Browsing by Subject "Nanotubes"
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Item Au nanoparticle assembly on cnts using flash induced solid-state dewetting(2015-04-28) Kulkarni, Ameya; Ryu, Jong Eun; Agarwal, Mangilal; Xie, Jian; Cheng, RuihuaCarbon Nanotubes (CNTs) are used extensively in various applications where substrate are required to be possessing higher surface area, porosity and electrical and thermal conductivity. Such properties can be enhanced to target a particular gas and biochemical for efficient detection when CNT matrix is functionalized with Nanoparticles (NPs). Conventional functionalization involves harsh oxidation repeated washing, filtration and sonication, which induce defects. The defects lead to hindered mobility of carriers, unwanted doping and also fragmentation of the CNTs in some cases. In this document we demonstrate functionalization of CNT with Au nanoparticles on a macro scale under dry and ambient condition using Xenon ash induced solid-state dewetting. A sputtered thin film was transformed into nanoparticles which were confirmed to be in a state of thermodynamic equilibrium. We worked on 3 nm, 6 nm, 9 nm, 15 nm, 30 nm initial thickness of thin films. Xenon ash parameters of energy, number of pulse, duration of pulse, duration of gap between consecutive pulses were optimized to achieve complete dewetting of Au thin films. 3 nm deposition was in the form of irregular nano-islands which were transformed into stable nanoparticles with a single shot of 10 J/cm2 of 2 ms duration. 6 nm and 9 nm deposition was in form of continues film which was also dewetted into stable nanoparticles with a single pulse but with an increased energy density of 20 J/cm2 and 35 J/cm2 respectively. In case of 15 nm and 30 nm deposition the thin film couldn't be dewetted with a maximum energy density of 50 J/cm2, it was observed that 3 and 4 pulses of 2 ms pulse duration and 2 ms gap duration with an energy density of 50 J/cm2 were required to completely dewet the thicker films. However irregularity was induced in the sizes of the NPs due to Ostwald ripening phenomenon which causes smaller particle within a critical difiusion length to combine and form a larger particle during or after dewetting process. For comparison, the Au thin films were also dewetted by a conventional process involving annealing of samples until the thin film was fully transformed into NPs and the size of NPs seized to grow. Scanning electron microscope (SEM) was used to characterize the samples. Thermodynamic stability of the particles was confirmed with statistical analyses of size distribution after every additional pulse.Item Doxycycline-loaded nanotube-modified adhesives inhibit MMP in a dose-dependent fashion(Springer Nature, 2018-04) Palasuk, Jadesada; Windsor, L. Jack; Platt, Jeffrey A.; Lvov, Yuri; Geraldeli, Saulo; Bottino, Marco C.; Biomedical Sciences and Comprehensive Care, School of DentistryOBJECTIVES: This article evaluated the drug loading, release kinetics, and matrix metalloproteinase (MMP) inhibition of doxycycline (DOX) released from DOX-loaded nanotube-modified adhesives. DOX was chosen as the model drug, since it is the only MMP inhibitor approved by the U.S. Food and Drug Administration. MATERIALS AND METHODS: Drug loading into the nanotubes was accomplished using DOX solution at distinct concentrations. Increased concentrations of DOX significantly improved the amount of loaded DOX. The modified adhesives were fabricated by incorporating DOX-loaded nanotubes into the adhesive resin of a commercial product. The degree of conversion (DC), Knoop microhardness, DOX release kinetics, antimicrobial, cytocompatibility, and anti-MMP activity of the modified adhesives were investigated. RESULTS: Incorporation of DOX-loaded nanotubes did not compromise DC, Knoop microhardness, or cell compatibility. Higher concentrations of DOX led to an increase in DOX release in a concentration-dependent manner from the modified adhesives. DOX released from the modified adhesives did not inhibit the growth of caries-related bacteria, but more importantly, it did inhibit MMP-1 activity. CONCLUSIONS: The loading of DOX into the nanotube-modified adhesives did not compromise the physicochemical properties of the adhesives and the released levels of DOX were able to inhibit MMP activity without cytotoxicity. CLINICAL SIGNIFICANCE: Doxycycline released from the nanotube-modified adhesives inhibited MMP activity in a concentration-dependent fashion. Therefore, the proposed nanotube-modified adhesive may hold clinical potential as a strategy to preserve resin/dentin bond stability.Item Effect of a chlorhexidine-encapsulated nanotube modified pit-and-fissure sealant on oral biofilm(J-STAGE, 2021-05) Feitosa, Sabrina; Carreiro, Adriana F. P.; Martins, Victor M.; Platt, Jeffrey A.; Duarte, Simone; Biomedical Sciences and Comprehensive Care, School of DentistryThe purpose of this study was to