Benzyldimethylhexadecylammonium Chloride Research Articles

Simultaneous determination of 10 quaternary ammonium salt bactericides in oral care products by high performance liquid chromatography-evaporative light-scattering detection

Quaternary ammonium salt bactericides are broad-spectrum bactericides often used in oral care products because of their high antibacterial efficacy, strong penetration, and low toxicity. However, the excessive use of quaternary ammonium salt bactericides may cause contact dermatitis, scalding poisoning, and even death. Existing methods to determine quaternary ammonium salt bactericides are unable to meet current requirements owing to the lack of determination components. Therefore, establishing a simple and accurate method for the simultaneous detection of more quaternary ammonium salt bactericides is necessary. In this study, a method that couples sample pretreatment with high performance liquid chromatography-evaporative light-scattering detection (HPLC-ELSD) was developed for the simultaneous determination of quaternary ammonium salt bactericides in oral care products, including dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, benzethonium chloride, tetradecyl trimethyl ammonium chloride, tetradecyldimethylbenzylammonium chloride, N-hexadecyltrimethylammonium chloride, benzyldimethylhexadecylammonium chloride, trimethylstearylammonium chloride, stearyldimethylbenzylammonium chloride, and docosyltrimethylammonium chloride. Some of these bactericides do not absorb ultraviolet light, so a universal evaporative light-scattering detector was used owing to testing cost and stability concerns. The paste samples contained thickening agents, which are highly soluble in water but insoluble in organic solvents; these agents can seriously affect the results of sample pretreatment and damage the chromatographic column. Hence, sample dehydration was necessary. In this study, four dehydration methods were compared. Anhydrous sodium sulfate (Na2SO4) was selected, and the amount of Na2SO4 was optimized. Based on the solubility of the 10 target compounds and extraction efficiency, three extraction solvents were compared, and ethanol was selected. Ultrasonic extraction was the primary extraction process used in this study. The effects of different ultrasonication times, temperatures, and powers on the extraction recoveries were also investigated. Ultimately, the optimized conditions were as follows: extraction of the dehydrated paste and powder samples using ethanol at room temperature (25 ℃) for 20 min under 100 W ultrasound power, and dilution of the liquid sample with ethanol. After extraction, the samples were separated on an Acclaim Surfactant column (150 mm×4.6 mm, 5 μm) with 50 mmol/L ammonium acetate aqueous solution (pH=5.5) (A) and acetonitrile (B) as mobile phases. The gradient elution program were as follows: 0-5.0 min, 75%A-35%A, 5.0-15.0 min, 35%A-20%A, 15.0-20.0 min, 20%A, 20.0-21.0 min, 20%A-75%A, 21.0-25.0 min, 75%A. An external standard method was used for quantitative determination. The 10 compounds were analyzed within 25 min. Linear equations, correlation coefficients, and linear ranges were obtained by analyzing a series of mixed standard working solutions. The limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) of the 10 components were determined. Stearyldimethylbenzylammonium chloride and docosyltrimethylammonium chloride showed good linear relationships in the range of 10-200 mg/L, while the other compounds demonstrated good linear relationships in the range of 5-100 mg/L. In all cases, correlation coefficients (R2) of no less than 0.9992 were obtained. The LODs and LOQs were in the range of 1.42-3.31 mg/L and 4.25-9.94 mg/L, respectively. Ten analytes were spiked in blank matrices, such as toothpaste (paste), mouthwash (liquid), and dentifrice powder (powder) at three levels, and the recoveries and precisions were calculated. The average recoveries were 87.9%-103.1%, and the corresponding relative standard deviations (RSDs) did not exceed 5.5% (n=6). The developed method was used to detect 109 oral care products. Benzyldimethylhexadecylammonium chloride and stearyldimethylbenzylammonium chloride revealed high detection rates. Moreover, the amount of stearyldimethylbenzylammonium chloride in one toothpaste sample exceeded regulatory requirements. Given its advantages of good precision and accuracy, the developed method is suitable for the quantitative analysis of the 10 aforementioned compounds in typical oral care products. The study findings can serve as a reference for the quality and safety monitoring of oral care products.

