Browsing by Author "Advincula, Rigoberto C."
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Item Antimicrobial Applications of Electroactive PVK-SWNT Nanocomposites(Environmental Science and Technology, 11/17/2011) Ahmed, Farid; Santos, Catherine M.; Vergara, Regina Aileen May V.; Tria, Maria Celeste R.; Advincula, Rigoberto C.; Rodrigues, Debora F.The antibacterial properties of a nanocomposite containing an electroactive polymer, polyvinyl-N-carbazole (PVK) (97 wt %), and single-walled carbon nanotubes (SWNT) (3 wt %) was investigated as suspensions in water and as thin film coatings. The toxic effects of four different PVK-SWNT (97:3 wt %) nanocomposite concentrations (1, 0.5, 0.05, and 0.01 mg/mL) containing 0.03, 0.015, 0.0015, and 0.0003 mg/mL of SWNT, respectively, were determined for planktonic cells and biofilms of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). The results showed that the nanocomposite PVK-SWNT had antibacterial activity on planktonic cells and biofilms at all concentration levels. Higher bacterial inactivation (94% for E. coli and 90% for B. subtilis) were achieved in planktonic cells at a PVK-SWNT concentration of 1 mg/mL. Atomic force microscopy (AFM) imaging showed significant reduction of biofilm growth on PVK-SWNT coated surfaces. This study established for the first time that the improved dispersion of SWNTs in aqueous solutions in the presence of PVK enhances the antimicrobial effects of SWNTs at very low concentrations. Furthermore, PVK-SWNT can be used as an effective thin film coating material to resist biofilm formation.Item Antimicrobial PVK:SWNT nanocomposite coated membrane for water purification: Performance and toxicity testing(Water Research, 8/1/2013) Ahmed, Farid; Santos, Catherine M.; Mangadlao, Joey D.; Advincula, Rigoberto C.; Rodrigues, Debora F.This study demonstrated that coated nitrocellulose membranes with a nanocomposite containing 97% (wt%) of polyvinyl-N-carbazole (PVK) and 3% (wt%) of single-walled carbon nanotubes (SWNTs) (97:3 wt% ratio PVK:SWNT) achieve similar or improved removal of bacteria when compared with 100% SWNTs coated membranes. Membranes coated with the nanocomposite exhibited significant antimicrobial activity toward Gram-positive and Gram-negative bacteria (?80–90%); and presented a virus removal efficiency of ?2.5 logs. Bacterial cell membrane damage was considered a possible mechanism of cellular inactivation since higher efflux of intracellular material (Deoxyribonucleic acid, DNA) was quantified in the filtrate of PVK-SWNT and SWNT membranes than in the filtrate of control membranes. To evaluate possible application of these membrane filters for drinking water treatment, toxicity of PVK-SWNT was tested against fibroblast cells. The results demonstrated that PVK-SWNT was non toxic to fibroblast cells as opposed to pure SWNT (100%). These results suggest that it is possible to synthesize antimicrobial nitrocellulose membranes coated with SWNT based nanocomposites for drinking water treatment. Furthermore, membrane filters coated with the nanocomposite PVK-SWNT (97:3 wt% ratio PVK:SWNT) will produce more suitable coated membranes for drinking water than pure SWNTs coated membranes (100%), since the reduced load of SWNT in the nanocomposite will reduce the use of costly and toxic SWNT nanomaterial on the membranes.Item CONTROLLED SYNTHESIS OF TOPOLOGICALLY TEMPLATED CATENANE AND KNOTTY POLYMER(2013-05) Bunha, Ajaykumar 1983-; Thummel, Randolph P.; Advincula, Rigoberto C.; Miljanić, Ognjen Š.; Czernuszewicz, Roman S.; Robertson, Megan L.The topologically interesting structure of polymer catenanes and knotty polymers are of high interest for their unique chemical and physical properties. However, the practical applications of these materials have not been explored well due to synthetic obstacles in obtaining high yields. Chapter 1 reviews template directed synthesis of low molecular weight catenanes and the trefoil knot. In addition, recent advances in synthesis of topologically similar cyclic polymer via end-to-end cyclization of linear analogue or ring-expansion polymerization from cyclic catalyst/initiator are also discussed. Chapter 2 demonstrates a novel route for the synthesis of polymer catenanes using supramolecularly templated Atom Transfer Radical Polymerization (ATRP) initiator for polymerization and subsequent closing of the resulting four-armed type polymer template by Atom Transfer Radical Coupling (ATRC). Direct visualization of the interlocked topology of polymer catenane was achieved by Atomic Force Microscopy (AFM) imaging technique. Chapter 3 reports an important extension of the above mentioned methodology to obtain a catenated block copolymer. The four-armed type homopolymer template was used as macroinitiator to polymerize another monomer by ATRP. The resulting block copolymer template was subjected to template-closing via slightly modified ATRC method. Chapter 4 demonstrates another novel approach to synthesize polymer catenanes by first grafting a preformed alkyne-functionalized linear polymer to an azide-functionalized supramolecular template, followed by ATRC of the resulting polymer template. Detailed analysis of AFM image reveals important information about the side