characterize a chlorhexidine-encapsulated nanotube modified pit-and-fissure sealant for biofilm development prevention. HS (commercial control); HNT (HS+15wt%Halloysite®-clay-nanotube); CHX10% (HS+15wt% HNT-encapsulated with chlorhexidine 10%); and CHX20% (HS+15wt% HNT-encapsulated with CHX20%) were tested. Degree-of-conversion (DC%), Knoop hardness (KHN), and viscosity were analyzed. The ability of the sealant to wet the fissures was evaluated. Specimens were tested for zones of inhibition of microbial growth. S. mutans biofilm was tested by measuring recovered viability. Data were statistically analyzed (p<0.05). DC% was significantly higher for the HNT-CHX groups. For KHN, CHX10% presented a lower mean value than the other groups. Adding HNT resulted in higher viscosity values. The biofilm on CHX10% and CHX20% sealants presented remarkable CFU/mL reduction in comparison to the HS. The experimental material was able to reduce the biofilm development in S. mutans biofilm without compromising the sealant properties.Item Effect of Chlorhexidine-Encapsulated Nanotube-Modified Adhesive System on the Bond Strength to Human Dentin(2019) Kalagi, Sara Arfan; Cook, N. Blaine; Diefenderfer, Kim; Bottino, Marco; Feitosa, SabrinaIntroduction: The resin-dentin interface undergoes degradation by endogenous matrix metalloproteinases (MMPs) after adhesive procedures. Application of several MMP inhibitors such as chlorhexidine (CHX) to the demineralized collagen dentin matrix after acid-etching has been suggested to be a successful approach to prevent degradation of the hybrid layer. Further, nanotubes (HNT) have been used as a reservoir for encapsulation and controlled delivery for several therapeutic drugs with sustained release. Therefore, HNT can be encapsulated with CHX and incorporated into dentin adhesives for the possibility of enhancing the longevity and durability of the hybrid layer. Objective: To evaluate the effect of a CHX-encapsulated nanotube-modified primer/PR and adhesive/ADH on the microtensile resin bond strength (µTBS) to dentin. Materials and Methods: A commercial adhesive and its respective primer were modified by adding CHX-encapsulated nanotubes at two distinct concentrations (10 and 20 wt.%). The experimental adhesives were evaluated by degree of conversion (DC) and viscosity. Meanwhile, only viscosity was determined for the experimental primers. The prepared HNT-encapsulated with CHX (10 and 20 wt.%) powders were incorporated into the primer and/or adhesive according to the groups: ADH (control); HNT (control); 0.2% CHX; PR+CHX10%; PR+CHX20%; ADH+CHX10%; ADH+CHX20%. Human molars were selected and autoclaved; mid-coronal dentin surfaces were exposed for bonding purposes. Dentin surfaces were etched, followed by primer and adhesive application, and restored with a resin composite. After 24 hours, the teeth were sliced into beams for µTBS testing; beams collected for each tooth were equally assigned into two testing condition groups: 24 hours and 6 months. Microtensile bond strength was tested using a universal testing machine, and the types of failure were classified as adhesive, mixed, and cohesive failure. Data from DC and viscosity tests were analyzed using one-way ANOVA. Bond strength data were analyzed by pair-wise comparisons using the Sidak method to control the overall significance level at 5% for each aging time separately. Weibull-distribution survival analysis was used to compare the differences in the microtensile bond strength results among the groups after 24 hours and 6 months. Results and Conclusion: DC analysis revealed no significant differences among adhesive groups. However, ADH group had a significantly lower viscosity than modified adhesive groups, and a significantly higher viscosity than modified primer groups. Test results of stress value (MPa) by each group for each aging time revealed no significant differences among groups after 24 hours. However, after 6-month storage, modified primer groups (PR+CHX10%, PR+CHX20%) and 0.2%CHX group showed a significant difference in µTBS compared to control groups (ADH, HNT) and modified adhesive groups (ADH+CHX10%, ADH+CHX20%) in the same aging time testing (p < 0.05). When comparing the µTBS after 24 hours and 6 months, there were no significant differences among the groups except for the ADH+CHX20% group, for which MPa values were higher after 24 hours than 6 months (p = 0.0487). In conclusion, this study has demonstrated the great potential of modified dental primers with CHX-encapsulated nanotubes in preservation of the resin-dentin bond strength over a 6-month time period. Additionally, modification of dental primers and adhesives was a successful approach that didn’t compromise the characteristics or the mechanical properties of the materials and has a promising long-term effect on resin-dentin bond strength.Item A Modified Adhesive System for Use in Treatment of Dentin Hypersensitivity(2020-08) AlShehri, Aram