Plasmid DNA Complexes in Powder Form Studied by Spectroscopic and Diffraction Methods.

Currently, new functional materials are being created with a strong emphasis on their ecological aspect. Materials and devices based on DNA biopolymers, being environmentally friendly, are therefore very interesting from the point of view of applications. In this paper, we present the results of research on complexes in the powder form based on plasmid DNA (pDNA) and three surfactants with aliphatic chains containing 16 carbon atoms (cetyltrimethylammonium chloride, benzyldimethylhexadecylammonium chloride and hexadecylpyridinium chloride). The X-ray diffraction results indicate a local hexagonal packing of DNA helices in plasmid DNA complexes, resembling the packing for corresponding complexes based on linear DNA. Based on the Fourier-transform infrared spectroscopy results, the DNA conformation in all three complexes was determined as predominantly of A-type. The two relaxation processes revealed by dielectric spectroscopy for all the studied complexes are connected with two different contributions to total conductivity (crystallite part and grain boundaries). The crystallite part (grain interior) was interpreted as an oscillation of the polar surfactant head groups and is dependent on the conformation of the surfactant chain. The influence of the DNA type on the properties of the complexes is discussed, taking into account our previous results for complexes based on linear DNA. We showed that the type of DNA has an impact on the properties of the complexes, which has not been demonstrated so far. It was also found that the layer of pDNA-surfactant complexes can be used as a layer with variable specific electric conductivity by selecting the frequency, which is interesting from an application point of view.

Comparison of aqueous and non-aqueous capillary electrophoresis for the determination of four benzalkonium chloride homologues in compound chemical disinfectants

A new method was established for the simultaneous analysis of four homologous benzalkonium chlorides (dodecyldimethylbenzyl ammonium chloride, tetradecyldimethylbenzyl ammonium chloride, hexadecyldimethylbenzyl ammonium chloride, and octadecyldimethylbenzyl ammonium chloride) in compound chemical disinfectants using non-aqueous capillary electrophoresis (CE) based on a micellar electrokinetic chromatography mode with direct ultraviolet detection. The separation was performed on an uncoated fused quartz capillary with a total length of 60.2 cm and a diameter of 25 μm. The separation buffer consisted of a mixture of methanol/acetonitrile (60:40, v/v) containing 70 mmol/L sodium acetate, 60 mmol/L trifluoroacetic acid and 20 mmol/L sodium dodecyl sulfate. The sample buffer was a methanol solution containing only 2 mmol/L trifluoroacetic acid. The separation voltage was set at 8 kV with a working current of approximately 2.3 μA. The detection wavelength was 214 nm. Under optimal conditions, the limit of detection and limit of quantification for these four benzalkonium chlorides (BACs) were 1.0 mg/L and 5.0 mg/L, respectively. Good linearities were observed in the concentration ranges from 5.0 to 100.0 mg/L, with correlation coefficients above 0.999 for all compounds. The recoveries of these four BACs ranged from 92.5 % to 109.1 % with relative standard deviations below 4.7 %. With the new method, all four BACs could be analyzed in a single injection. In contrast, the aqueous CE method in the National Standard GB/T 26369-2020 only allowed for the simultaneous analysis of the first three homologous. The new method demonstrated the improved peak shape compared to the aqueous CE method and then was successfully applied to the analysis of 19 commercially available samples, such as object table disinfectants, hand sanitizers, and disinfectant wipes, which claimed to contain quaternary ammonium compound. The results obtained using the new method were compared with those of the aqueous CE of the National Standard Method, and no statistically significant differences were observed. The new method is simple in pre-treatment and provides accurate results, making it highly suitable for routine analysis.

