Search

H-NOCBs exhibit superior cycling stability with the retained capacities of 178.8 mA h g−1 (500 mA g−1) and 123.3 mA h g−1 (1000 mA g−1) after 2500 and 10 000 cycles, respectively, demonstrating extremely stable performance for potassium ion storage.

Recently, halide perovskites (HPs) and layered two-dimensional (2D) materials have received significant attention from industry and academia alike. HPs are emerging materials that have exciting photoelectric properties, such as a high absorption coefficient, rapid carrier mobility and high photoluminescence quantum yields, making them excellent candidates for various optoelectronic applications. 2D materials possess confined carrier mobility in 2D planes and are widely employed in nanostructures to achieve interfacial modification. HP/2D material interfaces could potentially reveal unprecedented interfacial properties, including light absorbance with desired spectral overlap, tunable carrier dynamics and modified stability, which may lead to several practical applications. In this review, we attempt to provide a comprehensive perspective on the development of interfacial engineering of HP/2D material interfaces. Specifically, we highlight the recent progress in HP/2D material interfaces considering their architectures, electronic energetics tuning and interfacial properties, discuss the potential applications of these interfaces and analyze the challenges and future research directions of interfacial engineering of HP/2D material interfaces. This review links the fields of HPs and 2D materials through interfacial engineering to provide insights into future innovations and their great potential applications in optoelectronic devices.

Black arsenic-phosphorus (b-AsP), an alloy containing black phosphorus and arsenic in the form of b-As

Two-dimensional (2D) Bi2Sr2CaCu2O8+δ (BSCCO) is a emerming class of 2D materials with high-temperature superconductivity for which their electronic transport properties have been intensively studied. However, the optical properties, especially nonlinear optical response and the photonic and optoelectronic applications of normal state 2D Bi2Sr2CaCu2O8+δ (Bi-2212), have been largely unexplored. Here, the linear and nonlinear optical properties of mechanically exfoliated Bi-2212 thin flakes are systematically investigated. 2D Bi-2212 shows a profound plasmon absorption in near-infrared wavelength range with ultrafast carrier dynamics as well as tunable nonlinear absorption depending on the thickness. We demonstrated that 2D Bi-2212 can be applied not only as an effective mode-locker for ultrashort pulse generation but also as an active medium for infrared light detection due to its plasmon absorption. Our results may trigger follow up studies on the optical properties of 2D BSCCO and demonstrate potential opportunities for photonic and optoelectronic applications.

The ultrafast monitoring of deoxyribonucleic acid (DNA) dynamic structural changes is an emerging and rapidly growing research topic in biotechnology. The existing optical spectroscopy used to identify different dynamical DNA structures lacks quick response while requiring large consumption of samples and bulky instrumental facilities. It is highly demanded to develop an ultrafast technique that monitors DNA structural changes with the external stimulus or cancer‐related disease scenarios. Here, we demonstrate a novel photonic integrated graphene‐optofluidic device to monitor DNA structural changes with the ultrafast response time. Our approach is featured with an effective and straightforward design of decoding the electronic structure change of graphene induced by its interactions with DNAs in different conformations using ultrafast nanosecond pulse laser and achieving refractive index sensitivity of ~3 × 10−5 RIU. This innovative technique for the first time allows us to perform ultrafast monitoring of the conformational changes of special DNA molecules structures, including G‐quadruplex formation by K+ ions and i‐motif formation by the low pH stimulus. The graphene‐optofluidic device as presented here provides a new class of label‐free, ultrafast, ultrasensitive, compact, and cost‐effective optical biosensors for medical and healthcare applications.

Photodetectors based on intrinsic graphene can operate over a broad wavelength range with ultrafast response, but their responsivity is much lower than commercial silicon photodiodes. The combination of graphene with two-dimensional (2D) semiconductors may enhance the light absorption, but there is still a cutoff wavelength originating from the bandgap of semiconductors. Here, we report a highly responsive broadband photodetector based on the heterostructure of graphene and transition metal carbides (TMCs, more specifically Mo2C). The graphene–Mo2C heterostructure enhanced light absorption over a broad wavelength range from ultraviolet to infrared. In addition, there is very small resistance for photoexcited carriers in both graphene and Mo2C. Consequently, photodetectors based on the graphene–Mo2C heterostructure deliver a very high responsivity from visible to infrared telecommunication wavelengths.

