From Octahedron Crystals to 2D Silicon Nanosheets: Facet-Selective Cleavage and Biophotonic Applications.

2D silicon nanosheets (SiNSs) are promising materials for biomedicine but facile synthesis of SiNSs remains a challenge. Herein, by means of a sulfur-iodine co-assisted chemical vapor transport method, octahedron silicon (oct-Si) crystals with fully exposed {111} planes are prepared as precursors for efficient synthesis of SiNSs by facet-selective exfoliation. The 13 nm thick SiNSs have good biocompatibility and the sharp Raman scattering signal facilitates intracellular Raman imaging upon exposure to a near-infrared (NIR) laser. Furthermore, the SiNSs have excellent NIR photothermal characteristics such as a large extinction coefficient of 11.3 L g-1 cm-1 and high photothermal conversion efficiency of 21.4% at 1064 nm. In vitro experiments demonstrate superior NIR-II photothermal therapeutic effects in killing cancer cells. Comparing to conventional methods, the novel facet-selective cleavage strategy is more controllable and environmentally friendly boding well for the fabrication of non-van der Waals 2D materials. The multimodal photonic behavior also suggests large potential of the SiNSs pertaining to integrated multi-NIR biophotonic techniques using single nanomaterials.

Metabolizable Ultrathin Bi2 Se3 Nanosheets in Imaging-Guided Photothermal Therapy.

Poly(vinylpyrrolidone)-encapsulated Bi2 Se3 nanosheets with a thickness of 1.7 nm and diameter of 31.4 nm are prepared by a solution method. Possessing an extinction coefficient of 11.5 L g(-1) cm(-1) at 808 nm, the ultrathin Bi2 Se3 nanosheets boast a high photothermal conversion efficiency of 34.6% and excellent photoacoustic performance. After systemic administration, the Bi2 Se3 nanosheets with the proper size and surface properties accumulate passively in tumors enabling efficient photoacoustic imaging of the entire tumors to facilitate photothermal cancer therapy. In vivo biodistribution studies reveal that they are expelled from the body efficiently after 30 d. The ultrathin Bi2 Se3 nanosheets have large clinical potential as metabolizable near-infrared-triggered theranostic agents.

Surface Coordination of Black Phosphorus for Robust Air and Water Stability.

A titanium sulfonate ligand is synthesized for surface coordination of black phosphorus (BP). In contrast to serious degradation observed from the bare BP, the BP after surface coordination exhibits excellent stability during dispersion in water and exposure to air for a long period of time, thereby significantly extending the lifetime and spurring broader application of BP.

Vertically Oriented Quasi-2D Perovskite Grown In-Situ by Carbonyl Array-Synergized Crystallization for Direct X-Ray Detectors.

Quasi-2D perovskite quantum wells are increasingly recognized as promising candidates for direct-conversion X-ray detection. However, the fabrication of oriented and uniformly thick quasi-2D perovskite films, crucial for effective high-energy X-ray detection, is hindered by the inherent challenges of preferential crystallization at the gas-liquid interface, resulting in poor film quality. In addressing this limitation, a carbonyl array-synergized crystallization (CSC) strategy is employed for the fabrication of thick films of a quasi-2D Ruddlesden-Popper (RP) phase perovskite, specifically PEA2MA4Pb5I16. The CSC strategy involves incorporating two forms of carbonyls in the perovskite precursor, generating large and dense intermediates. This design reduces the nucleation rate at the gas-liquid interface, enhances the binding energies of Pb2+ at (202) and (111) planes, and passivates ion vacancy defects. Consequently, the construction of high-quality thick films of PEA2MA4Pb5I16 RP perovskite quantum wells is achieved and characterized by vertical orientation and a pure well-width distribution. The corresponding PEA2MA4Pb5I16 RP perovskite X-ray detectors exhibit multi-dimensional advantages in performance compared to previous approaches and commercially available a-Se detectors. This CSC strategy promotes 2D perovskites as a candidate for next-generation large-area flat-panel X-ray detection systems.