Potential–Dependent BDAC Adsorption on Zinc Enabling Selective Suppression of Zinc Corrosion for Energy Storage Applications

Utility-scale zinc (Zn) batteries are a promising solution to address the problem of intermittency of renewable energy sources; however, Zn-metal anodes in these batteries suffer from capacity loss due to spontaneous corrosion of the Zn especially when high-surface area anode configurations are employed. Additionally, Zn dendrites are known to form during battery charging limiting the cycle-life of these batteries. Electrolyte additives have been explored that prevent aforementioned issues, but these too come at a cost, i.e., surface-blocking additives polarize the electrode surface leading to loss in the voltaic and energy efficiencies of the battery. In this contribution, a novel electrolyte additive, benzyldimethylhexadecylammonium chloride (BDAC), is investigated for its ability to suppresses corrosion of Zn in an acidic (pH = 3) electrolyte. An attribute of BDAC distinct from previously studied additives is that it selectively suppresses electrochemical activity when the Zn electrode is at its corrosion potential; however, during high-rate Zn deposition (charging) or stripping (discharging), BDAC is essentially deactivated and thus it does not appreciably polarize the electrode surface, thus minimizing voltaic efficiency losses. This selective corrosion suppression behavior is explored using slow-scan voltammetry, which reveals hysteresis implying a potential- or current-dependent BDAC adsorption mechanism in which BDAC reaches higher surface coverages when the partial currents at the Zn surface are low (e.g., at or near the corrosion potential), but BDAC coverage is reduced considerably when the Zn deposition or stripping rates are increased. Numerical simulations of the BDAC diffusion-adsorption process corroborate this mechanism. Ramifications of our approach to the selective suppression of Zn dendrites are discussed.

The enhanced adsorption of diclofenac sodium (DCF) and ibuprofen (IBU) on modified montmorillonite with benzyldimethylhexadecylammonium chloride (HDBAC)

Benzyldimethylhexadecylammonium chloride (HDBAC) modified montmorillonite was synthesized and the compounds were used for the adsorption of diclofenac sodium (DCF) and ibuprofen (IBU). The adsorption effect was the best when the best dosage of the HDBAC was 1.6 CEC (cation exchange capacity). The adsorption capacity (qe) of H-Mt-1.6 for DCF and IBU was 125.55 mg/g and 81.64 mg/g, respectively. The qe of Ca-Mt for DCF and IBU was 54.02 mg/g and 13.14 mg/g, respectively. H-Mt-1.6 had higher adsorption effect than Ca-Mt. The adsorption process of H-Mt-1.6 on DCF followed the Langmuir adsorption model and the adsorption process of IBU followed the Freundlich adsorption model. The equilibrium could be reached after 120 min. The adsorption process of H-Mt-1.6 on DCF and IBU followed a pseudo-second-order kinetic model. The adsorption on DCF was endothermic, while adsorption on IBU was exothermic.

Adsorption behaviors of zearalenone in corn oil by montmorillonite modified with quaternary ammonium salts

The aim of this study was to explore the detoxification effect and mechanism of montmorillonite (MMT) modified with quaternary ammonium salts (QAS) on zearalenone (ZEN) in corn oil. Therefore, the characteristics and adsorption behavior of MMT before and after QAS modification were analyzed using scanning electron microscopy (SEM), nitrogen adsorption–desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and molecular dynamics simulations. The results showed that hexadecyl dimethyl benzyl ammonium chloride modified MMT (H-MMT) was an excellent adsorbent for removing ZEN from corn oil and the maximum adsorption amount of H-MMT (0.469 mg/g) for ZEN was 21.9 times that of MMT. This might be attributed to the numerous amounts of intercalation between MMT layers caused by QAS, which changed the appearance of MMT, increased the hydrophobicity, adsorption site, contact number and interaction energy of MMT with ZEN in corn oil. Adsorption experiments indicated that adsorption process of QAS modified MMT on ZEN was mainly chemical adsorption. Notably, H-MMT could not only remove pigment and ZEN in corn oil, but also improve oil quality by decreasing peroxide value and acid value. Therefore, H-MMT could be used as a potential adsorbent for the removal of ZEN from vegetable oil.

Benzyl-hexa-decyl-dimethyl-ammonium chloride dihydrate.

The title compound, C25H46N+·Cl-·2H2O, crystallizes in the space group P21 with one organic mol-ecule in the asymmetric unit. The compound belongs to a class of benzalkonium chlorides (BACs) with an alkyl chain length of 16 carbon atoms in an all-trans conformation.

