Chloroform Vapor Research Articles

Sensing Volatile Pollutants with Spin-Coated Films Made of Pillar[5]arene Derivatives and Data Validation via Artificial Neural Networks.

Different types of solvents, aromatic and aliphatic, are used in many industrial sectors, and long-term exposure to these solvents can lead to many occupational diseases. Therefore, it is of great importance to detect volatile organic compounds (VOCs) using economic and ergonomic techniques. In this study, two macromolecules based on pillar[5]arene, named P[5]-1 and P[5]-2, were synthesized and applied to the detection of six different environmentally volatile pollutants in industry and laboratories. The thin films of the synthesized macrocycles were coated by using the spin coating technique on a suitable substrate under optimum conditions. All compounds and the prepared thin film surfaces were characterized by NMR, Fourier transform infrared (FT-IR), elemental analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle measurements. All vapor sensing measurements were performed via the surface plasmon resonance (SPR) optical technique, and the responses of the P[5]-1 and P[5]-2 thin-film sensors were calculated with ΔI/Io × 100. The responses of the P[5]-1 and P[5]-2 thin-film sensors to dichloromethane vapor were determined to be 7.17 and 4.11, respectively, while the responses to chloroform vapor were calculated to be 5.24 and 2.8, respectively. As a result, these thin-film sensors showed a higher response to dichloromethane and chloroform vapors than to other harmful vapors. The SPR kinetic data for vapors validated that a nonlinear autoregressive neural network was performed with exogenous input for the best molecular modeling by using normalized reflected light intensity values. It can be clearly seen from the correlation coefficient values that the nonlinear autoregressive with exogenous input artificial neural network (NARX-ANN) model for dichloromethane converged more successfully to the experimental data compared to other gases. The correlation coefficient values of the dichloromethane modeling results were approximately 0.99 and 0.98 for P[5]-1 and P[5]-2 thin-film sensors, respectively.

Synthesis, Structural Characterization and Temperature Effects on Chloroform Vapor Sensing Properties of ZnO Nanocrystals

In this study, nanocrystalline ZnO were synthesized onto glass substrates by using sol-gel method. Structural characterizations were performed by XRD, SEM and AFM techniques. Potential application of nanocrystal ZnO as chloroform sensor was investigated. Response of the fabricated thin films of the ZnO nanocrystals towards chloroform vapor was investigated depending on gas concentration (750-15000 ppm) between the temperatures of 22‒150 ºC in nitrogen ambient. Gas flow rates were controlled by using flow controller and flow meters. All the measurement system was computerized. XRD results revealed that thin film of the ZnO nanocrystals on the glass substrate was in crystal form and can be characterized by 036-1451 JCPDS number. Crystallite sizes of the ZnO nanocrystals were determined both by SEM images and the Scherrer equation. The crystallite sizes were calculated between 27.9 – 50.4 nm using the Scherrer equation. The sensors showed reversible response towards the chloroform vapor in the measured temperature and gas concentration range. Response time and sensitivity values of the sensors towards the chloroform vapor were also calculated. The increase in temperature caused to increase in sensitivity values. The best sensitivity values were obtained at 150 ºC.

Antifungal Potential of Bioactive Metabolites Produced by Pseudomonas aeruginosa against Candida Species

Abstract: Background: The frequency of fungal infections targeting immune-suppressed patients has been prominently rising day by day. Among these infections, Candidiasis is one of the most common life-threatening systemic fungal infections in recent years. These infections are challenging to treat because of the inconvenience of effective antifungal drugs. Therefore, the insufficiency of current drug regimens coupled with constant mutations by the fungi to develop drug resistance can pose a potential problem for future anti-fungal treatments. This frequent increase in drug-resistant fungi has directed attention toward the use of alternative therapy from natural sources. Objective: This study aimed to evaluate Pseudomonas aeruginosa for its antifungal potential against Candida species. Materials and Methods: This study was conducted at the Federal Urdu University of Arts, Science and Technology, Karachi, Pakistan during 2021-2022. For the detection of the antifungal compound, a clinical isolate P. aeruginosa HS 28 (identified conventionally as well as by 16S r RNA analysis) was screened for its bioactivity against Candida species by using agar well diffusion technique. The growth kinetics as well as the effect of different physical and chemical factors were also determined in the study. The compound was also partially purified by ammonium sulfate precipitation. Result: This antifungal compound showed good inhibitory activity against Candida species such as Candida albicans, C. glabrata, C. tropicalis, C. krusei, etc. This compound retained its stability at a high range of temperatures, and varying pH. Moreover, its bioactivity was also conserved when treated with organic solvents, chloroform vapors, metal salts, and different surfactants/detergents. The growth kinetics analysis illustrated that the maximum production of antifungal compounds occurred in the log phase of growth and extended supreme until the late log phase. Furthermore, the highest saturation of this protein was achieved at the concentration of 60% ammonium sulfate. Conclusion: The overall results indicated the promising antifungal potential of the compound produced by Pseudomonas aeruginosa HS 28 against Candida species.

