Microbial contamination arising from pathogens poses serious threats to human health and in recent decades has presented an unprecedented challenge to antibacterial research. Of the various antibacterial agents that effectively kill pathogens, halogen-based antibacterial compounds have been successful in eliminating harmful pathogen-associated diseases and are becoming the most popular disinfectants. As a significant subcategory of halogen antibacterial agents, N-halamines have drawn increasing research interest into their chemistry and practical applications. N-Halamines have many advantages over other antibacterial agents, including effectiveness against a broad spectrum of microorganisms, long-term physicochemical stability, high structural durability, and the regenerability of their functional groups, with corresponding renewal of their antibacterial properties. This review examines recent progress and research trends in both theoretical and experimental studies of N-halamines, with the aim of providing a systematic and comprehensive survey and assessment of the significant advances in our understanding of antibacterial N-halamines. This review serves as a practical guide to developing N-halamines through both broad and in-depth basic research and offers suggestions for their potential future applications.

Designing hydrogels with tunable mechanical properties and self-healing effects is crucial to a variety of applications, such as bioremediation carriers. Here, we synthesized a series of hydrophobic associated hydrogels (HA-gels) through micellar copolymerization in sodium dodecyl sulfate (SDS) aqueous solution. The hydrophobic monomer used is fatty alcohol polyoxyethylene acrylate (AEO-AC), which is significantly more eco-friendly than the traditional octylphenol polyoxyethylene acrylate (OP-AC) hydrophobic monomer. Interestingly, the mechanical properties of HA-gels can be tuned controllably by varying the ratio of AEO-AC-10-5 to AEO-AC-13-5 (AEO-AC-n-5: CnH2n+1(OCH2CH2)5O–C(O)CHCH2; n = 10, 13). The longer and sheer straight carbon chain of AEO-AC-13-5 leads to stronger hydrophobic association point, while the shorter and branched carbon chain of AEO-AC-10-5 results in weaker hydrophobic association point. The resulting AEO-AC-13-5-AM gels possess tough mechanical strength (maximum broken stress is 318 kPa) and high elongation (1000–3000%). Then, we could tune the swelling and stress relaxation behaviors by varying the ratio of SDS to AEO-AC and obtain HA-gels that maintain their shapes in water nearly half a year, with low content of SDS. Lastly, our HA-gels also exhibit good self-healing capability, and offer great opportunities for a lot of prospective biomaterials.

•Core–shell nanoparticles were prepared readily by a self-templating method.•The method is exempted from removing the template and reduces reaction steps.•It is a wide range application route to coat functional compounds rapidly.Functional TiO2 core–shell nanoparticles hold great promise for the fabrication of photocatalyst. However, the current methods to fabricate core–shell TiO2 functional nanoparticles were onerous and easy to be polluted. We report herein a simple one-step self-templating method to synthesize the fluorescent core–shell nanoparticles in an O/W emulsion system. During the process, the core–shell structures were obtained by a rapid solidification reaction from the outer face toward the center of the emulsion, The whole process of coating was carried out by the emulsion system self and it required neither surface treatment for TiO2 nanoparticles nor additional surfactant or stabilizer to be the template. It is a wide range application route to coat function compounds rapidly and cleanly.A simple one-step self-templating method to synthesize the nanoparticles in an O/W emulsion system was developed.

Magnetic/antibacterial bifunctional nanoparticles were fabricated through the immobilization of antibacterial N-halamine on silica-coated Fe3O4-decorated poly(styrene-co-acrylate acid) (PSA) nanoparticles. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The N-halamine was developed from the precursor 5,5-dimethylhydantoin (DMH) by chlorination treatment, and experimental results showed that the loading amount of DMH on the silica-coated Fe3O4-decorated poly(styrene-co-acrylate acid) nanoparticles was adjustable. The as-synthesized nanoparticles exhibited superparamagnetic behavior and had a saturation magnetization of 18.93 emu g–1. Antibacterial tests showed that the resultant nanoparticles displayed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts.Keywords: bifunctional; Fe3O4; N-halamine; nanoparticles; poly(styrene-co-acrylate acid); SiO2;

Magnetic N-halamine nanocomposites were synthesized through the encapsulation of the magnetic silica nanoparticles with antibacterial N-halamine polymer. The as-synthesized sample was characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and thermogravimetric analysis (TGA). The fabricated magnetic N-halamine nanocomposites possessed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts. The effect of chlorine content of the magnetic N-halamine nanocomposites on the antibacterial activity was investigated. The magnetic N-halamine nanocomposites also exhibited super-paramagnetic behavior and had a saturation magnetization of 4.728 emu g−1 at room temperature, which made these nanocomposites separable magnetically after the antibacterial behavior. Performances derived from the synergism between magnetic core and antibacterial shell suggest that the magnetic N-halamine nanocomposites are qualified for antibacterial applications and separable by the aid of the external magnetic field.Graphical abstractMagnetic N-halamine nanocomposites with enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria were synthesized and can be separated magnetically through the application of a magnetic field after antibacterial performance.Highlights► Successful encapsulation of magnetic silica nanoparticles with antibacterial polymeric N-halamines. ► Enhanced antibacterial activity of the magnetic N-halamine nanocomposites compared with their bulk counterparts. ► Perfect combination of magnetic and antibacterial property into one single entity.

