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Papers by ka hei yung
Analytica chimica acta, Jan 16, 2015
We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried do... more We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried double junction (BDJ) photodiode that (i) provides a real-time output signal that is related to the intensity ratio at two emission wavelengths and (ii) simultaneously eliminates the need for an optical filter to block Rayleigh scatter. We demonstrate the BDJ platform performance for gaseous NH3 and aqueous pH detection. We also compare the BDJ performance to parallel results obtained by using a slew scanned fluorimeter (SSF). The BDJ results are functionally equivalent to the SSF results without the need for any wavelength filtering or monochromators and the BDJ platform is not prone to errors associated with source intensity fluctuations or sensor signal drift.
Sensors and Actuators B: Chemical, 2010
A new method for enhancement of luminescence from sol-gel based sensors is demonstrated, utilisin... more A new method for enhancement of luminescence from sol-gel based sensors is demonstrated, utilising the quenching effect and filtering effect of a gold film. Ruthenium (4,7-diphenyl-1,10-phenanthroline) 3 Cl 2 is encapsulated in a trimethoxysilane (TEOS) xerogel and spin-coated to an approximate thickness of less than 100 nm. Using off axis illumination of the xerogel film, luminescence was collected using a photodiode below the plane of the gold and doped thin film. The gold had the effect of improving all sensor figures of merit via two mechanisms. Firstly, the transmission spectrum of the gold film peaks at 520 nm but allows poor transmission of excitation light at 450 nm reducing stray light interference in addition to a 550 nm cut-on filter. Secondly, and more, importantly relatively insensitive luminophores within approximately 10 nm of the gold film are quenched resulting in a significant noise reduction by removal of insensitive residual metal ion-ligand complex luminescence. It is questioned whether an element of radiative-decay-engineering of luminescence is occurring with luminophore emission coupling to the gold film and initiating plasmonic emission from the underside of the film, but no evidence either in terms of solely p-polarisation or increased intensity of luminescence was evidenced. This confirms that the sensor enhancement mechanism is primarily the function of metal quenching as evidenced by reduced background intensity as noise and improved response time to oxygen quenching indicating that only the most sensitive luminophores are available to be dynamically quenched by formation of the ruthenium:oxygen charge transfer complex. This simple sensor geometry improves a basic oxygen sensor luminophore:matrix combination and stands comparison with more complex combinations such as those achieved with fluorinated sol-gel matrices.
Analytica chimica acta, Jan 16, 2015
We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried do... more We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried double junction (BDJ) photodiode that (i) provides a real-time output signal that is related to the intensity ratio at two emission wavelengths and (ii) simultaneously eliminates the need for an optical filter to block Rayleigh scatter. We demonstrate the BDJ platform performance for gaseous NH3 and aqueous pH detection. We also compare the BDJ performance to parallel results obtained by using a slew scanned fluorimeter (SSF). The BDJ results are functionally equivalent to the SSF results without the need for any wavelength filtering or monochromators and the BDJ platform is not prone to errors associated with source intensity fluctuations or sensor signal drift.
Sensors and Actuators B: Chemical, 2010
A new method for enhancement of luminescence from sol-gel based sensors is demonstrated, utilisin... more A new method for enhancement of luminescence from sol-gel based sensors is demonstrated, utilising the quenching effect and filtering effect of a gold film. Ruthenium (4,7-diphenyl-1,10-phenanthroline) 3 Cl 2 is encapsulated in a trimethoxysilane (TEOS) xerogel and spin-coated to an approximate thickness of less than 100 nm. Using off axis illumination of the xerogel film, luminescence was collected using a photodiode below the plane of the gold and doped thin film. The gold had the effect of improving all sensor figures of merit via two mechanisms. Firstly, the transmission spectrum of the gold film peaks at 520 nm but allows poor transmission of excitation light at 450 nm reducing stray light interference in addition to a 550 nm cut-on filter. Secondly, and more, importantly relatively insensitive luminophores within approximately 10 nm of the gold film are quenched resulting in a significant noise reduction by removal of insensitive residual metal ion-ligand complex luminescence. It is questioned whether an element of radiative-decay-engineering of luminescence is occurring with luminophore emission coupling to the gold film and initiating plasmonic emission from the underside of the film, but no evidence either in terms of solely p-polarisation or increased intensity of luminescence was evidenced. This confirms that the sensor enhancement mechanism is primarily the function of metal quenching as evidenced by reduced background intensity as noise and improved response time to oxygen quenching indicating that only the most sensitive luminophores are available to be dynamically quenched by formation of the ruthenium:oxygen charge transfer complex. This simple sensor geometry improves a basic oxygen sensor luminophore:matrix combination and stands comparison with more complex combinations such as those achieved with fluorinated sol-gel matrices.