Investigation of chromate adsorption efficacy on organo-bentonite as potential in-situ adsorbent for groundwater remediation

As potential in-situ chromate adsorbents for groundwater remediation, two different organo-bentonites having two structurally different surfactants with the same carbon chain length (hexadecyl trimethyl ammonium bromide (HDTMAB) and benzyl dimethyl hexadecyl ammonium chloride (BDMHDAC)) were prepared. The Fourier transformed infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and N2 adsorption-desorption isotherm characterization results of the prepared organoclays reveal that the HDTMAB and BDMHDAC moieties are mainly located on the interlayer and outer surface as HDTMAB-Bt (H-Bt) and BDMHDAC-Bt (B-Bt), respectively. Based on the chromate adsorption efficacy in terms of the amount of surfactant in organoclay, 1.5 times the cation exchange capacity of Bt was selected for further studies. The two different organoclays prepared herein exhibited fast chromate adsorption within 60 min and equilibrated at 240 min at 10 and 100 mg/L of chromate solution concentration. Based on the Langmuir and Freundlich isotherm analyses, H-Bt fitted well to the Langmuir isotherm, and B-Bt followed the Freundlich isotherm model owing to differences in the locations of the modified surfactants. In-situ chromate adsorption utilizing flow-through experiments were performed successfully under simulated soil conditions. The prepared B-Bt exhibited high chromate adsorption efficacy of around 81% at the adsorbent concentration of 3 g/300 mL within 170 min. Therefore, organoclays prepared using natural clay materials can be used as potential in-situ chromate adsorbents for groundwater remediation.

New Simple and Robust Method for Determination of Polarity of Deep Eutectic Solvents (DESs) by Means of Contact Angle Measurement.

The paper presents a new method for evaluating the polarity and hydrophobicity of deep eutectic solvents (DESs) based on the measurement of the DES contact angle on glass. DESs consisting of benzoic acid derivatives and quaternary ammonium chlorides–tetrabutylammonium chloride (TBAC) and benzyldimethylhexadecylammonium chloride (16-BAC)—in selected molar ratios were chosen for the study. To investigate the DESs polarity, an optical goniometer and an solvatochromic scale based on Reichardt’s dye were used. The research demonstrated the high accuracy and precision of the developed procedure. The simplicity of the examination and the availability of basic equipment allow for the implementation of the developed method in routine investigations of DESs.

Adsorption behaviors of modified clays prepared with structurally different surfactants for anionic dyes removal

In this study, the properties and adsorption behaviors of organoclays synthesized with two structurally different surfactants having the same carbon chain length (hexadecyltrimethylammonium bromide (HDTMAB) and benzyldimethylhexadecylammonium chloride (BDHAC)) were evaluated. The structural properties of the synthesized organoclays were examined using Fourier-transform infrared spectroscopy, zeta potential analysis, X-ray diffraction, and N2 adsorption-desorption test. The modified clays with increased surfactant loadings (from 0.5 CEC to 3 CEC) were prepared to find the optimal surfactant loading. As a result, 1.5 cation exchange capacity (CEC) was found to be the optimal surfactant loading. The organoclay prepared using HDTMAB (H-Bt) exhibited the maximum adsorption capacity of 114.3 mg/g for anionic Orange G dye, which was 1.74 times higher than that of the organoclay prepared using BDHAC (B-Bt). Furthermore, in the presence of a mixture of cationic and anionic dye molecules in water, H-Bt tended to remove more of the cationic target compound than B-Bt (i.e., methylene blue (MB)), suggesting that H-Bt can serve as a more efficient adsorbent for the uptake of environmental contaminants in practical scenarios. Moreover, this study examined the effects of surfactant molecules on the structural properties of organoclays and their adsorption behaviors in the uptake of dye molecules.