Antimicrobial composites with a well-defined core−shell nanostructure were prepared through immobilization of N-halamine on polystyrene-functionalized silica nanoparticles. Evidence for immobilization of N-halamine onto polystyrene-modified silica has been inferred from different techniques like transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), zeta potential analyses, and Fourier transform infrared (FTIR). Experimental results showed that structures and morphologies of the as-prepared hybrid nanoparticles could be well controlled. Resultant nanosized particles displayed 2−8 times higher biocidal activity against S. aureus and E. coil than the bulk counterparts, and tests indicated that these powerful and stable nanosized antimicrobials had higher biocidal efficacy against S. aureus than E. coli. The biocidal behavior makes these composite nanoparticles an ideal candidate for various important applications such as in disinfection of hygienic areas, water purification, and food packaging.

Stable magnetite nanoparticle aqueous dispersions were prepared by precipitating ferrous ions in the presence of an ionic liquid containing acrylic acid anion, viz., N-methylimidazolium acrylic acid (MImAA) in air at high pH. The size of the as-prepared magnetite nanoparticles could be tuned from 12 nm to 20 nm depending on the concentration of MImAA in the medium. X-ray diffractions showed the presence of only Fe3O4 phase in the nanoparticles. The ionic liquid with some dimers was demonstrated to be an effective stabilizer for magnetite nanoparticle dispersions. The FTIR and TGA analysis confirmed the attachment of the acrylic acid anion in ionic liquid predominantly on the particle surface in the chelating bidentate configuration.

Core−shell nanoparticles with 1,4-bis(o-cyanostyryl)benzene (CSB), which is a commonly used fluorescent agent, as the core and with nanosilica particles as the shell were prepared by a self-templating method. The morphologies, structure, particle size distribution, and optical properties of the resulting CSB−SiO2 nanoparticles were characterized. The effects of the reaction conditions on the structure and morphologies, their stability in aqueous solutions, and their optical properties were investigated. During the process, an oil-in-water emulsion system was formed, and the core−shell nanoparticles were obtained by a rapid solidification reaction from the outer surface toward the center of the emulsion. The whole process required neither surface treatment for nanosilica particles nor additional surfactant or stabilizer. Experimental results indicated that the resulting CSB−SiO2 nanoparticles were perfectly spherical with smooth particle surfaces and had distinct core−shell structures. The CSB−SiO2 nanopaticles had good stability in aqueous solutions for a period of time. The particle size and shell thickness could be readily tuned by altering reaction conditions. The resulting CSB−SiO2 core−shell nanoparticles exhibited strong UV absorption and fluorescence emission. In addition, the mechanism of the self-templating method for forming core−shell nanoparticles is discussed.

Sesbania gum supported dithiocarbamate chelating resin (SGDSA) was prepared. The epoxy functional groups were introduced into sesbania gum to produce the sesbania gum supported resins and then reacted with triethylenetetramine, and lastly were converted to the respective dithiocarbamates by reacting with carbon disulphide. The structure of functionalized resins was characterized by FT-IR. The influences of various reaction conditions on the epoxidation were discussed. The prepared SGDSA exhibited high adsorption capacity for metal ions and the adsorption equilibrium could be arrived at shorter time.

Nanostructure rutile TiO2 was prepared in a carboxyl-containing ionic liquid, 1-methylimidazolium-3-acetate chlorine ([AcMIm]Cl), by using TiOCl2 solution as a precursor at low temperature. The obtained nanostructure TiO2 was analyzed with fourier transform infrared (FTIR), X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The as-prepared TiO2 present only rutile crystal phase and a novel flower-like morphology. The as-prepared rutile TiO2 shows better photocatalytic performance in the degradation of methyl orange. The template-directing performance of ionic liquid is due to the bidentate chelating complexation between the carboxylic functional group of ionic liquid and titania.

The effect of salt solutions (NaCl, Na2SO4 and CaCl2) on the conformational properties of partially hydrolyzed polyacrylamide (HPAM) was investigated by using static laser light scattering (SLLS). The special interaction between CaCl2 solution and HPAM was also researched. Experimental results show that the chain structure of HPAM is interrelated with the charge density, the kind and the concentration of salt solutions. The mean-square radius of gyration (Rz) and the second virial coefficient (A2) of HPAM decrease with increasing concentration of salt solutions, and the salt effect tends towards the maximum when the concentration of salt solution is increased to some amount.

Nanostructured TiO2 particles were synthesized by sol–gel method with room temperature ionic liquid (RTIL) 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as a reaction medium. The structure and morphology of TiO2 nanoparticles were characterized with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The as-prepared TiO2 nanoparticles present anatase crystal phase even without being calcined at high temperature, and show better photocatalytic performance in the degradation of methyl orange. The photocatalytic efficiency increases evidently along with increasing the concentration of nanostructure TiO2, and the degradation percent can reach 100% at the optimal catalyst concentration (2.0 g/L).