Photoluminescence-based sensors

2 Structurally Integrated OLED/Sensing Component Modules 

The basic structure of a typical OLED is shown in Fig. 3.1 [35]. It consists of a transparent conducting anode, typically indium tin oxide (ITO) coated on a glass or plastic mechanical support, the organic layers, and a metal cathode. The thickness of OLEDs (excluding the mechanical support) is typically 0.5 j,m. Under forward bias electrons are injected from the low-workfunction cathode into the electron-transport layer (ETL). Similarly, holes are injected from the high-workfunction ITO into the hole-transport layer (HTL). Due to the applied bias, the electrons and holes drift toward each other, and typically recombine in a recombination zone near, or at, the ETL/HTL interface. A fraction of the recombination events forms radiative excited states. The radiative decay of these states provides the electroluminescence (EL) of the device. 

Electron Transport Layer(s) (ETLs) Emitting Layer (EWIL) 

3 Structural Integration of the OLED Array/Sensing Film 

The PD, e.g., a photomultiplier tube or a Si photodiode, can be placed in front of the sensing film ( front detection ) or behind the OLED array ( back detection ). The basic structure of the integrated OLED/sensor him in the back-detection geometry is shown in Fig. 3.2. In this configuration, the PD collects the PL that passes through the gaps between the OLED pixels. The 

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In principle, optical chemosensors make use of optical techniques to provide analytical information. The most extensively exploited techniques in this regard are optical absorption and photoluminescence. Moreover, sensors based on surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) have recently been devised. 

Castellano et al.221 reported the formation of a luminescence lifetime-based sensor for cyanide and other counterions using Ru11 diimines possessing MLCT excited states with the anion recognition capabilities of 2,3-di(l//-2-pyrrolyl)quinoxaline (DPQ). Using time-resolved photoluminescence decay, its viability as a lifetime-based sensor for anions has been tested. There were significant changes to the UV-vis and steady-state emission properties after the addition of several ions (e.g., fluoride, cyanide, and phosphate). 

Figure 26 (a) Quenching of the steady-state photoluminescence spectrum of the Ru(II)-based sensor measured throughout the cyanide... 

Starodub NF, Starodub VM (2004) Biosensors based on the photoluminescence of porous silicon overall characteristics and apphcation for the medical diagnostics. Sensors Electronics and Microsystem Technol 2 63-83... 

Starodub VM, Fedorenko LL, Starodub NF (1998) Control of a myoglobin level in solution by the bioaffine sensor based on the photoluminescence of porous sihcon. In Proceedings of the european conference on solid-state transducers and 9th UK conference on sensors and their apphcations, Southampton, UK, 2 817-820, 13-16 Sept 1998... 

Abstract We have achieved selective gas sensing based on different size semiconductor nanocrystals incorporated into rationally selected polymer matrices. From the high-throughput screening experiments, we have found that when CdSe nanocrystals of different size (2.8 and 5.6nm diameter) were incorporated into different types of polymer fdms, the photoluminescence (PL) response patterns upon laser excitation at 407-nm and exposure to polar and nonpolar solvent vapors were dependent on the nature of polymer. We analyzed the spectral PL response from both sizes of CdSe nanocrystals using multivariate analysis tools. Results of this multivariate analysis demonstrate that a single film with different size CdSe nanocrystals serves as a selective sensor. The stability of PL response to vapors was evaluated upon 16h of continuous exposure to laser excitation. 

Fig. 2 PSi microcavity-based detection of bacteriophage lambda (adapted from [9]). The solid line represents the photoluminescence spectrum of the DNA-derivatized device, while the dotted line shows the photoluminescence spectrum of the sensor following exposure to the bacteriophage virus...

Structurally Integrated Photoluminescent Chemical and Biological Sensors An Organic Light-Emitting Diode-Based Platform... 

This chapter overviews recent developments in photoluminescence (PL)-based chemical and biological sensors, where an array of organic light-emitting diode (OLED) pixels, integrated with a sensor film, serves as the excitation source. 

The band-edge photoluminescence (PL) of K-CaSe has been shown to respond to the adsorption of a variety of analytes to the semiconductor s surface. This conceivably can be used for sensor development. However, one major problem is the issue of selectivity. Although Lewis bases and acids can be readily distinguished due to their differential effect on the electronic properties of the semiconductor, analyte-specific analysis is difficult to achieve. Ellis and co-workers [64] have examined the effect of imprinted polymer coating on the surface on the response of the semiconductor. Without the coating, the bare surface of CdSe responds to the adsorption of ammonia, mono-, di-, and trimethylamine with similar PL enhancement. However, upon coating the surface with ammonia imprinted poly(arylic acid) (PAA), CdSe only responded to the presence of ammonia, but not trimethylamine. On the other hand, CdSe coated with trimethylamine-imprinted polymer does not provide this selectivity, indicating the selectivity was mostly due to the size effect. 

Current gold nanopaiticle solution based methods of biosensing are not limited strictly to this one type of nanopaiticle but can incorporate other particles as well. Peptide linked gold nanoparticle - quantum dot biosensors have been created by Chang et al., that rely on the ability of the gold nanoparticles to quench the photoluminescence of the quantum dots when in their close proximity bound state [26]. The method of sensing is also considered an on sensor since the default state of the particles is off (no luminescence), and it is converted to on (luminescence) once sensing takes place. 

Silicon-based materials with unique (opto)electronic properties photoluminescent materials for flat panel technology, displays, light-emitting diodes, sensors electroluminescence, nonmetallic conductors, e.g. siloles, polysilanes, 2,3-diphenyl-1-silacyclobutene chemistry design and application of liquid crystals. 

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