: The infection and spread of pathogens (e.g., COVID-19) pose an enormous threat to the safety of human beings and animals all over the world. The rapid and accurate monitoring and determination of pathogens are of great significance to clinical diagnosis, food safety and environmental evaluation. In recent years, with the evolution of nanotechnology, nano-sized graphene and graphene derivatives have been frequently introduced into the construction of biosensors due to their unique physicochemical properties and biocompatibility. The combination of biomolecules with specific recognition capabilities and graphene materials provides a promising strategy to construct more stable and sensitive biosensors for the detection of pathogens. This review tracks the development of graphene biosensors for the detection of bacterial and viral pathogens, mainly including the preparation of graphene biosensors and their working mechanism. The challenges involved in this field have been discussed, and the perspective for further development has been put forward, aiming to promote the development of pathogens sensing and the contribution to epidemic prevention.

The light-emitting electrochemical cell (LEC) exhibits capacity for efficient charge injection from two air-stable electrodes into a single-layer active material, which is commonly interpreted as implying that the LEC operation is independent of the electrode selection. Here, we demonstrate that this is far from the truth and that the electrode selection instead has a strong influence on the LEC performance. We systematically investigate 13 different materials for the positive anode and negative cathode in a common LEC configuration with the conjugated polymer Super Yellow as the electroactive emitter and find that Ca, Mn, Ag, Al, Cu, indium tin oxide (ITO), and Au function as the LEC cathode, whereas ITO and Ni can operate as the LEC anode. Importantly, we demonstrate that the electrochemical stability of the electrode is paramount and that particularly electrochemical oxidation of the anode can prohibit the functional LEC operation. We finally report that it appears preferable to design the device so that the heights of the injection barriers at the two electrode/active material interfaces are balanced in order to mitigate electrode-induced quenching of the light emission. As such, this study has expanded the set of air-stable electrode materials available for functional LEC operation and also established a procedure for the evaluation and design of future efficient electrode materials.

A series of new 2,7-dioctyl-substituted dibenzo[a,c]phenazine (BPz) derivatives were designed and synthesized as electron-deficient units, which were copolymerized with an electron-rich indacenodithiophene (IDT) to construct narrow-bandgap copolymers PIDT−OHBPz, PIDT−OFBPz, and PIDT−OBPQ via Stille polycondensation. The 2,7-dioctyl substituents enhanced solubility and offered a new approach for developing various BPz derivatives. All copolymers showed high hole mobilities above 0.01 cm 2 V −1 s −1 as measured by field effect transistors. The best performance of polymer solar cell was achieved based on PIDT−OFBPz with inverted device structure of ITO/ZnO/PFN/polymer:PC 61 BM/MoO 3 /Al, which showed an opencircuit voltage (V oc ) of 0.97 V, a short-circuit current (J sc ) of 8.96 mA/cm 2 , and a fill factor (FF) of 58.99%, leading to a high power conversion efficiency (PCE) of 5.13%. These results indicate that 2,7-alkyl-substituted BPz derivatives can be used as an excellent electron-deficient building block for the construction of high-performance organic electronic materials.

Carbon dots (CDs) have shown great potential in various applications including biomedicines and optoelectronics. However, the origin of their photoluminescence excitation dependence (PL-ED) still remains uncertain, and this can limit the full exploit of their wonderful optical properties. Here we studied the mechanism for the PL-ED of solvothermally synthesized CDs using an alkali treatment. As-synthesized CDs were found to agglomerate and exhibited multicolor emissions with strong PL-ED. The alkali treatment can effectively break down the clusters into individual CDs via the hydrolysis of the amide and ester bonds that link the CDs together. This process effectively narrowed the emission line width and suppressed the observed PL-ED. The understanding of the excitation dependence mechanism here outlined a novel strategy for tailoring of the PL-ED of CDs via a synergy of chemical and physical processes, thus enhancing the versatility of CDs for a broader spectrum of applications.