In-Situ Construction of Anti-Aggregation Tellurium Nanorods/Reduced Graphene Oxide Composite to Enable Fast Sodium Storage.

Sodium-ion batteries (SIBs) as a replaceable energy storage technology have attracted extensive attention in recent years. The design and preparation of advanced anode materials with high capacity and excellent cycling performance for SIBs still face enormous challenges. Herein, a solution method is developed for in situ synthesis of anti-aggregation tellurium nanorods/reduced graphene oxide (Te NR/rGO) composite. The material working as the sodium-ion battery (SIB) anode achieves a high reversible capacity of 338 mAh g-1 at 5 A g-1 and exhibits up to 93.4% capacity retention after 500 cycles. This work demonstrates an effective preparation method of nano-Te-based composites for SIBs.

2D BP/InSe Heterostructures as a Nonlinear Optical Material for Ultrafast Photonics.

The BP/InSe heterojunction has attracted the attention of many fields in successful combined high hole mobility of black phosphorus (BP) and high electron mobility of indium selenide (InSe), and enhanced the environmental stability of BP. Nevertheless, photonics research on the BP/InSe heterostructure was insufficient, while both components are considered promising in the field. In this work, a two-dimensional (2D) BP/InSe heterostructure was fabricated using the liquid-phase exfoliation method. Its linear and non-linear optical (NLO) absorption was characterized by ultraviolet-visible-infrared and Open-aperture Z-scan technology. On account of the revealed superior NLO properties, an SA based on 2D BP/InSe was prepared and embedded into an erbium-doped fiber laser, traditional soliton pulses were observed at 1.5 µm with the pulse duration of 881 fs. Furthermore, harmonic mode locking of bound solitons and dark-bright soliton pairs were also obtained in the same laser cavity due to the cross-coupling effect. The stable mode-locked operation can be maintained for several days, which overcome the low air stability of BP. This contribution further proves the excellent optical properties of 2D BP/InSe heterostructure and provides new probability of developing nano-photonics devices for the applications of double pulses laser source and long-distance information transmission.

[Near-infrared luminescence and energy transfer of ACaPO4 : Eu2+, Nd3+ (A = Li, K, Na)].

Near-infrared (NIR) luminescence phosphors ACaPO4 : Eu2+, Nd2+ (A = Li, K, Na) were prepared by conventional solid state method and the sensitization of Nd3+ near-infrared luminescence by Eu2+ was investigated. The characteristic NIR luminescence of Nd3+ in ACaPO4 matrix is greatly enhanced by co-doping of Eu2+. The fluorescence properties of ACaPO4 : Eu2+, the NIR luminescence properties of ACaPO4 : Eu2+, Nd3+ and the fluorescence lifetime were studied. The effect of emission wavelength of Eu2+ on NIR luminescence of Nd3+ was investigated; The energy transfer mechanism between Eu2+ and Nd3+ was also discussed. Emission peak wavelength of Eu2+ In ACaPO4 matrixes was found red shift with the series of A = Li, K, Na and the extent of the overlap with the different excitation peaks of Nd3+ changes obviously. It was concluded that the emission peak position of Eu2+ is a very important factor for energy transfer, and the optimal wavelength range for Eu2+ --> Nd3+ energy transfer is 500 to 550 nm.

Electromagnetic Interference Shielding of 2D Transition Metal Carbide (MXene)/Metal Ion Composites.

In this work, Ti3C2, which has a loosely packed accordion-like structure in transition metal carbide (MXene) form, is fabricated and adsorbed by three metal ions (Fe3+/Co2+/Ni2+). The electromagnetic interference (EMI) shielding performance of Ti3C2 and Ti3C2:Fe3+/Co2+/Ni2+ films is researched in detail, demonstrating that the EMI shielding effectiveness can be improved by adsorbing by Fe3+/Co2+/Ni2+ ions because the metal ion adsorbing can improve the absorption efficiency via electromagnetic wave scattering. The studied Ti3C2:Fe3+/Co2+/Ni2+ films can be used as good EMI shielding materials for communications, electronics, military, and other applications.

