Low Concentration Levels Research Articles

Transition to Metallic and Superconducting States Induced by Thermal or Electrical Deoxidation of the Dislocation Network in the Surface Region of SrTiO3

The question as to why deoxidized SrTiO3−δ becomes metallic and superconducting at extremely low levels of oxygen vacancy concentration has been a mystery for many decades. Here, we show that the real amount of effused oxygen during thermal reduction, which is needed to induce superconducting properties, is in the range of only 1014/cm3 and thus even lower than the critical carrier concentrations assumed previously (1017–1019/cm3). By performing detailed investigations of the optical and electrical properties down to the nanoscale, we reveal that filaments are forming during reduction along a network of dislocations in the surface layer. Hence, a reduced epi-polished SrTiO3−δ crystal has to be regarded as a nano-composite consisting of a perfect dielectric matrix with negligible carrier density, which is short-circuited by metallic filaments with a local carrier density in the range of 1020/cm3. We present that electro-degradation leads to a more pronounced evolution of filamentary bundles and thus can generate a superconducting state with higher TC than thermal reduction. These findings indicate that traditional homogeneous models of superconductivity in self-doped SrTiO3−δ need to be revised, and we propose an alternative explanation taking into account the coexistence of metallic dislocation cores with polar insulating regions allowing for polaronic coupling.

Antenna effect on Zn(II) porphyrin-based molecular ensembles for the detection of 2,4-dinitrophenol through energy and electron transfer process.

Twomodular systems were synthesizedcomposed of triphenylamine (ZnTPAP) and pyrene (ZnPyP) covalently linked at meso position of the Zn(II) porphyrins. Both compounds behaved as energy transfer antenna and orthogonal units to enhance the electron donating ability of Zn(II) porphyrins. Detailed photophysical and aggregation studies reveal that an appreciable electronic interaction exists between peripheral units to the porphyrin π-system so that they behave like strong donor materials. The electrochemical and computational studies demonstrate delocalization of the frontier highest occupied molecular orbital (-5.08eV) over the triphenylamine entities (ZnTPAP) in addition to the porphyrin macrocycle. Fluorescence experiments withZnTPAP and ZnPyP in the presence ofdifferent nitro analytes at various concentrations show turn-off fluorescence behaviour and exhibit superior selectivity towards 2,4-dinitrophenol (DNP) with limit of detection (LOD) of ~ 2.3 and 9.2ppm for ZnTPAP and ZnPyP. Photoinduced electron transfer process is involvedin the static and dynamicfluorescence quenching process. A Stern-Volmer quenching association constant (Ksv) determination revealed that ZnTPAP is more sensitive than the ZnPyP. This is attributed to thestrong donating behaviour of TPA unitscaused by intermolecular interaction through metal center and strong π-π interactions with nitro analytes. The present study provides new insights into the ability to tune the affinity and selectivity of porphyrin-based sensors utilising electronic factors associated with the central Zn(II) ion. Furthermore, a smartphone-interfaced portable fluorimetric method by recognising colour variations in RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentration levels will have a significant impact on development of a new class of chemosensors.

Comparative Study on the Effect of GiSelA 5 Rootstock Propagation Methods on Sweet Cherry Growth and Physiology

