Nonlinear optical (NLO) materials are of great importance in laser science and technology, as they can expand the wavelength range provided by common laser sources. Few NLO materials, except KBe 2 BO 3 F 2 (KBBF), can practically generate deep-ultraviolet coherent light by direct second-harmonic generation process, limited by the fundamental requirements on the structure-directing optical properties. However, KBBF suffers a strong layering tendency and high toxicity of the containing beryllium, which hinder the commercial availability of KBBF. Here we report a new beryllium-free borate, Li 4 Sr(BO 3 ) 2 , which preserves the structural merits of KBBF, resulting in the desirable optical properties. Furthermore, Li 4 Sr(BO 3 ) 2 mitigates the layering tendency greatly and enhances the efficiency of second-harmonic generation by more than half that of KBBF. These results suggest that Li 4 Sr(BO 3 ) 2 is an attractive candidate for the next generation of deep-ultraviolet NLO materials. This beryllium-free borate represents a new research direction in the development of deep-ultraviolet NLO materials.

A beryllium-free deep-ultraviolet (deep-UV) nonlinear optical (NLO) material K3Ba3Li2Al4B6O20F is developed mainly by the element substitution of Be for Al and Li from Sr2Be2B2O7 that was considered as one of the most promising deep-UV NLO materials. K3Ba3Li2Al4B6O20F preserves the structural merits of Sr2Be2B2O7 and thus exhibits no layering growth tendency and possesses the optical properties required for deep-UV NLO applications, including deep-UV transparency, phase-matchability, and sufficiently large second-harmonic generation (1.5 × KH2PO4). Furthermore, it overcomes the structural instability problem of Sr2Be2B2O7, which is confirmed by the obtainment of large single crystals and phonon dispersion calculations. These attributes make it very attractive for next-generation deep-UV NLO materials. The substitution of Be for Al and Li in beryllium borates provides a new opportunity to design beryllium-free deep-UV NLO materials with good performance.

Metal‐halide perovskites are recently emerging as the promising alternative for CPL detection owing to their CPL‐sensitive property induced by chiral organics and efficient charge transport of inorganic frameworks. However, most of these reported chiral perovskites involve high concentrations of toxic Pb which will become the potential bottleneck for their further application. Herein, we successfully developed two lead‐free halide double perovskites, [(R)‐β‐MPA]4AgBiI8 ((R)‐β‐MPA=(R)‐(+)‐β‐methylphenethylammonium, 1‐R), and [(S)‐β‐MPA]4AgBiI8 ((S)‐β‐MPA=(S)‐(−)‐β‐methylphenethylammonium, 1‐S). Circular dichroism measurements reveal that these perovskites exhibit notable chirality induced by organic cations to distinguish different polarization states of CPL photons. Significantly, they present unique chiral polar photovoltaic, and resulting self‐powered CPL detection without an external power source is unprecedentedly achieved. Furthermore, an anisotropy factor up to 0.3 is acquired for the self‐powered CPL detection, reaching the highest value among reported chiral perovskites. This work suggests hybrid double perovskites are promising photoelectronic candidates, and provides a new approach for exploring new “green” circularly polarized light‐sensitive materials with high performance.