An anthracene-containing crown ether: synthesis, host-guest properties and modulation of solid state luminescence.

Organic solid state vapochromic materials are of great significance for the development of supramolecular chemistry and materials science. Herein, we synthesize a crown ether derivative (An34C10) containing two anthracene units and construct new crown ether-based vapochromic host-guest co-crystals. Due to the presence of anthracene, An34C10 not only shows good fluorescence properties but also displays mechanochromism. Single crystal structural analysis, powder X-ray diffraction and differential scanning calorimetry experiments demonstrate that the transformation between different stacking modes of An34C10 is responsible for mechanochromism. In addition, An34C10 can complex with 1,2,4,5-tetracyanobenzene (TCNB) to form host-guest complex (An34C10@TCNB) co-crystals. Because organic solvent fuming alters charge-transfer interactions in An34C10@TCNB, the fluorescence of the co-crystals can be turned on and off by 4-methylpyridine and chloroform vapors, respectively, realizing selective detection with opposite emission outputs. Meanwhile, the stimuli-responsive properties of An34C10 and An34C10@TCNB possess good cycling performance. This work provides a new strategy for the construction of organic solid state luminescent materials.

Characterization of Lactoperoxidase (LPO) Enzyme Thin Films for Volatile Organic Compound (VOC) Sensing

Spin-coated thin films of lactoperoxidase enzyme (LPO) were used on conjunction with the bio-composite (chitosan–gelatin), glutaraldehyde and cysteine as first-layers to characterize the interactions on the sensing characteristics. The prospect of tuning these three under-layers is to investigate the change of active vapor binding sites of LPO film after inter-layer interactions. Initially, spin-coated thin film properties of three under-layers and LPO are investigated by reporting deposited mass and layer thickness using the quartz crystal microbalance (QCM) frequency change. LPO spin-coated films with different under-layers are exposed to formic acid, acetic acid, chloroform, acetone and ethyl acetate vapors. The response characteristics of LPO films are investigated via QCM using time dependence frequency recording. LPO films are sensitive to those five vapors and the chemical and the physical properties of the analytes affect the sensitivity and the response rate. The results showed that the structural changes in the thin film affect the number of active binding sites of sensitive layer and thus the sensor response can be enhanced.

Assessment of the Cytomorphology of the Cerebral Cortex of Wistar Rats Exposed to Eliozu Dumpsite Leachate

The cerebral cortex is the outermost layer of the cerebrum and plays a critical role in various cognitive, sensory and motor functions. It is highly folded and has distinct regions responsible for different functions. Leachate refers to the liquid that forms when water percolates through waste materials, such as landfills and dumpsite picking up various organic and inorganic compounds along the way. It is a complex mixture of chemicals, including heavy metals, volatile organic compounds (VOC) and other potentially harmful substances. Eliozu dumpsite is one of the biggest dumpsite in Port Harcourt metropolis. It receives deposits of both domestic and industrial wastes from Port Harcourt, these wastes are dumped untreated, and thus may pose serious environmental risks to inhabitants in the area. The present study focuses on the assessment of the cytomorphology of the cerebral cortex exposed to Eliozu dumpsite leachate using Wistar rats as model. Twenty five (25) male Wistar rats were divided into five groups of five animals each; the leachate was collected from the dumpsite and water from near-by borehole also collected. Group 1 which served as control group received 1ml of commercial bottle water, group 2 received 1ml of borehole water 1kilometer from the dumpsite, groups 3, 4 and 5 received different concentration of the leachate in 10%, 50% and 100% for ninety days, the animals were sacrificed after being anesthetized with chloroform vapor, the brains were collected and put in 10% formaldehyde, sectioned and stained with haematoxylin and eosin (H&E), special stain Gorgon and Sweet for histopathological studies. The slides were placed in a light microscope and analyzed by a consultant Anatomy pathologist. The results revealed that the Eliozu dumpsite leachate does have deleterious effect on the cytomorphology of the cerebral cortex. Eliozu dumpsite leachate has shown deleterious effect on cerebral cortex which is an indication of toxicity that may cause brain death to the experimental animals. Therefore, it is recommended that continued research, education and public awareness are essential to promote sustainable waste management practices and safeguard the integrity of the cerebral cortex.