The basis of orchard production is rootstocks that reduce the vigor of sweet cherry trees. However, not all rootstocks for this species can be easily propagated using traditional methods of stooling or cutting. Some of these must be propagated using the in vitro method. This is expensive and, consequently, increases the price of maiden sweet cherry trees. Our experiment assessed the growth of maiden trees of selected sweet cherry varieties (‘Bellise’, ‘Earlise’, ‘Lapins’, ‘Vanda’) depending on the method of propagation of a semi-dwarf GiSelA 5 rootstock. Additionally, the intensity of physiological processes taking place in the obtained maiden trees was also examined. The experiment compared one type of GiSelA 5 rootstock, obtained using a cheaper softwood cuttings method, with another rootstock propagated using an in vitro method. During the two years of study, there were no significant differences in the percentage of maiden trees obtained in the case of the propagation methods for both types of rootstocks, ranging from 77.43% to 87.74%. The vigor of maiden tree growth in the first year of this study was stronger than in the second year. In particular, the stem diameter of maiden trees varied from 7% to 39%, depending on the variety considered. With the exception of one variety, maiden trees produced from a rootstock propagated by stem cuttings were characterized by a larger stem diameter for the three varieties, ranging from 23% to 29%, and by a greater number of side shoots, ranging from 73% to 172%, compared to those from in vitro. Additionally, when using the stem cutting method of propagation, the rootstocks had a better developed root system, except for the ‘Earlise’ variety. However, most often, no significant differences were found between the methods of propagation regarding the fresh weight of the maiden trees and leaves and their leaf blade area. The activity of physiological processes of maiden sweet cherry trees varied, and no constant regularities were found. In the second year of the experiment, maiden trees were more often characterized by lower levels of net photosynthetic intensity and internal CO2 concentration, which was associated with worse growth results. Based on the collected results, it is recommended to propagate the considered rootstock using stem cuttings, which yields maiden trees with similar and sometimes even better growth parameters than those propagated using the in vitro method.

Orthogonal and antenna effects on the chemosensing behaviour of porphyrins towards 2,4,6-trinitrophenol: Colour recognition and portable photodiode device

In this work, we have developed two modular freebase porphyrins containing triphenylamine (H2TPAP) and pyrene (H2PyP) units at meso position to understand the role of antenna and orthogonal effects on photophysical and chemosensing behaviour with different nitroaromatic compounds (NACs). The fluorescence studies demonstrate that H2TPAP exhibit strong electronic coupling over H2PyP to induce energy transfer process from peripheral units to porphyrin π-system and behave like strong donor materials. The sequential energy and electron transfer process upon addition of different NACs reveals that H2TPAP show unprecedented selectivity towards the detection of 2,4,6-Trinitrophenol (TNP) with a limit of detection (LODs) of ∼2.3 and ∼6.8 ppm for H2PyP. The mechanistic investigations through NMR and other spectroscopic methods evident that the strong donor-acceptor interactions, protonation at the central core of H2TPAP show both colorimetric and fluorimetric changes with the order of quenching efficiency as TNP>4-NP>2,4-DNP > DUN>4-NBA. A handheld portable photodetector was developed to monitor the dynamic change in photocurrent response. Further, a smartphone interfaced portable fluorimetric method was developed by recognizing colour variations in terms of RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentrations levels will have a significant impact on the development of new handheld chemosensor devices for real time detection of explosive compounds.

Glucose influence cold tolerance in the fall armyworm, Spodoptera frugiperda via trehalase gene expression

The fall armyworm (FAW), Spodoptera frugiperda is a cold-sensitive species that overwinters in temperate climates without diapause. Overwintering in insects involves rapid cold hardening (RCH), supported by trehalose (TRE), which serves as an intermediate between glycogen (GLY) and glucose (GLU). However, both GLU and TRE help maintain homeostasis under stress. TRE is hydrolyzed by the enzyme trehalase (Treh) into GLU. This study retrieved Sf-Treh1a, Sf-Treh1b, and Sf-Treh2 from the FAW transcriptome analysis. RNA interference (RNAi) targeting these three Treh genes resulted in significant downregulation of mRNA levels and altered survival rates in RNAi-treated FAW larvae following RCH treatment. High-pressure liquid chromatography (HPLC) quantification of TRE and GLU in treated groups suggests that GLU is an essential component of the hemolymph for survival adaptation to cold conditions in S. frugiperda. This study reveals limited cold adaptability of FAW, as evidenced by lower glucose concentration levels. We found that FAW requires alternative molecules, in conjunction with glucose and trehalose for freeze tolerance and survivability. Our study aims to discover the molecular mechanisms that contribute to freeze tolerance in FAW by exploring the roles of trehalose, glucose, and glycogen.

How components of ESG performance impact corporate risk-taking?

Corporate risk-taking (CRT) is crucial for sustainable business development. The focus of this study is to examine the relationship between components of ESG performance (ESGP) and corporate risk-taking. We conduct an empirical analysis using CSI ESG score data of A-share listed companies on the Shanghai and Shenzhen stock exchanges from 2009 to 2022. The conclusions are as follows: (1) ESGP exerts a facilitating effect on CRT. Specifically, environmental performance inhibit CRT, whereas social responsibility and corporate governance performance enhance CRT. (2) The facilitating effect of ESGP on CRT is more pronounced at lower levels of equity concentration. (3) ESGP enhances CRT by increasing the level of innovation and institutional investor shareholding. The contribution of this study is to help firms change CRT by adjusting the components of ESGP.

