Effect of TiO_2 Functionalization on Nano-Porous Silicon for Selective Alcohol Sensing at Room Temperature

Room temperature operated sensor for detection of alcohol vapours in low ppm range based on TiO_2 functionalized nano-porous silicon（PSi） is demonstrated. The effect of functionalization by TiO_2 on PSi is investigated using SEM, EDX, Raman spectroscopy, XRD and contact angle measurements. Sensing is accomplished by measuring change in resistance of the sensing layer using Cr-Au inter-digitatedelectrode（IDE） structure formed on top of the functionalized PSi layer. The sensors were tested for volatile organic compounds（VOCs） and water vapours in the wide range of 5–500 ppm concentration at room temperature. Functionalization of the nanostructured PSi by sputter deposited TiO_2 results in significant enhancement of sensitivity and inverse change in selectivity. PSi sensors have displayed strong response to water vapours whereas after functionalization, selective sensing to ethanol is depicted. Minimum detection by PSi sensors is portrayed at 100 ppm and that of functionalized sensors is at 10 ppm. Sensing mechanism is explained on the basis of surfaces and structures of both PSi and TiO_2. This study incites the importance of surface treatment of PSi for tuning the sensing properties and is useful in the development of selective alcohol sensors.

Accuracy of three-dimensional quantification of left ventricular function using magnetic sensor acquisition: a dynamic in vitro model

Objective To evaluate the accuracy of a three-dimensional (3D) magnetic position sensor system in the quantification of ventricular stroke volumes in a dynamic model.Methods A latex balloon model of the left ventricle was suspended in a water bath connected to a pump producing 10 different pulsatile stroke volumes (15-65mi/beat). Scanning was performed using a 5.0 mHz transducer mounted with a Flock of Birds (FOB) magnetic receiver (GE System Five). The probe was scanned to sweep continuously across and over the balloon volume over 3 - 7 seconds. Digital loops were stored on magneto-optical disks and reviewed retrospectively using 3D Echopac software (GE)based on Simpson's method and compared with a two-dimensional (2D) biplane area-length method (1/2L x R) measurements at end systole and end diastole. Both 3D and 2D derived stroke volumes were compared with the reference stroke volume calculated by direct measurement of balloon capacity.Results There was an improved correlation between 3D stroke volume and reference stroke volume ( y = 0.91 x + 0.41, r = 0.97, SEE = 2.83 ml, P = 0.0001 ) compared to 2D stroke volume and reference stroke volume (y=0.49x+8.68, r=0.87, SEE=3.87 ml, P=0.0011, difference between 2D and 3D P＜0.003).Conclusion 3D magnetic FOB scanning is practical, accurate and should facilitate assessment of left ventricular function.