Engineering titanium carbide ultra-thin nanosheets for enhanced fire safety of intumescent flame retardant polylactic acid

As a biodegradable polymeric material, the polylactic acid (PLA) has broad applications resulting from its various advantages and unique characteristics. Nevertheless, the application of PLA in various fields is greatly limited by its high flammability . Our recent effort focuses on the manipulation of benzyldimethylhexadecylammonium chloride (HDBAC) modified titanium carbide (Ti 3 C 2 T x ) ultra-thin nanosheets which are then used to improve the fire safety of PLA composites filled with silicon microencapsulated ammonium polyphosphate (SiAPP). The flame retardant evaluation showed that when 2.0 wt% HDBAC modified Ti 3 C 2 T x (HDBAC-Ti 3 C 2 T x ) and 13.0 wt% SiAPP were added, the LOI value was increased to 33.3%, and the UL-94 V-0 level was obtained, besides the peak heat release rate , total heat release, peak smoke production rate and total smoke release decreased by 49.8%, 31.9%, 60.3% and 52.7%, respectively. The barrier and catalytic effects of the modified Ti 3 C 2 T x nanosheets together with the subsequently formed TiO 2 and phosphorus-containing species forming intact expanded carbon layers and interrupting the combustion route are responsible for remarkably improving flame retardancy and suppressing toxic gases of PLA. This work provides a new approach for greatly reducing the fire hazard of PLA.

Deep Eutectic Solvent-Based Coating Sorbent for Preconcentration of Formaldehyde by Thin-Film Solid-Phase Microextraction Technique

A thin-film solid-phase microextraction method with a sorbent composed of a deep eutectic solvent was developed for the preconcentration of formaldehyde from river and lake water samples. Four new deep eutectic solvents (DESs) were synthesized, each in molar ratios 1:1, 1:2, and 1:3. Among prepared compounds, the greatest efficiency in the proposed method of preconcentration of formaldehyde derivatized with Nash reagent was demonstrated by DES-3 consisting of benzyldimethylhexadecylammonium chloride and lauric acid, in a molar ratio of 1:3. For the proposed method, the parameters affecting the extraction efficiency of formaldehyde were optimized (including the choice of DES-based sorbent and desorption solvent as well as the sample volume and pH, the salting-out effect, the extraction time, and the desorption time). Under optimal conditions, the proposed method achieved good precision between 3.3% (for single sorbent) and 4.8% (for sorbent-to-sorbent) as well as good recovery ranging from 78.0 to 99.1%. The limits of detection and quantitation were 0.15 ng mL−1 and 0.50 ng mL−1, respectively. The enrichment factor was equal to 178. The developed method was successfully applied to determine formaldehyde in environmental water samples.

How does coal interact with organic groups in an aqueous solution?

Interactions between coal matrix and organics are vital for adsorption [1], surfactant adsorption on lignite [2-5], and solid–liquid separation of coal slurry [6-10]. Herein, for studying the interaction between hydrophobic surface (coal surface) and small molecules (organics), we measured interactions between organics [nitro and phenyl, pyridine, phenyl, alkyl chain (hexyl) or cycloalkyl (hexyl)] and the coal matrix (liptinite or inertinite) using atomic force microscopy. The strength of interaction followed the order: nitro and phenyl > pyridine > phenyl > alkyl chain (hexyl) > cycloalkyl (hexyl), and liptinite > inertinite. The liptinite has a greater hydrophobicity than inertinite, the greater the attraction force. The lignite surface and coal slurry were modified in an aqueous solution using five surfactants (dodecyl trimethyl ammonium chloride, DTAC; hexadecyl trimethyl ammonium chloride, CTAC; octadecyl trimethyl ammonium chloride, STAC; hexadecyl dimethyl benzyl ammonium chloride, HDBAC; and cetyl pyridine chloride, CPC). Subsequently, the moisture adsorption on treated lignite coal surface and the sedimentation of the treated tails was compared to characterize hydrophobic modifications which showed the order of CTAC > HDBAC > DTAC > CPC > STAC. Thus, the interaction between coal surface and organics needs to consider two rules: 1) The desolvation or the hydrophobic property of the coal surface; 2) The VDW force of the organics. The nature of the difference between rules No. 1 and 2 is that with the size of hydrophobic molecules increased to a surface, the H-bond structure between water molecules in the around would change a lot, which formats great hydrophobic property or desolvation. SynopsisInteraction between organic reagents and coal reveals the mechanism of restraining moisture reabsorption of lignite and solid–liquid separation of coal slurry by organics.