Photodetectors based on intrinsic graphene can operate over a broad wavelength range with ultrafast response, but their responsivity is much lower than commercial silicon photodiodes. The combination of graphene with two-dimensional (2D) semiconductors may enhance the light absorption, but there is still a cutoff wavelength originating from the bandgap of semiconductors. Here, we report a highly responsive broadband photodetector based on the heterostructure of graphene and transition metal carbides (TMCs, more specifically Mo

Broadband photodetectors are essential for various applications including spectroscopy, communication, imaging and sensing. Even though few materials show broadband photodetection, they are only capable of detecting light in limited spectral ranges from infrared (IR) to ultraviolet (UV) wavelengths. However, their functionalities at much shorter wavelengths such as ionizing radiation still present a challenge because of the limitations from the material properties. Here we demonstrate a room temperature, high performance broadband photodetector based on van der Waals (vdWs) magnetic material CrSiTe3 (CST) that can efficiently detect both soft X-rays and light in the near-infrared (NIR) and visible wavelength ranges. The CrSiTe3 based device can work with a high sensitivity (≈463 μC Gyair−1 cm−2) under synchrotron soft X-rays, which is more than twenty times more sensitive than the conventional α-Se device. In the NIR range, the device can achieve a maximum responsivity of around 206 A W−1 at 785 nm, an extremely high external quantum efficiency (EQE) of 32 600%, a detectivity of 1.25 × 1012 cm Hz1/2 W−1 and a relatively fast photoresponse time (rise time ∼43 ms under X-rays, 17 ms under a 785 nm laser). Together these results demonstrate a high-performance broadband photo and X-ray detector, offering intriguing opportunities for novel optoelectronic applications.

Bulk germanium as a group-IV photonic material has been widely studied due to its relatively large refractive index and broadband and low propagation loss from near-infrared to mid-infrared. Inspired by the research of graphene, the 2D counterpart of bulk germanium, germanene, has been discovered and the characteristics of Dirac electrons have been observed. However, the optical properties of germanene still remain elusive. In this work, several layers of germanene are prepared with Dirac electronic characteristics and its morphology, band structure, carrier dynamics, and nonlinear optical properties are systematically investigated. It is surprisingly found that germanene has a fast carrier-relaxation time comparable to that of graphene and a relatively large nonlinear absorption coefficient, which is an order of magnitude higher than that of graphene in the near-infrared wavelength range. Based on these findings, germanene is applied as a new saturable absorber to construct an ultrafast mode-locked laser, and sub-picosecond pulse generation in the telecommunication band is realized. The results suggest that germanene can be used as a new type of group-IV material for various nonlinear optics and photonic applications.

Heavily doped colloidal plasmonic nanocrystals have attracted great attention because of their lower and adjustable free carrier densities and tunable localized surface plasmonic resonance bands in the spectral range from near-infra to mid-infra wavelengths. With its plasmon-enhanced optical nonlinearity, this new family of plasmonic materials shows a huge potential for nonlinear optical applications, such as ultrafast switching, nonlinear sensing, and pulse laser generation. Cu(3−)(x)P nanocrystals were previously shown to have a strong saturable absorption at the plasmonic resonance, which enabled high-energy Q-switched fiber lasers with 6.1 μs pulse duration. This work demonstrates that both high-quality mode-locked and Q-switched pulses at 1560 nm can be generated by evanescently incorporating two-dimensional (2D) Cu(3−x)P nanocrystals onto a D-shaped optical fiber as an effective saturable absorber. The 3 dB bandwidth of the mode-locking optical spectrum is as broad as 7.3 nm, and the corresponding pulse duration can reach 423 fs. The repetition rate of the Q-switching pulses is higher than 80 kHz. Moreover, the largest pulse energy is more than 120 µJ. Note that laser characteristics are highly stable and repeatable based on the results of over 20 devices. This work may trigger further investigations on heavily doped plasmonic 2D nanocrystals as a next-generation, inexpensive, and solution-processed element for fascinating photonics and optoelectronics applications. [Image: see text]

Rational design of highly efficient electrocatalysts for sustainable energy conversion is critical but also challenging. Both the composition and surface property of catalyst are pivotal for the advanced water electrolysis. Herein, the Ru/Co(OH)2 nanosheet array with tunable compactness on carbon cloth is designed via a facile two-step process. Especially, the as-synthesized Ru/Co(OH)2 nanosheet array with superhydrophilicity and superaerophobicity surface is conducive to the acceleration of mass transport, which is realized by facilitating the access of electrolyte and alleviating the “bubble shielding effect” for gas bubble diffusion. Consequently, the fabricated nanostructured Ru/Co(OH)2 array based catalyst shows an outstanding HER performance in 1.0 M KOH, which only requires a low overpotential of 35 mV to reach 10 mA cm−2 and demonstrates strong stability at a high current density of 500 mA cm−2 upon long-term duration operation. Additionally, the enhanced Faradic efficiency under high current density is achieved by the optimized nanoarray structure. It is believed the present work could provide a novel perspective for tuning the catalytic activities of nanostructured electrode and beyond.

Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, and black phosphorus, have attracted intense interest for applications in ultrafast pulsed laser generation, owing to their strong light–matter interactions and large optical nonlinearities. However, due to the mismatch of the bandgap, many of these 2D materials are not suitable for applications at near-infrared (NIR) waveband. Here, we report nonlinear optical properties of 2D α-Mo2C crystals and the usage of 2D α-Mo2C as a new broadband saturable absorber for pulsed laser generation. It was found that 2D α-Mo2C crystals have excellent saturable absorption properties in terms of largely tunable modulation depth and very low saturation intensity. In addition, ultrafast carrier dynamic results of 2D α-Mo2C reveal an ultrashort intraband carrier recovery time of 0.48 ps at 1.55 μm. By incorporating 2D α-Mo2C saturable absorber into either an Er-doped or Yb-doped fiber laser, we are able to generate ultrashort pulses with ver...

Phonon polaritons (PhPs) have attracted significant interest in the nano-optics communities because of their nanoscale confinement and long lifetimes. Although PhP modification by changing the local dielectric environment has been reported, controlled manipulation of PhPs by direct modification of the polaritonic material itself has remained elusive. Here, chemical switching of PhPs in α-MoO3 is achieved by engineering the α-MoO3 crystal through hydrogen intercalation. The intercalation process is non-volatile and recoverable, allowing reversible switching of PhPs while maintaining the long lifetimes. Precise control of the intercalation parameters enables analysis of the intermediate states, in which the needle-like hydrogenated nanostructures functioning as in-plane antennas effectively reflect and launch PhPs and form well-aligned cavities. We further achieve spatially controlled switching of PhPs in selective regions, leading to in-plane heterostructures with various geometries. The intercalation strategy introduced here opens a relatively non-destructive avenue connecting infrared nanophotonics, reconfigurable flat metasurfaces and van der Waals crystals., Phonon polaritons hold promises for nanophotonic applications but external control of phonon polaritons remains challenging. Here, the authors achieve reversible and non-volatile switching of phonon polariton by modifying crystal structure and lattice vibrations via hydrogenation.

High-performance infrared (IR) photodetectors made by low dimensional materials promise a wide range of applications in communication, security and biomedicine. Moreover, light-harvesting effects based on novel plasmonic materials and their combinations with two-dimensional (2D) materials have raised tremendous interest in recent years, as they may potentially help the device complement or surpass currently commercialized IR photodetectors. Graphene is a particularly attractive plasmonic material because graphene plasmons are electrically tunable with a high degree of electromagnetic confinement in the mid-infrared (mid-IR) to terahertz regime and the field concentration can be further enhanced by forming nanostructures. Here, we report an efficient mid-IR room-temperature photodetector enhanced by plasmonic effect in graphene nanoresonators (GNRs)/graphene heterostructure. The plasmon polaritons in GNRs are size-dependent with strong field localization. Considering that the size and density of GNRs are controllable by chemical vapor deposition method, our work opens a cost-effective and scalable pathway to fabricate efficient IR optoelectronic devices with wavelength tunability.

Two-dimensional (2D) materials, which commonly have much higher optical nonlinearity and faster carrier dynamics than their bulk counterparts, hold huge potential for use in nonlinear optical devices, especially in ultrafast mode-locked fiber lasers. Graphene has ultrafast carrier dynamics but the optical absorption is low and the modulation depth is small. It is nontrivial to combine graphene with other 2D materials so as to form a heterostructure with improved optical properties. In particular, recent research has shown that the 2D transition metal carbide (TMC) Mo2C has a very large nonlinear absorption coefficient and can be used as a saturable absorber for mode-locking pulse generation. However, the nonlinear optical properties of the graphene-Mo2C heterostructure have not been investigated. In this work, by directly growing Mo2C nanosheets on the monolayer graphene film and forming the heterostructure, a new kind of saturable absorber was prepared with considerate nonlinear absorption coefficient and large modulation depth. Such a new saturable absorber was evanescently interacted with the side-polished fiber and successfully delivered femtosecond pulse generation at 1550 nm. The combination of two semi-metal 2D materials has enabled the ease of mode locking and stable soliton state pulse generation.

Methylammonium tin triiodide (CH3NH3SnI3) as a kind of lead-free perovskite semiconductor materials has emerged as a star material for photonic applications. Herein, for the first time, we demonstrate CH3NH3SnI3 microcrystals grown directly on D-shaped fibers as saturable absorber for generating mode-locked pulses in fiber laser. The saturable absorber device shows a high nonlinear optical modulation depth of 15.2% and considerably low saturation absorption intensity of 76.5 MW cm−2. By incorporating the CH3NH3SnI3 saturable absorber into an ytterbium-doped (Yb-doped) fiber laser, stable mode-locking pulses were produced with a duration of 1.77 ns, maximum output power of 28.19 mW, 3 dB bandwidth of about 8.09 nm and a central wavelength at 1064 nm. The output pulses show representative characteristics of dissipative soliton with excellent long term stability and an energy efficiency of 5.6%. This study may facilitate the development of ultrafast photonic and optoelectronic functional devices based on lead-free perovskites.