Nonlinear optical materials are essential for the development of solid-state lasers. KBeBOF (KBBF) is a unique nonlinear optical material for generation of deep-ultraviolet coherent light; however, its industrial application is limited. Here, we report a new material NHBOF, which exhibits a wide deep-ultraviolet transparent range and suitable birefringence that enables frequency doubling below 200 nm. NHBOF possesses large nonlinear coefficients about 2.5 times that of KBBF. In addition, it is easy to grow bulk crystals and does not contain toxic elements.

Deep-ultraviolet nonlinear optical (DUV NLO) crystals are the key materials to extend the output range of solid-state lasers to below 200 nm. The only practical material KBe BO F suffers high toxicity through beryllium and strong layered growth. Herein, we propose a beryllium-free material design and synthesis strategy for DUV NLO materials. Introducing the (BO F) , (BO F ) , and (BOF ) groups in borates could break through the fixed 3D B-O network that would produce a larger birefringence without layering and simultaneously keep a short cutoff edge down to DUV. The theoretical and experimental studies on a series of fluorooxoborates confirm this strategy. Li B O F is identified as a DUV NLO material with a large second harmonic generation efficiency (0.9×KDP) and a large predicted birefringence (0.07) without layering. This study provides a feasible way to break down the DUV wall for NLO materials.

As important materials in modulating the polarization of light, birefringent crystals have attracted considerable attention and played crucial roles in the field of optical communication and the laser industry. Limited by the transparency range, few birefringent crystals can be used in the deep-ultraviolet (DUV) region, except for α-BaBO (α-BBO). However, the application of α-BBO in the DUV range is restricted by the relatively high cutoff edge and low transmittance rate below 200 nm. In this paper, we design and synthesize a new fluoroborate, NaBOF, by introducing fluorine into borate system. It possesses a short cutoff edge of 169 nm and birefringence larger than 0.080 at 589.3 nm. The NaBOF crystals with sizes up to 3.0 mm × 1.5 mm × 0.2 mm have been grown with good quality by a high-temperature solution method in the open system. First-principles calculations were carried out to understand the optical properties.

Deep-ultraviolet nonlinear optical (DUV NLO) crystals are the key materials to extend the output range of solid-state lasers to below200 nm. The only practical material KBe 2 BO 3 F 2 suffers high toxicity through beryllium and strong layered growth. Herein, we propose ab eryllium-free material design and synthesis strategy for DUV NLO materials. Introducing the (BO 3 F) 4À ,( BO 2 F 2 ) 3À ,a nd (BOF 3 ) 2À groups in borates could break through the fixed3DB-O network that would produce al arger birefringence without layering and simultaneously keep as hort cutoff edge down to DUV.T he theoretical and experimental studies on as eries of fluorooxoborates confirm this strategy.L i 2 B 6 O 9 F 2 is identified as aDUV NLO material with alarge second harmonic generation efficiency (0.9 KDP) and al arge predicted birefringence (0.07) without layering.T his study provides af easible way to break down the DUV wall for NLO materials.

Chemical reactions converting sp 2 to sp 3 hybridization have been demonstrated to be a fascinating yet challenging route to functionalize graphene. So far, it has not been possible to precisely control the reaction sites nor their lateral order at the atomic/molecular scale. The application prospects have been limited for reactions requiring long soaking, heating, electric pulses, or probe tip press.Herein, we demonstrate a spatially-selective photocycloaddition reaction of a two-dimensional (2D) molecular network with defect-free basal plane of single-layer graphene. Directly visualized at the sub-molecular level, the cycloaddition is triggered by ultraviolet irradiation in ultrahigh vacuum, requiring no aid of the graphene Moiré pattern. The reaction involves both [2+2] and [2+4] cycloaddition, with the reaction sites aligned into a 2D extended and well-ordered array, inducing a bandgap for the reacted graphene layer. This work provides a solid base for designing and engineering graphene-based optoelectronic and microelectronic devices.

K B O F , a first fluorooxoborate containing four different units, that is, [BO ] , [BO ] , [BO F] , and [BO F ] , has been designed and synthesized by two different routes. The unique anionic 2∞ [B O F ] layers avoid forming terminal oxygen atoms, which are beneficial to enlarge the band gap. The structure-properties relationship of the title compound is discussed.

Ethanol (C 2 H 5 OH) is an economically ideal C 2 product in electrochemical CO 2 reduction. However, the CO 2 -to-C 2 H 5 OH conversion yield has been rather low and the underlying catalytic mechanism remains vague or unexplored in most cases. Herein, by decorating small Cu 2 S nanocrystals uniform ly on Cu nanosheets, three desirable features are integrated into the electrocatalyst, including a relatively high positive local charge on Cu (Cu δ+ ), abundant interfaces between Cu δ+ and zero-valence Cu 0 , and a non-flat, stepped catalyst surface, leading to the promoted affinity of *CO, decreased *COCO formation barrier, and thermodynamically preferred *CH 2 CHO-to-*CH 3 CHO conversion. As a result, a high partial current density of ∼20.7 mA cm −2 and a Faraday efficiency of 46% for C 2 H 5 OH are delivered at −1.2 V vs reversible hydrogen electrode in an H-cell containing a 0.1 M KHCO 3 solution. This work proposes an efficient strategy for the high-yield CO 2 -to-C 2 H 5 OH conversion, emphasizing the promise for the industrial production of alcohol and related products from CO 2 .

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