Disinfectant and Antimicrobial Susceptibility Studies of Staphylococcus aureus Strains and ST398-MRSA and ST5-MRSA Strains from Swine Mandibular Lymph Node Tissue, Commercial Pork Sausage Meat and Swine Feces.

Staphylococcus aureus (S. aureus) causes gastrointestinal illness worldwide. Disinfectants are used throughout the food chain for pathogenic bacteria control. We investigated S. aureus bioavailability in swine Mandibular lymph node tissue (MLT) and pork sausage meat (PSM), established susceptibility values for S. aureus to disinfectants, and determined the multilocus sequence type of MRSA strains. Antimicrobial and disinfectant susceptibility profiles were determined for 164 S. aureus strains isolated from swine feces (n = 63), MLT (n = 49) and PSM (n = 52). No antimicrobial resistance (AMR) was detected to daptomycin, nitrofurantoin, linezolid, and tigecycline, while high AMR prevalence was determined to erythromycin (50.6%), tylosin tartrate (42.7%), penicillin (72%), and tetracycline (68.9%). Methicillin-resistant S. aureus (MRSA) strains, ST398 (n = 6) and ST5 (n = 1), were found in the MLT and PSM, 4 MRSA in MLT and 3 MRSA strains in the PSM. About 17.5% of feces strains and 41.6% of MLT and PSM strains were resistant to chlorhexidine. All strains were susceptible to triclosan and benzalkonium chloride, with no cross-resistance between antimicrobials and disinfectants. Six MRSA strains had elevated susceptibilities to 18 disinfectants. The use of formaldehyde and tris(hydroxylmethyl)nitromethane in DC&R was not effective, which can add chemicals to the environment. Didecyldimethylammonium chloride and benzyldimethylhexadecylammonium chloride were equally effective disinfectants. ST398 and ST5 MRSA strains had elevated susceptibilities to 75% of the disinfectants tested. This study establishes susceptibility values for S. aureus strains from swine feces, mandibular lymph node tissue, and commercial pork sausage against 24 disinfectants. Since it was demonstrated that S. aureus and MRSA strains can be found deep within swine lymph node tissue, it may be beneficial for the consumer if raw swine lymph node tissue is not used in uncooked food products and pork sausage.

Physicochemical characterization of the DNA complexes with different surfactants

DNA complexes with cetyltrimethylammonium chloride (CTMA), benzyldimethylhexadecylammonium chloride (BAC) and hexadecylpyridinium chloride (HDP) surfactants as powder samples were studied by Fourier-transform middle infrared spectroscopy, X-ray diffraction and dielectric spectroscopy methods. Complexation as electrostatic interactions was confirmed by FT-MIR spectroscopy. The width of DNA-surfactant complexes was estimated to 61–73 Å based on modeling with the semi-empirical PM7 method. Based on SAXS results we propose the packing model for the complex molecules as hexagonal or slightly distorted hexagonal depending on the surfactant. For the first time the dielectric process registered in the low frequency range for all complexes was interpreted as oscillation of surfactant ions (BAC+, HDP+ or CTMA+), analogous to the oscillation of ions (e.g. Na+) in solutions of pure DNA. The influence of the structure of the complex-forming surfactant molecule on the value of the relaxation time distribution parameter is discussed.

