RUI: Regenerative Electroless Etching for the Production of Si Nanostructures

纳米结构硅的应用，例如，消费品、纳米医学和可充电电池将受益于以千克到吨的规模经济生产多孔硅粉末，这是国家繁荣所必需的新技术。无电蚀刻，这是一种电化学工艺，被认为具有工业潜力，但需要在其再现性、可控性、纯度、成本和规模方面取得进展。本研究将开发一种新的电化学工艺，称为再生无电蚀刻（ReEtching），这是无电湿法蚀刻的一个新概念，具有生产纳米结构和分级结构半导体的能力。再蚀刻是一种方法，其中使用一种氧化剂来连续再生反应中使用的反应混合物中的低浓度的第二氧化剂。这些研究将把化学蚀刻从一个不可再生的过程转化为一个过程，可以产生任意厚度的均匀多孔膜，产生任意长度的柱撑颗粒，产生结晶或无定形柱，产生具有中孔内的纳米孔或大孔内的纳米孔的分级多孔材料。这项工作是在一个以本科为主的机构进行的，具有很强的国际成分，为参与研究的本科生提供了独特的国际研究经验。再生无电蚀刻（ReEtching）是一种无电湿法蚀刻工艺，具有生产纳米结构和分级结构半导体的能力。再蚀刻在氧化剂（Ox1）用作催化剂以促进半导体与在初级反应中不反应的第二氧化剂（Ox2）之间的反应的工艺中产生纳米结构的半导体。Ox2用于再生能够引发蚀刻的Ox1。反应的程度由Ox2的加入量控制，反应速率由Ox2的注入速率控制。一个具体的例子是通过在HF（aq）中与V2O5（催化剂）和H2O2（再生剂）反应来生产高度发光的纳米晶多孔Si粉末。因为它有助于控制反应速率，而不依赖于反应的程度，ReEtching具有以前无法达到的处理能力。该授权将无电蚀刻从不可再生的过程转变为可以产生任意厚度的均匀多孔膜、产生任意长度的柱撑颗粒、产生结晶或无定形柱、产生具有中孔内部的纳米孔或大孔内部的纳米孔的分级多孔材料的过程。这些介观到纳米结构将通过光致发光来表征，并与材料的结构参数相关。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Applications of nanostructured silicon in, e.g., consumer products, nanomedicine and rechargeable batteries, would benefit from economical production of porous silicon powder on the kilogram-to-ton scale needed in new technologies essential for national prosperity. Electroless etching, which is an electrochemical process that is recognized possessing industrial potential but requiring advances in its reproducibility, controllability, purity, cost and scaling. This research will develop a new electrochemical process called regenerative electroless etching (ReEtching), a new concept in electroless wet etching with the capability of producing nanostructured and hierarchically structured semiconductors. ReEtching is a method in which one oxidant is used to continuously regenerate a low concentration of a second oxidant in the reaction mixture which is used in the reaction. These investigations will transform electroless etching from an irreproducible procedure into a process that can produce homogeneous porous films of arbitrary thickness, produce pillared particles of arbitrary length, produce either crystalline or amorphous pillars, produce hierarchical porous materials with nanopores inside of mesopores or nanopores inside of macropores. This work is carried out in a primarily undergraduate institution with strong international components providing the undergraduates involved in the research a unique international research experience.Regenerative electroless etching (ReEtching) is a electroless wet etching process with the capability of producing nanostructured and hierarchically structured semiconductors. ReEtching produces nanostructured semiconductors in a process which an oxidant (Ox1) is used as a catalytic agent to facilitate reaction between a semiconductor and a second oxidant (Ox2) that would be unreactive in the primary reaction. Ox2 is used to regenerate Ox1, which is capable of initiating etching. The extent of reaction is controlled by the amount of Ox2 added and the rate of reaction is controlled by the injection rate of Ox2. A specific example is the production of highly luminescent, nanocrystalline porous Si powder through reaction with V2O5 (the catalytic agent) and H2O2 (the regeneration agent) in HF(aq). Because it facilitates control the rate of reaction independent of the extent of reaction, ReEtching possesses previously unattainable processing capabilities. This grant will transform electroless etching from an irreproducible procedure into a process that can produce homogeneous porous films of arbitrary thickness, produce pillared particles of arbitrary length, produce either crystalline or amorphous pillars, produce hierarchical porous materials with nanopores inside of mesopores or nanopores inside of macropores. These meso-to-nanostructures will be characterized by photoluminescence and correlated with the materials structural parameters. Extension to other semiconductors will be developed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.