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Summary Ferroelectrics with switchable spontaneous polarization have taken a dominant position as the nonlinear optical candidates, of which birefringence is an essential merit to optical devices. Despite the increasing advance of hybrid perovskite ferroelectrics, it remains a great challenge to control and tune their birefringence, thus hindering their practical optical applications. Here, we present a 2D trilayered hybrid perovskite-type ferroelectric obtained by 3D-to-2D dimensional tailoring, [(CH3)2CH(CH2)2NH3]2(CH3NH3)2Pb3Cl10, showing biaxial polarizations of ∼5 μC/cm2 and a relatively wide optical band gap. The intrinsic 2D architecture results in highly anisotropic principal refractive indices, namely, the optical birefringence. Interestingly, its birefringence can be reversibly switched through ferroelectric-to-paraelectric symmetry breaking. The birefringence tuning is further established by virtue of pretransitional modulation of ferroelectricity, exhibiting unusual polarization-dependent behaviors. In our judgment, this study on the polarization-dependent birefringence of hybrid perovskite ferroelectrics will provide a new pathway toward modulating nonlinear optical properties for smart devices.

Atomically thin two‐dimensional (2D) bismuth oxychalcogenides (Bi2O2X, X = S, Se, Te) have recently attracted extensive attention in the material research community due to their unique structure, outstanding long‐term ambient stability, and high carrier mobility, which enable them as promising candidates for high‐performance electronic and optoelectronic applications. Herein, we present a comprehensive review on the recent advances of 2D bismuth oxychalcogenides research. We start with an introduction of their fundamental properties including crystal structure and electronic band structure. Next, we summarize the common techniques for synthesizing these 2D structures with high crystallinity and large lateral size. Furthermore, we elaborate on their device applications including transistors, artificial synapses, optical switch and photodetectors. The last but not the least, we summarize the existing challenges and prospects for this emerging 2D bismuth oxychalcogenides field.

Two-dimensional (2D) ternary materials have sprung up in a broad variety of optoelectronic applications due to their robust degree of freedom to design the physical properties of the materials through adjusting the stoichiometric ratio. However, the controlled growth of high-quality 2D ternary materials with good chemical stoichiometry remains challenging, which severely impedes their further development and future device applications. Herein, we synthesize ternary Bi2Te2Se (BTS) flakes with a thickness down to 4 nm and a lateral dimension about 60 μm by an atmospheric-pressure solid source thermal evaporation method on a mica substrate. The phonon vibration and electrical transportation of 2D BTS are respectively investigated by temperature-dependent Raman spectrum and conductivity measurements. Furthermore, the photodetector based on 2D BTS exhibits excellent performance with a high light on/off ratio of 1300 (365 nm), a wide spectral response range from 365 to 980 nm, and an ultra-fast response speed up to 2 μs. In addition, its electrical and photoelectric properties can be modulated by the gate voltage, offering an improved infrared responsivity to 2.74 A W−1 and an on/off ratio of 2266 under 980 nm. This work introduces an effective approach to obtain 2D BTS flakes and demonstrates their excellent prospects in optoelectronics.

Two-dimensional (2D) organic-inorganic hybrid perovskites, benefiting from their natural anisotropy of quantum-well motifs and optical properties, have shown remarkable polarization-dependent responses superior to the 3D counterparts. Here, for the first time, multiwavelength polarization-sensitive detectors were fabricated by using single crystals of a guanidine-based 2D hybrid perovskite, (BA)2 (GA)Pb2 I7 (where BA+ is n-butylammonium and GA+ is guanidium). Its unique 2D quantum-well structure results in strong crystallographic-dependence of optical absorption. Strikingly, our crystal-based photodetector exhibits a prominent photocurrent dichroic ratio (Imax /Imin ) of ∼2.2 at 520 nm, higher than the typical 2D inorganic materials (GeSe, ∼1.09, PdSe2 , ∼1.8). In addition, notable dichroic ratios of 1.29 and 1.23 at 405 nm and 637 nm are also created for the multiwavelength polarized-light detection. The prominent detecting performances, including low dark current (1.6×10-11 A), considerable on/off ratio (∼2×103 ), high photodetectivity (∼3.3×1011 Jones) and responsivity (∼12.01 mA W-1 ), make (BA)2 (GA)Pb2 I7 a promising candidate for polarized-light detection. This work sheds light on the rational engineering of new 2D hybrid perovskites for the high-performance optoelectronic device applications.

Through a functional unit-transmutation strategy, a fatigue-free layered hybrid perovskite ferroelectric (C6H5CH2NH3)(2)CsPb2Br7 (BCPB) has been developed, which demonstrates stable spontaneous polarization (P-s) of 6.5 mu C cm(-2) and high Curie temperature up to 425 K. Meanwhile, BCPB shows splendid bulk photovoltaic effect (BPVE) properties with noticeable zero-bias photocurrent density (5 mu A cm(-2)), and high on/off switching ratio of current (over 3x10(5)); these merits even overmatch the most known ferroelectric semiconductor BiFeO3. The unique structure with self-regulated net electrical charged layers gives rise to the fatigue-free feature of P-s and BPVE (no significant fatigue after 10(8) polarity switching cycles), promoting the potential applications of BCPB in photovoltaic non-volatile memories. This work offers an efficient approach for exploring fatigue-free semiconducting ferroelectrics as well as excavates their further applications in next-generation electronic devices.

Children (n = 240) between the ages of 2 and 17 years were randomly selected from three cities in China. The total amount of soil and dust (SD) on their hands was measured and ranged from 3.50–187.39 mg (median = 19.49 mg). We screened for seven elements (Ce, V, Y, Al, Ba, Sc, and Mn), and Ce levels were used to calculate hand SD by variability and soil elements. The main factors affecting SD amount were location and age group, as identified using a conditional inference tree. Hand SD and the hand SD intake rate were highest in Gansu Province, followed by Guangdong and Hubei provinces, respectively. Hand SD and the hand SD intake rate were highest among children in primary school, followed by kindergarten and secondary school, respectively. The hand SD intake rate of the three typical areas was 11.9 mg/d, which was about 26.6% of the children’s soil intake rate (44.8 mg/d), indicating that hand-to-mouth contact is not the main route for children’s soil intake in the three areas of China.