products of ATRC such as inter-molecular coupling and other isomer formation. Chapter 5 reports on a preliminary study of thermally initiated ring-expansion Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization from cyclic RAFT initiator. A novel dixanthate type cyclic RAFT initiator was synthesized and used in a thermally initiated free radical polymerization of N-vinylcarbazole. The cyclic topology of the resulting polyvinylcarbazole was confirmed by Gel Permeation Chromatography (GPC) and AFM analysis. Chapter 6 demonstrates for the first time the synthesis of trefoil knot polymer (knotty polymer) via grafting of an alkyne-functionalized polymer to azide-functionalized double helical type supramolecular template. A well-defined knotty polymer was then obtained by closing the polymer template via ATRC method. Finally in Chapter 7, conclusions, perspectives, and future work on these topics are discussed.Item Dendron Stabilized Hybrid nanoparticles: Synthesis: Characterization, and Energy Transfer Studies(2012-08) Puno, Katherine 1974-; Lee, T. Randall; Advincula, Rigoberto C.; Thummel, Randolph P.; Czernuszewicz, Roman S.; Rodrigues, Debora F.Hybrid organic-inorganic nanoparticles are developed as a new class of material with a wide range of application based on their spectroscopic and electrochemical properties. Designing these materials to fine tune their properties as an energy or charge transfer pair calls for an ease of synthesis to produce stable and tunable nanoparticles. Chapter 2 describes a facile synthesi of a nanoparticle-cored dendrimer with electroactive carbazole dendron conjugated onto the amine surface of a generation three cystamine-core PAMAM dendrimer. The disulfide on the cystamine core of this dendrimer is reduced to produce dendrons that stabilize the AuNPs. Such manner of synthesis avoids the tedious stepwise process of attaching the dendrons to the AuNOs by convergent approach. Spectroscopic and electrochemical properties of this system are reported. Chapter 3 discusses the energy transfer involved between CdSe quantum dots and Au nanoparticles placed proximal to each other. The CdSe quantum dots are stabilized by generational carbazole dendrons which provide a control in the distance of these nanoparticles thereby controlling the donor-acceptor interaction. Quite uniquely, the reduction of the Au3+ ions did not necessitae any external reducing agent. The formation of this hybrid nanoparticle is a one-pot synthesis wherein the reduction of the Au3+ to Au(0) provides a simultaneous cross-linking of the carbazole units which overall affords a formation of a three-component hybrid nanoparticles. Generally, there is a potential in exploring the optimization of this facile synthetic protocol to produce the customized hybrid nanoparticles needed for specific optoelectronic applications.Item Electrochemically-Grafted Biotinylated Carbazoles(2012-05) Worlikar, Deepali 1985-; Advincula, Rigoberto C.; Rodrigues, Debora F.; May, Jeremy A.; Thummel, Randolph P.; Xu, ShoujunBiotin-Streptavidin is known to be one of the strongest non-covalent interactions with dissociation constant, Kd ~ 10-15. Non-specific adsorption of proteins is one of the major concerns in the design of a biosensor device which causes bio-fouling and ultimately reduces the life span of a bio-device. The main challenge in the surface functionalization for affinity-based methods is to immobilize one of the interacting compounds on the surface in such a way that nonspecific interactions of the protein with the surface are minimized. Taking into consideration the possibility of both, specific and nonspecific adsorption of streptavidin on surfaces, this study is designed to incorporate poly(ethyleneglycol) as a protein resistant functional moiety, and biotin for the formation of biotin-streptavidin bridge for protein immobilization. PEGylated carbazole compounds were first synthesized via a series of organic reactions. These compounds were further biotinylated through EDC-DMAP coupling chemistry. The biotinylated compounds were characterized by 1H NMR, 13C NMR, and ultraviolet-visible spectroscopy. Thin films of the biotinylated carbazole compounds were then fabricated on a quartz crystal of QCM by electrochemical deposition method. The electrodeposited films were further tested for the selective binding of streptavidin. In brief, the study aims to provide a new platform for the immobilization of streptavidin via electrochemical grafting. The ability to fine-tune the formation of a polymer film with electrochemically-controlled thickness will potentially enable the engineering of new molecular templates for biosensor applications.Item FUNCTIONAL AND PATTERNABLE ELECTRO-GRAFTED COATINGS(2012-08) Foster, Edward 1982-; Lee, T. Randall; Advincula, Rigoberto C.; Miljanić, Ognjen Š.; Czernuszewicz, Roman S.; Stein, Gila E.The use of electro-grafted materials provided a quick and efficient route to functionalize conducting surfaces. The unique properties of electroactive materials allow for large surface areas to be covered by the material being deposited. Chapter 1 reviews recent developments and practices in the use of electro-grafted materials. Chapter 2 reports the fabrication of patterned binary