THE SENSING PERFORMANCE OF SURFACE-MODIFIED POROUS SILICON GAS SENSORS FOR NON-POLAR GAS DETECTION

Gas sensors are important devices in various industrial and environmental monitoring applications. Toluene and chloroform are harmful non-polar gases that are produced in various combustion processes and are associated with air pollution and respiratory diseases. Porous silicon (PS) has shown promising results as a material for ammonia and ethanol gas sensing applications. However, there is potential for further improvement by optimizing their surface properties for non-polar gas sensing applications. Chemical treatment has been widely utilized to modify the surface characteristics of materials, including semiconductors, for various applications. We have deposited nickel (Ni) layer on PS surface using chemical treatment. In comparison to the PS sample, it was discovered that the Ni-deposited PS sample was more sensitive to 0.1 ppm concentrations of non-polar toluene and chloroform vapours, increasing from 1% to 39% and 32.6%, respectively. This study provides valuable insights into the surface modification techniques for enhancing the performance of gas sensors, which can have a significant impact on the development of advanced sensing technologies for environmental and industrial applications.

Alzheimer’s- and Multiple Sclerosis-Like Features on Key Brain Centres of Wistar Rats Exposed to Cypermethrin and Dichlorvos

Insecticides are suspected environmental factors in the aetiology of Alzheimer’s and multiple sclerosis diseases. Several studies have reported long-term exposure to insecticides in the development of plaques, neurofibrillary tangles, and demyelination. However, there is no literature on the impact of short-term combined insecticide exposure on specific neurological conditions. This investigation assessed the role of short-term exposure to the mixture of cypermethrin and dichlorvos on Alzheimer’s- and multiple sclerosis-like features. Thirty-two male adult Wistar rats were divided into four groups: the control group was exposed to normal atmospheric air, and the test groups were exposed to a combined cypermethrin and dichlorvos at 2, 3, and 4 h/day [LC50 of 5 mm-1 (4.4 ppm) of dichlorvos and 10 mm-1 (8.7 ppm) of cypermethrin] for four weeks. In the last three days of exposure, neurobehavioural tests were conducted. Twenty-four hours after the last exposure, the animals were anesthetized using chloroform vapour. The brains were harvested by making an occipitofrontal incision for biochemical and histological assessment. The fixation was done in 10% neutral buffered formalin for 48 h following the brain mapping to isolate the brain tissue of interest. The insecticide-exposed rats showed significant (p<=0.05) progressive behavioural deficits and oxidative stress when compared to the control group. Neurofibrillary tangles, senile plaques, and demyelination of the neurons were observed in the brains of the insecticide-exposed rats. This study indicates that the mixture of cypermethrin and dichlorvos can induce the development of Alzheimer’s and multiple sclerosis within a short time

A new approach for the adsorption kinetics using surface plasmon resonance results

This work is focused on a new approach to determine the adsorption kinetics of Surface Plasmon Resonance (SPR) measurement data yielded from Calix[4]arene Langmuir-Blodgett (LB) thin films upon exposure to a range of volatile organic vapors such as benzene, chloroform, toluene and ethyl acetate. Experimental results were analyzed using the well known Pseudo first-order and second-order, Ritchie and Elovich adsorption models. The validity of these models was assessed by using the correlation coefficient (R2) as an indicator of the conformity between the model prediction and experimental adsorption data. Sorption capacity, adsorption rate constant and the amount of vapor molecules were calculated and discussed. The values of R2 = 0.96, R2 = 0.94, and R2 = 0.98 for chloroform vapor were calculated for Pseudo-first order, Pseudo-second order and Elovich models respectively. Pseudo-second order model gave the best fit values for benzene (R2 =0.9991), toluene (R2 =0.999) and ethanol (R2 =0.993).

