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In this research, a novel organic-inorganic hybrid salt, namely, N 1 ,N 1 ,N 2 ,N 2-tetramethyl-N 1 ,N 2-bis(sulfo)ethane-1,2-diaminium tetrachloroferrate ([TMBSED] [FeCl 4 ] 2) was prepared and characterized by Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermal gravimetric (TG), differential thermal gravimetric (DTG), and vibrating-sample magnetometry (VSM) analyses. Catalytic activity of the hybrid salt was tested for the synthesis of N,N 0-alkylidene bisamides through the reaction of benzamide (2 eq.) and aromatic aldehydes (1 eq.) under solvent-free conditions in which the products were obtained in high yields and short reaction times. The catalyst was superior to many of the reported catalysts in terms of two or more of these factors: the reaction medium and temperature, yield, time, and turnover frequency (TOF). [TMBSED][FeCl 4 ] 2 is a Brønsted-Lewis acidic catalyst; there are two SO 3 H groups (as Brønsted acidic sites) and two tetrachloroferrate anions (as Lewis acidic sites) in its structure. Highly effectiveness of the catalyst for the synthesis of N,N 0-alkylidene bisamides can be attributed to synergy of the Brønsted and Lewis acids and also possessing two sites of each acid.

The current study describes design and synthesis of silica‐coated zinc oxide nanoparticles containing Ponceau 4R food colorant (named as ZnO@SiO2@APTMS/P4R). The interactions of Ponceau 4R and ZnO@SiO2@APTMS/P4R with calf thymus‐DNA were investigated It should be noted that the competitive binding experiment revealed that both Ponceau 4R and ZnO@SiO2@APTMS/P4R could release Hoechst 33258. As inferred from the results the binding of the Ponceau 4R and ZnO@SiO2@APTMS/P4R with DNA were surface binding, mainly due to groove binding. Furthermore, antibacterial properties of ZnO, Ponceau 4R and ZnO@SiO2@APTMS/P4R samples against gram‐positive bacteria and gram‐negative bacteria were examined and the resulting data were compared with the known antibiotic tetracycline. Interestingly, in most cases Ponceau 4R performs antimicrobial activities better than tetracycline that it is important for food preservation containing this colorant. In addition, the ZnO@SiO2@APTMS/P4R exhibited good antimicrobial effectiveness not only to Gram‐positive but also to Gram‐negative bacteria. Novelty impact statement The silica‐coated zinc oxide nanoparticles containing Ponceau 4R have been synthesized and fully characterized by FT‐IR, TEM, TGA, XRD, SEM/EDX and Zeta potential analysis. The results showed that the Ponceau 4R food colorant and the nanoparticles interact with calf thymus‐DNA as groove binders. Interestingly, Ponceau 4R performs excellent antibacterial activities against both gram‐positive and gram‐negative in comparison to tetracycline and it is important for food preservation containing this colorant.

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In the present work, preparation and full characterization of the silica‐coated zinc oxide nanoparticles containing Brilliant black food colorant (denoted as ZnO@SiO2@APTES/BB) is reported. The interactions of Brilliant black food colorant and the nanoparticles containing food colorant (ZnO@SiO2@APTES/BB) with calf thymus‐DNA (ct‐DNA) were then investigated by UV‐vis and fluorescence spectroscopies. In the absorption spectra of ct‐DNA, the band centered at 260 nm exposes hyperchromism in the presence of Brilliant black and also ZnO@SiO2@APTES/BB. Moreover, the binding constant (Kb) of Brilliant black and ZnO@SiO2@APTES/BB with DNA were 2.8 × 103 M−1 and 1.87 × 104 M−1 at 25°C, respectively. From the fluorescence spectroscopy, the enthalpy and entropy changes (ΔH0 and ΔS0) for Brilliant black–DNA and ZnO@SiO2@APTMS/BB–DNA formation were determined. In addition, the competitive binding experiments revealed that the Brilliant black and ZnO@SiO2@APTMS/BB could release Hoechst 33,258 from grooves of DNA. Finally, the potential of antibacterial activities of ZnO nanoparticles, Brilliant black, and ZnO@SiO2@APTMS/BB samples was evaluated and compared with tetracycline antibiotic. It is interesting to note that Brilliant black showed excellent antibacterial activity against gram‐negative and gram‐positive bacteria as compared to known tetracycline antibiotic while the ZnO@SiO2@APTMS/BB acts as a weak antibacterial agent against gram‐negative and gram‐positive bacteria. Novelty impact statement The silica‐coated zinc oxide nanoparticles containing Brilliant black food colorant was synthesized and characterized. Brilliant black and the nanoparticles containing Brilliant black interact with calf thymus‐DNA as groove binders. Brilliant black showed excellent antibacterial activity in comparison to tetracycline drug and it is important for food preservation containing this colorant.