Thermodynamic Micellization of Cationic-Nonionic Surfactants in Aqueous Solution Using Conductivity and Surface Tension Measurements

In the current work, we discuss the mixed micelles and thermodynamic micellization of aqueous binary mixture of polyoxyethylene - 20 sorbitan-monododecanoate (Tween 20) as nonionic surfactant and Benzyldimethylhexadecyl ammonium chloride (HDBAC) as cationic surfactant using conductivity and surface tension (γ) estimations in the temperatures range (288 -318K). Critical micelle concentration (CMC) and variables of micellization, like the standard thermodynamic functions: Gibbs free energy (Δ𝐺𝑚 ⁰ ), enthalpyΔ𝐻𝑚 ⁰ ) and entropy (Δ𝑆𝑚 ⁰ ) were calculated using the variation of conductivity and γ with molar concentration and the variation of ln XCMC with temperature. The experimental CMC values were applied to calculate the mole fractions of surfactant in the mixed micelle (𝑋1 𝑚 ), the β parameter and the coefficient of activity f1and f2, using the equations proposed by Clint and Rubingh, which indicate the β parameter, is always negative. In addition, the results of thermodynamic parameters show that ΔG⁰m are negative for both individual and mixture of HDBAC-Tween20 surfactants and the values negatively increased with increasing temperature while its negative values decreasing with decreasing initial mole fraction of HDBAC.

Cross-linking of antimicrobial polymers with hexamethylene diamine to prevent biofouling in marine applications

The design of antimicrobial polymers is a growing field, as they may replace conventional antimicrobial agents leading to plenty of advantages in marine applications. Polymers with active functional groups may act as carriers for antimicrobial agents. The antimicrobial polymers P(SSAmC16-co-GMAx) and P(VBCHAM-co-AAx) bearing quaternary ammonium compounds, either electrostatically bound (cetyltrimethylammonium 4-styrene sulfonate, SSAmC16) or covalently attached (vinyl benzyl dimethylhexadecylammonium chloride, VBCHAM), were prepared in the present work. The cross-linking agent hexamethylene diamine (HMDA) was used for the reaction between copolymers’ reactive groups, epoxide groups of glycidyl methacrylate (GMA) or carboxylic groups of acrylic acid (AA), with the amine groups. Various blends of each reactive copolymer with hexamethylene diamine in different compositions were prepared and the cross-linking reaction was explored through solution casting after curing at room temperature (RT), 80 °C and 120 °C for 24 h in order to find the best conditions for the designing of a firm and strong coating. In a further step, specific blend combinations of the reactive antimicrobial copolymers combined with hexamethylene diamine were used to coat pre-weighed aquaculture nets which were cross-linked at 120 °C and used in laboratory accelerated conditions as well as in real conditions by immersion of the nets at an aquaculture unit in the Saronic Bay of Greece. The modified nets along with blank nets were tested in terms of antifouling efficacy for 35 days in accelerated conditions and 30 days in real conditions. The novel cross-linked antimicrobial coatings indicated high antifouling activity and high cleaning efficacy as the fouling microorganisms at the end of the test were easily removed from the coated net in contrast to the uncoated net after high pressure cleaning.

Disinfectant and antimicrobial susceptibility studies of the foodborne pathogen Campylobacter jejuni isolated from the litter of broiler chicken houses

Foodborne illness is an ongoing problem worldwide and is caused by bacteria that invade the food chain from the farm, slaughter house, restaurant or grocery, or in the home and can be controlled by strategies using biocides (antiseptics and disinfectants). Susceptibility profiles were determined for 96 Campylobacter jejuni strains obtained in 2011–2012 from broiler chicken house environments to antimicrobials and disinfectants as per the methods of the Clinical and Laboratory Standards Institute and TREK Diagnostics using CAMPY AST Campylobacter plates. Low prevalence of antimicrobial resistance was observed in C. jejuni strains to tetracycline (TET; 21.9%), ciprofloxacin (CIP; 13.5%), and nalidixic acid (NAL; 12.5%). The resistance profiles had a maximum of 3 antimicrobials, CIP-NAL-TET, with TET being the main profile observed. No cross-resistance was observed between antimicrobials and disinfectants. The C. jejuni strains (99%) were resistant to triclosan, 32% were resistant to chlorhexidine, and they all were susceptible to benzalkonium chloride. The strains had low-level minimum inhibitory concentrations (MICs) to the disinfectants P-128, Food Service Sanitizer, F-25 Sanitizer, Final Step 512 Sanitizer, OdoBan, dioctyldimethylammmonium chloride, didecyldimethylammonium chloride (C10AC), benzyldimethyldodecylammonium chloride (C12BAC), and benzyldimethyltetradecylammonium chloride (C14BAC). Intermediate MICs against DC&R, cetylpyridinium bromide hydrate, hexadecylpyridinium chloride, ethylhexadecyldimethylammonium bromide, and hexadecyltrimethylammonium bromide with elevated intermediate MICs against Tek-Trol, benzyldimethylhexadecylammonium chloride, tris(hydroxylmethyl)nitromethane (THN), and formaldehyde. The highest MIC were obtained for povidone-iodine. The components THN and the benzylammonium chlorides C12BAC and C14BAC were responsible for the inhibition by DC&R. The components C10AC and C12BAC may act synergistically causing inhibition of C. jejuni by the disinfectant P-128. The formaldehyde component in DC&R was not effective against C. jejuni compared with the ammonium chloride components. Its use in disinfectants may result in additional unnecessary chemicals in the environment. Didecyldimethylammonium chloride is the most effective ammonium chloride component against C. jejuni.

