Recent progresses on solution-processed silver nanowire based transparent conducting electrodes for organic solar cells

Organic photovoltaics (OPVs) are considered as a future alternative for conventional silicon based solar cells, owing to their low cost, ease of production and high-throughput. The transparent conducting electrode (TCE) is a fundamental component of OPVs. Traditionally, indium tin oxide (ITO) has been mainly utilized as a TCE in OPV applications due to its relatively high transparency and low sheet resistance. However, increasing demand for the optoelectronic devices has led to large fluctuations in ITO prices in the past decade and ITO is known to account more than 50% of the total cost of OPV devices. Thus, it is believed that development of solution-processable alternative materials is of great importance in reducing the cost of OPVs. Numerous materials, including silver nanowires, carbon nanotubes, graphene and conducting polymers, have been offered as replacements for ITO. This article reviews recent progress on fabrication of TCE via solution based coating techniques of silver nanowires (Ag NWs). In addition, performance of the Ag NWs based TCE in OPVs is summarized. Finally, we explore the future outlook for Ag NWs based TCE at the end of the review.     

Residue analysis of triazine herbicides in soil: Comparison of a capillary gas chromatographic and a high-performance liquid chromatographic method

Summary Two methods for the determination of triazines in soil were developed and compared. After extraction of the residues with methanol and clean-up by gel permeation chromatography, the samples evaporated were analysed for triazines by splitless capillary gas-chromatography with NP-detector (GC-NPD) and microbore high performance liquid chromatography with UV detector (HPLC-UV) at 222 nm. Both methods gave similar results. The microbore HPLC method was suitable for the analysis of a number of triazines at 10 ppb whereas capillary GC method was used for the analysis of triazines at 5 ppb. Satisfactory average recoveries for the two methods were obtained at 80 ppb and 20 ppb, respectively.

---

Rückstandsanalytik von Triazin-Herbiciden im Boden: Vergleich zwischen einer capillar-gas-chromatographischen und einer hochleistungs-flüssig-chromatographischen Methode

Zusammenfassung Zwei Methoden zur Bestimmung von Triazinen im Boden wurden entwickelt und miteinander verglichen. Nach der Extraktion der Rückstände mit Methanol und clean-up durch Gelpermeations-Chromatographie wurden die Proben eingeengt und auf Triazin-Rückstände hin untersucht. Zur Detektion wurden die splitlose Capillar-Gas-Chromatographie mit NP-Detektor (GC-NPD) und die Microbore-Hochdruckflüssig-Chromatographie mit UV-Detektor (HPLC-UV) bei 222 nm verwendet. Beide Methoden ergaben vergleichbare Ergebnisse bei einem Minimum an Zeit- und Materialaufwand und der Möglichkeit der Automatisation der Rückstandsanalytik. Die Microbore-HPLC-Methode erreichte nach einfachem GPC clean-up eine Nachweisgrenze von 10 ppb im Vergleich zu 5 ppb bei der Capillar-GC-Methode. Zufriedenstellende Wiederfindungsraten wurden für beide Methoden bei 80 ppb und 20 ppb ermittelt.

---

---

On leave from: Institute of Hydrobiology, Academia Sinica, Wuhan, P. R. China     

Pediatric abdominal masses: diagnostic accuracy of diffusion weighted MRI

Purpose

To retrospectively identify apparent diffusion coefficient (ADC) values of pediatric abdominal mass lesions, to determine whether measured ADC of the lesions and signal intensity on diffusion-weighted (DW) images allow discrimination between benign and malignant mass lesions.

Materials and Methods

Approval for this retrospective study was obtained from the institutional review board. Children with abdominal mass lesions, who were examined by DW magnetic resonance imaging (MRI) were included in this study. DW MR images were obtained in the axial plane by using a non breath-hold single-shot spin-echo sequence on a 1.5-T MR scanner. ADCs were calculated for each lesion. ADC values were compared with Mann–Whitney U test. Receiver operating characteristic curve analysis was performed to determine cut-off values for ADC. The results of visual assessment on b800 images and ADC map images were compared with chi-square test.

