Benzothiadiazole versus Thiazolobenzotriazole: A Structural Study of Electron Acceptors in Solution-Processable Organic Semiconductors.

Despite the rapid progress of organic electronics, developing high-performance n-type organic semiconductors is still challenging. Donor-acceptor (D-A) type conjugated structures have been an effective molecular design strategy to achieve chemically-stable semiconductors and the appropriate choice of the acceptor units determines the electronic properties and device performances. We have now synthesized two types of A1 -D-A2 -D-A1 type conjugated molecules, namely, NDI-BTT-NDI and NDI-TBZT-NDI, with different central acceptor units. In order to investigate the effects of the central acceptor units on the charge-transporting properties, organic field-effect transistors (OFETs) were fabricated. NDI-TBZT-NDI had shallower HOMO and deeper LUMO levels than NDI-BTT-NDI. Hence, the facilitated charge injection resulted in ambipolar transistor performances with the optimized hole and electron mobilities of 0.00134 and 0.151 cm2 V-1 s-1 , respectively. In contrast, NDI-BTT-NDI displayed only an n-channel OFET performance with the electron mobility of 0.0288 cm2 V-1 s-1 . In addition, the device based on NDI-TBZT-NDI showed a superior air stability to that based on NDI-BTT-NDI. The difference in these OFET performances was reasonably explained by the contact resistance and film morphology. Overall, this study demonstrated that the TBZ acceptor is a promising building block to create n-type organic semiconductors.

RNA fluorescence in situ hybridization hybridisation using photo-cross-linkable beacon probes containing pyranocarbazole in living E. coli.

Understanding intracellular nucleic acids is very important for analysing RNA function and for the diagnosis of genetic diseases. In this study, we demonstrated RNA fluorescence in situ hybridisation in living cells. The described method does not a washing procedure, which affects the detection sensitivity for RNAs with secondary structures and, therefore, is a major limitation of conventional approaches. Ultrafast RNA photo-crosslinking using pyranocarbazole accelerated the invasion of FISH probes, enabling them to target RNAs with secondary structures. Thus, the newly developed method successfully increased the detection sensitivity by 5.4-fold following photo-irradiation at 400 nm for 120 s. In addition, we optimised the beacon probe for detecting target nucleic acids under physiological conditions at 37 °C.