Polar hybrid perovskites have been explored for self-powered photodetection benefitting from prominent transport of photo-induced carriers and the bulk photovoltaic effect (BPVE). However, these self-powered photodetection ranges are relatively narrow depending on their intrinsic wide bandgaps (>2.08 eV), and the realization of broad-spectrum self-powered photodetection is still a difficult task. Herein, we successfully obtained a polar multilayered perovskite, (I-BA)2(MA)2Pb3I10 (IMP, MA+ = methylammonium and I-BA+ = 4-iodobutylammonium), via rational dimension reduction of CH3NH3PbI3. It features the narrowest bandgap of 1.71 eV in a BPV material. As a consequence, the integration of narrow bandgap and BPVE causes the self-powered photodetection to extend to 724 nm for IMP, and a repeatable photovoltaic current reaching 1.0 μA cm−2 is acquired with a high “on/off” ratio of ∼103 and photodetectivity (∼109 Jones) at zero bias. This innovative research provides a foothold for adjusting the physical properties of hybrid perovskites and will expand their potential for self-powered broad-spectrum detection., A polar hybrid perovskite with a wide-spectrum absorption extending to 724 nm was obtained . Benefitting from the narrow bandgap and bulk photovoltaic effects, self-powered broad-spectrum photodetection was achieved in hybrid perovskites.

Two-dimensional (2D) materials, in particular emerging 2D layered hybrid perovskites, have manifested excellent potential for polarization-sensitive photodetection recently due to their highly intrinsic anisotropy, characteristic quantum-well structure and intriguing semiconducting properties. However, most of the reported 2D hybrid perovskites still suffer from limited crystal dimensions or narrow spectral photoresponse to the polarized light. Herein, we have developed a new layered iodide perovskite (s-BA)2(MA)Pb2I7 (1, s-BA+ is sec-butylammonium and MA+ is methylammonium) through symmetry-reduction and halide remolding, which exhibits highly structural anisotropy and a narrow bandgap of 2.02 eV. Strikingly, centimeter-sized crystals with dimensions up to 19 × 19 × 3 mm3 can be obtained via temperature cooling method. Based on such large crystals, photodetectors were fabricated which manifest impressive response to polarized light with a large dichroism ratio of about 1.16, notable responsivity of 97.22 mA W−1 and considerable detectivity of 2.79 × 1011 Jones. This work offers a new candidate to the further exploration of highly anisotropic hybrid perovskites for extended spectral polarization-sensitive photodetection.

Halide double perovskites have emerged as remarkable semiconductors owing to their nontoxicity and superior optoelectronic features. Despite recent exciting progress, halide double perovskites with...

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 self-powered 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 PbBr4 (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 UV-polarized photodetectors (ZnO, GaN, and GeS2 ).

3D perovskite CsPbBr3 has recently taken a blooming position for optoelectronic applications. However, due to the lack of natural anisotropy of optical attributes, it is a great challenge to fulfil polarization-sensitive photodetection. Here, for the first time, we exploited dimensionality reduction of CsPbBr3 to tailor a 2D-multilayered hybrid perovskite, (TRA)2 CsPb2 Br7 (1, in which TRA is (carboxy)cyclohexylmethylammonium), serving as a potential polarized-light detecting candidate. Its unique quantum-confined 2D structure results in intrinsic anisotropy of electrical conductivity, optical absorbance, and polarization-dependent responses. Particularly, it exhibits remarkable dichroism with the photocurrent ratio (Ipc /Ipa ) of ≈2.1, being much higher than that of the isotropic CsPbBr3 crystal and reported CH3 NH3 PbI3 nanowire (≈1.3), which reveals its great potentials for polarization-sensitive photodetection. Further, crystal-based detectors of 1 show fascinating responses to the polarized light, including high detectivity (>1010 Jones), fast responding time (≈300 μs), and sizeable on/off current ratios (>104 ). To our best knowledge, this is the first study on 2D Cs-based hybrid perovskite exhibiting strong polarization-sensitivity. The work highlights an effective pathway to explore new polarization sensitive candidates for hybrid perovskites and promotes their future electronic applications.

Polarized light detection is attracting increasing attention for its wide applications ranging from optical switches to high-resolution photodetectors. Two-dimensional (2D) hybrid perovskite-type ferroelectrics combining inherent light polarization dependence of bulk photovoltaic effect (BPVE) with excellent semiconducting performance present significant possibilities. Now, the BPVE-driven highly sensitive polarized light detection in a 2D trilayered hybrid perovskite ferroelectric, (allyammonium)(2)(ethylammonium)(2)Pb3Br10 (1), is presented. It shows a superior BPVE with near-band gap photovoltage of ca. 2.5 V and high on/off switching ratio of current (ca. 10(4)). Driven by the superior BPVE, 1 exhibits highly sensitive polarized light detection with a polarization ratio as high as ca. 15, which is far more beyond than those of structural anisotropy-based monocomponent devices. This is the first realization of BPVE-driven polarized light detection in hybrid perovskite ferroelectrics.