Responsive polymer thin films

Responsive polymer thin films

EFFECTS OF RED BANANA MEAL SUPPLEMENTED WITH VITAMIN ON RATS BIOCHEMICAL INDICES

This study aimed at comparing the effects of peeled and unpeeled red banana meal with vitamin C, B12 andB complex supplementation on some biochemical indices of different groups of Wistar rats. Forty eight (48)weanling albino Wistar rats weighing between 41 – 57 g were used. They were randomly selected into six(6) groups consisting of eight (8) rats. Coded as Unpeeled Red Banana with Vitamin (URWV), UnpeeledRed Banana without Vitamin (URWO), Peeled Red Banana with Vitamin (PRWV), Peeled Red Bananawithout Vitamin (PRWV), nutribom and normal rat pellet. They experimental animals were acclimatized for3days and animals were given food and water for 21days the left overs were recorded daily. At the end ofthe 21days feeding, animals were anesthetized using chloroform vapour, blood sample taken for biochemicalanalyses serum AST, ALT, ALP, lipid profile were assayed .The results of the study showed that serum ALTof rat fed with unpeeled red banana with vitamin (URWV) was 26.88 ± 2.65µl/L while rat fed with nutribom(control) was 26.75 ± 1.60 µl/L. The ALP of rats fed with URWV was 239.43 ± 35.25 µl/L which increasedsignificantly (P ? 0.05) when compared with control (184.11 ± 16.68 µl\L/). Total cholesterol increasedsignificantly in URWV 3.87 ± 0.13 µl/L (p ? 0.05) when compared with control 1.86 ± 0.17 µl/L, TG & HDLlevel were not significantly higher than the control in URWV, PRWV and PRWO. Total protein, albumin andglobulin in all the groups were not significantly different (p ? 0.05) when compared with nutribom thecontrol.

Sterilize Methods Comparison for Soils: Cost, Time, and Efficiency

Soil sterilization is generally used to eliminate or reduce microbial activity in studies involving microbial inoculations, soil enzymes, among others. Achieving an adequate sterility condition is not straightforward due to the variety of resistance structures that are generated in soil microbial ecosystems and the reservoirs that can form between soil aggregates. This is why finding an effective method to achieve good sterilization is important in methodological terms, so the present work aims to compare the effectiveness of three widely used methodologies to sterilize soil and to evaluate their cost/benefit in terms of time and inputs invested. Four treatments were tested: gamma irradiation, sterilization cycles at different times: three cycles of 1 h each and four cycles of 15 min each, and chloroform vapors. The evaluation and comparison of all samples sterilized by the different methodologies were based on the total aerobic heterotrophic bacterial count. The results of this study suggest that it is more efficient to use autoclaving methods because the process is more accessible in terms of equipment and methodologies, and the final results are the same. In the case of this work, sterilization with chloroform vapors had to be rejected. While the use of gamma radiation may be more efficient in terms of time, it can be a costly and inaccessible service for some laboratories that do not have the equipment. Therefore, the most viable options in terms of time, cost, and benefit are those using autoclaves. Among these, shorter treatment times mean a reduction in the cost of using the equipment, so the option of 15-minute cycles is desirable.

PLA 3D Printing as a Straightforward and Versatile Fabrication Method for PDMS Molds.

3D printing is gaining traction in research and development as a way to quickly, cheaply, and easily manufacture polydimethylsiloxane (PDMS) molds. The most commonly used method is resin printing, which is relatively expensive and requires specialized printers. This study shows that polylactic acid (PLA) filament printing is a cheaper, more readily available alternative to resin printing, that does not inhibit the curing of PDMS. As a proof of concept, a PLA mold for PDMS-based wells was designed, and 3D printed. We introduce an effective method to smooth the printed PLA mold, based on chloroform vapor treatment. After this chemical post-processing step, the smoothened mold was used to cast a ring of PDMS prepolymer. The PDMS ring was attached to a glass coverslip after oxygen plasma treatment. The PDMS-glass well showed no leakage and was well suited to its intended use. When used for cell culturing, monocyte-derived dendritic cells (moDCs) showed no morphological anomalies, as tested by confocal microscopy, nor did they show an increase in cytokines, as tested using ELISA. This underlines the versatility and strength of PLA filament printing and exemplifies how it can be valuable to a researcher's toolset.

