LDH-based nanomaterials for photocatalytic applications:A comprehensive review on the role of bi/trivalent cations, anions,morphology, defect engineering, memory effect, and heterojunction formation

Using sunlight to drive chemical reactions via photocatalysis is paramount for a sustainable future.Among several photocatalysts,employing layered double hydrides(LDH) for photocatalytic application is most straightforward and desirable owing to their distinctive two-dimensional(2D) lamellar structure and optical attributes.This article reviews the advancements in bimetallic/trimetallic LDHs and various strategies to achieve high efficiency toward an outstanding performing photocatalyst.Firstly,the tuning of LDH components that control the electro nic and structural properties is explained.The tu ning obtained through the adoption,combination,and incorporation of different cations and anions is also explained.The progress of modification methods,such as the adoption of different morphologies,delamination,and defect engineering towards enhanced photocatalytic activities,is discussed in the mainstream.The band engineering,structural characteristics,and redox tuning are further deliberated to maximize solar energy harvesting for different photocatalytic applications.Finally,the progress obtained in forming hierarchical heterostructures through hybridization with other semiconductors or conducting materials is systematically disclosed to get maximum photocatalytic performance.Moreover,the structural changes during the in-situ synthesis of LDH and the stability of LDH-based photocatalysts are deliberated.The review also summarizes the improvements in LDH properties obtained through modification tactics and discusses the prospects for future energy and environmental applications.

Petrogenesis of the Late Cretaceous Tholeiitic Volcanism and Oceanic Island Arc Affinity of the Chagai Arc, Western Pakistan

The Late Cretaceous Chagai arc outcrops in western Pakistan,southern Afghanistan and eastern Iran.It is in the Tethyan convergence zone,formed by northward subduction of the Arabian oceanic plate beneath the Afghan block.The oldest unit of the Chagai arc is the Late Cretaceous Sinjrani Volcanic Group.This is composed of porphyritic lava flows and volcaniclastic rocks,and subordinate shale,sandstone,limestone and chert.The flows are fractionated low-K tholeiitic basalts,basalticandesites,and andesites.Relative enrichment in their LILE and depletion in HFSE,and negative Nb and Ta and positive K,Ba and Sr anomalies point to a subduction-related origin.Compared to MORB,the least fractionated Chagai basalts have low Na_2O,Fe_2O_3~T,CaO,Ti,Zr,Y and ^(87)Sr/^(86)Sr.Rather than an Andean setting,these results suggest derivation from a highly depleted mantle in an intraoceanic arc formed by Late Cretaceous convergence in the Ceno-Tethys.The segmented subduction zone formed between Gondwana and a collage of small continental blocks(Iran,Afghan,Karakoram,Lhasa and Burma) was accompanied by a chain of oceanic island arcs and suprasubduction ophiolites including Semail,Zagros,Chagai-Raskoh,Kandahar,Muslim Bagh,Waziristan and Kohistan-Ladakh,Nidar,Nagaland and Manipur.These complexes accreted to the southern margin of Eurasia in the Late Cretaceous.