Organic–inorganic hybrid perovskites, most remarkably CH3NH3PbI3, have drawn a worldwide range of attention due to their great potential in optoelectronic and photovoltaic applications. Nevertheless, the concern on the toxicity of the lead (Pb) element in chemical composition deserves to be addressed before it is further commercialized. In the present study, a new lead-free hybrid perovskite-like compound, namely (C5H11N3)SbI5 (1, where C5H11N32+ is histaminium), has been synthesized and belongs to the chiral space group, P212121. Structurally, 1 features a distinct perovskite-type architecture of one-dimensional (1D) zigzag chains formed by the corner-sharing SbI6 octahedra with organic histaminium cations linked to the 1D chain framework via strong N–H⋯I hydrogen bonds. It is noteworthy to mention that 1 enables a wide absorption cutoff at 693 nm, corresponding to the narrow optical bandgap (Eg) of ∼1.79 eV. Consequently, the distinct semiconducting behaviors and notable photoresponses in the visible-light range have been observed in 1, of which the photocurrent on/off ratio reaches up to ∼100 under light illumination at 650 nm. Density functional theory calculation reveals that the 1D zigzag chains formed by inorganic SbI6 octahedra determine its electronic structure and photoelectric activities. In addition to the excellent repeatability of photo-induced currents, 1 also demonstrates superior phase stability and thermal stability. We believe that this study throws light on the further exploration of new lead-free hybrid perovskites for optoelectronic applications.

Recently, organic–inorganic hybrid lead halide perovskites have attracted great attention for optoelectronic applications, such as light-emitting diodes, photovoltaics and optoelectronics. Meanwhile, the flexible organic components of these compounds give rise to a large variety of important functions, such as dielectric phase transitions. However, those containing Pb are harmful to the environment in vast quantities. Herein, a lead-free organic–inorganic hybrid, (C6H14N)2BiCl5 (CHA; C6H14N+ is cyclohexylaminium), has been successfully developed. As expected, CHA exhibits an above-room-temperature solid phase transition at 325 K (Tc), which was confirmed by the differential scanning calorimetry measurement and variable temperature single crystal X-ray diffraction analyses. Further analyses indicate the phase transition is mainly governed by the order–disorder transformation of organic cyclohexylaminium cations. Interestingly, during the process of phase transition, the dielectric constant (e′) of CHA shows an obvious step-like anomaly, which displays a low dielectric constant state below Tc and a high dielectric constant state above Tc. Furthermore, variable temperature conductivity combined with theoretical calculations demonstrate the notable semiconducting feature of CHA. It is believed that our work will provide useful strategies for exploring lead-free organic–inorganic semiconducting hybrid materials with above room temperature dielectric phase transitions.

A new iodide layered double perovskite (C3H9NI)4AgBiI8 (IPAB) has been developed based on a short-chain spacer cation, which is the first homologous compound in iodide double perovskites that adopt the Ruddlesden-Popper structure type. Importantly, IPAB is a promising environmentally friendly alternative to the recently rapidly progressing lead halide semiconductors owing to its narrow direct-bandgap of 1.87 eV and excellent stability.

Due to the breakthrough development of layered hybrid perovskites, the multilayered hybrid double perovskites have emerged as outstanding semiconducting materials owing to their environmental friendliness and superior stability. Despite recent booming advances, the realization of above-room temperature ferroelectricity in this fascinating family remains a huge challenge. Herein, when the molecular design strategy of aromatic cation alloying is applied, an above-room temperature "green" bilayered hybrid double perovskite photoferroelectric, (C6H5CH2NH3)2CsAgBiBr7 (BCAB), is successfully developed with a notable saturation polarization of 10.5 μC·cm-2 and high-Curie temperature (Tc ∼ 483 K). Strikingly, such a Tc achieves a new record in multilayered hybrid perovskite ferroelectrics, which extends the ferroelectric working temperature to a high level. Further computational investigation reveals that the high-Tc originated from the high phase-transition energy barrier switched by the rotation of the aromatic cation in the confined environment of the inorganic layers. In addition, benefiting from the attractive polarization and remarkable photoelectric properties, a bulk photovoltaic effect (BPVE) with a prominent zero-bias photocurrent (2.5 μA·cm-2) is achieved. As far as we know, such a high-Tc multilayered hybrid double perovskite ferroelectric is unprecedented, which sheds light on the rational design of an environmental photoferroelectric for high performance photoelectric devices.

Circularly polarized light (CPL)-sensitive direct detection is attracting increasing attention owing to its various optical technology applications and ultracompact device structures. However, current CPL-sensitive direct detection mainly focuses on a single mode, whereas the visible-near-infrared (vis-NIR) dual-modal detection, which is important for improving device sensitivity and night-vision performance, still remains to be explored. Here, for the first time, the vis-NIR dual-modal CPL-sensitive direct detection is presented in bulk single crystals of two-dimensional chiral perovskite (R-BPEA)2PbI4 (R-BPEA = (R)-1-(4-bromophenyl)ethylammonium). Benefiting from the strong light-matter interaction of the layered structure, (R-BPEA)2PbI4 shows a two-photon absorption (TPA) coefficient of up to 55 cm/MW, which almost falls around the highest value of 2D hybrid perovskites. Notably, (R-BPEA)2PbI4 exhibits a high vis-NIR dual-modal CPL-sensitive direct detecting performance under both visible light (520 nm) and NIR light (800 nm), with the on/off ratios of current higher than 103, and the anisotropy factors for photocurrent higher than 0.1. This work will shed light on the design of new chiral semiconductors with a large TPA coefficient and promote their applications in vis-NIR dual-modal CPL-sensitive direct detection.

Halide hybrid perovskites are attracting considerable attention as highly promising candidates for directly sensing X-ray radiation, but it is challenging to realize passive X-ray detection without an external power supply. However, the bulk photovoltaic effect (BPVE) in ferroelectrics promotes the independent separation of photoexcited carriers. Herein, by dimensionality reconstruction of a pure-two-dimensional (P-2D) monolayered perovskite (CH3 OC3 H9 N)2 PbBr4 , we obtained a quasi-two-dimensional (Q-2D) ferroelectric (CH3 OC3 H9 N)2 CsPb2 Br7 . Converting P-2D into Q-2D perovskite stimulates a significant BPVE associated with robust ferroelectricity, as well as an enhanced mobility lifetime product. These features show the potential of the first passive X-ray detector based on ferroelectrics with an impressive sensitivity up to 410 μC Gy-1 cm-2 at zero bias, which is even superior to the value of the state-of-the-art α-Se detector operated at relatively high bias.

