Region specific enhancer activity of the identified CNSs.

<p>(<b>A-B</b>) CNS8 and CNS9, located in the vicinity of the <i>lhx5</i> promoter region give rise to broad reporter EGFP expression in the forebrain regions. (<b>C</b>) CNS2 located approximately 50 kb upstream of the <i>lhx5</i> coding region gives rise to restricted EGFP signal in the anterior ventral forebrain. (<b>D</b>) CNS4 located 40 kb upstream of the <i>lhx5</i> coding region, gives rise to restricted EGFP expression in the diencephalic region. (<b>E</b>) Vector construct gives rise to basal non-tissue specific EGFP expression in transient expression assay. Lateral view of the forebrain regions of embryos at 24 hpf, anterior to the left. Scale bar: 50μm.</p

CNS2 contains hypothalamic enhancer activity and responses to FGF signaling.

<p>(<b>A-B</b>) Double in situ hybridization results indicate CNS2 contains hypothalamic enhancer activity. The hypothalamic marker <i>nkx2</i>.<i>1a</i> and <i>nkx2</i>.<i>2b</i> are stained in dark blue, reporter <i>egfp</i> stained in red. (<b>C-D</b>) SU5402 treatment severely reduces CNS2 activity. Vehicle DMSO treated embryos show restricted hypothalamic EGFP reporter expression (pointed by the arrow in C). Embryos treated with the FGF signaling inhibitor SU5402 during the segmentation stage (10-24hpf) show minimal EGFP signals in the hypothalamic region (arrow in D, n = 48/55). (<b>E-F</b>) SU5402 treatment down-regulates endogenous <i>lhx5</i> expression in the hypothalamic region. Endogenous <i>lhx5</i> shows robust expression in the hypothalamic region (pointed by the arrow in E). SU5402 treatment during the segmentation stage down-regulates <i>lhx5</i> expression in the hypothalamic region (arrow in F, n = 25/28). (<b>G</b>) Multiple sequence alignments of the CNS2 region in the five teleost species. The identified FGF downstream factor Pea3 binding site is highlighted in blue. Lateral view of the forebrain regions of embryos at 24 hpf (A-F), anterior to the left. Scale bar: 40μm in A-B; 50μm in C-D.</p

Conserved Noncoding Sequences Regulate <i>lhx5</i> Expression in the Zebrafish Forebrain

<div><p>The LIM homeobox family protein Lhx5 plays important roles in forebrain development in the vertebrates. The <i>lhx5</i> gene exhibits complex temporal and spatial expression patterns during early development but its transcriptional regulation mechanisms are not well understood. Here, we have used transgenesis in zebrafish in order to define regulatory elements that drive <i>lhx5</i> expression in the forebrain. Through comparative genomic analysis we identified 10 non-coding sequences conserved in five teleost species. We next examined the enhancer activities of these conserved non-coding sequences with Tol2 transposon mediated transgenesis. We found a proximately located enhancer gave rise to robust reporter EGFP expression in the forebrain regions. In addition, we identified an enhancer located at approximately 50 kb upstream of <i>lhx5</i> coding region that is responsible for reporter gene expression in the hypothalamus. We also identify an enhancer located approximately 40 kb upstream of the <i>lhx5</i> coding region that is required for expression in the prethalamus (ventral thalamus). Together our results suggest discrete enhancer elements control <i>lhx5</i> expression in different regions of the forebrain.</p></div

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

Over recent years, tremendous efforts have been invested in the search and development of active and durable semiconductor materials for photoelectrochemical (PEC) water splitting, particularly for photoanodes operating under a highly oxidizing environment. CuWO₄ is an emerging candidate with suitable band gap and high chemical stability. Nevertheless, its overall solar-to-electricity remains low because of the inefficient charge separation process. In this work, we demonstrate that this problem can be partly alleviated through designing three-dimensional hierarchical nanostructures. CuWO₄ nanoflake arrays on conducting glass are prepared from the chemical conversion of WO₃ templates. Resulting electrode materials possess large surface areas, abundant porosity and small thickness. Under illumination, our CuWO₄ nanoflake array photoanodes exhibit an anodic current density of ∼0.4 mA/cm² at the thermodynamic potential of water splitting in pH 9.5 potassium borate buffer  the largest value among all available CuWO₄-based photoanodes. In addition, we demonstrate that their performance can be further boosted to >2 mA/cm² by coupling with a solution-cast BiVO₄ film in a heterojunction configuration. Our study unveils the great potential of nanostructured CuWO₄ as the photoanode material for PEC water oxidation

