LiJiong

A class of peasecod‐like hollow Yb³⁺/Er³⁺‐doped Li₄ZrF₈ upconverting nanocrystals (UCNCs) that features a 2D layered crystal lattice is reported. Abnormal green upconverting luminescence that cannot be achieved in the solid UCNCs is observed in these peasecod‐like hollow UCNCs, thereby making them suitable as supersensitive nanothermometers with a wide temperature range for optical temperature sensing.

Abstract

Trivalent lanthanide (Ln³⁺)‐doped hollow upconversion nanocrystals (UCNCs) usually exhibit unique optical performance that cannot be realized in their solid counterparts, and thus have been receiving tremendous interest from their fundamentals to diverse applications. However, all currently available Ln³⁺‐doped UCNCs are solid in appearance, the preparation of hollow UCNCs remains nearly untouched hitherto. Herein, a class of UCNCs based on Yb³⁺/Er³⁺‐doped tetralithium zirconium octafluoride (Li₄ZrF₈:Yb/Er) featuring 2D layered crystal lattice is reported, which makes the fabrication of hollow UCNCs with a peasecod‐like shape possible after Ln³⁺ doping. By employing the first‐principle calculations, the unique peasecod‐like hollow nanoarchitecture primarily associated with the hetero‐valence Yb³⁺/Er³⁺ doping into the 2D layered crystal lattice of Li₄ZrF₈ matrix is revealed. Benefiting from this hollow nanoarchitecture, the resulting Li₄ZrF₈:Yb/Er UCNCs exhibit an abnormal green upconversion luminescence in terms of the population ratio between two thermally coupled states (²H_11/2 and ⁴S_3/2) of Er³⁺ relative to their solid Li₂ZrF₆:Yb/Er counterparts, thereby allowing to prepare the first family of hollow Ln³⁺‐doped UCNCs as supersensitive luminescent nanothermometer with almost the widest temperature sensing range (123–800 K). These findings described here unambiguously pave a new way to fabricate hollow Ln³⁺‐doped UCNCs for numerous applications.

Nature Photonics, Published online: 29 June 2020; doi:10.1038/s41566-020-0653-6

The inflammation attenuation capability of porous silicon nanoparticles (PSi NPs) under an acute liver inflammation condition is positively correlated with the protein corona formation process. The detailed composition of protein corona composition of each type of PSi NPs is identified and confirmed by both proteomic and R‐language analyses, highlighting the role of PSi NPs in the prognosis of the disease.

Abstract

The analysis of nanoparticles’ biocompatibility and immunogenicity is mostly performed under a healthy condition. However, more clinically relevant evaluation conducted under pathological condition is less known. Here, the immunogenicity and bio–nano interactions of porous silicon nanoparticles (PSi NPs) are evaluated in an acute liver inflammation mice model. Interestingly, a new mechanism in which PSi NPs can remit the hepatocellular damage and inflammation activation in a surface dependent manner through protein corona formation, which perturbs the inflammation by capturing the pro‐inflammatory signaling proteins that are inordinately excreted or exposed under pathological condition, is found. This signal sequestration further attenuates the nuclear factor κB pathway activation and cytokines production from macrophages. Hence, the study proposes a potential mechanism for elucidating the altered immunogenicity of nanomaterials under pathological conditions, which might further offer insights to establish harmonized standards for assessing the biosafety of biomaterials in a disease‐specific or personalized manner.

High‐quality aluminum nitride (AlN) film with low strain and low dislocation density is realized by graphene (Gr)‐driven quasi‐2D growth mode. Thus‐obtained AlN film enables much better photoelectric performance of the as‐fabricated deep ultraviolet light‐emitting diode (DUV‐LED) devices, which demonstrates practical applications for directly grown Gr film and may bring the disruptive technology for the growth of high‐quality AlN and high efficiency of DUV‐LEDs.