Measurements of Heavy Elements and Radioactivity Concentration Levels in Types of Fertilizers and Pesticides Commonly Used in Sana’a Yemen

This study aims to measure heavy metals (HMs) concentration and radioactivity concentration levels in fertilizer and pesticide samples collected from local markets in Sana’a, Yemen. Gamma spectroscopy employing a Survey Sodium Iodide NaI (TI) RIIDEYM-G detector was used for radiation and dose assessments. As for heavy metal analyses, this study used Inductively Coupled Optical Emission Spectroscopy (ICP-OES). Thirty samples were collected from local markets in Sana’a, Yemen. Radioactivity measurements show low levels of radioactivity concentration. The average dose rates due to fertilizer and pesticide samples were 1.14 and 1.07 mSv/y, respectively. These values are nearly equal to the recommended annual radiation dose rate limit (1mSv/y) recommended by the International Commission on Radiological Protection (ICRP). For heavy metal analysis, it was found that the average concentrations of heavy metals (HMs) (cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn)) in the fertilizer samples were 1.08 mg/kg, 4.944 mg/kg, 13.8495 mg/kg, 274.371 mg/kg, 3.30446 mg/kg, 15.35686 mg/kg, and 24.4547 mg/kg, respectively. Heavy metal concentrations in fertilizer samples were mainly less than European (EU) guideline limits, with the exception of a few samples. The average concentrations of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) in the pesticide samples were 0.8 mg/kg, 0.5784 mg/kg, 52.280 mg/kg, 73.4651 mg/kg, 2.4482 mg/kg, 3.199 mg/kg, and 1.1309 mg/kg, respectively. The heavy metal concentrations in pesticide samples were less than the corresponding values in fertilizer samples.

Updating information of mycoses and antifungal medicines to find effective platforms for the production of new thiazole compounds

Introduction. Information about mycoses and antifungal drugs of the modern type is often fragmentary and unsystematic, which requires correction.Aim. To systematize the latest information about fungi and mycoses, means of combating them and the problems encountered along the way, to highlight the latest achievements in the field of synthesis and research of the activities of 1,2,4-triazole as a potential fungicidal compound.Materials and methods. The materials were the authors' research published in advanced scientific journals, conducted around the world in the field of studying fungi, antifungal drugs, and the search for new antifungal agents.Results and discussion. The article provides an overview of current information on the morphobiological features of fungi, updating their taxonomy and nomenclature, shows the role of fungi in nature and the development of fungal infections in humans and animals, structured information on the classification of mycoses and their pathogens. The latest information is also provided on the pharmacological properties of the main currently existing antifungal drugs, the mechanisms of formation of resistance to them in fungi, in a comparative aspect with other groups of antimycotic drugs, the prospects of azoles and their derivatives as new fungicidal drugs and disinfectants are shown. Literature studies have shown that 1,2,4-triazole derivatives have a wide range of antifungal activity, which extends to other types of activity.Conclusion. It was noted that the significant prospects of triazoles are due, among other things, to the fungicidal effect on resistant strains of fungi-pathogens of human and animal infections. The advantage of the new derivatives is the low level of concentrations suppressing fungi, low cytotoxicity, which allows them to be used for intravenous administration in the future. Updating information on the effectiveness of new antifungal compounds will help researchers systematize knowledge about the properties of azoles, which can contribute to the search and development of new potential candidates for antifungal drugs with high efficiency and selectivity, and contribute to the formation of new research directions for the search for effective means of combating mycoses in various fields of human activity.

Glycan-Evocated Metallization for Amplification-Free Electrochemical Detection of Glycoproteins at Low Concentration Levels.

