2 research outputs found
In Situ Transformation of Chitosan Films into Microtubular Structures on the Surface of Nanoengineered Titanium Implants
There is considerable interest in
combining bioactive polymers
such as chitosan with titanium bone implants to promote bone healing
and address therapeutic needs. However, the fate of these biodegradable
polymers especially on titanium implants is not fully explored. Here
we report in situ formation of chitosan microtube (CMT) structures
from chitosan films on the implant surface with titania nanotubes
(TNTs) layer, based on phosphate buffer-induced transformation and
precipitation process. We have comprehensively analyzed this phenomenon
and the factors that influence CMT formation, including substrate
topography, immersion solution and its pH, effect of coating thickness,
and time of immersion. Significance of reported in situ formation
of chitosan microtubes on the TNTs surface is possibly to tailor properties
of implants with favorable micro and nano morphology using a self-ordering
process after the implant’s insertion
Graphene Oxide-Assisted Liquid Phase Exfoliation of Graphite into Graphene for Highly Conductive Film and Electromechanical Sensors
Here, we report a
new method to prepare graphene from graphite
by the liquid phase exfoliation process with sonication using graphene
oxide (GO) as a dispersant. It was found that GO nanosheets act a
as surfactant to the mediated exfoliation of graphite into a GO-adsorbed
graphene complex in the aqueous solution, from which graphene was
separated by an additional process. The preparation of isolated graphene
from a single to a few layers is routinely achieved with an exfoliation
yield of up to higher than 40% from the initial graphite material.
The prepared graphene sheets showed a high quality (C/O ∼ 21.5),
low defect (<i>I</i><sub>D</sub>/<i>I</i><sub>G</sub> ∼ 0.12), and high conductivity (6.2 × 10<sup>4</sup> S/m). Moreover, the large lateral size ranging from 5 to
10 μm of graphene, which is believed to be due to the shielding
effect of GO avoiding damage under ultrasonic jets and cavitation
formed by the sonication process. The thin graphene film prepared
by the spray-coating technique showed a sheet resistance of 668 Ω/sq
with a transmittance of 80% at 550 nm after annealing at 350 °C
for 3 h. The transparent electrode was even greater with the resistance
only 66.02 Ω when graphene is deposited on an interdigitated
electrode (1 mm gap). Finally, a flexible sensor based on a graphene
spray-coating polydimethylsiloxane (PDMS) is demonstrated showing
excellent performance working under human touch pressure (<10 kPa).
The graphene prepared by this method has some distinct properties
showing it as a promising material for applications in electronics
including thin film coatings, transparent electrodes, wearable electronics,
human monitoring sensors, and RFID tags