios of HCl and LA were studied. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the acidity and concentration of the acid solution had direct impacts on the chitosan structure. The thermal melting effect of chitosan was improved with increasing lactic acid concentration in the LA solution and HCl concentration in MA solution. The sheet light transmission, hydrophobicity, thermal stability and mechanical properties of thermoplastic chitosan could be adjusted by changing the ratios of hydrochloric acid and lactic acid in the MA solution. This work expanded the theoretical knowledge of acid solution modified thermoplastic chitosan.

Lithium incorporation assisted synthesis of ultra-small Mo2C nanodots as efficient photocatalytic H2 evolution cocatalysts

Photocatalytic H2 production is a promising way utilizing solar energy to replace fossil fuels. To develop highly efficient, earth-abundant, and low-cost cocatalysts to replace Pt is significant for the scalable solar H2 production. Herein, a lithium incorporation assisted method is developed to synthesize ultra-small Mo2C nanodots, whose cocatalytic activity is 12.23 times of the pristine MoC coupled with CdS. Morevoer, the photocatalytic performance of Mo2C/CdS measured in the lactic acid aqueous solution is 5.81 times of Pt/CdS under the same condition and 71% of Pt/CdS measured in the Na2S/Na2SO3 solution. The apparent quantum yield (AQY) at 420 nm is as high as 39%. And it shows a better cocatalytic performance than Pt loaded on g-C3N4. The high cocatalytic performance is attributed to the more exposed active surface area because of the small size and high loading amounts of Mo2C on carbon. The mechanism study suggests that the Li ion incorporation is beneficial for the formation of ultra-small MoO2 nanodots intermediate during the pyrolysis of ammonium molybdate and ultra-small MoO2 nanodots are transformed to ultra-small Mo2C nanodots accompanying with the Li ion removal after the further carbonization. It is expected that this strategy can be applied to synthesize other ultra-small metal compound nanodots.

Nitrogen defects-rich porous graphitic carbon nitride for efficient photocatalytic hydrogen evolution

Graphitic carbon nitride (CN) is considered as a promising photocatalyst for solar energy conversion. However, low specific surface area and fast electrons and holes recombination restrict the photocatalytic applications of CN material. Herein, a nitrogen defect-rich and highly porous CN nanostructure (CN-LT) was prepared by combining two strategies, i.e., LiOH treatment and heat etching. The as-prepared nitrogen defect-rich porous CN-LT not only has a larger specific surface area, as compared with pristine CN, but also the photogenerated electron-hole separation was boosted remarkably. Using Pt as a co-catalyst and lactic acid aqueous solutions as sacrificial reagent under visible light irradiation (λ > 400 nm), the hydrogen evolution reaction (HER) rate for CN-LT (1.54 mmol h−1 g−1) was 19.25 times higher than that for pristine CN (0.08 mmol h−1 g−1). While subjecting pristine CN to heat etching under the same experimental conditions, excepting the use of LiOH (CN-T), an increase in HER rate of 7.5 times was obtained. Our current study may shed more light on the enhancement of the photocatalytic activity of bulk CN materials by altering their microstructure.

Quantitative analysis of total acidity in aqueous lactic acid solutions by direct potentiometric titration

In aqueous solutions of concentrated lactic acid (>30 wt%), oligomers of lactic acid can produce via the intermolecular esterification of lactic acid, and thus the amount of titratable acidity is often less than that of total acidity. In this paper, the hydrolysis of oligomers of lactic acid was investigated at different temperatures in detail. The experimental results showed that when the content of total acidity is lower than 30 wt% in aqueous lactic acid solutions, the oligomers of lactic acid can been completely hydrolyzed to give monomeric lactic acid and the monomeric lactic acid is stable at temperatures of 8–33 °C, thus the total acidity is equivalent to the titratable acidity and can be determined quantitatively by a direct potentiometric titration. The results for determining total acidities were in good agreement with those obtained from a back titration by a two tailed t-test. Compared with the back titration, the novel method's procedure is simpler and reducing sugars do not interfere with measurements. The relative standard deviation (RSD) was less than 0.7% and 1.1% for the direct potentiometric and back titrations, respectively, which indicated that the direct potentiometric titration has a higher precision.