Glycoproteins have become the most often screened tumor markers in the in vitro diagnostics. Although a large number of electrochemical methods have been proposed to sensitively detect glycoproteins, most of them involve the aid of laborious signal amplification. Herein, we report the use of glycan-evocated metallization (GlyMetal) for the amplification-free electrochemical detection of glycoproteins at low concentration levels. Briefly, the glycoproteins of interest are captured by an aptamer recognition layer, and then the glycans of targets are oxidized by NaIO4 to convert the 1,2-diol sites into aldehyde groups for the silver deposition-based metallization, followed by the electrochemical stripping assay of the deposited metallic silver for glycoprotein quantification via the established solid-state Ag/AgCl voltammetric process. As GlyMetal can enable the deposition of a large amount of metallic silver and a high signal-to-background ratio can be obtained for the solid-state Ag/AgCl voltammetric stripping assay, the developed GlyMetal-based electrochemical method is applicable to the amplification-free detection of glycoproteins. As a proof of concept, a detection limit of 1.65 pg/mL has been achieved for carcinoembryonic antigen (CEA) detection. In addition to the high selectivity, desirable results have been obtained with respect to the use of the method for CEA detection in serum samples. In consideration of the desirable simplicity, short assay time, and cost-effectiveness of the amplification-free approach, the GlyMetal-based electrochemical method shows great promise in the point-of-care detection of glycoproteins.

Positional assessment of Concentration among Mysore University Inter-collegiate Male Hockey Players

The Purpose of this investigation was to explore the level of Concentration between different positional play of Mysore University Inter-Collegiate Male Hockey players, the aged between 18 to 22 years. The researcher has randomly selected 165 Male Field Hockey Players those who were Participated in Mysore city inter collegiate Hockey tournament and those who are practicing regularly. The researcher was classified the total samples into eleven (11) categories according to positional play, such as Center forward, right in and right out, Left in and Left out, Center Mid, Right and Left Mid, Left defender, Right & Left Defender and Goal Keeper and the samples were consisted fifteen (N=15) for each position. The Knox Cube imitation test was administered to know the level of concentration among selected subjects. In order to examine the hypotheses of the study one-way ANOVA test was used for multiple comparisons between mean scores of players in different positions for variables of concentration. The findings of the investigation showed that, the Concentration level was found to be higher for goal keeper than the other positional players. Whereas, the left midfielder had low level of concentration when compare with others which was clearly indicated that, there were significant differences in concentration of selected field hockey players with positional wise. On the basis of the present investigation, it will be summarized that the concentration was influencing by different positional play.

Guinea pig spermatozoa adhesion to an immobilized fibronectin matrix alters their physiology and increases their survival.

Isthmus is the region of the oviduct considered a reservoir for spermatozoa, where they are retained and then released synchronously with ovulation. Integrins mediate this interaction, and it is suggested that they regulate the viability and capacitation of spermatozoa. Spermatozoa retained in the oviductal epithelial cells show specific characteristics: normal morphology, intact acrosome and plasma membrane, no DNA fragmentation, and low levels of intracellular Ca2+ and protein phosphorylation at Tyr. This work aimed to define spermatozoa's ability to adhere to an immobilized fibronectin matrix and its effects on their viability and capacitation. We found that guinea pig spermatozoa showed a high affinity for adhering to an immobilized fibronectin matrix but not to those made up of type 1 collagen or laminin. This interaction was mediated by integrins that recognize the RGD domain. Spermatozoa adhered to an immobilized fibronectin matrix were maintained in a state of low capacitation: low levels of intracellular concentration of Ca2+, protein phosphorylation in Tyr and F-actin. Also, spermatozoa kept their plasma membrane and acrosome intact, flagellum beating, and showed low activation of caspases 3/7. The spermatozoa adhered to the immobilized fibronectin matrix, gradually detached, forming rosettes and did not undergo a spontaneous acrosomal reaction but were capable of experiencing a progesterone-induced acrosomal reaction. In conclusion, the adhesion of spermatozoa to an immobilized fibronectin matrix alters the physiology of the spermatozoa, keeping them in a steady state of capacitation, increasing their viability in a similar way to what was reported for spermatozoa adhered to oviductal epithelial cells.