Cyanobacteriochromes are phytochrome homologues in cyanobacteria that act as sensory photoreceptors. We compare two cyanobacteriochromes, RGS (coded by slr1393) from Synechocystis sp. PCC 6803 and AphC (coded by all2699) from Nostoc sp. PCC 7120. Both contain three GAF (cGMP phosphodiesterase, adenylyl cyclase and FhlA protein) domains (GAF1, GAF2 and GAF3). The respective full-length, truncated and cysteine point-mutated genes were expressed in Escherichia coli together with genes for chromophore biosynthesis. The resulting chromoproteins were analyzed by UV-visible absorption, fluorescence and circular dichroism spectroscopy as well as by mass spectrometry. RGS shows a red-green photochromism (k max = 650 and 535 nm) that is assigned to the reversible 15Z ⁄ E isomerization of a single phycocyanobilin-chromophore (PCB) binding to Cys528 of GAF3. Of the three GAF domains, only GAF3 binds a chromophore and the binding is autocatalytic. RGS autophosphorylates in vitro; this reaction is photoregulated: the 535 nm state containing E-PCB was more active than the 650 nm state containing Z-PCB. AphC from Nostoc could be chromophorylated at two GAF domains, namely GAF1 and GAF3. PCB-GAF1 is photochromic, with the proposed 15E state (k max = 685 nm) reverting slowly thermally to the thermostable 15Z state (k max = 635 nm). PCB-GAF3 showed a novel red-orange photochromism; the unstable state (putative 15E, k max = 595 nm) reverts very rapidly (s 20 s) back to the thermostable Z state (k max = 645 nm). The photochemistry of doubly chromophorylated AphC is accordingly complex, as is the autophosphorylation: E-GAF1 ⁄ E-GAF3 shows the highest rate of autophosphorylation activity, while E-GAF1 ⁄ Z-GAF3 has intermediate activity, and Z-GAF1 ⁄ Z-GAF3 is the least active state. Structured digital abstractl AphC phosphorylates AphC by protein kinase assay (View interaction) l RGS phosphorylates RGS by protein kinase assay (View interaction) Abbreviations AphC, protein encoded by aphC = all2699; CBR, cyanobacteriochrome; GAF, cGMP phosphodiesterase, adenylyl cyclase and FhlA protein domain (SMART acc. no. SM00065); KPB, potassium phosphate buffer; Nostoc, Anabaena (Nostoc) sp. PCC 7120; P XXX ⁄ P YYY , the two photoconvertible states of CBR or Phy designated by the absorption maxima, with the stable generally 15Z state (k max = XXX nm) preceding the light-activated generally 15E-configured state (k max = YYY nm); PAS, period circadian protein, Ah receptor nuclear translocator protein and single-minded protein domain (SMART acc. no. SM00091); PCB, phycocyanobilin; Phy, phytochrome; PVB, phycoviolobilin; PFB, phytochromobilin; RGS, red-green switchable protein encoded by rgs = slr1393; Synechocystis, Synechocystis sp. PCC 6803.

A highly stable porous lanthanide metal-organic framework, Y(BTC)(H2O).4.3H2O (BTC = 1,3,5-benzenetricarboxylate), with pore size of 5.8 A has been constructed and investigated for hydrogen storage. Gas sorption measurements show that this porous MOF exhibits highly selective sorption behaviors of hydrogen over nitrogen gas molecules and can take up hydrogen of about 2.1 wt % at 77 K and 10 bar. Difference Fourier analysis of neutron powder diffraction data revealed four distinct D2 sites that are progressively filled within the nanoporous framework. Interestingly, the strongest adsorption sites identified are associated with the aromatic organic linkers rather than the open metal sites, as occurred in previously reported MOFs. Our results provide for the first time direct structural evidence demonstrating that optimal pore size (around 6 A, twice the kinetic diameter of hydrogen) strengthens the interactions between H2 molecules and pore walls and increases the heat of adsorption, which thus allows for enhancing hydrogen adsorption from the interaction between hydrogen molecules with the pore walls rather than with the normally stronger adsorption sites (the open metal sites) within the framework. At high concentration H2 loadings (5.5 H2 molecules (3.7 wt %) per Y(BTC) formula), H2 molecules form highly symmetric novel nanoclusters with relatively short H2-H2 distances compared to solid H2. These observations are important and hold the key to optimizing this new class of rare metal-organic framework (RMOF) materials for practical hydrogen storage applications.

Self-powered photodetection driven by ferroelectric polarization has shown great potential in next-generation optoelectronic devices.H ybrid perovskite ferroelectrics that combine polarization and semiconducting properties have ap romising position within this portfolio.H erein, we demonstrate the realization of self-powered photodetection in an ew developed biaxial ferroelectric,( EA) 2 (MA) 2 Pb 3 Br 10 (1,E Ai s ethylammonium and MA is methylammonium), whichd isplaysh igh Curie temperature (375 K), superior spontaneous polarization (3.7 mCcm À2 ), and unique semiconducting nature. Strikingly,w ithout an external energy supply, 1 exhibits an direction-selectable photocurrent with fascinating attributes including high photocurrent density ( % 4.1 mAcm À2 ), high on/ off switching ratio (over 10 6 ), and ultrafast response time (96/ 123 ms);s uch merits are superior to those of the most active ferroelectric oxide BiFeO 3 .F urther studies reveal that strong inversion symmetry breaking in 1 provides adesirable driving force for carrier separation, accounting for such electrically tunable self-powered photoactive behaviors.T his work sheds light on exploring new multifunctional hybrid perovskites and advancing the design of intelligent photoelectric devices.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