The Improved Non-Polar Gas Sensing Performance of Surface-Modified Porous Silicon-Based Gas Sensors

The present article studied gas sensor sensing characteristics based on surface-modified porous silicon (PS) by depositing the metal oxide semiconductor layer. The PS layer was prepared through the electrochemical etching of crystalline silicon in an HF-based solution. DC magnetron sputtering technology was used to obtain the p-CuO layer on the surface of the p-PS. The obtained material’s structural, morphological, and sensing behavior were investigated using SEM, XRD, Raman spectra, and the current–voltage characteristics. For the detection of toluene and chloroform vapors, a planar structure was used. The sensing response value revealed that the CuO/PS-based gas sensors have good sensitivity for toluene and chloroform vapors. The sensing mechanism is explained using schematic energy band diagrams. Therefore, this approach is helpful for the development of a simple, cost-effective sensor for detecting non-polar chemical analytes.

Surface plasmon resonance chemical sensor modified with α-naphthylmethacrylate nano thin film for chloroform detection

The research on the rapid and sensitive detection of pollution caused by the products and technologies used has recently attracted attention in the literature. In the detection of volatile organic compounds (VOCs), polymers/monomers are used in the production of sensitive, fast-responding, reversible thin-film gas sensor elements. In this work, the monomer α-Naphthylmethacrylate was selected as thin film sensor element. The α-Naphthylmethacrylate-based nano thin films were prepared with technique of LB. Monomer LB thin films fabricated onto gold-coated glass substrate to investigate their vapour sensing properties by using Surface Plasmon Resonance (SPR) optical technique. This prepared monomer-based thin film sensor exposed to five different concentrations of chloroform vapors varying between 13.98x103-69.9x103 ppm and the sensor response values were recorded. Swelling dynamics’ of this monomer thin film sensor was also illuminated by using Fick's early-time diffusion law. Diffusion coefficients of α-Naphthylmethacrylate LB thin film sensor materials exposed to the five different concentrations of chloroform vapor were calculated with the help of reflected light intensity graph data and Fick's Law as a function of time. It was determined that the diffusion coefficient values of the first and second slope regions as varying between 5.72x10-17-21.97x10-17 cm2s-1 and 3.06x10-17-6.25x10-17 cm2s-1, respectively. SPR kinetic measurement results showed that α-Naphthylmethacrylate material is promising for the detection of chloroform vapor.

Langmuir-Blodgett Films of Arachidic and Stearic Acids as Sensitive Coatings for Chloroform HF SAW Sensors.

Properties of the Langmuir-Blodgett (LB) films of arachidic and stearic acids, versus the amount of the films' monolayers were studied and applied for chloroform vapor detection with acoustoelectric high-frequency SAW sensors, based on an AT quartz two-port Rayleigh type SAW resonator (414 MHz) and ST-X quartz SAW delay line (157.5 MHz). Using both devices, it was confirmed that the film with 17 monolayers of stearic acid deposited on the surface of the SAW delay line at a surface pressure of 30 mN/m in the solid phase has the best sensitivity towards chloroform vapors, compared with the same films with other numbers of monolayers. For the SAW resonator sensing using slightly longer arachidic acid molecules, the optimum performance was reached with 17 LB film layers due to a sharper decrease in the Q-factor with mass loading. To understand the background of the result, Atomic Force Microscopy (AFM) in intermittent contact mode was used to study the morphology of the films, depending on the number of monolayers. The presence of the advanced morphology of the film surface with a maximal average roughness (9.3 nm) and surface area (29.7 µm2) was found only for 17-monolayer film. The effects of the chloroform vapors on the amplitude and the phase of the acoustic signal for both SAW devices at 20 °C were measured and compared with those for toluene and ethanol vapors; the largest responses were detected for chloroform vapor. For the film with an optimal number of monolayers, the largest amplitude response was measured for the resonator-based device. Conversely, the largest change in the acoustic phase produced by chloroform adsorption was measured for delay-line configuration. Finally, it was established that the gas responses for both devices coated with the LB films are completely restored 60 s after chamber cleaning with dry air.