Halide double perovskites have recently bloomed as the green candidates for optoelectronic applications, such as X-ray detection. Despite great efforts, the exploration of promising organic-inorganic hybrid double perovskites toward X-ray detection remains unsuccessful. Now, single crystals of the lead-free hybrid double perovskite, (BA)2 CsAgBiBr7 (BA+ is n-butylammonium), featuring the unique 2D multilayered quantum-confined motif, enable quite large μτ (mobility-lifetime) product up to 1.21×10-3 cm2 V-1 . This figure-of-merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CH3 NH3 PbI3 wafers. (BA)2 CsAgBiBr7 crystals also exhibit other intriguing attributes for X-ray detection, including high bulk resistivity, low density of defects and traps, and large X-ray attenuation coefficient. Consequently, a vertical-structure crystal device under X-ray source yields a superior sensitivity of 4.2 μC Gyair-1 cm-2 .

Self-powered photodetection driven by ferroelectric polarization has shown great potential in next-generation optoelectronic devices. Hybrid perovskite ferroelectrics that combine polarization and semiconducting properties have a promising position within this portfolio. Herein, we demonstrate the realization of self-powered photodetection in a new developed biaxial ferroelectric, (EA)2 (MA)2 Pb3 Br10 (1, EA is ethylammonium and MA is methylammonium), which displays high Curie temperature (375 K), superior spontaneous polarization (3.7 μC cm-2 ), and unique semiconducting nature. Strikingly, without an external energy supply, 1 exhibits an direction-selectable photocurrent with fascinating attributes including high photocurrent density (≈4.1 μA cm-2 ), high on/off switching ratio (over 106 ), and ultrafast response time (96/123 μs); such merits are superior to those of the most active ferroelectric oxide BiFeO3 . Further studies reveal that strong inversion symmetry breaking in 1 provides a desirable driving force for carrier separation, accounting for such electrically tunable self-powered photoactive behaviors. This work sheds light on exploring new multifunctional hybrid perovskites and advancing the design of intelligent photoelectric devices.

Organic–inorganic hybrid perovskites, most markedly CH3NH3PbI3, have attracted extensive interest because of their potential use in optoelectronic and photovoltaic applications. Nevertheless, the t...

Inorganic-organic hybrid perovskites, especially two-dimensional (2D) layered halide perovskites, have attracted significant attention due to their unique structures and attractive optoelectronic properties, which open up a great opportunity for next-generation photosensitive devices. Herein, we report a new 2D bilayered inorganic-organic hybrid perovskite, (C6 H13 NH3 )2 (NH2 CHNH2 )Pb2 I7 (HFA, where C6 H13 NH3 + is hexylaminium and NH2 CHNH2 + is formamidinium), which exhibits a remarkable photoresponse under broadband light illumination. Structural characterizations demonstrate that the 2D perovskite structure of HFA is constructed by alternant stacking of inorganic lead iodide bilayered sheets and organic hexylaminium layers. Optical absorbance measurements combined with density functional theory (DFT) calculations suggest that HFA is a direct band gap semiconductor with a narrow band gap (Eg ) of ≈2.02 eV. Based on these findings, photodetectors based on HFA crystal wafer are fabricated, which exhibit fascinating optoelectronic properties including large on/off current ratios (over 103 ), fast response speeds (τrise =310 μs and τdecay =520 μs) and high responsivity (≈0.95 mA W-1 ). This work will contribute to the design and development of new two-dimensional bilayer inorganic-organic hybrid perovskites for high-performance photosensitive devices.

Nonlinear optical (NLO) switches driven by a solid-state structural phase transition have attracted extensive attention; however, above-room-temperature solid-state NLO switch materials are still sparse. Herein, we report an above-room-temperature tin halide organic-inorganic hybrid quadratic NLO switchable material, N-methylpyrrolidinium trichloride stannite ([C5 H12 N]SnCl3 , MPSC). The MPSC crystal exhibits a phase-matchable NLO property that is 1.1 times that of KH2 PO4 (KDP) and NLO switching behavior, changing from a high second harmonic generation (SHG) response to a low SHG response at 383 K, thereby demonstrating its prospective applications in the field of nonlinear optics. Variable-temperature crystal structural analysis combined with theoretical calculations revealed that the large NLO response stems from the inorganic SnCl3 moiety, whereas the high-performance NLO switching properties mainly originate from the order/disorder transformation of the N-methylpyrrolidinium. This work provides a new approach to designing and exploring new high-performance quadratic NLO switches involving tin halide organic-inorganic hybrids.

Two-dimensional (2D) materials have been well developed for polarization-sensitive photodetection, while new 2D members used in shortwave region (>2.5 eV) still remain scarce. The family of 2D hybrid perovskite ferroelectrics, in which the coupling of spontaneous polarization (Ps) and light benefits dissociation of photoinduced carriers, has shown great potential in this portfolio. Here, we report a new 2D hybrid perovskite ferroelectric, [CH3(CH2)3NH3]2(CH3NH3)Pb2Br7 (1), which exhibits a superior Ps of 3.6 μC/cm2 and a relatively wide bandgap (∼2.55 eV). The unique 2D perovskite motif results in an intrinsic anisotropy of optical absorption (the ratio αc/αa ≈ 1.9 at 405 nm), involving its polarization-sensitive activity. As expected, the strongest photoresponses were observed along the c-axis (i.e., parallel to Ps), along with a large dichroism ratio (Iphc/Ipha ≈ 2.0) and highly sensitive detectivity up to ∼109 Jones. Further, crystal-device of 1 shows a fast responding rate (∼20 μs) and excellent antif...

