RESUMEN
We introduce a methodology to reversibly pattern planar surfaces via the light-induced dimerization of anthracenes, particularly involving a 9-triazolylanthracene motif. Specifically, we demonstrate that the visible light-induced forward reaction can be employed to pattern small molecule species as well as polymers in a spatially resolved fashion. Under UV irradiation, the generated patterns can be erased to regenerate reactive areas, which are then available for a new functionalization step. The dynamic change in surface chemistry is evidenced by ToF-SIMS.
RESUMEN
A degradable polyphthalaldehyde-polystyrene block copolymer generated by modular ligation is reported for the first time serving as a nanochannel template for the formation of nanostructured materials. The polyphthalaldehyde-b-polystyrene copolymer was spin-coated onto a surface with subsequent polyphthalaldehyde block removal. Block conjugation and block removal were confirmed by H-NMR, SEC, AFM, and SEM.
RESUMEN
Intrinsically glucoside-based microspheres are prepared in olive oil via a water in oil inverse suspension polymerization. The microspheres are characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) microscopy, and X-ray photoelectron spectroscopy (XPS), evidencing the intrinsic glucose character of the spheres. A novel boronic acid fluorescent molecule was subsequently conjugated to the microspheres in an aqueous environment, exhibiting the spatial and uniform distribution of glucoside as well as the affinity of the microspheres to bind with boron, evidenced via fluorescence spectroscopy measurements.
Asunto(s)
Boro/química , Glucósidos/química , Polímeros/química , Microscopía Electrónica de Rastreo , Microesferas , Espectroscopía de Fotoelectrones , Polimerizacion , Polímeros/síntesis química , Propiedades de SuperficieRESUMEN
Boronic acid-functionalized microspheres are prepared for the first time via mild epoxide ring opening based on porous cross-linked polymeric microspheres (diameter ≈ 10 µm, porosity ≈ 1000 Å). Quantitative chemical analysis by XPS and EA evidences that there is a greater functionalization with boronic acid when employing a sequential synthetic method [1.7 atom% boron (XPS); 1.12 wt% nitrogen (EA)] versus a one-pot synthetic method [0.2 atom% boron (XPS); 0.60 wt% nitrogen (EA)] yielding grafting densities ranging from approximately 2.5 molecules of boronic acid per nm(2) to 1 molecule of boronic acid per nm(2), respectively. Furthermore, the boronic acid-functionalized microspheres are conjugated with a novel fluorescent glucose molecule demonstrating a homogeneous spatial distribution of boronic acid.
Asunto(s)
Ácidos Borónicos/química , Técnicas de Química Sintética/métodos , Polímeros/síntesis química , Microesferas , Estructura Molecular , Polímeros/químicaRESUMEN
We fabricate unique photoluminescent three dimensional graphene oxide (GO) architectures, so-called GO flowers, by self-assembly onto silicon substrates via solvent-mediated volume-controlled growth. The GO flowers exhibited bright photoluminescence and a photoresponse demonstrating their potential for advanced optical and electronic applications, such as advanced photovoltaic devices and organic light emitting diodes.
Asunto(s)
Grafito/química , Sustancias Luminiscentes/química , Nanoestructuras/ultraestructura , Óxidos/química , Microscopía Electrónica de Rastreo , Nanoestructuras/química , Fotoquímica , Espectrofotometría UltravioletaRESUMEN
A novel surface modification technique was employed to produce a polymer modified positive contrast agent nanoparticle through attachment of well-defined homopolymers synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A range of RAFT homopolymers including poly[N-(2-hydroxypropyl)methacrylamide], poly(N-isopropylacrylamide), polystyrene, poly(2-(dimethylamino)ethyl acrylate), poly(((poly)ethylene glycol) methyl ether acrylate), and poly(acrylic acid) were synthesized and subsequently used to modify the surface of gadolinium (Gd) metal-organic framework (MOF) nanoparticles. Employment of a trithiocarbonate RAFT agent allowed for reduction of the polymer end groups under basic conditions to thiolates, providing a means of homopolymer attachment through vacant orbitals on the Gd3+ ions at the surface of the Gd MOF nanoparticles. Magnetic resonance imaging (MRI) confirmed the relaxivity rates of these novel polymer modified structures were easily tuned by changes in the molecular weight and chemical structures of the polymers. When a hydrophilic polymer was used for modification of the Gd MOF nanoparticles, an increase in molecular weight of the polymer provided a respective increase in the longitudinal relaxivity. These relaxivity values were significantly higher than both the unmodified Gd MOF nanoparticles and the clinically employed contrast agents, Magnevist and Multihance, which confirmed the construct's ability to be utilized as a positive contrast nanoparticle agent in MRI. Further characterization confirmed that increased hydrophobicity of the polymer coating on the Gd MOF nanoparticles yielded minimal changes in the longitudinal relaxivity properties but large increases in the transverse relaxivity properties in the MRI.