Results

Thirty-one abdominal mass lesions (16 benign, 15 malignant) in 26 patients (15 girls, 11 boys, ranging from 2 days to 17 years with 6.9 years mean) underwent MRI. Benign lesions had significantly higher ADC values than malignant ones (P<.001). The mean ADCs of malignant lesions were 0.84±1.7×10⁻³ mm²/s, while the mean ADCs of the benign ones were 2.28±1.00×10⁻³ mm²/s. With respect to cutoff values of ADC: 1.11×10⁻³ mm²/s, sensitivity and negative predictive values were 100%, specificity was 78.6% and positive predictive value was 83.3%. For b800 and ADC map images, there were statistically significant differences on visual assessment. All malignant lesions had variable degrees of high signal intensity whereas eight of the 16 benign ones had low signal intensities on b800 images (P<.001). On ADC map images, all malignant lesions were hypointense and most of the benign ones (n=11, 68.7%) were hyperintense (P<.001).

Conclusion

DW imaging can be used for reliable discrimination of benign and malignant pediatric abdominal mass lesions based on considerable differences in the ADC values and signal intensity changes.     

Silbermercaptide und -mercaptokomplexe

The complex formation of silver(I) has been studied with the anions of simple mercaptans RSH which have been rendered soluble by replacing some H in the substituent R by OH. All equilibria constants refer to a solvent of ionic strength μ = 0,1 and 20°C. Monothioglycol HO? CH₂? CH₂? SH (pK = 9.48) forms an amorphous insoluble mercaptide {AgSR} (s), ionic product [Ag⁺] [SR^?] = 10^?19.7. The solution in equilibrium with the solid contains the molecule AgSR at a constant concentration of 10^?6.7 M which furnishes the formation constant of the 1:1-complex: K₁ = 10^{13. 0}. The solid is soluble in excess of mercaptide (AgSR+SR^? → Ag(SR)₂^?: K₂ = 10^{4. 8}) as well as in an excess of silver ion (AgSR + Ag⁺ → Ag₂SR⁺K ≈? 10⁶). With the bulky monothiopentaerythrite (HO? CH₂? )₃C? CH₂? SH (pK = 9.89) no precipitation occurs with silver when the mercaptan concentration is below 10^{?3. 2}M. A single polynuclear Ag₁₀(SR)₉⁺ (β_10.9 = 10¹⁷⁵) is formed in acidic solutions which breaks up with the formation of Ag₂SR⁺ (β_2.1 = 10^19.0) when an excess of silver ion is added. Below the mononuclear wall ([RS]_total < 10^?6) Ag₂SR⁺ is formed via the mononuclear AgSR (K₁ = 10¹³). At higher mercaptan concentrations ([RS]_tot > 10^?3.2) an amorphous precipitate is formed which has almost the same solubility product as silver thioglycolate ([Ag⁺] [SR^?] = 10^?19.1). Apparently silver(I) forms with mercaptans always the complexes Ag₂SR⁺, AgSR and Ag(SR)₂^?. Above the mononuclear wall, these species condense to chain-like polynuclears which are cations Ag(SRAg)_n⁺ in presence of an excess of Ag⁺, and anions SR (AgSR)_n^? when the concentration [RS^?] is larger than [Ag⁺]. Usually n becomes rapidly very large as soon as the condensation starts (n → ∞: precipitate). The decanuclear Ag(SRAg)₉⁺ formed with thiopentaerythrit is somewhat more stable than the shorter chains (n < 9) and larger chains (n > 9), because it can tangle up to a ball by coordination of bridging mercapto-sulfur to the terminal silver ions (figure 12, page 2179). This ball seems to be further stabilized by hydrogen bonds between the many alcoholic OH groups of the substituent R = (HO? CH₂)₃C? CH₂? . The stability of the bonds Ag? S, however, is little influenced by the substituent R which carries the mercaptide sulfure.     

Determination of arsenic in the presence of high copper concentrations using flow-injection analysis-hydride atomic absorption spectrometry

Summary Arsenic is determined in environmental samples containing metal ions up to 10,000 mg/l copper, 200 mg/l lead, 200 mg/l iron and 200 mg/l nickel by using the FIA-hydride-AAS technique. In the presented sample preparation method arsenic is prereduced and the interfering metal ions are precipitated. As signal depressions from metal ions are excluded, a detection limit of 1 g/l arsenic is achieved.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday