Post transition metal substituted Keggin-type POMs as thin film chemiresistive sensors for H2O and CO2 detection

Chemiresitive sensing allows the affordable and facile detection of small molecules such as H2O and CO2. Herein, we report a novel class of Earth-abundant post transition metal substituted Keggin polyoxometalates (POMs) for chemiresistive sensing applications, with conductivities up to 0.01 S cm−1 under 100% CO2 and 65% Relative Humidity (RH)

From Monochrome to Technicolor: Simple Generic Approaches to Multicomponent Protein Nanopatterning Using Siloxanes with Photoremovable Protein-Resistant Protecting Groups.

We show that sequential protein deposition is possible by photodeprotection of films formed from a tetraethylene-glycol functionalized nitrophenylethoxycarbonyl-protected aminopropyltriethoxysilane (NPEOC-APTES). Exposure to near-UV irradiation removes the protein-resistant protecting group, and allows protein adsorption onto the resulting aminated surface. The protein resistance was tested using proteins with fluorescent labels and microspectroscopy of two-component structures formed by micro- and nanopatterning and deposition of yellow and green fluorescent proteins (YFP/GFP). Nonspecific adsorption onto regions where the protecting group remained intact was negligible. Multiple component patterns were also formed by near-field methods. Because reading and writing can be decoupled in a near-field microscope, it is possible to carry out sequential patterning steps at a single location involving different proteins. Up to four different proteins were formed into geometric patterns using near-field lithography. Interferometric lithography facilitates the organization of proteins over square cm areas. Two-component patterns consisting of 150 nm streptavidin dots formed within an orthogonal grid of bars of GFP at a period of ca. 500 nm could just be resolved by fluorescence microscopy

A coordination polymer for the site-specific integration of semiconducting sequences into DNA-based materials

Advances in bottom-up material design have been significantly progressed through DNA-based approaches. However, the routine integration of semiconducting properties, particularly long-range electrical conduction, into the basic topological motif of DNA remains challenging. Here, we demonstrate this with a coordination polymer derived from 6-thioguanosine (6-TG-H), a sulfur-containing analog of a natural nucleoside. The complexation reaction with Au(I) ions spontaneously assembles luminescent one-dimensional helical chains, characterized as {Au (μ-6-TG)} , extending many μm in length that are structurally analogous to natural DNA. Uniquely, for such a material, this gold-thiolate can be transformed into a wire-like conducting form by oxidative doping. We also show that this self-assembly reaction is compatible with a 6-TG-modified DNA duplex and provides a straightforward method by which to integrate semiconducting sequences, site-specifically, into the framework of DNA materials, transforming their properties in a fundamental and technologically useful manner.Integration of semiconducting properties into the basic topological motif of DNA remains challenging. Here, the authors show a coordination polymer derived from 6-thioguanosine that complexes with Au(I) ions to form a wire-like material that can also integrate semiconducting sequences into the framework of DNA materials

A coordination polymer for the site-specific integration of semiconducting sequences into DNA-based materials

Integration of semiconducting properties into the basic topological motif of DNA remains challenging. Here, the authors show a coordination polymer derived from 6-thioguanosine that complexes with Au(I) ions to form a wire-like material that can also integrate semiconducting sequences into the framework of DNA materials

Hierarchical self-assembly in an RNA-based coordination polymer hydrogel

An RNA-based coordination polymer is formed by the aqueous reaction of CuI ions with the thionucleoside enantiomer (−)6-thioguanosine, (6tGH). The resulting polymer, [CuI(μ3-S-thioG)]n1, has a one-dimensional structure based on a [Cu4–S4] core and undergoes extensive hierarchical self-assembly transforming from oligomeric chains → rod → cable → bundle through which a fibrous gel forms, that undergoes syneresis to form a self-supporting mass. The assembly involves the formation of helical cables/bundles and, in combination with the intrinsic photoemission of the polymer, results in the material exhibiting circularly polarised luminescence (CPL)

Generic Methods for Micrometer- And Nanometer-Scale Surface Derivatization Based on Photochemical Coupling of Primary Amines to Monolayers of Aryl Azides on Gold and Aluminum Oxide Surfaces

A series of aryl azide terminated thiols and phosphonic acids has been synthesized, and used to prepare self-assembled monolayers on (respectively) gold and aluminum oxide surfaces. The rates of photoactivation were determined using contact angle measurement and X-ray photoelectron spectroscopy (XPS). The behavior of a diazirine functionalized aryl thiol was also studied. The rates of activation were found to be similar for all five adsorbates. However, the extent of photochemical coupling of a primary amine was significantly greater for the aryl azides than for the diazirine. A range of primary amines was successfully coupled to all of the azides with high yield. Little difference in reactivity was observed following perfluorination of the aromatic ring. Micrometer-scale patterns were fabricated by carrying out exposures of the aryl azide terminated SAMs through a mask submerged under a film of primary amine. Contrasting amines could be introduced to unreacted regions in a subsequent maskless step. A scanning near-field optical microscope was used to fabricate nanopatterns. Exposure of the azides to irradiation at 325 nm in air enabled selective deactivation of azides. The surrounding surface was functionalized with a primary amine in a maskless process; when a protein-resistant oligo­(ethylene glycol) functionalized amine was used it was possible to produce protein nanopatterns, by adsorbing protein to features defined using near-field exposure

Two-Dimensional Frameworks Based on Ag(I)–N Bond Formation: Single Crystal to Single Molecular Sheet Transformation

A series of new two-dimensional coordination framework materials, based on Ag­(I)–N bond formation, has been synthesized and structurally characterized by single crystal methods. Reactions between the poly-monodentate bridging ligand <i>N</i>,<i>N</i>′-((1r,4r)-cyclohexane-1,4-diyl)­bis­(1-(pyridin-3-yl)­methanimine), <b>L1</b>, and silver salts yield compounds {[Ag­(<b>L1</b>)­(MeCN)]­(CF₃SO₃^–)}_<i>n</i>, <b>1</b>, {[Ag­(<b>L1</b>)­(PF₂O₂^–)]·H₂O}_<i>n</i>, <b>2</b>, and {Ag₂(<b>L1</b>)­(tosylate)₂}_<i>n</i>, <b>3</b>. The frameworks of these materials exhibit two distinct net topologies: 3⁶.4⁶.5³ (<b>1</b> and <b>2</b>) and 4⁴.6² (<b>3</b>). In all cases, <b>L1</b> ligands are found to be fully saturated, in terms of metal ion binding, with both sets of pyridyl and imino N atoms involved, though in <b>1</b> and <b>2</b>, crystallographically independent <b>L1</b> moieties also display pyridyl-only binding. Either solvent (<b>1</b>) or the anion (<b>2</b> and <b>3</b>) acts as a terminal ligand to support interlayer interactions in the solid state. For <b>2</b> and <b>3</b> the molecular sheet orientation lies in the plane of the largest crystal face, indicating that crystal growth is preferentially driven by coordinate bond formation. Despite the relatively labile nature, typical of such Ag­(I)–N bonds, solvent-based exfoliation of crystals of <b>3</b> was shown to provide dispersions of large, μm², flakes which readily deposit on oxide surfaces as single-molecule sheets, as revealed by atomic force microscopy

Two-Dimensional Frameworks Based on Ag(I)–N Bond Formation: Single Crystal to Single Molecular Sheet Transformation

A series of new two-dimensional coordination framework materials, based on Ag­(I)–N bond formation, has been synthesized and structurally characterized by single crystal methods. Reactions between the poly-monodentate bridging ligand <i>N</i>,<i>N</i>′-((1r,4r)-cyclohexane-1,4-diyl)­bis­(1-(pyridin-3-yl)­methanimine), <b>L1</b>, and silver salts yield compounds {[Ag­(<b>L1</b>)­(MeCN)]­(CF₃SO₃^–)}_<i>n</i>, <b>1</b>, {[Ag­(<b>L1</b>)­(PF₂O₂^–)]·H₂O}_<i>n</i>, <b>2</b>, and {Ag₂(<b>L1</b>)­(tosylate)₂}_<i>n</i>, <b>3</b>. The frameworks of these materials exhibit two distinct net topologies: 3⁶.4⁶.5³ (<b>1</b> and <b>2</b>) and 4⁴.6² (<b>3</b>). In all cases, <b>L1</b> ligands are found to be fully saturated, in terms of metal ion binding, with both sets of pyridyl and imino N atoms involved, though in <b>1</b> and <b>2</b>, crystallographically independent <b>L1</b> moieties also display pyridyl-only binding. Either solvent (<b>1</b>) or the anion (<b>2</b> and <b>3</b>) acts as a terminal ligand to support interlayer interactions in the solid state. For <b>2</b> and <b>3</b> the molecular sheet orientation lies in the plane of the largest crystal face, indicating that crystal growth is preferentially driven by coordinate bond formation. Despite the relatively labile nature, typical of such Ag­(I)–N bonds, solvent-based exfoliation of crystals of <b>3</b> was shown to provide dispersions of large, μm², flakes which readily deposit on oxide surfaces as single-molecule sheets, as revealed by atomic force microscopy

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel

The aqueous equimolar reaction of Ag(I) ions with the thionucleoside enantiomer (-)6-thioguanosine, ((-)6tGH), yields a one-dimensional coordination polymer {Ag(-)tG}n, the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra. At concentrations >15 mmol l^-1 reactions form a sample-spanning hydrogel which shows self-repair capabilities with instantaneous recovery in which the dynamic reversibility of the coordination chains appears to play a role. The resulting gel exhibits circularly polarised luminescence (CPL) with a large dissymmetry factor of -0.07 +/- 0.01 at 735 nm, a phenomenon not previously observed for this class of coordination polyme

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel

The aqueous equimolar reaction of Ag(I) ions with the thionucleoside enantiomer (−)6-thioguanosine, ((−)6tGH), yields a one-dimensional coordination polymer {Ag(−)tG}n, the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra. At concentrations ≥15 mmol l−1 reactions form a sample-spanning hydrogel which shows self-repair capabilities with instantaneous recovery in which the dynamic reversibility of the coordination chains appears to play a role. The resulting gel exhibits circularly polarised luminescence (CPL) with a large dissymmetry factor of −0.07 ± 0.01 at 735 nm, a phenomenon not previously observed for this class of coordination polymer