Facile preparation and high photocatalytic activity of crystalline graphitic carbon nitride in hydrogen evolution from electron donor solutions under visible light

The synthesis of nanostructured crystalline graphitic carbon nitride (CGCN) by a treatment of bulk g-C3N4 in a KCl + LiCl melt, both in an argon stream and air, is described. The materials obtained were investigated using X-ray diffraction, infrared, UV-vis, and photoluminescence spectroscopy, scanning electron microscopy, and X-ray photoemission spectroscopy. The activity of the treated samples of CGCN in the photocatalysis of H2 evolution from aqueous solutions of lactic acid and ethanol under visible light exceeds the activity of the initial g-C3N4 by more than an order of magnitude. The CGCN photocatalyst synthesized by the thermal treatment of bulk g-C3N4 in the air is practically not inferior to the materials produced in an inert atmosphere, which opens up the possibility of scaling up their synthesis. The optimum conditions for obtaining initial g-C3N4 for synthesizing CGCN samples with high photocatalytic activity were determined.

Synthesis of Ag nano-chitosan in lactic acid solvent by irradiation method

Colloidal Silver Nanoparticles were synthesized by Gamma ray irradiation in aqueous lactic acid solution containing chitosan as stabilizer. The aim of this research is to know the effect of irradiation dose and concentration of chitosan in the formation of Nano-silver. Silver Nitrate of 2 mM is dissolved in the chitosan solution. The effect of chitosan concentration which varied 0,.3%, 0. 5%, and 0. 7%(b/v) were irradiated with gamma ray at dose of 5, 10 and 15 kGy. The formed of silver Nano were identified using UV–Vis spectrophotometer, particle size analyzer (PSA) and FTIR. The result shows, the concentration of chitosan (0.3 – 0,7%) in the irradiated solution also considerably affected the silver Nano particles size which decreased with increasing of irradiation dose. Due to the unique features of the processing procedures, thus γCo-60 ray irradiation has been considered as a suitable method for synthesis of colloidal silver nanoparticles.

Chemical degradation of dental CAD/CAM materials.

The chemical properties of the oral environment have an appreciable influence on the in vivo degradation of CAD/CAM materials. The aim of the present study was to investigate the effect of organic acids, heptane and ethanol (the food-simulating liquids) on CAD/CAM restorative materials. Four CAD/CAM materials were selected: (1) 3M ESPE LAVA Ultimate, (2) VITA Enamic, (3) IPS e.max CAD, (4) VITA Suprinity. Seven different samples were fabricated in 15 × 4 × 1.2 mm dimensions from each material (n = 7, N = 140). The materials were conditioned for 7 days at 37 °C as follows: artificial saliva, 75% ethanol, heptane, 0.02 N citric acid, 0.02 N lactic acid in aqueous solution and were tested to obtain flexural strength, surface micro-hardness and wear characteristics. After conditioning, the flexural strength values were assessed using a universal testing machine (1 mm/min crosshead speed) and the fractured samples were used for determination of Vickers hardness values using a digital micro-hardness tester (100 g/10 s) and determination of wear using a chewing simulator. Two factor analysis of variance with interaction model and Tukey's post hoc test were used for statistical analysis. The highest mechanical property values were found for IPS e.max and VITA Suprinity and the lowest values were found for LAVA Ultimate. Organic acids negatively affected the mechanical properties of e.max CAD and Suprinity. Ethanol and heptane were more effective on LAVA Ultimate and Enamic. There were significant differences among groups (p <0.05). The mechanical properties of CAD/CAM restorative materials are influenced by food-simulating liquids.