Enhanced efficiency of water purification plant by combined riverbank filtration

Water shortages occur due to several factors, with drought being one of the biggest drivers. Another major environmental issue related to the contamination of freshwater systems worldwide is thousands of micropollutants, although they generally occur at low concentration levels. The provision of safe drinking water to the population in rural developing nations remains a problem, in particular when surface water and shallow wells or non-watertight headworks wells serve as sources of drinking water. Dramatically changing raw water qualities, floods and high rainfall events anthropogenic pollution, lack of electricity supply in developing regions demand new and adapted solutions for treatment and rendering water safe for distribution. Our study aimes to find another source of water supply using riverbank filtration (RBF). The RBF is a water treatment method that removes water from rivers by pumping wells into a nearby alluvial aquifer. Several physical, chemical, and biological processes that occur underground improve the quality of surface water and eliminate the need for traditional potable water treatment. Additional treatment techniques in this process include biological degradation, sorption, and filtration. Physical, chemical, and microbiological variables were used to assess the effectiveness of the RBF system in Upper Egypt. Our study proposes a workable water treatment strategy that replaces RBF treatment or pretreatment technique for high-quality Nile water to eliminate or reduce surface water pollutants without the use of chlorine.

Quantitative determination by UHPLC-MS/MS of 18 common drugs of abuse and metabolites, including THC and OH-THC, in volumetric dried blood spots: a sustainable method with minimally invasive sampling

The increased use of drugs of abuse urges forensic toxicologists to create quick, simple, minimally invasive sampling techniques for biological fluids combined with analytical methods assuring accurate results. To this purpose, a method was developed aimed at quantifying 18 drugs of abuse and metabolites in DBS. Validation of the method was conducted by spiking blank whole blood with the analytes on Capitainer® B cards. The extracts were analyzed by a targeted UHPLC-MS/MS method. Linear calibration was achieved in the range of 1–100 ng/mL for: amphetamine, MDA, MDMA, methamphetamine, cocaine, codeine, benzoylecgonine, cocaethylene, morphine, 6-MAM, buprenorphine, methadone, EDDP, ketamine, norbuprenorphine norketamine, THC, and OH-THC. Experimental LOD was found at 0.5 ng/mL for all analytes except for norbuprenorphine, THC and THC-OH which yielded a LOD of 1 ng/mL. Intra- and inter-day accuracy was satisfactory with bias% resulting within 5%. Evaluation of intra- and inter-day precision yielded CV% values within 20%, for all compounds except EDDP. Average extraction recovery calculated at low (2 ng/mL) and high (75 ng/mL) concentration levels was 63% while average matrix effect determined at the same levels was found to be within 85% − 115% for all analytes except from codeine (70%) and MDMA (131%). The method was applied to authentic blood samples spotted onto the DBS card and the minimum value detected was 1.3 ng/mL. HPLC-MS/MS proved capable to identify all the targeted analytes at low concentrations in the small blood volumes obtainable from DBS cards, which in turn confirmed to be effective and sustainable micro-sampling devices.

Eu-MOF-based highly sensitive and selective luminescence probe for trace, in situ and visual detection of flunitrazepam

Flunitrazepam, as an emerging new psychoactive substance classified as a third-generation drug that is more harmful and camouflaged, is gradually proliferating globally. Maliciously used as a criminal tool in homicide and rape cases, it has already caused serious harm to public safety and social stability. Owing to its special molecular structure, low concentration level and rapid metabolic process in the human body, accurate detection of flunitrazepam remains a major challenge, especially for real sample and on-site detection. In this paper, a lanthanide MOF (Eu-MOF) based on bi-ligand was constructed as a luminescence probe and used for the first time to detect trace amounts of flunitrazepam. The ’antenna effect’ promotes strong luminescence of Eu-MOF, while the lower LUMO orbital energy level of flunitrazepam allows it to accept electrons from the electron donor leading to quenching of Eu-MOF luminescence. The probe has a high sensitivity and can detect flunitrazepam in the range of 0–800 μM with a detection limit as low as 73 nM. Moreover, flunitrazepam was detected in urine from real samples as well as in a variety of beverages to further validate its accuracy and practicality. The reported Eu-MOF represents one of the pioneering luminescence probes for the detection of flunitrazepam, which offers great promise for the on-site or on-line analysis of flunitrazepam.