Abstract

Efficient and low‐cost production of high‐quality aluminum nitride (AlN) films during heteroepitaxy is the key for the development of deep ultraviolet light‐emitting diodes (DUV‐LEDs). Here, the quasi‐2D growth of high‐quality AlN film with low strain and low dislocation density on graphene (Gr) is presented and a high‐performance 272 nm DUV‐LED is demonstrated. Guided by first‐principles calculations, it is found that AlN grown on Gr prefers lateral growth both energetically and kinetically, thereby resulting in a Gr‐driven quasi‐2D growth mode. The strong lateral growth mode enables most of dislocations to annihilate each other at the AlN/Gr interface, and therefore the AlN epilayer can quickly coalesce and flatten the nanopatterned sapphire substrate. Based on the high quality and low strain of AlN film grown on Gr, the as‐fabricated 272 nm DUV‐LED shows a 22% enhancement of output power than that with low‐temperature AlN buffer, following a negligible wavelength shift under high current. This facile strategy opens a pathway to drastically improve the performance of DUV‐LEDs.

A design of halide perovskites (HP) for use in resistive switching memory (RSM) by combining first‐principles screening and experimental verification is conducted. First‐principles calculations identify 2D HP structure (AB₂X₅) as the best candidate for RSM. To verify the calculation results, 2D‐layered CsPb₂Br₅ is synthesized and applied to RSM. The CsPb₂Br₅‐based RSM shows stable operation with low operating voltages.

Abstract

Memory devices have been advanced so much, but still it is highly required to find stable and reliable materials with low‐power consumption. Halide perovskites (HPs) have been recently adopted for memory application since they have advantages of fast switching based on ionic motion in crystal structure. However, HPs also suffer from poor stability, so it is necessary to improve the stability of HPs. In this regard, combined first‐principles screening and experimental verification are performed to design HPs that have high environmental stability and low‐operating voltage for memory devices. First‐principles screening identifies 2D layered AB₂X₅ structure as the best candidate switching layer for memory devices, because it has lower formation energy and defect formation energy than 3D ABX₃ or other layered structures (A₃B₂X₇, A₂BX₄). To verify results, all‐inorganic 2D layered CsPb₂Br₅ is synthesized and used in memory devices. The memory devices that use CsPb₂Br₅ show much better stability and lower operating voltages than devices that use CsPbBr₃. These findings are expected to provide new opportunity to design materials for reliable device applications based on calculation, screening, and experimental verification.

Nature Photonics, Published online: 15 April 2020; doi:10.1038/s41566-020-0635-8

It is shown that upon incorporation of sufficient levels of Cd²⁺ cations, the isotropic 3D cubic lattice of CsPbBr₃ nanocrystals gives way to a transformation to the 1D anisotropic hexagonal lattice, which allows 1D growth of alloyed CsPb_{1‐ x} Cd _x Br₃ nanorods to be realized whose bandgaps can be tailored all across the blue spectral range from 2.40 eV for x = 0.10 to 2.74 eV for x = 0.96.

Abstract

One‐dimensional semiconductor nanostructures have already been used for a variety of optoelectronic applications. Metal halide perovskites have emerged in recent years as promising high‐performance optoelectronic materials, but reports on 1D nanorods (NRs) of all‐inorganic halide perovskites are still scarce. This work demonstrates a synthetic strategy toward cesium‐based inorganic perovskite NRs by exploiting composition‐controlled crystal phase engineering. It is accomplished for Cd‐rich mixed‐cation CsPb_{1‐ x} Cd _x Br₃ nanocrystals, where the initial 1D hexagonal perovskite phase drives the growth of the 1D NRs, as supported by first‐principles calculations. The band gaps of the resulting NRs are tunable by varying the Cd‐content, and the highly uniform CsPb_0.08Cd_0.92Br₃ NRs (with an average length of 84 nm and width of 16 nm) exhibit a true blue‐color emission centered at 460 nm, with a high quantum yield of 48%. Moreover, this work also demonstrates the tunability of the Fermi levels in the films made of CsPb_{1‐ x} Cd _x Br₃ alloyed nanocrystals, where samples with highest Cd content show an increase of the electron concentration and a related increase in the conductivity.

Nature Photonics, Published online: 02 December 2019; doi:10.1038/s41566-019-0559-3