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Surface-enhanced Raman scattering (SERS) spectroscopy is an ultra-sensitive analytical method with the powerful signal-molecule detection capability. Coupling with the polydimethylsiloxane (PDMS) material, SERS can be enabled on a polymeric substrate for fast-developing bio-compatible sensing applications. However, due to PDMS’s high viscosity, conventional PDMS-SERS substrates are typically thick and stiff, limiting their freedom for engineering flexible micro/nano functioning devices. To address this issue, we propose to adopt a low viscosity decamethylcyclopentasiloxane (D5) solvent as a diluent solution. Via controlling the mixture ratio of D5 and PDMS and the spin-coating speed for deposition, this method resulted in a film of a well-defined thickness from sub-millimeter down to a 100 nm scale. Furthermore, thanks to the unsaturated Si-H chemical bonds in the PDMS curing agent, the PDMS film could effectively reduce the Ag+ ions to Ag nanoparticles (NPs) directly bonding onto the substrate surface uniformly. Via adjusting the size and density of the AgNPs through reaction temperature and time, strong SERS was achieved and verified using R6G with the detection limit down to 0.1 ppm, attributed to the AgNPs’ plasmonic enhancement effect.

Natural dyes exhibit a low dye uptake when cellulosic fiber dyeing is carried out using a conventional water bath dyeing process. In this research, cotton fabric was exhaust dyed in a microemulsion dyebath containing cacao husk extracts dye and decamethylcyclopentasiloxane (D5) to achieve higher dye exhaustion percentage on cotton fiber, which is an environmentally beneficial dyeing process. The adsorption behavior of cacao husk extract dye in a D5 microemulsion system was investigated under conditions of varied dye mass (1–8% o.w.f), dyeing time (5–500 min), and dyeing temperatures (333–373 K). Kinetic modelling of cacao husk extracts dye/D5 adsorption on cotton fiber was studied by fitting experimental data to pseudo first-order and pseudo second-order kinetics, and the intraparticle diffusion model. Early results indicated that the kinetic model of adsorption of cacao husk extracts dye on cotton fiber followed the pseudo second-order model. Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherm models were employed to analyze the adsorption isotherms, and the results showed that the adsorption process fit well with the Langmuir model compared to the Freundlich isotherm. The mean adsorption energy from the Dubinin–Radushkevich isotherm model implied that adsorption of the cacao husk extracts onto cotton was accompanied with a physical process. The values of standard enthalpy (ΔH° > 0), standard entropy (ΔS° > 0), and Gibbs free energy (ΔG° < 0) strongly reflected that the adsorption of the cacao husk extracts onto cotton was thermodynamically favourable and feasible. Thus, waterless dyeing of cotton fabric using a natural dye/D5 system explores a sustainable dyeing technology with higher dye exhaustion percentage.Graphic abstract

Organosiloxanes are industrially produced worldwide in millions of tons per annum and are widely used by industry, professionals, and consumers. Some of these compounds are PBT (persistent, biaccumulative and toxic) or vPvB (very persistent and very bioaccumulative). If organosiloxanes react at all in the environment, Si–O bonds are hydrolyzed or Si–C bonds are oxidatively cleaved, to result finally in silica and carbon dioxide. In strong contrast and very unexpectedly, recently formation of new Si–CH 3 bonds from siloxanes and methane by the action of microorganisms under mild ambient conditions was proposed (in landfills or digesters) and even reported (in a biotrickling filter, 30 °C). This is very surprising in view of the harsh conditions required in industrial Si–CH 3 synthesis. Here, we scrutinized the pertinent papers, with the result that evidence put forward for Si–C bond formation from siloxanes and methane in technical microbiological systems is invalid, suggesting such reactions will not occur in the environment where they are even less favored by conditions. The claim of such reactions followed from erroneous calculations and misinterpretation of experimental results. We propose an alternative explanation of the experimental observations, i.e., the putative observation of such reactions was presumably due to confusion of two compounds, hexamethyldisiloxane and dimethylsilanediol, that elute at similar retention times from standard GC columns.

Feasibility and applicability of rhamnolipid (RL) microbial biosurfactant-based reverse micellar non-aqueous system in different solvent medium for dyeing of cotton fabrics was investigated. In this study, several solvents, including heptane, octane, nonane, decamethylcyclopentasiloxane (D5), and paraffin liquid (PL), were chosen as the dyeing medium for non-aqueous dyeing of cotton fabrics with fixed dyeing parameters. The dyeing properties of these RL reverse micellar dyed samples in different solvent medium were examined and compared with the conventional water-dyed samples in terms of color yield ( K/S sum value), CIE L * a * b * values, color levelness and reflectance. Most non-aqueous RL reverse micellar dyed samples exhibited better color yield than conventional water-dyed samples. The surface morphology of dyed cotton samples and the dye encapsulation morphology in different solvent medium were observed by SEM and TEM, respectively. Most non-aqueous dyed samples yielded good to excellent levelness comparable to water-dyed samples. However, poor levelness and bad levelness were found for D5-and PL-dyed samples. Further modification of dyeing parameters would be needed to obtain the best dyeing results for D5-dyed and PL-dyed samples. Graphical Abstract