Beryllium-free nonlinear optical (NLO) crystal K3Ba3Li2Al4B6O20F (KBLABF) is a newly reported promising candidate in the generation of the significant UV coherent light. A 17 × 12 × 8 mm3 bulk single crystal is successfully grown with an optimized flux molar ratio. The crystal specific heat increases from 0.65 J·g–1·°C–1 to 0.96 J·g–1·°C–1 with the increasing temperature. Meanwhile, the a-direction thermal conductivity of KBLABF is 1.11 W·m–1·K–1 at 25 °C, which is also equivalent to that of the famous NLO crystal β-BaB2O4 (1.25 W·m–1·K–1). The KBLABF crystal has moderate Vickers hardness along the a-axis and c-axis (165.1 HV0.1 and 257.7 HV0.1, respectively), which indicates it is easy to be cut and polished. Remarkably, the laser damage threshold of KBLABF is 3.32 GW·cm–2 (1064 nm, 8 ns), which even exceeds those of some famous commercial NLO crystals. This result demonstrates that KBLABF is suitable for high-power NLO applications. This work will establish the foundation for the future NLO applications...

Polarization-sensitive photodetection is central to optics applications and has been successfully demonstrated in photodetectors of two-dimensional (2D) materials, such as layered hybrid perovskites; however, achieving high polarization sensitivity in such a photodetector remains extremely challenging. Here, for the first time, we demonstrate a high-performance polarization-sensitive photodetector using single-crystalline 2D/3D perovskite heterostructure, namely, (4-AMP)(MA)2Pb3Br10/MAPbBr3 (MA = methylammonium; 4-AMP = 4-(aminomethyl)piperidinium), which exhibits ultrahigh polarization sensitivity up to 17.6 under self-driven mode. To our knowledge, such a high polarization selectivity has surpassed all of the reported perovskite-based devices, and is comparable to, or even better than, the traditional inorganic heterostructure-based photodetectors. Further studies reveal that the built-in electric field formed at the junction can spatially separate the photogenerated electrons and holes, reducing their recombination rate and thus enhancing the performance for polarization-sensitive photodetection. This work provides a new source of polarization-sensitive materials and insights into designing novel optoelectronic devices., High-quality 2D/3D perovskite heterostructure crystals have been successfully created to demonstrate a self-driven polarization-sensitive photodetector, which achieves a record-high polarization sensitivity up to 17.6.

High color purity and color rendition of 2D luminescent materials have long been pursued for applications in low-dimensional lighting, display, biolabeling, and laser. However, the reported photoluminescence (PL) linewidth of most 2D luminescent materials is about dozens of meV. Herein, a brand-new luminescent system of 2D rare earth (RE) material EuOCl (1.1 nm) with ultra-narrow linewidth (1.2 meV) at room temperature is successfully synthesized via chemical vapor deposition (CVD). The linewidth of EuOCl flakes at room temperature is even narrower than most 2D luminescent materials and heterostructures detected at below 10 K. Impressively, the as-synthesized EuOCl flakes show abnormal temperature-dependent photoluminescent properties, which is absolutely different from the relatively stable 4f-4f transitions in RE owing to shielding from outer shell electrons. J-mixing effect has been successfully applied for this phenomenon. Undoubtedly, luminescent 2D EuOCl flakes will open new territory for the applications of 2D RE materials in the 2D luminescent areas, especially for the applications at room temperature.

Potentially toxic element (PTE) contamination is a common environmental issue in offshore regions worldwide. Water and sediment samples were collected from the Yellow River downstream and adjacent Laizhou Bay to investigate the residues, sources, and ecological risks of 11 typical PTEs (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sc, V, and Zn). The results indicated that the concentrations of PTEs in the sediments decreased from the Yellow River Estuary to the inner Laizhou Bay under the long-term effect of the Yellow River input. Principal component analysis (PCA) identified three potential sources: natural origins, coastal anthropogenic activities (e.g., oil exploration and steel refining), and marine production (e.g., marine aquaculture and transportation). Among the PTEs, Cd was the most significant contaminant, with a contamination factor (CF) of 2.06 ± 0.78. Furthermore, Cd was the most sensitive factor used in evaluating the overall ecological risk using Monte Carlo analysis, with a contribution of up to 96%. Although the overall contamination and risk levels were low in the bay, a higher pollution load index (PLI) and risk index (RI) adjacent to the Yellow River Estuary indicated that the Yellow River remained the primary contributor to the PTEs contamination in the bay.

We investigated the spatiotemporal distributions, risks, and prioritization of 15 widely used antibiotics in Laizhou Bay (LZB). Water samples (145) were collected from LZB and its estuaries and analyzed. Twelve antibiotics, with total concentrations of 241–1450 and 69–289 ng L−1 in estuarine water and seawater, respectively, were detected, with the contributions of norfloxacin, ciprofloxacin, and amoxicillin exceeding 70%. Amoxicillin was firstly determined, which contributed to 20% and 46% of the total antibiotics during summer and spring, respectively. Higher antibiotic concentrations were observed in the sea located adjacent to aquaculture bases and the Yellow River Estuary, which are significantly influenced by mariculture and riverine inputs, respectively. Veterinary antibiotics showed higher total concentrations in summer compared to spring, indicating a higher degree of their usage in mariculture in summer. The antibiotic mixtures posed high risk to algae and low to medium risks to crustaceans and fish. Amoxicillin and norfloxacin were identified as high-risk pollutants. Additionally, amoxicillin and ciprofloxacin showed medium to high resistance development risks. Previous studies on antibiotics in the LZB did not determined amoxicillin and thus underestimated antibiotic contamination, ecological risk, and resistance development risk. Amoxicillin, norfloxacin, and ciprofloxacin should be prioritized in risk management.