Mushabbab; Sochacki, Sabrina Feitosa; Hara, Anderson; Platt, Jeffrey A.; Windsor, L. JackItem Paper-based lithium-Ion batteries using carbon nanotube-coated wood microfiber current collectors(2013-11-06) Aliahmad, Nojan; Varahramyan, Kody; Agarwal, Mangilal; Shrestha, Sudhir; Rizkalla, Maher E.; King, BrianThe prevalent applications of energy storage devices have incited wide-spread efforts on production of thin, flexible, and light-weight lithium-ion batteries. In this work, lithium-ion batteries using novel flexible paper-based current collectors have been developed. The paper-based current collectors were fabricated from carbon nanotube (CNT)-coated wood microfibers (CNT-microfiber paper). This thesis presents the fabrication of the CNT-microfiber paper using wood microfibers, coating electrode materials, design and assemblies of battery, testing methodologies, and experimental results and analyses. Wood microfibers were coated with carbon nanotubes and poly(3,4-ethylenedioxythiophene) (PEDOT) through an electrostatic layer-by-layer nanoassembely process and formed into a sheet, CNT-microfiber paper. The CNT loading of the fabricated paper was measured 10.1 μg/cm2 subsequently considered. Electrode material solutions were spray-coated on the CNT-microfiber paper to produce electrodes for the half and full-cell devices. The CNT current collector consists of a network structure of cellulose microfibers at the micro-scale, with micro-pores filled with the applied conductive electrode materials reducing the overall internal resistance for the cell. A bending test revealed that the paper-based electrodes, compared to metal ones, incurred fewer damages after 20 bends at an angle of 300o. The surface fractures on the paper-based electrodes were shallow and contained than metallic-based electrodes. The micro-pores in CNT-microfiber paper structure provides better adherence to the active material layer to the substrate and inhibits detachment while bending. Half-cells and full-cells using lithium cobalt oxide (LCO), lithium titanium oxide (LTO), and lithium magnesium oxide (LMO) were fabricated and tested. Coin cell assembly and liquid electrolyte was used. The capacities of half-cells were measured 150 mAh/g with LCO, 158 mAh/g with LTO, and 130 mAh/g with LMO. The capacity of the LTO/LCO full-cell also was measured 126 mAh/g at C/5 rate. The columbic efficiency of the LTO/LCO full-cell was measured 84% for the first charging cycle that increased to 96% after second cycle. The self-discharge test of the full-cell after charging to 2.7 V at C/5 current rate is showed a stable 2 V after 90 hours. The capacities of the developed batteries at lower currents are comparable to the metallic electrode-based devices, however, the capacities were observed to drop at higher currents. This makes the developed paper-based batteries more suitable for low current applications, such as, RFID tags, flexible electronics, bioassays, and displays. The capacities of the batteries at higher current can be improved by enhancing the conductivity of the fibers, which is identified as the future work. Furthermore, fabrication of an all solid state battery using solid electrolyte is also identified as the future work of this project.Item Physicochemical and Biological Properties of Novel Chlorhexidine-Loaded Nanotube-Modified Dentin Adhesive(Wiley, 2018-09-10) Feitosa, Sabrina A.; Palasuk, Jadesada; Geraldeli, Saulo; Windsor, L. Jack; Bottino, Marco C.; Biomedical Sciences and Comprehensive Care, School of DentistryA commercially available three-step (etch-and-rinse) adhesive was modified by adding chlorhexidine (CHX)-loaded nanotubes (Halloysite®, HNT) at two concentrations (CHX10% and CHX20%). The experimental groups were: SBMP (unmodified adhesive, control), HNT (SBMP modified with HNT), CHX10 (SBMP modified with HNT loaded with CHX10%), and CHX20 (SBMP modified with HNT loaded with CHX20%). Changes in the degree of conversion (DC%), Knoop hardness (KHN), water sorption (WS), solubility (SL), antimicrobial activity, cytotoxicity, and anti-matrix metalloproteinase [MMP-1] activity (collagenase-I) were evaluated. In regards to DC%, two-way ANOVA followed by Tukey’s post-hoc test revealed that only the factor “adhesive” was statistically significant (p<0.05). No significant differences were detected in DC% when 20 s light-curing was used (p>0.05). For Knoop microhardness, one-way ANOVA followed by the Tukey’s test showed statistically significant differences when comparing HNT (20.82±1.65) and CHX20% (21.71±2.83) with the SBMP and CHX10% groups. All adhesives presented similar WS and cytocompatibility. The CHX-loaded nanotube-modified adhesive released enough CHX to inhibit the growth of S. mutans and L. casei. Adhesive eluates were not able to effectively inhibit MMP-1 activity. The evaluation of higher CHX concentrations might be necessary to provide an effective and predictable MMP inhibition.