Neurotoxic Effects of Mixtures of Perfluoroalkyl Substances (PFAS) at Environmental and Human Blood Concentrations.

Per- and polyfluoroalkyl substances (PFAS) may cause various deleterious health effects. Epidemiological studies have demonstrated associations between PFAS exposure and adverse neurodevelopmental outcomes. The cytotoxicity, neurotoxicity, and mitochondrial toxicity of up to 12 PFAS including perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, 6:2 fluorotelomer sulfonic acid (6:2 FTSA), and hexafluoropropylene oxide-dimer acid (HPFO-DA) were tested at concentrations typically observed in the environment (e.g., wastewater, biosolids) and in human blood using high-throughput in vitro assays. The cytotoxicity of all individual PFAS was classified as baseline toxicity, for which prediction models based on partition constants of PFAS between biomembrane lipids and water exist. No inhibition of the mitochondrial membrane potential and activation of oxidative stress response were observed below the cytotoxic concentrations of any PFAS tested. All mixture components and the designed mixtures inhibited the neurite outgrowth in differentiated neuronal cells derived from the SH-SY5Y cell line at concentrations around or below cytotoxicity. All designed mixtures acted according to concentration addition at low effect and concentration levels for cytotoxicity and neurotoxicity. The mixture effects were predictable from the experimental single compounds' concentration-response curves. These findings have important implications for the mixture risk assessment of PFAS.

The potential of local exhaust combined with mixing and displacement ventilation systems to mitigate COVID-19 transmission risks

The performance of two types of air diffusers, a perforated duct and a low-velocity unit coupled with local exhausts, on airborne transmission and cross-infection was investigated in a meeting room. The effect of air diffusers’ locations on airborne transmission was investigated. Six local exhausts were installed above six workstations at 2.0 m height. Respiratory-generated airborne pathogens were simulated using SF6 in the exhaled air of the manikin acting as an infected person. The SF6 concentration in the inhaled air of five susceptible persons remained steady with perforated duct located on the ceiling and at 1.7 m height attached to the corridor wall, but fluctuated greatly when perforated duct were located on the floor, although with a much lower concentration level. The perforated duct under the warm window showed the best potential for mitigating airborne transmission. The concentration in the inhaled air was varied with horizontally supplied low-velocity unit, but much steadier with low-velocity unit at 1.7 m attached to the wall. With an adjusted airflow pattern from low-velocity unit, the inhaled concentration was much lower and uniform among the five susceptible persons. The contaminant removal effectiveness (CRE) was 4.3 with perforated duct under a warm window on the floor. With an adjusted airflow pattern from low-velocity unit, the CRE was much more consistent and increased from 2.1 to 3.9 with an airflow rate from 61 l/s to 116 l/s. The infection probability was the lowest with the perforated duct on the floor and adjusted low-velocity unit.

An In Vitro Study on the Antioxidant Properties of Cistus incanus Extracts

This paper concerns the evaluation of the antioxidant activity (AA) of extracts obtained from cistus herbs grown in Albania and Turkey. The extracts were prepared in a Soxhlet apparatus, as well as by the maceration and infusion methods, similar to the home method of preparing herbal teas. AA was determined using the DPPH (2,2′-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (ferric reducing antioxidant power) and β-carotene methods. It was proven that the AA of extracts depends not only on the extraction technique and AA assessment method but also on the place of plant cultivation. The smallest activity was determined using the β-carotene bleaching method, while the highest values were obtained using the FRAP method. On the other hand, the ABTS method showed a greater activity of the Albanian herb prepared using the Soxhlet technique. In addition, the antioxidant properties of extracts were compared with those of rutin standard solutions, showing that this characteristic component of cistus is not the only one that determines AA of extracts. As a result, the rutin content is not an indicator of the antioxidant properties of extracts. The other polyphenolic compounds, although occurring at lower concentration levels compared to rutin, modify the resultant AA of extracts. These studies confirmed the biological activity of cistus as a valuable source of polyphenolic compounds in the human diet.