Polarized-light detection in solar-blind ultraviolet region is indispensable for optoelectronic applications, whereas new 2D candidates targeted at solar-blind UV range remain extremely scarce. 2D hybrid perovskite ferroelectrics that combine polarization and semiconducting properties have taken a booming position within this portfolio. Here, using the 3D-to-2D dimensional reduction of CH3NH3PbCl3, we successfully designed a multilayered hybrid perovskite ferroelectric, (CH3CH2NH3)2(CH3NH3)2Pb3Cl10 , which shows notable spontaneous polarization and a high Curie temperature (390 K) comparable with that of BaTiO3 (393 K). Strikingly, the wide bandgap (~3.35 eV) and anisotropic absorbance stemming from its intrinsic 2D motif, greatly favor its polarization-sensitive activity in UV region. Consequently, the device displays excellent polarization-sensitive behaviours under 266 nm, along with a large dichroic ratio (~1.38) and high on/off current ratio (~2.3*103 ). This study sheds light on the further exploration of 2D hybrid perovskite ferroelectrics toward new optoelectronic device application.

Ferroelectric semiconductors, combining semiconduction, spontaneous polarization, and photoinduced excitation, show great promise to enhance the performance of solar cells, pressure sensors, and photodetectors. Particularly, organic-inorganic lead halide perovskite ferroelectrics have been explored for their prominent carrier transport properties and structural tunability. However, a high concentration of toxic Pb is a stumbling block for their further application. Here, we present a lead-free hybrid perovskite semiconductor, (C4H9NH3)2(NH3CH3)2Sn3Br10 (1), which exhibits a large spontaneous polarization of 11.76 μC cm-2 at room temperature. Significantly, 1 presents a spontaneous polar ordering transition, similar to the better-known perovskite ferroelectrics, and exhibits ferroelectric phase transition behaviors. To our best knowledge, 1 is the first example of a Sn-based hybrid perovskite semiconductor featuring ferroelectric performance. Mechanistic studies reveal that such ferroelectricity can be attributable to the synergistic effects of ordering of organic cations and stereochemically active lone-pair electrons inducing distortion of inorganic octahedra. This work provides an effective way to explore "green" ferroelectric semiconductors with potentially enhanced energy conversion efficiency.

With existing and emerging technologies urgently demanding the expansion of the laser wavelengths, high-performance nonlinear optical (NLO) crystals are becoming indispensable. Here, a prospective NLO crystal, Li2ZrTeO6, is rationally designed by the element substitution of Nb for Zr and Te from LiNbO3, which has been recognized as one of the most commercial NLO crystals. Li2ZrTeO6 with R3 symmetry inherits the structural merits of LiNbO3 (space group R3 c) and thus meets the requirements for NLO applications, including noncentrosymmetric crystal structure, moderate birefringence, and phase-matchability. Moreover, it can be exploited to achieve more outstanding optical damage resistant behavior (>1.3 GW cm-2), exceeding 22 times that of LiNbO3, which is more suitable for high-energy laser applications. Notably, this compound displays the widest IR absorption edge (7.4 μm) among all of the noncentrosymmetric tellurates reported so far. These excellent attributes suggest that Li2ZrTeO6 is a promising candidate for providing high NLO performance. The substitution of Nb for Zr and Te from LiNbO3 demonstrates a viable strategy toward the rational design of NLO crystals with anticipated properties.

Perovskite ferroelectrics, in which the spontaneous polarization (Ps) is conducive to the separation of photoexcited charge carriers, have shown great potential for self-powered photodetection. Nev...

We present an instructional design strategy to tune the optical absorption ability of organic–inorganic hybrids by managing the internal iodide state. Three bismuth-based hybrids with different internal iodide states were synthesized and display tunable bandgaps from 1.91 eV to 1.87 eV and finally to 1.59 eV.

Fast switching of spontaneous polarization (Ps ) is one of the most essential requirements for ferroelectrics used in the field of data storage. However, in contrast to inorganic counterparts, the low operating frequency (

Soil ingestion by people is an important route of exposure to environmental contaminants. Studies on soil ingestion using tracer mass-balance method are mainly for young children and adults, scarcely for teenagers. In such case, the soil ingestion rate for teenagers recommended by regulators is generally identical to that of adults based on one activity pattern modeling study. However, teenagers are expected to have different soil ingestion exposure via ingestion pathway due to different activity patterns and exposure scenarios. We conducted a pilot study on soil ingestion in 30 teenage children aged 12.0-16.5 years from Hubei Province of China, using the best tracer method, with the results compared with previous soil ingestion studies. The estimated mean and median soil ingestion rates for teenagers in this study based on the best five tracers (Al, Ce, Sc, V, and Y) were 45.2 mg d-1 and 44.8 mg d-1 respectively, with the 95% confidence interval of the mean value ranging from 28.0 mg d-1 to 50.9 mg d-1. These soil ingestion rate estimates were slightly higher than the recommended values for adults by U.S. EPA, but lower than those for Chinese younger children observed in the other similar study. The result in this study is important to access the health risk resulting from exposure to toxic substances in soil via direct soil ingestion pathway by teenagers in China as well as other countries.

Bismuth-based hybrid perovskites have recently attracted great attention for their environmentally friendly processing, chemical stability, and photoresponsive properties. However, most of the known lead-free hybrids show wide band gaps (Eg > 1.9 eV) that afford weak visible-light absorption. Here, we show a newly conceptual design strategy of intercalating triiodide to decrease the prototypic band gap by ca. ∼0.44 eV. A new hybrid semiconducting material of (4-methylpiperidinium)4·I3·BiI6 (MP-T-BiI6), adopting the zero-dimensional (0D) perovskite-like framework, was reconstructed from its prototype of (4-methylpiperidinium)3Bi2I9 (MP-Bi2I9). It is noteworthy that MP-T-BiI6 has a narrow band gap of 1.58 eV, almost comparable to that of CH3NH3PbI3 (∼1.5 eV), which reveals its potential as the highly efficient light absorber. Importantly, its semiconducting properties were solidly confirmed by notable hole mobility (∼12.8 cm2 V–1 s–1), charge-trap density (∼1.13 × 1010 cm–3), and photoconductive behaviors. ...

