Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with builtin electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H-2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (< 5 mu W), room temperature operation. (C) 2015 AIP Publishing LLC.

Lesion Detection in Breast Ultrasound Images Using Tissue Transition Analysis

Breast cancer is one of the leading cause of cancer related deaths in women and early detection is crucial for reducing mortality rates. In this paper, we present a novel and fully automated approach based on tissue transition analysis for lesion detection in breast ultrasound images. Every candidate pixel is classified as belonging to the lesion boundary, lesion interior or normal tissue based on its descriptor value. The tissue transitions are modeled using a Markov chain to estimate the likelihood of a candidate lesion region. Experimental evaluation on a clinical dataset of 135 images show that the proposed approach can achieve high sensitivity (95 %) with modest (3) false positives per image. The approach achieves very similar results (94 % for 3 false positives) on a completely different clinical dataset of 159 images without retraining, highlighting the robustness of the approach.

Tetraphenylethene-Based Conjugated Fluoranthene: A Potential Fluorescent Probe for Detection of Nitroaromatic Compounds

This study reports the synthesis and photophysical properties of a star-shaped, novel, fluoranthene-tetraphenylethene (TFPE) conjugated luminogen, which exhibits aggregation-induced blue-shifted emission (AIBSE). The bulky fluoranthene units at the periphery prevent intramolecular rotation (IMR) of phenyl rings and induces a blueshift with enhanced emission. The AIBSE phenomenon was investigated by solvatochromic and temperature-dependent emission studies. Nanoaggregates of TFPE, formed by varying the water/THF ratio, were investigated by SEM and TEM and correlated with optical properties. The TFPE conjugate was found to be a promising fluorescent probe towards the detection of nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) with high sensitivity and a high Stern-Volmer quenching constant. The study reveals that nanoaggregates of TFPE formed at 30 and 70% water in THF showed unprecedented sensitivity with detection limits of 0.8 and 0.5ppb, respectively. The nanoaggregates formed at water fractions of 30 and 70% exhibit high Stern-Volmer constants (K-sv=79998 and 51120m(-1), respectively) towards PA. Fluorescence quenching is ascribed to photoinduced electron transfer between TFPE and NACs with a static quenching mechanism. Test strips coated with TFPE luminogen demonstrate fast and ultra-low-level detection of PA for real-time field analysis.