Whispering gallery modes (WGMs) have been widely studied over the past 20 years for various applications, including biological sensing. While the WGM-based sensing approaches reported in the literature have shown tremendous performance down to single molecule detection, at present such sensing technologies are not yet mature and still have significant practical constraints that limit their use in real-world applications. Our work has focused on developing a practical, yet effective, WGM-based sensing platform capable of being used as a dip sensor for in-vivo biosensing by combining WGM fluorescent microresonators with silica Microstructured Optical Fibers (MOFs).

We recently demonstrated that a suspended core MOF with a dye-doped polymer microresonator supporting WGMs positioned onto the tip of the fiber, can be used as a dip sensor. In this architecture the resonator is anchored to one of the MOF air holes, in contact with the fiber core, enabling a significant portion of the evanescent field from the fiber to overlap with the sphere and hence excite the fluorescent WGMs. This architecture allows for remote excitation and collection of the WGMs. The fiber also permits easy manipulation of the microresonator for dip sensing applications, and hence alleviates the need for a complex microfluidic interface. More importantly, it allows for an increase in both the excitation and collection efficiency compared to free space coupling, and also improves the Q factor.

In this paper we present our recent results on microstructured fiber tip WGM-based sensors and show that this sensing platform can be used in clinical diagnostics, for detecting various clinically relevant biomarkers in complex clinical samples.

Silicon nanocrystals (SiNCs) are quantum dots that do not contain toxic metals and exhibit a photoluminescent response that may be tailored via changes in particle dimension as well as surface chemistry. Herein, we present a promising hybrid nanomaterial that combines the favourable properties (e.g., photoluminescence, biocompatibility, and surface chemistry) of SiNCs with the magnetic characteristics of Fe3O4 nanoparticles (NPs). Linking these two complementary nanomaterials via DCC coupling has yielded a new advanced hybrid material that possesses the characteristics of its constituents and affords a photoluminescent system that responds to permanent magnets.

Ge-Si alloy nanoparticles (NPs) covering the full range of compositions were studied in regard to their suitability as semiconducting channel layer in thin-film transistors (TFTs). Special focus is given to the influence of annealing and encapsulation techniques on the contact and channel properties. Therefore, electrical characterization methods separating contact from channel characteristics are highlighted and applied. It is demonstrated that appropriate passivation of the nanoparticle surfaces can improve the Ion/Ioff ratios by modulation of the density of free charge carriers and also can suppress hysteresis effects. Ge-rich NP alloys can generally be passivated more effectively regardless if passivation is done with solution-processed poly(methyl methacrylate) (PMMA) or by aluminum oxide (Al2O3) from Atomic Layer Deposition (ALD). Sufficient annealing improves the contact formation between aluminum electrodes and Ge-Si particles by modification of charge injection. The presented analysis leads to a better understanding interface and surface effects in porous nanoparticle semiconductors for application in TFT devices.

We report observation of narrow nanowires and high density nanodots on the Si(001) surfaces when they are exposed to a single application of interferential irradiation of laser pulses of 7 ns. These nanostructures form selectively depending on interference parameters so that their placements can be controlled by controlling the parameters. The morphologies of the nanostructures are studied by atomic force microscopy. The nanowire width increases with interference period. The narrowest nanowires observed have the width smaller than 26 nm, which is eight times smaller than the interference period while the nanodots have a very large density of 1.8 ± 0.45) × 1011/cm2.

The reaction pathway for shallow arsenic doping of silicon by methylarsenic acid molecules directly grafted on oxide-free, H-terminated Si(111) surfaces is unraveled combining Infrared absorption spectroscopy, X-ray Photoelectron Spectroscopy, Low Energy Ion Scattering and ab initio Molecular Dynamics simulations. The overall driving force is identified as a thermodynamic instability of As+5 in contact with silicon, which initiates a self-decomposition of chemisorbed methylarsenic molecules at ∼600 K. As the temperature is increased, the As-C bond breaks -- the weakest link of the adsorbed molecule -- with release of the organic ligand and a rearrangement from a monodentate to a bidentate bonding configuration. In this process, oxygen atoms evolve by partial desorption as H2O and partial incorporation into the surface Si atom backbonds. At ∼1050 K, diffusion of As into the sub-surface region of silicon is observed. There is no evidence for As desorption and no remaining C contamination.