Heterogeneous Ultrathin Films Based On The Ordered Co-assembly Of Biomolecules And Fluorescent Dyes With Layered Double Hydroxides: Fabrication And Fluorescent Sensor Application

Layered double hydroxides （LDHs） are a large class of inorganiclayered materials, the general formula of which can be described as:[M_1-x^ⅡM_x^Ⅲ（OH）₂]^z+A_z/n^n-yH₂O.M^Ⅱ and M^Ⅲare divalent and trivalentmetals ions, respectively; A^n- are the guest anions presenting between thehydroxide layers. LDHs have attracted considerable interest for theirpotential applications as catalysts, pharmaceutically active materials, andelectrical/optical functional materials.The controllable assembly of the biomolecules （such as proteins,DNA and RNA） into functional nanostructures have recently receivedmuch attention not only for fundamental scientific interests but also forpotential clinical applications. To meet the need of new generation of biosensor and drug delivery carrier, it is of critical importance to fabricatebiomolecular film materials with highly ordered orientation. This paperdescribes the construction of ordered organic/inorganic hybrid ultrathinfilms （UTFs） based on biomolecules, fluorescent dyes and Mg-Al-layereddouble hydroxide （LDH） nanosheets as building blocks by usinglayer-by-layer （LBL） assembly method, The fabrication process and theultrathin films are Characterized by UV-vis absorption, fluorescencespectroscopy, atomic force microscopy, and scanning electronmicroscopy. The frameworks of this study are as follows:1. This work firstly describes the construction of orderedorganic/inorganic hybrid ultrathin films （UTFs） based on four nucleotides,adenosine5’-monophosphate （5’-AMP）, uridine5’-monophosphate（5’-UMP）, guanosine5’-monophosphate （5’-GMP）, cytidine5’-monophosphate （5’-CMP） and Mg-Al-layered double hydroxide （LDH）nanosheets as building blocks by using layer-by-layer （LBL） assemblymethod. The successful assembly of the nucleotide anions and LDHsnanosheets can be attributed to the electrostatic and thehydrogen-bonding interactions. Then the fabrication process of theultrathin films are Characterized by UV-vis absorption, atomic forcemicroscopy and scanning electron microscopy.2. The attention was focused on the assembly of heterogeneousUTFs by alternative assembly of the nucleotides and fluorescent stilbene-type anion （bis（2-sulfonatostyryl） biphenyl, BSB） with LDHnanosheets. UV-vis absorption and fluorescence spectroscopy, atomicforce microscopy, and scanning electron microscopy demonstrate astepwise and regular growth of the UTFs with a thickness of4.24nm perbilayer upon increasing deposited cycles. Fluorescent spectra confirm thatthe as-prepared （nucleotides/LDH/BSB/LDH）nUTFs exhibit well-definedblue fluorescence.3. The （ssDNA/LDH）n hybrid ultrathin films （UTFs） based onsingle-stranded DNA and Mg-Al-layered double hydroxide （LDH）nanosheets as building blocks by using layer-by-layer （LBL） assemblymethod. Then the （ssDNA/LDH）n hybrid ultrathin films （UTFs）immersed into the ethidium bromide （EB）solution. The fabricationprocess of the ultrathin films are Characterized by UV-vis absorption,atomic force microscopy and scanning electron microscopy.