Photodetectors with broadband detection capability are desirable for sensing applications in the coming age of the internet-of-things. Although 2D layered materials (2DMs) have been actively pursued due to their unique optical properties, by far only graphene and black arsenic phosphorus have the wide absorption spectrum that covers most molecular vibrational fingerprints. However, their reported responsivity and response time are falling short of the requirements needed for enabling simultaneous weak-signal and high-speed detections. Here, a novel 2DM, black phosphorous carbide (b-PC) with a wide absorption spectrum up to 8000 nm is synthesized and a b-PC phototransistor with a tunable responsivity and response time at an excitation wavelength of 2004 nm is demonstrated. The b-PC phototransistor achieves a peak responsivity of 2163 A W and a shot noise equivalent power of 1.3 fW Hz at 2004 nm. In addition, it is shown that a response time of 0.7 ns is tunable by the gating effect, which renders it versatile for high-speed applications. Under the same signal strength (i.e., excitation power), its performance in responsivity and detectivity in room temperature condition is currently ahead of recent top-performing photodetectors based on 2DMs that operate with a small bias voltage of 0.2 V.

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Developing noble metal-free electrocatalysts toward hydrogen evolution reaction (HER) that can work well at ultrahigh current density are crucial components in renewable energy technologies. Herein, we have reported a strongly coupled 3D hybrid electrocatalyst, which consists of N-doped MoO 2 with Ni 3 S 2 grown on Ni foam (N-MoO 2 /Ni 3 S 2 NF) through an annealing treatment, followed by a thermal ammonia reaction. This N-MoO 2 /Ni 3 S 2 with a particle size of ∼50 nm was evenly grown on the Ni substrate in this 3D hybrid system. Benefiting from the strong coupling effect, the N-MoO 2 /Ni 3 S 2 NF exhibited a high HER performance in basic media, with a small value of the Tafel slope (76 mV dec −1 ) and a low potential of 517 mV at 1000 mA cm −2 , which was superior to that of Pt/C (631 mV at 1000 mA cm −2 ). Experimental results revealed that constructing a coupling interface between N-MoO 2 and Ni 3 S 2 facilitated the absorption and dissociation of water molecules, consequently boosting the HER activity. Additionally, the 3D N-MoO 2 /Ni 3 S 2 NF hybrid could act as a bifunctional electrode for both anode (biomass upgrading) and cathode (HER), which only required a lower potential of 2.08 V at 100 mA cm −2 as compared to the overall water splitting (2.25 V) and achieved a high biomass conversion ratio of over 90%. Moreover, substituting oxygen evolution reaction by urea oxidation reaction also can assist energy-saving hydrogen evolution for 3D N-MoO 2 /Ni 3 S 2 NF.

Tailoring photonics for monolithic integration beyond the diffraction limit opens a new era of nanoscale electronic-photonic systems, including graphene plasmonics which exhibits low level of losses and high degree of spatial confinement. Limited to its isotropic optical conductivity, searching for new plasmonic building blocks which offer tunability and design flexibility beyond graphene is becoming quite crucial for next-generation optoelectronic device. Here, motivated by the recent emergence of a new 2D material, we develop a mid-infrared (mid-IR) metasurface by nanostructuring a thin layer of black phosphorus carbide (b-PC) and realize efficient excitation of hybrid plasmon mode at deep subwavelength-scale. Far-field infrared spectroscopy demonstrates that the hybrid plasmon mode displays an anticrossing behavior of two splitting optical modes, which can be attributed to the Fano resonance between plasmons and IR-active optical phonons in b-PC. Significantly, it further presents a strong anisotropic behavior along different crystal orientations, which arises from its peculiar puckered lattice structure with two clearly distinguishable axes. The results illustrate that anisotropic b-PC plasmon not only represents an important advance in subwavelength optoelectronics, but also provides a viable platform for hyperbolic metamaterials, bringing widespread applications into biosensors, single-photon source, nanoantenna, and subwavelength resolution imaging.

The narrow band gap property of black phosphorus (BP) that bridges the energy gap between graphene and transition metal dichalcogenides holds great promise for enabling broadband optical detection from ultraviolet to infrared wavelengths. Despite its rich potential as an intriguing building block for optoelectronic applications, however, very little progress has been made in realizing BP-based infrared photodetectors. Here, we demonstrate a high sensitivity BP phototransistor that operates at a short-wavelength infrared (SWIR) of 2 μm under room temperature. Excellent tunability of responsivity and photoconductive gain are acquired by utilizing the electrostatic gating effect, which controls the dominant photocurrent generation mechanism via adjusting the band alignment in the phototransistor. Under a nanowatt-level illumination, a peak responsivity of 8.5 A/W and a low noise equivalent power (NEP) of less than 1 pW/Hz are achieved at a small operating source-drain bias of -1 V. Our phototransistor demonstrates a simple and effective approach to continuously tune the detection capability of BP photodetectors, paving the way to exploit BP to numerous low-light-level detection applications such as biomolecular sensing, meteorological data collection, and thermal imaging.

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The impact of the synthesis conditions on the formation of the monomer sequences of styrene (S) and methyl methacrylate (MMA) gradient copolymers synthesized by forced gradient copolymerization with nitroxide-mediated controlled radical polymerization (NM-CRP) was investigated using kinetic Monte Carlo (KMC) simulations. The factors affecting the formation of the individual segments, arrangement of these segments along the chain, and the uniformity of monomer sequences were investigated. It was shown that instantaneous segment lengths increase exponentially as a function of monomer composition. The concentration of nitroxyl radicals also plays a key role in the formation of segment lengths. In addition, the arrangement of the segments mainly depends on the feed profile of the second monomer. A constant feed profile, which is widely used in current syntheses of gradient copolymers, is shown to not be suitable to make a structural gradient along the chain. It was also demonstrated that the uniformity of sequence patterns can be affected by the entire growth history of the chains, and thus strong control over the uniformity of chain growth is required throughout the reaction in order to achieve sequences in different chains that resemble one another.

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