The adsorption of tetracycline and vancomycin onto nanodiamond with controlled release.

The unique properties and tailorable surface of detonation nanodiamonds have given rise to an abundance of potential biomedical applications. Very little is known about the details of adsorption/desorption equilibria of drugs on/from nanodiamonds with different purity, surface chemistry, and agglomeration state. The studies presented here delve into the details of adsorption and desorption of tetracycline (TET) and vancomycin (VAN) on nanodiamond, which are critically important for the rational design of the nanodiamond drug delivery systems. The nanodiamonds studied in these experiments were as-received (ND), purified and carboxyl terminated (ND-COOH), and aminated (ND-NH2). The monolayer capacities of the drugs loaded onto the nanodiamonds are reported herein using Langmuir and Freundlich isotherm models. The results from the desorption studies demonstrate that, by changing the pH environment of drug loaded nanodiamond using buffers of pH 4.09, 7.45, 8.02, and a phosphate buffered saline (PBS) solution, the drug release can effectively be triggered.

Stability of Grafted Polymer Nanoscale Films toward Gamma Irradiation.

The present article focuses on the influence of gamma irradiation on nanoscale polymer grafted films and explores avenues for improvements in their stability toward the ionizing radiation. In terms of applications, we concentrate on enrichment polymer layers (EPLs), which are polymer thin films employed in sensor devices for the detection of chemical and biological substances. Specifically, we have studied the influence of gamma irradiation on nanoscale poly(glycidyl methacrylate) (PGMA) grafted EPL films. First, it was determined that a significant level of cross-linking was caused by irradiation in pure PGMA films. The cross-linking is accompanied by the formation of conjugated ester, carbon double bonds, hydroxyl groups, ketone carbonyls, and the elimination of epoxy groups as determined by FTIR. Polystyrene, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, dimethylphenylsilanol, BaF2, and gold nanoparticles were incorporated into the films and were found to mitigate different aspects of the radiation damage.

Label-free water sensors using hybrid polymer-dielectric mid-infrared optical waveguides.

A chip-scale mid-IR water sensor was developed using silicon nitride (SiN) waveguides coated with poly(glycidyl methacrylate) (PGMA). The label-free detection was conducted at λ=2.6-2.7 µm because this spectral region overlaps with the characteristic O-H stretch absorption while being transparent to PGMA and SiN. Through the design of a hybrid waveguide structure, we were able to tailor the mid-IR evanescent wave into the PGMA layer and the surrounding water and, consequently, to enhance the light-analyte interaction. A 7.6 times enhancement of sensitivity is experimentally demonstrated and explained by material integration engineering as well as waveguide mode analysis. Our sensor platform made by polymer-dielectric hybrids can be applied to other regions of the mid-IR spectrum to probe other analytes and can ultimately achieve a multispectral sensor on-a-chip.

Flexible and conductive MXene films and nanocomposites with high capacitance.

MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti3C2T(x) MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti3C2T(x)/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10(4) S/m in the case of the Ti3C2T(x)/PVA composite film and 2.4 × 10(5) S/m for pure Ti3C2T(x) films. The tensile strength of the Ti3C2T(x)/PVA composites was significantly enhanced compared with pure Ti3C2T(x) or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm(3) for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.

Temperature controlled shape change of grafted nanofoams.

We demonstrated that nanoscale-level actuation can be, in principle, achieved with grafted polymer nanofoams by forces associated with conformational changes of stretched macromolecular chains. The nanofoams are fabricated via a two-step procedure. First, the "grafting to" technique is used to obtain a 20-200 nm anchored and cross-linked poly(glycidyl methacrylate) film. Second, the film is swollen in solvent and freeze dried until the solvent is sublimated. The grafted nanofoam possesses the behavior of a shape-memory material, exhibiting gradual mechanical contraction at the nanometer scale as temperature is increased. Both the thickness and shape-recovery ratio of the nanofoam have a close to linear dependency on temperature. We also demonstrated that by modification of the poly(glycidyl methacrylate) nanofoam with grafting low molecular weight polymers, one can tune an absolute nanoscale mechanical response of the porous polymer film.

Mid-infrared materials and devices on a Si platform for optical sensing.

In this article, we review our recent work on mid-infrared (mid-IR) photonic materials and devices fabricated on silicon for on-chip sensing applications. Pedestal waveguides based on silicon are demonstrated as broadband mid-IR sensors. Our low-loss mid-IR directional couplers demonstrated in SiN x waveguides are useful in differential sensing applications. Photonic crystal cavities and microdisk resonators based on chalcogenide glasses for high sensitivity are also demonstrated as effective mid-IR sensors. Polymer-based functionalization layers, to enhance the sensitivity and selectivity of our sensor devices, are also presented. We discuss the design of mid-IR chalcogenide waveguides integrated with polycrystalline PbTe detectors on a monolithic silicon platform for optical sensing, wherein the use of a low-index spacer layer enables the evanescent coupling of mid-IR light from the waveguides to the detector. Finally, we show the successful fabrication processing of our first prototype mid-IR waveguide-integrated detectors.

Towards universal enrichment nanocoating for IR-ATR waveguides.

Polymer multilayered nanocoating capable of concentrating various chemical substances at IR-ATR waveguide surfaces is described. The coating affinity to an analyte played a pivotal role in sensitivity enhancement of the IR-ATR measurements, since the unmodified waveguide did not show any analyte detection.