The Effect of Surface Modification of Gold Nanotriangles for Surface-Enhanced Raman Scattering Performance.

A surface modification of ultraflat gold nanotriangles (AuNTs) with different shaped nanoparticles is of special relevance for surface-enhanced Raman scattering (SERS) and the photo-catalytic activity of plasmonic substrates. Therefore, different approaches are used to verify the flat platelet morphology of the AuNTs by oriented overgrowth with metal nanoparticles. The most important part for the morphological transformation of the AuNTs is the coating layer, containing surfactants or polymers. By using well established AuNTs stabilized by a dioctyl sodium sulfosuccinate (AOT) bilayer, different strategies of surface modification with noble metal nanoparticles are possible. On the one hand undulated superstructures were synthesized by in situ growth of hemispherical gold nanoparticles in the polyethyleneimine (PEI)-coated AOT bilayer of the AuNTs. On the other hand spiked AuNTs were obtained by a direct reduction of Au3+ ions in the AOT double layer in presence of silver ions and ascorbic acid as reducing agent. Additionally, crumble topping of the smooth AuNTs can be realized after an exchange of the AOT bilayer by hyaluronic acid, followed by a silver-ion mediated reduction with ascorbic acid. Furthermore, a decoration with silver nanoparticles after coating the AOT bilayer with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC) can be realized. In that case the ultraviolet (UV)-absorption of the undulated Au@Ag nanoplatelets can be tuned depending on the degree of decoration with silver nanoparticles. Comparing the Raman scattering data for the plasmon driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) one can conclude that the most important effect of surface modification with a 75 times higher enhancement factor in SERS experiments becomes available by decoration with gold spikes.

Surface tension of the oppositely charged sodium poly(styrene sulfonate) /benzyldimethylhexadecylammonium chloride and sodium poly(styrene sulfonate)/polyallylamine hydrochloride mixtures

Oppositely charged polyelectrolyte/surfactant and the coacervate polyanion/polycation mixtures are known to display complex properties at water/air interface which are not fully elucidated. The change in surface tension of the anionic polyelectrolyte sodium poly(styrene sulfonate) (NaPSS) with either benzyldimethylhexadecylammonium chloride (BAC) as the cationic surfactant or the cationic polyelectrolyte polyallylamine hydrochloride (PAACl) as a function of temperature and added salts was investigated. Neither of the pure polyelectrolytes showed significant surface activity; however, addition of oppositely charged surfactant or polyelectrolyte to varying concentrations of NaPSS solutions had changed the surface activity drastically. The surface tension of the NaPSS/BAC complex is lower than that of pure BAC surfactant. The surface tension of these complexes showed significant decrease with increasing temperatures and the surface excess entropy was deduced from these measurements. Addition of ionic salts enhanced the association of the polyelectrolyte/surfactant mixture but had little effect on the polyelectrolytes coacervate. The surface tension of low concentrations of NaPSS/PAACl coacervate displayed a peak which can be attributed to charge inversion.