Decentralized manufacturing for biomimetics through cooperation of digitization and nanomaterial design.

The blooming development of biomimetics has demonstrated infinite possibilities in providing solutions for our technical or engineering problems. Therefore, it makes sense to develop an efficient manufacturing system for biomimetic products to transfer biological techniques to engineering. Compared with conventional manufacturing, the decentralized one assisted by additive manufacturing brings the production process closer to the customized requirement of end users due to the accompanying manufacturing freedom in terms of both architecture coding and functionality distribution. Decentralized manufacturing is implemented through firstly deconstructing and analyzing the organism and subsequently establishing the manufacturing scheme. In this minireview, we take a bird's-eye view on the latest progress of biomimetic manufacturing through a decentralized and reverse perspective right from the selected characteristics of natural organisms, and call for a cooperation of digitization design and nanomaterial design. With further synergetic development of biomimetics, nanomaterial science and digitization-assisted additive manufacturing technology, it is anticipated that the decentralized approach will provide a shortcut towards a high-efficiency manufacturing way for biomimetic products.

Two Dimensional ß-InSe with Layer-Dependent Properties: Band Alignment, Work Function and Optical Properties.

Density functional theory calculations of the layer (L)-dependent electronic band structure, work function and optical properties of ß-InSe have been reported. Owing to the quantum size effects (QSEs) in ß-InSe, the band structures exhibit direct-to-indirect transitions from bulk ß-InSe to few-layer ß-InSe. The work functions decrease monotonically from 5.22 eV (1 L) to 5.0 eV (6 L) and then remain constant at 4.99 eV for 7 L and 8 L and drop down to 4.77 eV (bulk ß-InSe). For optical properties, the imaginary part of the dielectric function has a strong dependence on the thickness variation. Layer control in two-dimensional layered materials provides an effective strategy to modulate the layer-dependent properties which have potential applications in the next-generation high performance electronic and optoelectronic devices.

Fluorination-Enhanced Ambient Stability and Electronic Tolerance of Black Phosphorus Quantum Dots.

The environmental instability and uneliminable electronic trap states in black phosphorus quantum dots (BPQDs) limit the optoelectronics and related applications of BPQDs. Here, fluorinated BPQDs (F-BPQDs) are successfully synthesized by using a facile electrochemical exfoliation and synchronous fluorination method. The F-BPQDs exhibit robust ambient stability and limited fluorination capability, showing a nonstoichiometric fluorination degree (DF) maximum of ≈0.68. Density functional theory calculations confirm that due to the edge etching effect of fluorine adatoms, the simulated F-BPQDs become structurally unstable when DF surpasses the limit. Furthermore, the trap states of BPQDs can be effectively eliminated via fluorination to obtain a coordination number of 3 or 5 for fluorinated and unfluorinated phosphorus atoms. The results reveal that the air-stable F-BPQDs exhibit fluorine defect-enhanced electronic tolerance, which is crucial for nanophotonics and nanoelectronics applications.

Black Phosphorus Nanosheets as a Robust Delivery Platform for Cancer Theranostics.

2D black phosphorus (BP) nanomaterials are presented as a delivery platform. The endocytosis pathways and biological activities of PEGylated BP nanosheets in cancer cells are revealed for the first time. Finally, a triple-response combined therapy strategy is achieved by PEGylated BP nanosheets, showing a promising and enhanced antitumor effect.

Dynamically Tuning the Up-conversion Luminescence of Er(3+)/Yb(3+) Co-doped Sodium Niobate Nano-crystals through Magnetic Field.