Efficient Photoelectrochemical Hydrogen Evolution on Silicon Photocathodes Interfaced with Nanostructured NiP₂ Cocatalyst Films

Increasing attention has now been focused on the photoelectrochemical (PEC) hydrogen evolution as a promising route to transforming solar energy into chemical fuels. Silicon is one of the most studied PEC electrode materials, but its performance is still limited by its inherent PEC instability and electrochemical inertness toward water splitting. To achieve significant PEC activities, silicon-based photoelectrodes usually have to be coupled with proper cocatalysts, and thus, the formed semiconductor–cocatalyst interface presents a critical structural parameter in the rational design of efficient PEC devices. In this study, we directly grow nanostructured pyrite-phase nickel phosphide (NiP₂) cocatalyst films on textured pn⁺-Si photocathodes via on-surface reaction at high temperatures. The areal loading of the cocatalyst film can be tailored to achieve an optimal balance between its optical transparency and electrocatalytic activity. As a result, our pn⁺-Si/Ti/NiP₂ photocathodes demonstrate a great PEC onset potential of 0.41 V versus reversible hydrogen electrode (RHE), a decent photocurrent density of ∼12 mA/cm² at the thermodynamic potential of hydrogen evolution, and an impressive operation durability for at least 6 h in 0.5 M H₂SO₄. Comparable PEC performance is also observed in 1 M potassium borate buffer (pH = 9.5) using this device

Controllably Interfacing with Ferroelectric Layer: A Strategy for Enhancing Water Oxidation on Silicon by Surface Polarization

Silicon (Si) is an important material in photoelectrochemical (PEC) water splitting because of its good light-harvesting capability as well as excellent charge-transport properties. However, the shallow valence band edge of Si hinders its PEC performance for water oxidation. Generally, thanks to their deep valence band edge, metal oxides are incorporated with Si to improve the performance, but they also decrease the transportation of carriers in the electrode. Here, we integrated a ferroelectric poly­(vinylidene fluoride–trifluoroethylene) [P­(VDF–TrFE)] layer with Si to increase the photovoltage as well as the saturated current density. Because of the prominent ferroelectric property from P­(VDF–TrFE), the Schottky barrier between Si and the electrolyte can be facially tuned by manipulating the poling direction of the ferroelectric domains. The photovoltage is improved from 460 to 540 mV with a forward-poled P­(VDF–TrFE) layer, while the current density increased from 5.8 to 12.4 mA/cm² at 1.23 V bias versus reversible hydrogen electrode

Silicon/Organic Heterojunction for Photoelectrochemical Energy Conversion Photoanode with a Record Photovoltage

Silicon (Si) is a good photon absorption material for photoelectrochemical (PEC) conversion. Recently, the relatively low photovoltage of Si-based PEC anode is one of the most significant factors limiting its performance. To achieve a high photovoltage in PEC electrode, both a large barrier height and high-quality surface passivation of Si are indispensable. However, it is still challenging to induce a large band bending and passivate Si surface simultaneously in Si-based PEC photoanodes so far, which hinders their performance. Here, we develop a simple Si/poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) heterojunction with large band banding and excellent surface passiviation for efficient PEC conversion. A chemically modified PEDOT:PSS film acts as both a surface passiviation layer and an effective catalyst simultaneously without sacrificing band bending level. A record photovoltage for Si-based PEC photoanodes as high as 657 mV is achieved <i>via</i> optimizing the PEDOT:PSS film fabrication process. The density of electron state (DOS) measurement is utilized to probe the passivation quality of the organic/inorganic heterojunction, and a low DOS is found in the Si/PEDOT:PSS heterojunction, which is in accordance with the photovoltage results. The low-temperature solution-processed Si/organic heterojunction photoanode provides a high photovoltage, exhibiting the potential to be the next-generation economical photoanode in PEC applications