The female reproductive system becomes fertile through the action of hormones involved in the hypothalamic-pituitary-ovarian axis. On the other hand, estrogen-like endocrine disruptors released into the environment come into contact with humans by various routes and affect the reproductive system. Exposure to these chemicals can cause problems with the reproductive process, from egg ovulation to implantation, or cause female reproductive diseases. These reproductive problems cause infertility. Decamethylcyclopentasiloxane (D5) is used for lubrication in silicone polymers, households, and personal care products. In the case of D5, it is discharged through factory wastewater and can bioaccumulate. Therefore, it accumulates in the human body. In this study, D5 was administered orally for four weeks to determine the effects of D5 on the reproductive process. As a result, D5 increases the number of follicles in the ovary and suppresses the expression of genes related to the growth of follicles. In addition, it increases the gonadotropin hormone, inducing estradiol enhancement and progesterone reduction. Because of these changes in the reproductive system when exposed to D5, the industry should reconsider using D5.

D5, a member of the cyclic siloxane family, is widely used in personal care products such as shampoo, cosmetics, and deodorant and as an industrial intermediate. D5 can mainly be absorbed orally or through inhalation. Through these routes, people are exposed to D5 daily. However, the risk of prenatal exposure to D5 has not been fully elucidated. In this study, the effect of D5 on neural development was established through behavioral tests on offspring mice. The result confirmed that the maternal administration of 12 mg/kg of D5 showed depression in tail suspension and decreased performance in the forced swimming test as well as an increase in repetitive activity in both the marble-burying test and grooming test compared to the vehicle group. Furthermore, the 12 mg/kg group showed a decrease in cognitive ability and social behavior in the three-chamber test. In the novel object recognition test, memory impairment and a lack of exploring ability were found in the 12 mg/kg group. In conclusion, it is suggested that maternal D5 exposure has developmental neurotoxicity and can cause behavioral disorders in the offspring of mice. Thus, the usage of D5 needs to be considered carefully.

In this study, we propose Maghnite- H + , as an ecological, cost-effective and easily renewable catalyst, for the polymerization of decamethylcyclopentasiloxane (D5). The Maghnite is a clay consisting primarily of smectite minerals (montmorillonite group), which can be activated/reactivated through a simple process, by replacing interlayer cations by protons. Linear polymers with higher molecular mass and narrower molecular mass distribution (MMD) can be obtained with less cyclic by-products, using Maghnite- H + . The reaction was investigated in bulk, taking into account the effect of time, temperature and amount of catalyst on the monomer conversion and MMD. When the yield rises to 96%, the MMD is broadened, suggesting the formation of cyclic oligomers and/or crosslinking bonds, this was confirmed experimentally by infra-red spectroscopy, proton nuclear magnetic resonance ( 1 H NMR) and 13 C NMR analyses. The kinetics have been also studied; the reaction is first order in the monomer. The proposed reaction mechanism shows clearly the role of Maghnite- H + for D5 polymerization.

Siloxanes present in the biogas produced during anaerobic digestion in wastewater treatment plants (WWTPs) can damage the mechanism of cogeneration heat engines and obstruct the process of energy valorization. The objective of this research is to detect the presence of siloxanes in the biogas and evaluate a procedure for their elimination. A breakthrough curve of a synthetic decamethylcyclopentasiloxane on an experimental bed of activated carbon was modeled and the theoretical mathematical model of the adsorption process was adjusted. As a result, the constants of the model were obtained: the mass transfer constant, Henry's equilibrium constant, and the Eddy diffusion. The procedure developed allows the adsorption equilibrium of siloxanes on activated carbon to be predicted, and makes it possible to lay the basis for the design of an appropriate activated carbon module for the elimination of siloxanes in a WWTP.

Background In the treatment of human head lice infestation, healthcare providers are increasingly concerned about lice becoming resistant to existing pesticide treatments. Traditional pesticides, used to control these pests, have a neurological mechanism of action. This publication describes a topical solution with a non-traditional mechanism of action, based on physical disruption of the wax layer that covers the cuticle of the louse exoskeleton. This topical solution has been shown clinically to cure 82% of patients with only a 10-minute treatment time, repeated once after 7 days. All insects, including human head lice, have a wax-covered exoskeleton. This wax, composed of hydrocarbons, provides the insect with protection against water loss and is therefore critical to its survival. When the protective wax is disrupted, water loss becomes uncontrollable and irreversible, leading to dehydration and death. A specific pattern of hydrocarbons has been found in all of the head louse cuticular wax studied. Iso-octane effectively removes these hydrocarbons from human head lice’s cuticular wax. Methods A method of head louse cuticle wax extraction and analysis by gas chromatography was developed. Human head lice ( Pediculus humanus capitis ) were collected from infested patients and subjected to any of three extraction solvents comprising either the test product or one of two solvents introduced as controls. A gas chromatograph equipped with a flame ionization detector (GC/FID) was used to determine the presence of hydrocarbons in the three head lice extracts. Results In the study reported herein, the test product isopropyl myristate/cyclomethicone D5 (IPM/D5) was shown to perform comparably with iso-octane, effectively extracting the target hydrocarbons from the cuticular wax that coats the human head louse exoskeleton. Conclusions Disruption of the integrity of the insect cuticle by removal of specific hydrocarbons found in the cuticular wax appears to offer a mechanism for killing lice without the likelihood of encountering genetic resistance.