Orientation control of the hexagonal and lamellar phases in thin block copolymer films using in-plane AC electric field

Lamellar and hexagonal pattern rearrangements in thin films of polystyrene–block–poly(2-vinyl pyridine) and polystyrene–block–poly(4-vinyl pyridine) copolymers simultaneously exposed to an in-plane AC electric field and saturated chloroform vapor are studied with atomic force microscopy and analyzed via the numerical solution of the self-consistent field theory equations. It is demonstrated that the use of AC field with the root-mean-square strength higher than 8 V⋅μm−1 allows one to effectively orient microphase-separated domains along the field direction on the tens of microns scale. At the same time, the AC field considerably lowers the risk of breakdown and eliminates effects related to ionic transport in the presence of solvent vapor. The role of such factors as the exposure time, field strength and frequency is investigated. Theoretical considerations prove the equivalent effect of AC and DC fields on the structure of the copolymer film in a wide frequency range. Self-consistent field theory calculations of the free energy as a function of film thickness make it possible to exactly identify which phase dominates in the film. In particular, an apparent transformation of standing cylinders into long threads aligned in the field direction should be interpreted as the phase transition from the perpendicular to parallel hexagonal phase, which can take place in a certain range of film thicknesses, provided the electric field strength exceeds a certain threshold value. In the case of a perpendicular lamellar phase, the domain orientation along the direction of the electric field is always profitable. The observed morphological rearrangements under an in-plane field, which preserve connectivity between the film surfaces through the domains of the minor copolymer block, can be important for practical applications.

Mini-review on a polymers film detector for chloroform vapour: julolidine as fluorescent molecular rotors (JCFMRs)

Mini-review on a polymers film detector for chloroform vapour: julolidine as fluorescent molecular rotors (JCFMRs)

Large-area homoporous membranes (HOMEs) enabled by multiple annealing

Homoporous membranes (HOMEs) featuring through pores with almost identical apertures, are highly desired for high-precision separations. It remains a major challenge to produce large-area HOMEs because the microstructure control and defect annihilation become increasingly difficult when membrane sizes are dramatically increased. Herein, we propose a multiple annealing strategy to fabricate large-area HOMEs. Polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) films are first coated on smooth and large substrates. Being annealed by chloroform vapor, perpendicularly aligned P2VP cylinders are formed within the films, and further converted into through pores via the mechanism of selective swelling-induced pore generation. It is shown that the conventional single-time annealing is inadequate to create the ordered through pores, because P2VP chains may have no sufficient time to locomote to the right position as required for the ideal hexagonally arranged ordering. By virtue of the multiple annealing, well-defined through pores can be generated after consecutive annealing for three times, as more P2VP chains aggregate into the ideally ordering position. The films are transferred and composited onto macroporous substrates, producing composite membranes with an effective area of up to ∼100 cm2. The resultant membranes exhibit excellent separation performances. Importantly, HOMEs can be fabricated on low-cost substrates via this strategy, highlighting their great promise in real-world applications of high-precision separations.

Organic Vapor Sensing Mechanisms by Large-Area Graphene Back-Gated Field-Effect Transistors under UV Irradiation.

The gas sensing properties of graphene back-gated field-effect transistor (GFET) sensors toward acetonitrile, tetrahydrofuran, and chloroform vapors were investigated with the focus on unfolding possible gas detection mechanisms. The FET configuration of the sensor device enabled gate voltage tuning for enhanced measurements of changes in DC electrical characteristics. Electrical measurements were combined with a fluctuation-enhanced sensing methodology and intermittent UV irradiation. Distinctly different features in 1/f noise spectra for the organic gases measured under UV irradiation and in the dark were observed. The most intense response observed for tetrahydrofuran prompted the decomposition of the DC characteristic, revealing the photoconductive and photogating effect occurring in the graphene channel with the dominance of the latter. Our observations shed light on understanding surface processes at the interface between graphene and volatile organic compounds for graphene-based sensors in ambient conditions that yield enhanced sensitivity and selectivity.