Organic–inorganic hybrid nonlinear optical (NLO) switches have recently attracted intensive attention as potential candidates for optical applications. Herein, by introducing an organic triamine cation, we obtain a lead-free Bi-based organic–inorganic hybrid, (C4H16N3)BiBr6 (1), which behaves as a promising above-room-temperature modulator of quadratic NLO responses. More importantly, 1 possesses a remarkable NLO switching contrast of up to ∼35 and a notable switching repeatability. Additionally, microscopic single-crystal structural analyses reveal that the coordinated distortion of inorganic [BiBr6]3− octahedra and the order–disorder transformation of the flexible organic triamine cations synergistically contribute to its NLO switching behavior. We believe that this work will promote the development of high-performance NLO switching materials based on devisable organic–inorganic metal–halide hybrids.

Inspired by the breakthrough of three-dimensional hybrid perovskite CH3NH3PbI3, two-dimensional (2D) layered organic–inorganic halide perovskites are emerging as another promising class of hybrid materials for optoelectronic devices, such as photodetectors fabricated on lead halide perovskites. However, the majority of such 2D materials exhibit photosensitivity to visible light, while few candidates have been reported to exhibit visible-blind ultraviolet (UV) photoelectric response. Here, we present a new hybrid material, (1,4-butyldiammonium)CdBr4 (1), in which the corner-sharing CdBr6 octahedra construct the 2D perovskite-type inorganic frameworks. The optical bandgap (Eg) of 1 is estimated to be ∼3.45 eV. Particularly, 1 shows spectral-selective photoconductivity, that is, it is sensitive to UV-light illumination below 360 nm but almost blind to the standard visible light (above 400 nm), disclosing the potential of 1 for visible-blind ultraviolet photodetection. Further theoretical analyses of its electronic structure and energy gap disclose that the inorganic perovskite architecture dominates the optical bandgap. It is believed that this work provides a potential route for the design and fabrication of new 2D hybrid perovskite materials with a UV photoelectric response.

Organic–inorganic hybrid perovskites (most notably CH3NH3PbI3) have recently been demonstrated as high-performance and low cost hybrid materials for photovoltaic application because of their prominent light-absorbing capacity and excellent optoelectronic properties. However, some serious concerns, including the potential toxicity of lead and chemical/phase instability of such hybrid perovskites, have become bottlenecks for their commercialization. In this study, through utilizing an alternative trivalent cation Sb3+ with the ns2np0 electronic configuration, we designed a new lead-free hybrid material, [tert-butylammonium]4[Sb4I16]·2H2O (1), which adopts a zero-dimensional architecture consisting of corner-sharing SbI6 octahedra. It is noteworthy that 1 shows evident light-absorbance with a narrow optical bandgap of ∼2.06 eV, along with positive temperature-dependent conductivity and notable photo-conductive response. Moreover, 1 displays phase stability under ambient conditions, which is superior to that of CH3NH3PbI3. The obtained results suggest the potential of 1 as a light absorbing material for photovoltaic applications.

Endocrine-disrupting chemicals (EDCs) in water are receiving particular attention as they pose adverse effects on aquatic systems, even at trace concentrations. A comprehensive study was conducted on 14 EDCs (five estrogens and nine household and personal care products (HPCPs)) in the water of the urbanized Jiaozhou Bay in the Yellow Sea during summer and winter. Results showed that the total concentration of 14 EDCs ranged from 100 to 658 ng L−1 and 56.7–212 ng L−1 in the estuarine and bay water, respectively. The average total concentration of five estrogens in summer was significantly (p 1) to mollusks, crustaceans, and fish, and low to moderate risks (RQ 1).

Chiral hybrid organic-inorganic perovskites (HOIPs) have been well developed for circularly polarized light (CPL) detection, while new members that target at solar-blind ultraviolet (UV) region remain completely unexplored. Here, an effective design strategy to demonstrate circular polarization-sensitive solar-blind UV photodetection by growing wide-bandgap chiral HOIP [(R)-MPA]2 PbCl4 ((R)-MPA = methylphenethylammonium) single crystals onto silicon wafers, with well-defined heterostructures, is reported. The solid mechanical and electrical connection between the chiral HOIP and silicon wafer results in strong built-in electric field at heterojunction, providing a desirable driving force for separating/transporting carriers generated under CPL excitation at 266 nm. Unexpectedly, during such a transport process, not only the chirality of HOIP crystal is transferred to the heterostructure, but also the circular polarization sensitivity is significantly amplified. Consequently, anisotropy factor of the resultant detectors can reach up to 0.4 at zero bias, which is much higher than that of the pristine single-phase chiral HOIP (≈0.1), reaching the highest among the reported CPL-UV photodetectors. As far as we know, the integration of chiral HOIP crystals with silicon technology is unprecedent, which paves a way for designing boosted-performance CPL detectors in solar-blind UV region as well as for other advanced optoelectronic devices.

Efficient separation and extraction of photo-induced carriers are crucial aspects of efficient semiconductor photocatalytic systems employed for photocatalytic oxidation (PCO) technology. In this study, a Pt-loaded KSr2Nb5O15 composite, as a novel photocatalyst, is reported for gaseous ethylene photo-oxidation, performing excellent PCO activity. Tungsten bronze-type KSr2Nb5O15 (KSNO) with surface oxygen vacancies is prepared by a facile and low-cost molten salt synthesis method at 1200 °C for 6 h and a possible morphology evolution process was proposed. Pt was loaded on KSNO through a facile photodeposition method. The strong metal–support interaction (SMSI) between the Pt nanoparticles and the oxygen-deficient KSNO support is beneficial for superior photocatalytic efficiency and stability toward ethylene photo-oxidation. What's more, the structure and charge transfer path in the synthesized photocatalysts were investigated by X-ray photoelectron spectroscopy (XPS), high-resolution electron microscopy, and electron paramagnetic resonance (EPR).

