Spherical LDH-Ag°-montmorillonite heterocoagulated system with a pH-dependent sol-gel structure for controlled accessibility of AgNPs immobilized on the clay lamellae.

Aqueous suspensions of spherical ZnMgAl-layered double hydroxides [LDH(sph)] and antibacterial silver nanoparticles (AgNPs) deposited on the lamellae of montmorillonite were used for the synthesis of composites, which behave like coherent gels at low pH (≲4.5) and incoherent sols at higher pH (≳4.5). The composition of the composite was chosen as LDH(sph)/Ag°-montm. = 25:75 wt % in order to ensure a sol-gel transition that can also be characterized by viscometry. This pH-sensitive heterocoagulated system consisting of oppositely charged colloid particles was suitable for the release of antimicrobial AgNPs immobilized on the clay lamellae via a pH-controlled gel-sol transition. The heterocoagulation process was also characterized by surface charge titration measurements. Spherical LDH/Ag°-montmorillonite composite samples were identified by X-ray diffraction (XRD) measurements. The morphological properties of the composites were studied, and the presence of the heterocoagulated structure was confirmed by scanning electron microscopy (SEM). The nanoscale structure of the LDH(sph)-Ag°-montmorillonite composite obtained was also verified by small-angle X-ray scattering (SAXS), and the rheological characteristics were studied at various pH values. The viscosity and yield value of the composite decreased by an order of magnitude upon increasing the pH from 3.0 to 5.5. The sol-gel transition of the composite suspension was reversible in the previously mentioned pH range.

[1]  R. Frost,et al.  Synthesis of organoclays: A critical review and some unresolved issues , 2014 .

[2]  L. Janovák,et al.  Synthesis of pH-sensitive copolymer thin solid films embedded with silver nanoparticles for controlled release and their fungicide properties , 2014 .

[3]  N. S. Amin,et al.  Photocatalytic reduction of carbon dioxide with water vapors over montmorillonite modified TiO2 nanocomposites , 2013 .

[4]  Jeehyeong Khim,et al.  Photocatalyst separation from aqueous dispersion using graphene oxide/TiO2 nanocomposites , 2013 .

[5]  I. Pálinkó,et al.  Radiation induced topotactic [2 + 2] dimerisation of acrylate derivatives among the layers of a CaFe layered double hydroxide followed by IR spectroscopy , 2013 .

[6]  M. Louloudi,et al.  Thiamine pyrophosphate intercalation in layered double hydroxides (LDHs): An active bio-hybrid catalyst for pyruvate decarboxylation , 2013 .

[7]  Wei‐De Zhang,et al.  Preparation of nanostructured microspheres of Zn–Mg–Al layered double hydroxides with high adsorption property , 2012 .

[8]  I. Dékány,et al.  Effect of pH on stability and plasmonic properties of cysteine-functionalized silver nanoparticle dispersion. , 2012, Colloids and surfaces. B, Biointerfaces.

[9]  C. Johnston,et al.  Interaction of biological molecules with clay minerals: a combined spectroscopic and sorption study of lysozyme on saponite. , 2012, Langmuir : the ACS journal of surfaces and colloids.

[10]  F. Besenbacher,et al.  Engineered morphologies of layered double hydroxide nanoarchitectured shell microspheres and their calcined products , 2011 .

[11]  Huaiyong Zhu,et al.  Integrating efficient filtration and visible-light photocatalysis by loading Ag-doped zeolite Y part , 2011 .

[12]  P. Yuan,et al.  Organoclays prepared from montmorillonites with different cation exchange capacity and surfactant configuration , 2010 .

[13]  L. Janovák,et al.  Optical properties and electric conductivity of gold nanoparticle-containing, hydrogel-based thin layer composite films obtained by photopolymerization , 2010 .

[14]  B. Dudek,et al.  Porous clay heterostructures (PCHs) intercalated with silica-titania pillars and modified with transition metals as catalysts for the DeNOx process , 2009 .

[15]  Hasmukh A. Patel,et al.  Montmorillonite intercalated with vitamin B1 as drug carrier , 2009 .

[16]  R. Chandra,et al.  Synthesis and characterization of silver and gold nanoparticles in ionic liquid. , 2009, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[17]  Shaomin Liu,et al.  Surface charging of layered double hydroxides during dynamic interactions of anions at the interfaces. , 2008, Journal of colloid and interface science.

[18]  Jin-Ho Choy,et al.  Clay minerals and layered double hydroxides for novel biological applications , 2007 .

[19]  C. Caramella,et al.  Use of clays as drug delivery systems: Possibilities and limitations , 2007 .

[20]  F. Leroux,et al.  Synthesis and characterization of macroporous MgAl LDH using polystyrene spheres as template , 2006 .

[21]  J. Besse,et al.  Intercalation of noble metal complexes in LDH compounds , 2004 .

[22]  G. Lagaly,et al.  Colloidal magnesium aluminum hydroxide and heterocoagulation with a clay mineral. II. Heterocoagulation with sodium montmorillonite , 2001 .

[23]  Dirk Penner,et al.  Influence of anions on the rheological properties of clay mineral dispersions , 2001 .

[24]  Meier,et al.  The Lower Cation Exchange Capacity Limit of Montmorillonite. , 1999, Journal of colloid and interface science.

[25]  I. Kiricsi,et al.  Amino acids, precursors for cationic and anionic intercalation synthesis and characterization of amino acid pillared materials , 1999 .

[26]  T. Pinnavaia,et al.  Iron oxide pillared clay with large gallery height: Synthesis and properties as a Fischer-Tropsch catalyst , 1991 .

[27]  J. Lee,et al.  Pentachlorophenol Sorption by Organo-Clays , 1988 .