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Microwave-assisted flow digestion systems open up new possibilities in fully automated sample preparation for element analysis. For an extensive and fast oxidation of organic materials with nitric acid, temperatures of more than 200 [degrees] C are necessary. To achieve the desired temperatures of [approximately]250 [degrees] C, it is essential that the pressure in the system can be increased up to 35 bar. The teflon tubes used, however, do not withstand the vapor pressure of the digestion mixture at these temperature levels. A high-pressure flow digestion device is described that enables the application of such high temperatures by means of a novel pressure equilibration system. PTFE or PFA tubes can be used up to 250 [degrees] C if no mechanical stress is applied to the tube wall. The pressure equilibration system keeps the pressure inside and outside the digestion tube equal even for extremely fast oxidation reactions. The digestion of easy, medium, and difficult oxidizable substances (glucose, glycine, and phenylalanine, respectively) shows the importance of digestion temperatures around 250 [degrees] C. The extremely violent digestion of glucose with concentrated nitric acid can be carried out as easy as the difficult oxidation of phenylalanine by means of this system. The SRM TORT 2 (defatted lobster hepatopancreas tissue) was digested under different conditions to indicate the high oxidation capabilities in comparison with a commercial medium-pressure flow digestion device. The analysis of the SRMs milk powder (BCR 063, BCR 151), bovine liver (BCR185), and pig kidney (BCR 186) after digestion at 245 [degrees] C and 5 min showed good agreement with the certified values.

The internal morphology and crystallographic properties of a complete organic thin film multilayer stack are characterized via x-ray scattering techniques, atomic force microscopy (AFM), and scanning electron microscopy. The stack consists of the three organic layers - copper(II)phthalocyanine (CuPc), perylene tetracarboxylic bisbenzimidazole (PTCBI), and aluminum-tris(8-hydroxychinolin) (Alq3) - sandwiched between an optically semitransparent gold layer and a top silver electrode. The interface roughness progress is determined by the x-ray reflectivity, which is confirmed by the surface roughness determination via AFM. The crystallographic properties are characterized via x-ray diffraction. The CuPc layer is highly crystalline with preferentially oriented crystallites but forms a rough interface (σRMS = 5.5 nm) toward the PTCBI layer. The PTCBI layer grows with randomly distributed crystallites in a worm-like morphology with an interface roughness of σRMS = 6.4 nm toward the Alq3 layer. The amorphous Alq3 layer acts as smoothing layer and reduces the roughness σRMS to 5.8 nm. Within this study we demonstrate the applicability of x-ray reflectivity in characterizing the interface morphology of an organic multilayer stack device. [ABSTRACT FROM AUTHOR]

We report on the structuring of the backside surface of sapphire substrates in high-power flip-chip light-emitting diodes (LEDs) by femtosecond laser direct writing. Varying the laser powers has been found to affect the sizes of the inscribed patterns on a submicron scale which facilitates the control of the structure sizes with high precision. Accordingly, since on the one hand the light extraction efficiency reveals a strong dependence on pattern sizes, and on the other hand, femtosecond laser structuring provides a simple opportunity to inscribe diverse structures along the LED surfaces, LEDs with laterally controlled light extraction efficiencies can be fabricated. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterisation of entirely inkjet-printed organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxithiophene) poly(styrenesulfonate) (PEDOT:PSS). These transistors were used to evaluate the assumed geometry-performance relationship of OECTs by changing the transistor dimensions and monitoring the output characteristics. We could show that the on-current depends on the PEDOT:PSS thickness and that the on-to-off current ratio is related to the distance between the printed electrodes. Taking these results into account, we fabricated entirely inkjet printed electrochemical inverters with a switching time of about 4 s. These inverters outline a first step from organic electrochemical transistors towards logic circuits. [ABSTRACT FROM AUTHOR]