Aluminum Oxide Nanostructured Microcantilever Arrays for Nanomechanical-Based Sensing

Abstract

Novel nanostructured microcantilever (MC) surfaces were developed by modifying the active side of the MCs with aluminum oxide nanoparticles (AONP) for purposes of enhancing sensitivity in nanomechanical-based sensing. Uniform layers of AONP were spin coated and chemically immobilized on the surfaces of MCs with tetramethoxysilane (TMOS) as a cross-linker. Optimization studies on MC modification were performed for better surface uniformity and higher surface area, based on scanning electron microscope (SEM) images. The AONP-modified MC array (MCA) were subsequently functionalized by being immersed in parallel configured capillaries filled with different reagents for immobilizing chemical or biological receptors onto the MC surfaces. A MCA prepared for chemical sensing was exposed to the samples made of headspace vapor of different volatile organic compounds (VOCs). The characteristic response signatures for each gas phase VOC analyte showed substantial diversity. Immersion time in the capillary and the chemical nature of the reagents used for functionalization were both optimized to achieve the highest sensitivity and long-term reproducibility in nanomechanical responses to the test analytes. A second MCA functionalized with two different immunological receptors was prepared and exposed to three biological analytes in the liquid phase, with a highly selective response obtained for each analyte. Fluorescence microscope images and FT-IR spectra were used in this work to validate the controlled, variable chemical nature of the MC surfaces.

Quantitative Evaluation of Biological Reaction Kinetics in Confined Nanospaces

“…PAA membranes with thickness of 81 μm, diameter of 1.2 cm, geometry area of 1.13 cm 2 , and pore diameters of 25 ± 5, 55 ± 15, 90 ± 10, and 130 ± 20 nm were washed by ethanol and double distilled water to remove any impurities in the nanochannels. After drying in a nitrogen flow at room temperature, the PAA membranes were immersed into a 1 mL ethanol solution containing 5% APTES and shaken gently for 12 h. − Then the PAA membranes were washed with ethanol to remove any residual silane in the nanochannels and last dried in a nitrogen flow at room temperature. After that, a 100 μL solution of DNA at a concentration of 10 μM prepared in PBS (10 mM, pH 7.0) was dropped onto the surface of the PAA membrane for 24 h. Thus, the DNA was assembled onto the inner wall of the nanochannels through a Schiff reaction between the −CHO group in DNA and the amino group on the nanochannels of PAA under mild reaction conditions. , The remaining amino groups were further blocked by immersing the PAA membrane into 1 mL of PBS (10 mM, pH 7.0) containing 0.1% benzaldehyde and shaking gently for 12 h. The unbound DNA and residual benzaldehyde were removed by rinsing with PBS.…”

Surface Pretreatment Boosts the Performance of Supramolecular Affinity Materials on Quartz Crystal Microbalances for Sensor Applications

“…Since aluminum oxide is used in various sensor applications for humidity or volatile organic compounds (VOCs) detection as an adsorbant, the discrimination of a particular analyte from humidity and interfering and ubiquitous VOCs, which are continuously released by different sources in the environment like petroleum, humans, or cosmetics, is essential. Under the assumption that the depth diffusion of small molecules cannot be prevented by the affinity material itself without high synthetic work, a suitable method for the protection of the QCM electrode surface is highly desired.…”