polymer brushes via colloidal particle templating combined with electrodeposited atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer radical polymerization (RAFT), and ring opening metathesis polymerization (ROMP) initiators. Chapter 3 demonstrates a new approach of creating topologically and well-defined patterned polymeric surfaces via the “grafting to” approach. This was accomplished by either using colloidally templated “clickable” arrays, whereby the chemistry was performed directly onto the pattern or by subsequent backfilling with azido terminated self-assembled monolayers (SAM). Similarly, direct grafting of electroactive temperature-responsive oligo(ethylene glycol) methacrylic polymers to colloidally templated surfaces allowed for tunable ion gate formation. In chapter 4, a novel one step approach to fabricate superhydrophobic and superoleophilic coatings is reported. Due to the incorporation of an ATRP moiety into the coating, surface initiated ATRP (SI-ATRP) was performed to change the wettability of the substrates towards a variety of liquids. Chapter 5 reports the fabrication of polymerizable superhydrophobic coating by using a facile one step procedure i.e. electrodeposition. These coating exhibited tunable bacterial adhesion, self-cleaning capabilities, and corrosion resistance. Similarly, surface initiated ATRP of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate (HDFM) was performed on a steel slide. Subsequent static water, diiodomethane, and hexadecane contact angles revealed that the steel coated surface was now superamphiphobic. In chapter 6 the fabrication of pendant terthiophene polymer brushes and their application as ultrathin films is demonstrated. Ellipsometry and atomic force microscopy (AFM) studies showed differences in the film structure at various stages of film development. These films were subsequently employed for the investigation of electrochemical nanopatterning using current sensing AFM as a writing technique. The pattern formation was demonstrated in order to show the possibility for future applications, such as information storage devices and nanowires. Finally in chapter 7, conclusions, perspectives, and future work based on chapters 2-5 is presented.Item Permeability of anti-fouling PEGylated surfaces probed by fluorescence correlation spectroscopy(Colloids Surf B Biointerfaces, 2017-10) Daniels, Charlisa R.; Reznik, Carmen; Kilmer, Rachel; Felipe, Mary J.; Tria, Maria C. R.; Kourentzi, Katerina D.; Chen, Wen-Hsiang; Advincula, Rigoberto C.; Willson, Richard C.; Landes, Christy F.The present work reports on in situ observations of the interaction of organic dye probe molecules and dye-labeled protein with different poly(ethylene glycol) (PEG) architectures (linear, dendron, and bottle brush). Fluorescence correlation spectroscopy (FCS) and single molecule event analysis were used to examine the nature and extent of probe朠EG interactions. The data support a sieve-like model in which size-exclusion principles determine the extent of probe朠EG interactions. Small probes are trapped by more dense PEG architectures and large probes interact more with less dense PEG surfaces. These results, and the tunable pore structure of the PEG dendrons employed in this work, suggest the viability of electrochemically-active materials for tunable surfaces.Item Tunable Protein and Bacterial Cell Adsorption on Colloidally Templated Superhydrophobic Polythiophene Films(Chemistry of Materials, 6/1/2011) Pernites, Roderick B.; Santos, Catherine M.; Maldonado, Miguel; Ponnapati, Ramakrishna R.; Rodrigues, Debora F.; Advincula, Rigoberto C.A facile approach for enabling or inhibiting the adsorption of protein and adhesion of bacterial cells on a potential-induced reversibly wettable polythiophene film is described. The superhydrophobic polymeric surface was first prepared by a two-step process that combines the layering of polystyrene (PS) latex particles via a Langmuir–Blodgett (LB)-like technique followed by cyclic voltammetric (CV)–electrodeposition of polythiophene from a terthiophene ester monomer. The polythiophene conducting polymer coating enabled control of the wettability of the surface by simply changing its redox property via potential switching. The influence of morphology on this switching behavior is also described. The wettability in return controls the adsorption of protein and adhesion of bacterial cells. For instance, the undoped polythiophene film, which is superhydrophobic, inhibits the adhesion of fibrinogen proteins and Escherichia coli (E. coli) cells. On the other hand, the doped film, which is hydrophilic, leads to increased attachment of both protein and bacteria. Unlike most synthetic antiwetting surfaces, the as-prepared superhydrophobic coating is nonfluorinated. It maintains its superhydrophobic property at a wide range of pH (pH 1–13) and temperature (below ?10 °C and between 4 and 80 °C). Moreover, the surface demonstrated self-cleaning properties at a sliding angle as low as 3° ± 1. The proposed methodology and material should find application in the preparation of smart or tunable biomaterial surfaces that can be either resistant or susceptible to proteins and bacterial cell adhesion by a simple potential switching.