Pejova Biljana, Eid Arej, Lari Leonardo, Althumali Ahmad, Šiller Lidija, Kerrigan Adam, Pejov Ljupcho, Lazarov Vlado K
Institute of Chemistry, Faculty of Natural Sciences and Mathematics, SS. Cyril and Methodius University, POB 162, 1000 Skopje, Macedonia.
School of Physics Engineering and Technology, University of York, York, UK.
Nanoscale. 2024 Oct 24;16(41):19485-19503. doi: 10.1039/d4nr03255a.
A surfactant-free ammonia and carbamide precursor-modulated engineering of self-assembled flower-like 3D NiO nanostructures based on ordered β-Ni(OH) and turbostratic Ni(OH)(NO) nanoplate-structured intermediates is reported. By employing complementary structural and spectroscopic techniques, fundamental insights into structural and chemical transformations from intermediates to NiO nanoparticles (NPs) are provided. FTIR, Raman and DSC analyses show that the transformation of intermediates to NiO NPs involves subsequent loss of NO and OH species through a double-step phase transformation at 306 and 326 °C corresponding to the loss of free interlayer ions and HO species, respectively, followed by the loss of chemically bonded OH and NO ions. Transformation to NiO NPs the ammonia route proceeds as single-phase transition, accompanied with a loss of OH species at 298 °C. The full transformation to NiO NPs of both intermediates is achieved at 350 °C through annealing in the air atmosphere. Ammonia-derived NPs maintain nanoflower morphology by self-assembling into nanoplates, which is enabled by HO-mediated adhesion on the NiO NPs' {100} neutral surfaces. Structural transformations of turbostratic Ni(OH)(NO) nanoplates result in the formation of NiO NPs dominantly shaped by inert polar OH-terminated (111) atomic planes, leading to the loss of the initial self-assembled 3D structure. DFT calculations support these observations, confirming that HO adsorbs dissociatively on polar {111} surfaces, while only physisorption is energetically feasible on {100} surfaces. NiO NPs obtained two different routes have overall different properties: carbamide-derived NPs are 3 times larger (15.5 . 5.4 nm), possess a larger band gap (3.6 . 3.2 eV) and are more Ni deficient. The intensity ratio of surface optical (SO) modes to transversal and longitudinal optical modes is ∼40 times higher in the NiO NPs obtained from β-Ni(OH) compared to Ni(OH)(NO)-derived NPs. The SO phonon lifetime is an order of magnitude shorter in NiO obtained from β-Ni(OH), reflecting a much smaller NP size. The choice of a precursor defines the size, morphology, crystallographic surface orientations and band gap of the NiO NPs, with Ni deficiency providing pathways for utilizing them as p-type materials, allowing for the precise nanoengineering of polar and neutral surface-dominated NiO NPs, which is of exceptional importance for use in catalysis.
报道了一种基于有序β-Ni(OH)和乱层状Ni(OH)(NO)纳米板结构中间体的无表面活性剂氨和尿素前驱体调控的自组装花状3D NiO纳米结构工程。通过采用互补的结构和光谱技术，提供了对从中间体到NiO纳米颗粒（NPs）的结构和化学转变的基本见解。傅里叶变换红外光谱（FTIR）、拉曼光谱和差示扫描量热法（DSC）分析表明，中间体向NiO NPs的转变涉及到在306和326℃通过两步相变分别失去NO和OH物种，这分别对应于自由层间离子和HO物种的损失，随后是化学键合的OH和NO离子的损失。通过氨路线向NiO NPs的转变以单相转变进行，在298℃伴有OH物种的损失。通过在空气气氛中退火，两种中间体在350℃时完全转变为NiO NPs。氨衍生的NPs通过自组装成纳米板保持纳米花形态，这是由HO介导的在NiO NPs的{100}中性表面上的粘附实现的。乱层状Ni(OH)(NO)纳米板的结构转变导致形成主要由惰性极性OH终止的(111)原子平面塑造的NiO NPs，导致初始自组装3D结构的丧失。密度泛函理论（DFT）计算支持这些观察结果，证实HO在极性{111}表面上解离吸附，而在{100}表面上只有物理吸附在能量上是可行的。通过两种不同路线获得的NiO NPs具有总体不同的性质：尿素衍生的NPs大三倍（15.5对5.4 nm），具有更大的带隙（3.6对3.2 eV）并且Ni缺陷更多。与Ni(OH)(NO)衍生的NPs相比，从β-Ni(OH)获得的NiO NPs中表面光学（SO）模式与横向和纵向光学模式的强度比高约40倍。从β-Ni(OH)获得的NiO中SO声子寿命短一个数量级，反映出NP尺寸小得多。前驱体的选择定义了NiO NPs的尺寸、形态、晶体表面取向和带隙，Ni缺陷为将它们用作p型材料提供了途径，允许对极性和中性表面主导的NiO NPs进行精确的纳米工程，这对于催化应用尤为重要。
