Emily P. Nguyen

Field Effect Biosensing Platform Based on 2D α-MoO3

Electrical-based biosensing platforms offer ease of fabrication and simple sensing solutions. Recently, two-dimensional (2D) semiconductors have been proven to be excellent for the fabrication of field effect transistors (FETs) due to their large transconductance, which can be efficiently used for developing sensitive bioplatforms. We present a 2D molybdenum trioxide (MoO3) FET based biosensing platform, using bovine serum albumin as a model protein. The conduction channel is a nanostructured film made of 2D α-MoO3 nanoflakes, with the majority of nanoflake thicknesses being equal to or less than 2.8 nm. The response time is impressively low (less than 10 s), which is due to the high permittivity of the 2D α-MoO3 nanoflakes. The system offers a competitive solution for future biosensing applications.

Electronic Tuning of 2D MoS2 through Surface Functionalization

The electronic properties of thiol-functionalized 2D MoS2 nanosheets are investigated. Shifts in the valence and conduction bands and Fermi levels are observed while bandgaps remain unaffected. These findings allow the tuning of energy barriers between 2D MoS2 and other materials, which can lead to improved control over 2D MoS2 -based electronic and optical devices and catalysts.

2D MoS2 PDMS Nanocomposites for NO2 Separation

At a relatively low loading concentration (≈0.02 wt%) of 2D MoS 2 flakes in PDMS, the composite membrane is able to almost completely block the permeation of NO2 gas molecules at ppm levels. This major reduction is ascribed to the strong physisorption of NO2 gas molecules onto the 2D MoS2 flake basal planes.

Excitation dependent bidirectional electron transfer in phthalocyanine-functionalised MoS2 nanosheets

Two-dimensional (2D) transition metal chalcogenides such as 2D MoS2 are considered prime candidate materials for the design of next generation optoelectronics. Functionalisation of these materials is considered to be a key step in tailoring their properties towards specific applications and unlocking their full potential. Here we present a van der Waals functionalisation strategy for creating MoS2 nanosheets decorated with free base phthalocyanine chromophores. The semiconducting sheets are found to intimately interact with these optoelectronically active chromophores, resulting in an electronic heterostructure that exhibits enhanced optoelectronic properties and exploitable charge transfer. We show that by utilising laterally confined MoS2 nanosheets, the conduction band of the semiconductor could be positioned between the chromophores S1 and S2 states. Consequently, bidirectional photoinduced electron transfer processes are observed, with excitation of the functionalised nanosheets semiconductor transition resulting in electron transfer to the phthalocyanines LUMO, and excitation of the chromophores S2 state leading to electron injection into the MoS2 conduction band. However, charge transfer from the dyes S1 transition to the MoS2 nanosheet is found to be thermodynamically unfavourable, resulting in intense radiative recombination. These findings may enable controlling and tuning the charge carrier density of semiconducting nanosheets via optical means through the exploitation of photoinduced electron transfer. Furthermore this work provides access to 2D semiconductor-hybrids with tailored absorption profiles and photoluminescence.

A unique in vivo approach for investigating antimicrobial materials utilizing fistulated animals

Unique in vivo tests were conducted through the use of a fistulated ruminant, providing an ideal environment with a diverse and vibrant microbial community. Utilizing such a procedure can be especially invaluable for investigating the performance of antimicrobial materials related to human and animal related infections. In this pilot study, it is shown that the rumen of a fistulated animal provides an excellent live laboratory for assessing the properties of antimicrobial materials. We investigate microbial colonization onto model nanocomposites based on silver (Ag) nanoparticles at different concentrations into polydimethylsiloxane (PDMS). With implantable devices posing a major risk for hospital-acquired infections, the present study provides a viable solution to understand microbial colonization with the potential to reduce the incidence of infection through the introduction of Ag nanoparticles at the optimum concentrations. In vitro measurements were also conducted to show the validity of the approach. An optimal loading of 0.25 wt% Ag is found to show the greatest antimicrobial activity and observed through the in vivo tests to reduce the microbial diversity colonizing the surface.

Liquid Exfoliation of Layered Transition Metal Dichalcogenides for Biological Applications.

Known to possess distinctive properties that differ greatly from their bulk form, layered two‐dimensional materials have been extensively studied and incorporated into many versatile applications ranging from optoelectronics to sensors. For biomedical research, two‐dimensional transition metal dichalcogenides (2D TMDs) have garnered much interest as they have been shown to exhibit relatively low toxicity, high stability in aqueous environments, and the ability to adhere to biological materials such as proteins. These materials are promising candidates, demonstrating potential applications in biosensing, cell imaging, diagnostics, and therapeutics. Preparation and exfoliation of 2D TMDs play an important part in these various applications as their properties are heavily dependent on the number of layers and lateral size. Described in this article are protocols for the liquid exfoliation of 2D TMDs from their bulk materials. Additional protocols are also provided for functionalizing or modifying the surface of the exfoliated 2D TMDs.

Hybrid Surface and Bulk Resonant Acoustics for Concurrent Actuation and Sensing on a Single Microfluidic Device

While many microfluidic devices have been developed for sensing and others for actuation, few devices can perform both tasks effectively and simultaneously on the same platform. In piezoelectric sensors and actuators, this is due to the opposing operating requirements for sensing and actuation. Sensing ideally requires narrow resonant peaks characterized by high quality factors, such as those found in quartz crystals. However, these materials usually have poor electromechanical coupling coefficients that are not ideal for actuation. In this work, we show that it is possible to achieve both sensing and actuation simultaneously on a shared device by exploiting the distinct advantages of both bulk waves for effective mass sensing and surface waves for highly efficient microfluidic actuation through a unique hybrid surface and bulk acoustic wave platform. In light of the recent resurgence of interest in portable inhaled insulin devices for personalized diabetes management, we demonstrate the use of this technology for efficient aerosolization of insulin for inhalation without denaturing the protein, while being able to concurrently detect the residual mass of the un-nebulized insulin remaining on the device such that the actual dose delivered to the patient can be determined in real time.

Assessment of a Raman micro-spectroscopy/microfluidics unit using a model E. coli/glucose bio-system

Incorporating Raman micro-spectroscopy into microfluidic units provides certain opportunities for in situ monitoring of bio-systems at the micro scale. Specifically, it allows for the observation of exchange, release and uptake of biochemical components within and in proximity of microorganisms in the highly controlled liquid phase environments of microfluidics. However, such systems are still in infancy and their capabilities need to be explored further. In this paper, the Escherichia coli (E. coli)/glucose bio-system is used for assessing a Raman/microfluidics unit. Two scenarios were used in the observations: the first that includes nutrient rich broth, ideal for E. coli growth, and the second using simplified deionised water.