In this work, we show here that the up-conversion luminescence of NaNbO3:Er(3+)/Yb(3+) nano-materials can be modulated by magnetic field and a enhancement of up-conversion intensities by a factor of about 2 for Er(3+):(4)S3/2 → (4)I15/2 obtained at 30 T and about 5.4 for Er(3+):(4)F9/2 → (4)I15/2 obtained at 20 T. The increased up-conversion luminescence are mainly interpreted in terms of the enhanced non-radiation transition from (4)I11/2 to (4)I13/2 of Er(3+) ions and the spin-orbital coupling (that is "mixing" effect) in crystal field by an external magnetic field. Meanwhile, we observed continuously spectra broadening with growing the magnetic field intensity, which is ascribed to the "mixing" effect induced by magnetic field and the difference of g factor of sub-bands. This bi-functional material with controllable optical-magnetic interactions has various potential applications, such as optical detection of magnetic field, etc.

Controllable Phase Transformation and Mid-infrared Emission from Er(3+)-Doped Hexagonal-/Cubic-NaYF4 Nanocrystals.

The morphology of hexagonal phase NaYF4:Er(3+) nanorods synthesized by hydrothermal method changed greatly after a continuing calcination, along with a phase transformation to cubic phase. Photoluminescence (PL) spectra indicated that mid-infrared (MIR) emission was obtained in both hexagonal and cubic phase NaYF4:Er(3+) nanocrystals for the first time. And the MIR emission of NaYF4:Er(3+) nanocrystals enhanced remarkably at higher calcination temperature. To prevent uncontrollable morphology from phase transformation, the cubic phase NaYF4:Er(3+) nanospheres with an average size of ~100 nm were prepared via a co-precipitation method directly. In contrast, the results showed better morphology and size of cubic phase NaYF4:Er(3+) nanocrystals have realized when calcined at different temperatures. And PL spectra demonstrated a more intense MIR emission in the cubic phase NaYF4:Er(3+) nanocrystals with an increasing temperature. Besides, the MIR emission peak of Er(3+) ions had an obvious splitting in cubic phase NaYF4. Therefore, cubic phase NaYF4:Er(3+) nanospheres with more excellent MIR luminescent properties seems to provide a new material for nanocrystal-glass composites, which is expected to open a broad new field for the realization of MIR lasers gain medium.

Evaporative Self-Assembly of Gold Nanorods into Macroscopic 3D Plasmonic Superlattice Arrays.

Millimeter-scale 3D superlattice arrays composed of dense, regular, and vertically aligned gold nanorods are fabricated by evaporative self-assembly. The regular organization of the gold nanorods into a macroscopic superlattice enables the production of a plasmonic substrate with excellent sensitivity and reproducibility, as well as reliability in surface-enhanced Raman scattering. The work bridges the gap between nanoscale materials and macroscopic applications.

Biodegradable black phosphorus-based nanospheres for in vivo photothermal cancer therapy.

Photothermal therapy (PTT) offers many advantages such as high efficiency and minimal invasiveness, but clinical adoption of PTT nanoagents have been stifled by unresolved concerns such as the biodegradability as well as long-term toxicity. Herein, poly (lactic-co-glycolic acid) (PLGA) loaded with black phosphorus quantum dots (BPQDs) is processed by an emulsion method to produce biodegradable BPQDs/PLGA nanospheres. The hydrophobic PLGA not only isolates the interior BPQDs from oxygen and water to enhance the photothermal stability, but also control the degradation rate of the BPQDs. The in vitro and in vivo experiments demonstrate that the BPQDs/PLGA nanospheres have inappreciable toxicity and good biocompatibility, and possess excellent PTT efficiency and tumour targeting ability as evidenced by highly efficient tumour ablation under near infrared (NIR) laser illumination. These BP-based nanospheres combine biodegradability and biocompatibility with high PTT efficiency, thus promising high clinical potential.