Organic–inorganic hybrid materials crystallized in noncentrosymmetric (NCS) structures have been receiving considerable attention due to their fascinating physical properties and promising applications. Herein, bulk single crystals of an NCS organometallic compound, MnHg(SCN)4 (MMTC), are grown via a temperature lowering method. The grown crystals present negative uniaxial characteristics with large birefringence, good optical homogeneity and high thermal conductivities. In addition, their Raman scattering properties are measured using spontaneous Raman spectroscopy, which show that the MMTC crystal exhibits a large Raman shift (2148.1 cm−1), narrow line-width (4.468 cm−1) and high Raman gain coefficient (1.753 times higher than that of crystalline YVO4). Moreover, the direct current conductivity, dielectric, and piezoelectric constants of MMTC are also measured, which display that the crystal also possesses a strong piezoelectric response of d15 = 22.7 pC N−1. Furthermore, structure property relationships are discussed on the basis of the structure of the crystal. As a multi-functional crystal, MMTC is a particularly promising candidate for stimulated Raman scattering in the visible and near-infrared regions and piezoelectric applications at room temperature.

Multiaxial molecular ferroelectrics, in which multiple-directional switching of spontaneous polarization creates diverse properties, have shown many intriguing advantages, making them indispensable complements to conventional inorganic oxides. Despite recent blooming advances, multiaxial molecular ferroelectric with bulk photovoltaic effects still remains a huge blank. Herein, we report a biaxial lead halide ferroelectric, EA4Pb3Br10 (1, EA = ethylammonium), which adopts the unique trilayered perovskite motif with a high Curie temperature of ∼384 K. Particularly, for 1, the distinct symmetry breaking with 4/ mmmF mm2 species leads to the emergence of four equivalent polarization directions in the ferroelectric phase. Based on its biaxial nature, the bulk photovoltaic effect of 1 can be facilely tuned between such multiple directions through electric poling. As far as we know, this is the first report on biaxial hybrid perovskite ferroelectric showing directionally tunable photovoltaic activity. This work provides an avenue to control the bulk physical properties of multiaxial molecular ferroelectrics, and highlights their potential for further applications in the field of smart devices.

The occurrence, temporal variation, and spatial variation of antibiotics in coastal bays and estuaries worldwide are not well documented or understood. Fifteen target antibiotics within the five classes of β-lactams, amphenicols, macrolides, fluoroquinolones, and sulfonamides were measured during the summer and winter in the water of Jiaozhou Bay in China, which is a semi-enclosed urbanized bay. Fourteen antibiotics (excluding tylosin) were detected, thus demonstrating the widespread occurrence of their residues in the bay. The total antibiotic concentration ranged from 71.8 ng L−1 to 840 ng L−1 for the estuarine water, which was significantly higher than that for the bay water (38.7–181 ng L−1). The antibiotic classes in the bay water were dominated by fluoroquinolones and β-lactams, which accounted for nearly 90% of the total antibiotic concentration. In addition, amoxicillin contamination was the most prominent among the 14 detected antibiotics as it accounted for ~44% of the total antibiotic concentration. The concentrations of amoxicillin, leucomycin, enrofloxacin, and sulfamonomethoxine in the bay water were usually higher than those reported for coastal bays and estuaries worldwide. The average total antibiotic concentration in the bay water was 84.7 ng L−1 during the summer, which was significantly lower than that during the winter (129.0 ng L−1). This was mainly due to high dilution by runoff during the summer. The florfenicol concentration in the bay water was significantly higher during the summer than in winter due to its higher usage in aquaculture during the summer. Spatially, the total antibiotic concentration (both summer and winter) was higher in the water along the eastern coast of the bay, where the population and hospital densities are high. However, the sum of the veterinary antibiotic concentrations was higher in the northeastern aquaculture area of the bay during the summer. A risk assessment revealed that amoxicillin and enrofloxacin could pose high risks (risk quotient of > 1) to algae in the bay. The synergic effects of pharmaceutical mixtures and the bioaccumulation of antibiotics through the food web should be considered in future studies.

Ferroelectric perovskites have attracted extensive attention recently, because of their fascinating physical properties and novel characteristics owing to the coupling of electric polarization with other functional properties. Herein, single crystals of a bismuth layered-perovskite ferroelectric oxide Bi2WO6 (BWO) were grown by a flux growth method. The grown crystals exhibit platelet morphology with a dominant (001) orientation face. The linear and nonlinear optical properties of BWO crystals were studied in detail. The optical transmittance spectrum shows that BWO is a direct transition semiconductor with a band gap of 2.75 eV and a wide transmission window up to 5 μm. Second harmonic generation (SHG) measurements indicate that the crystal is also a phase matchable nonlinear optical material with a large SHG response of approximately 2.1 times that of KH2PO4. The dielectric and ferroelectric properties measured perpendicular to the ab plane exhibit an oxygen vacancy associated dielectric loss peak and a non-ferroelectric P–E loop. Moreover, we found that the BWO crystal possesses a significant photoresponse in the broadband wavelength of visible light, showing fast response ( 103), excellent flexibility and robustness. The origin of physical properties was interpreted on the basis of the crystal structure combined with density functional theory (DFT) calculations. The BWO single crystals with large SHG response, rich electrical behavior and broad spectral photoresponse are promising materials for nonlinear optical, electrical and optoelectronic applications.