The photocatalysis of H 2 O into H 2 and O 2 via aqueous suspensions of metal-oxide powders has drawn increasing attention in recent years, as noted in several reviews. [1][2][3] Numerous solids (> 30) reportedly exhibit high quantum efficiencies (QEs) for H 2 O photocatalysis at ultraviolet wavelengths, including NaTaO 3 (56 % QE), [4] (27 %), [6] and La 4 CaTi 5 O 17 (20 %).[5a] The metal oxides are typically loaded with co-catalysts on their surfaces, such as Pt, NiO, or RuO 2 , as active sites for H 2 and/or O 2 production, and display catalytic rates that are stable for hundreds of hours and longer time spans. Contrasted to this has been the relative failure to obtain efficient photocatalysis for the visible (400-700 nm) and predominant region of the solar spectrum, as reported for a-Fe 2 O 3 (∼ 2 %) or In 1-x Ni x TaO 4 (0.66 %), [7,8] though the theoretical requirement for H 2 O → H 2 + 1/2 O 2 is k ≤ 1008 nm. [9] One limiting barrier is the requirement for a metal oxide to have a bandgap appropriate for the absorption of visible light (≤ 3.0 eV), while also having a conduction band edge, or flat-band potential, above the potential of the H 2 /H 2 O redox couple. [9,10] Empirical relationships have been formulated that predict a visible-light bandgap can only be obtained at the expense of high conduction band levels (with a few exceptions) in transition-metal oxides (e.g., E fb = 2.94 -E g ; E fb = flat band potential, and must be < 0 for reduction of H 2 O; E g = bandgap). [10][11][12] This relationship derives from the idea that while the valence band originates primarily from the O 2p orbitals and is fairly constant among metal oxides, the conduction band levels are determined by the metal-based d orbitals. Alternate solid-state approaches include the substitution of nitrogen/sulfur for oxygen or various transition-metal dopants, [13][14][15] but so far have shown relatively low photocatalytic efficiencies for H 2 production. Current progress suggests that development of novel materials and photocatalysis mechanisms would be valuable in reaching more efficient solar photocatalysts of H 2 O.Among new types of materials, the rapidly growing field of composited solids is being fueled through the advent of lowtemperature synthetic pathways, such as the hydrothermal synthesis of SrTiO 3 , [16] Figures 1B,C, confirmed the presence of the characteristic peaks for Fe 2 O 3 , BiFeO 3 , and SrTiO 3 in each of their respective systems. These measurements also confirmed the absence of additional products and that relatively limited reaction/diffusion might have occurred between the two solids. To test the results of a reaction between SrTiO 3 and BiFeO 3 , the system was reacted at 850°C and formed a solid solution, [24] as shown by the merging of the two sets of diffraction peaks in Figure 1A. BiFeO 3 and SrTiO 3 have similar lattice constants (a = 3.962 Å, COMMUNICATIONS 514

Polarization-sensitive ultraviolet (UV) photodetection is highly indispensable in military and civilian applications and has been demonstrated with various wide-band photodetectors. However, it still remains elusive to achieve the selfpowered devices, which can be operated in the absence of external bias. Herein, for the first time, ferroelectricity-driven self-powered photodetection towards polarized UV light was successfully demonstrated in a 2D wide-band gap hybrid ferroelectric (BPA) 2 PbBr 4 (BPA = 3-bromopropylammonium) (1). We found that the prominent spontaneous polarization in 1 results in a bulk photovoltaic effect (BPVE) of 0.85 V, that independently drives photoexcited carriers separation and transport and thus supports self-powered ability. This self-powered detector shows strong polarization sensitivity to linearly polarized UV illumination with a polarization ratio up to 6.8, which is superior to that of previously reported UVpolarized photodetectors (ZnO, GaN, and GeS 2). Polarization-sensitive photodetectors have attracted extensive attention owing to their remarkable polarization dependent optoelectronic properties. [1-3] Among them, polarizationsensitive ultraviolet (UV) photodetection capable of detecting polarized UV light is a significant branch of optoelectronics and has been adapted to various fields, ranging from communication, near field imaging, remote sensing, as well as to military surveillance. [4-9] During the past decades, most attention on polarization-sensitive UV photodetection was devoted to conventional wide band gap semiconductor medium with nanowire geometry, such as GaN [4] and ZnO. [5] Recently, anisotropic 2D semiconductor GeS 2 also has been demonstrated to be potential building element for UVpolarized detection due to the intrinsic anisotropic crystal structure. [10] However, an external power source was usually required as driving force in all above mentioned devices to separate the photogenerated carriers, which not only consumed energy but also largely increased the system size and integrated cost. Self-powered photodetectors represent a new type of candidate without external energy supply, which can