New methods for the preparation of mixed NHC/phosphine Ni­(II) complexes have been developed. It was shown that the quaternary ammonium cation in the easily available Ni­(II) complexes [NEt4]­[Ni­(PPh3)­X3] (X = Cl and Br) can act as a good leaving group in reactions of [NEt4]­[Ni­(PPh3)­X3] with the bulky ItBu (ItBu = 1,3-ditertbutylimidazol-2-ylidene) or IPr [IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene] ligand, resulting in the corresponding mixed NHC/PPh3 Ni­(II) complexes Ni­(PPh3)­(ItBu)­X2 (X = Cl, 1; X = Br, 2) or Ni­(PPh3)­(IPr)­Br2 (3) in high yields. The PPh3 ligand in these obtained mixed NHC/PPh3 Ni­(II) complexes can be easily substituted by a more electron-donating phosphine ligand, i.e., PCy3, resulting in the corresponding mixed NHC/PCy3 Ni­(II) complexes Ni­(PCy3)­(ItBu)­Br2 (4) and Ni­(PCy3)­(IPr)­Br2 (5) in high yields. The crystal structures of these Ni­(II) complexes have been characterized, which revealed a trans disposition of the NHC ligand to the phosphine ligand. The catalytic behaviors of them on varying the carbene ligand (ItBu vs IPr) as well as the phosphine ligand (PPh3 vs PCy3) were investigated in the cross-coupling of aryl Grignard reagents with a wide range of electrophiles. In addition to a significant synergic effect on their catalytic activities, high selectivity for the activation and transformation of C–Cl, C–F and C–O bonds was achieved based on the rational structural design. Complex 2 showed the highest catalytic activity for the cross-coupling of aryl chlorides and fluorides with aryl Grignard reagents, but exhibit little activity for the cross-coupling of aryl methyl ethers with aryl Grignard reagents. On contrast, complex 4 showed great potential for the aryl methyl ethers involved cross-coupling reactions, although its reactivity for the activation of the C–X bond is very poor. The difference in catalytic activity between 2 and 4 has been successfully employed to construct oligoarenes by selective cross-coupling reactions.

The first nickel-catalyzed, magnesium-mediated reductive cross-coupling between benzyl chlorides and aryl chlorides or fluorides is reported. A variety of diarylmethanes can be prepared in good to excellent yields in a one-pot manner using easy-to-access mixed PPh3/NHC Ni(II) complexes of Ni(PPh3)(NHC)Br2 (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr, 1a; 1,3-di-tert-butylimidazol-2-ylidene, ItBu, 1b) as catalyst precursors. Activation of polychloroarenes or chemoselective cross-coupling based on the difference in catalytic activity between 1a and 1b is used to construct oligo-diarylmethane motifs.

A novel n-type conjugated polymer containing dibenzothiophene-S,S-dioxide (FSO), bispyridinium, and fluorene scaffolds in the backbone (PFSOPyCl) was synthesized and used in the cathode interfacial layers (CILs) of conventional polymer solar cells (PSCs). The high electron affinities and large planar structures of the FSO and bispyridinium units endowed this polymer with good energy level alignments with [6,6]-phenyl-C butyric acid methyl ester (PCBM) and metal cathode, and excellent electron transport and extraction properties. Polymer solar cells (PSCs) based on the poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):PCBM system with PFSOPyCl CIL exhibited simultaneous enhancement in open-circuit voltage (V), short-circuit current density (J), and fill factor (FF), while the power conversion efficiency increased from 5.47% to 6.79%, relative to the bare Al device. Besides, PSC based on the poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b']dithio-phene-2,6-diyl-alt-ethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl] (PTB7):PCBM system achieved a PCE of 8.43% when using PFSOPyCl as CIL. Hence, PFSOPyCl is a promising candidate CIL for PSCs.

Blue light-emitting polymers were synthesized via introducing a 9,9-dioctylfluorene bis[2,3-b;6,7-b]benzo-[d]thiophene-S,S-dioxide (FBTO) unit into the polyfluorene or polycarbazole backbone.