ABSTRACT
A simple electrochemical fabrication of graphene nanomesh (GNM) via colloidal templating is reported for the first time. The process involves the arraying of polystyrene (PS) spheres onto a CVD-deposited graphene, electro-deposition of carbazole units, removal of the PS template and electrochemical oxidative etching. The GNM was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy.
Subject(s)
Electrochemical Techniques , Graphite/chemistry , Nanostructures/chemistry , Carbazoles/chemistry , Colloids/chemistry , Molecular Structure , Particle Size , Polystyrenes/chemistry , Surface PropertiesABSTRACT
The Langmuir-Blodgett (LB) technique was used to immobilize flat graphene oxide (GO) sheets on a PET substrate to ascertain as to whether the edges of GO play an integral part in its antimicrobial mechanism. The observed antibacterial activity suggests that contact with the edges is not a fundamental part of the mechanism.
ABSTRACT
The complete and reversible charge-selective sequestration of fluorophores by a weak polyelectrolyte brush, poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) was demonstrated using fluorescence correlation spectroscopy (FCS). The chemistry and thickness of the weak polyelectrolyte PDMAEMA was tuned reversibly between neutral and cationic polymer forms. Thus, by switching the pH successively, the brush architecture was tuned to selectively trap and release anionic dye probes while continuously excluding cationic molecules. In addition, line-scan FCS was implemented and applied for the first time to a synthetic polymer system and used to identify a new, slower diffusion time on the order of seconds for the sequestered anionic probe under acidic conditions. These results, which quantify the selective sequestration properties of the PDMAEMA brush, are important because they enable a better understanding of transport in polymers and establish a spectroscopic means of evaluating materials with proposed applications in separations science, charge storage/release, and environmental remediation.
Subject(s)
Methacrylates/chemistry , Nylons/chemistry , Diffusion , Electrolytes/chemistry , Fluorescent Dyes/chemistry , Hydrogen-Ion Concentration , Rhodamines/chemistry , Spectrometry, Fluorescence , Static Electricity , Surface PropertiesABSTRACT
The synthesis of homopolymer and diblock copolymers on surfaces was demonstrated using electrodeposition of a methacrylate-functionalized carbazole dendron and subsequent reversible addition-fragmentation chain transfer (RAFT) "grafting-through" polymerization. First, the anodically electroactive carbazole dendron with methacrylate moiety (G1CzMA) was electrodeposited over a conducting surface (i.e. gold or indium tin oxide (ITO)) using cyclic voltammetry (CV). The electrodeposition process formed a crosslinked layer of carbazole units bearing exposed methacrylate moieties. This film was then used as the surface for RAFT polymerization process of methyl methacrylate (MMA), styrene (S), and tert-butyl acrylate (TBA) in the presence of a free RAFT agent and a free radical initiator, resulting in grafted polymer chains. The molecular weights and the polydispersity indices (PDI) of the sacrificial polymers were determined by gel permeation chromatography (GPC). The stages of surface modification were investigated using X-ray photoelectron spectroscopy (XPS), ellipsometry, and atomic force microscopy (AFM) to confirm the surface composition, thickness, and film morphology, respectively. UV-Vis spectroscopy also confirmed the formation of an electro-optically active crosslinked carbazole film with a [Formula: see text] - [Formula: see text] absorption band from 450-650nm. Static water contact angle measurements confirmed the changes in surface energy of the ultrathin films with each modification step. The controlled polymer growth from the conducting polymer-modified surface suggests the viability of combining electrodeposition and grafting-through approach to form functional polymer ultrathin films.
Subject(s)
Electroplating/methods , Methacrylates/chemistry , Polymerization , Polymers/chemistry , Acrylates/chemistry , Anthracenes/chemistry , Carbazoles/chemistry , Electric Conductivity , Electrochemistry , Electrodes , Optical Phenomena , Styrene/chemistry , Surface PropertiesABSTRACT
A novel class of dendrons and dendrimers containing all-azobenzene units (up to 29 azobenzene groups) was designed and synthesized by the convergent method using a protected orthogonal AB(2) monomer (10) and tetra-functionalized core (11) as building blocks. The preparation of the key monomer (10) involved condensation of a protected nitroso compound (9) and 5-aminoisophthalic acid. These are the first examples of photoresponsive dendrimers with all-azobenzene repeating units. [structure: see text]
