We report the liquid exfoliation of black phosphorus in N-methyl-2-pyrrolidone to form few-layer phosphorene nanosheets.

Research into layered transition metal dichalcogenides (TMDCs), most notably those of molybdenum and tungsten disulfides, has become extensive, involving fields as diverse as optoelectronics, spintronics, energy storage, lubrication, and catalysis. The modification of TMDCs by transition metal doping can improve their performance in such applications and hence extend their potential for technological applications. This review concerns the synthetic strategies that have been used to incorporate transition metals into TMDCs and the applications of the resultant materials and relevant computational studies on the predicted properties of the doped materials.

The liquid-phase exfoliation of tin(II) sulfide to produce SnS nanosheets in N-methyl-2-pyrrolidone is reported. The material is characterized by Raman spectroscopy, atomic force microscopy, lattice-resolution scanning transmission electron microscope imaging, and energy dispersive X-ray spectrum imaging. Quantum chemical calculations on the optoelectronic characteristics of bulk and 10-layer down to monolayer SnS have been performed using a quantum chemical density functional tight-binding approach. The optical properties of the SnS and centrifugally fractionated SnS nanosheet dispersions were compared to that predicted by theory. Through centrifugation, bilayer SnS nanosheets can be produced size-selectively. The scalable solution processing of semiconductor SnS nanosheets is the key to their commercial exploitation and is potentially an important step toward the realization of a future electronics industry based on two-dimensional materials.

We report the electrochemical detection of the redox active cardiac biomarker myoglobin (Mb) using aptamer-functionalised black phosphorus nanostructured electrodes by measuring direct electron transfer. The as-synthesised few layer black phosphorus nanosheets have been functionalised with poly-L-lysine (PLL) to facilitate binding with generated anti-Mb DNA aptamers on nanostructured electrodes. This aptasensor platform has a record-low detection limit (~0.524 pg mL-1) and sensitivity (36 µA pg-1 mL cm-2) towards Mb with a dynamic response range from 1 pg mL-1 to 16 µg mL-1 for Mb in serum samples. This strategy opens up avenues to bedside technologies for multiplexed diagnosis of cardiovascular diseases in complex human samples.

Fully printed humidity sensors based on two-dimensional (2D) materials are described. Monolayer graphene oxide (GO) and few-layered black phosphorus (BP) flakes were dispersed in low boiling point solvents suitable for inkjet printing. The humidity sensors were fabricated by printing GO and BP sensing layers on printed silver nanoparticle electrodes. The electrical response of the GO and BP sensors to humidity levels ranges from 11 to 97% relative humidity, which revealed a high capacitance sensitivity of 4.45 × 10⁴ times for the GO sensor and 5.08 × 10³ times for the BP sensor at 10 Hz operation frequency. Response/recovery times of the GO and BP sensor were found to be 2.7/4.6 s and 4.7/3.0 s respectively. These sensors also showed sensitive and fast response to a proximal human fingertip, showing potential applications in contactless switching.