Rapid Detection of Ultralow H2S Concentration with on-chip Fabrication of SnO2-based Gas Sensors by Direct Electrodeposition from Non-Aqueous Solvents

Hydrogen sulfide (H2S) causes significant impacts on human health and the environment due to its highly toxic properties. Thus, the design and development of gas sensors to detect and monitor H2S (especially at extremely low concentrations) are challenging tasks for scientists. In this work, SnO2 gas sensors were successfully synthesized directly on a chip by Sn electrodeposition from ethylene glycol solutions + a post-treatment (calcination) stage (to form and stabilize SnO2). Mechanisms and kinetics of Sn electrodeposition on Pt microelectrodes were thoroughly studied using electrochemical techniques. These fabricated gas sensors exhibit a high selectivity toward H2S gas and an effective response to low-level concentrations of H2S in the range of 0.1 ppm–1 ppm at different working temperatures. The influence of electrodeposition conditions and calcination temperatures on the gas response of sensors were also examined. The results have verified that the electrodeposition method from ethylene glycol solutions is promising for the fabrication of ultrasensitive on-chip gas sensors.

Emerging 2D nanoscale metal oxide sensor: semiconducting CeO2nano-sheets for enhanced formaldehyde vapor sensing.

Herein, we fabricated nanoscale 2D CeO2sheet structure to develop a stable resistive gas sensor for detection of low concentration (ppm) level formaldehyde vapors. The fabricated CeO2nanosheets (NSs) showed an optical band gap of 3.53 eV and cubic fluorite crystal structure with enriched defect states. The formation of 2D NSs with well crystalline phases is clearly observed from high-resolution transmission electron microscope (HRTEM) images. The NSs have been shown tremendous blue-green emission related to large oxygen defects. A VOC sensing device based on fabricated two-dimensional NSs has been developed for the sensing of different VOCs. The device showed better sensing for formaldehyde compared with other VOCs (2-propanol, methanol, ethanol, and toluene). The response was found to be 4.35, with the response and recovery time of 71 s and 310 s, respectively. The device showed an increment of the recovery time (71 s to 100 s) with the decrement of the formaldehyde ppm (100 ppm to 20 ppm). Theoretical fittings provided the detection limit of formaldehyde ≈8.86 ± 0.45 ppm with sensitivity of 0.56 ± 0.05 ppm-1. The sensor device showed good reproducibility with excellent stability over the study period of 135 d, with a deviation of 1.8% for 100 ppm formaldehyde. The average size of the NSs (≈24 nm) calculated from HRTEM observation showed lower value than the calculated Debye length (≈44 nm) of the charge accumulation during VOCs sensing. Different defect states, interstitial and surface states in the CeO2NSs as observed from the Raman spectrum and emission spectrum are responsible for the formaldehyde sensing. This work offers an insight into 2D semiconductor-based oxide material for highly sensitive and stable formaldehyde sensors.

Development and validation of a green analytical method for determining fourteen bisphenols in bee pollen by ultra-high-performance liquid chromatography-tandem mass spectrometry

A new analytical method was developed and validated to determine fourteen bisphenols (A, B, C, E, F, M, P, S, Z, AF, AP, BP, FL, PH) in bee pollen using ultra-high-performance liquid chromatography-tandem mass spectrometry. Two different sample treatments were proposed and evaluated: one based on the QuEChERS (quick, easy, cheap, effective, rugged & safe) approach and the other utilizing microextraction with a supramolecular solvent (SUPRAS). In both cases, average analyte recovery ranged between 71 % and 114 %, and the matrix effect was between −45 % and +5 %, although it was not significant when using the QuEChERS-based method (<±20 %). The environmental impact of both sample treatments was assessed using different analytical metrics, with both procedures classified as environmentally friendly, though slightly better results were obtained for SUPRAS. The method was fully validated, showing that the QuEChERS approach had better overall performance, particularly regarding sensitivity and matrix effect. Consequently, the QuEChERS methodology was applied to determine bisphenols in thirty bee pollen samples from different Spanish regions. Residues of three bisphenols (M, P, and S) were detected, although only bisphenol S was quantified in several samples at low concentration levels (<7 μg kg−1), which is below the established specific migration limit (SML; 50 μg kg−1). However, regarding human health, the estimated daily intake, target hazard quotient, and hazard index assessed were higher than acceptable limits, suggesting a potential risk for human consumers.