Fine-tuning Of Surface Chemistry Research Articles

Nanoscale Zirconium-Abundant Surface Layers on Lithium- and Manganese-Rich Layered Oxides for High-Rate Lithium-Ion Batteries.

Battery performance, such as the rate capability and cycle stability of lithium transition metal oxides, is strongly correlated with the surface properties of active particles. For lithium-rich layered oxides, transition metal segregation in the initial state and migration upon cycling leads to a significant structural rearrangement, which eventually degrades the electrode performance. Here, we show that a fine-tuning of surface chemistry on the particular crystal facet can facilitate ionic diffusion and thus improve the rate capability dramatically, delivering a specific capacity of ∼110 mAh g-1 at 30C. This high rate performance is realized by creating a nanoscale zirconium-abundant rock-salt-like surface phase epitaxially grown on the layered bulk. This surface layer is spontaneously formed on the Li+-diffusive crystallographic facets during the synthesis and is also durable upon electrochemical cycling. As a result, Li-ions can move rapidly through this nanoscale surface layer over hundreds of cycles. This study provides a promising new strategy for designing and preparing a high-performance lithium-rich layered oxide cathode material.

A novel generation of hybrid photochromic vinylidene-naphthofuran silica nanoparticles through fine-tuning of surface chemistry

Novel photochromic 1-vinylidene-naphtho[2,1-b]furan derivatives (VNF-1 and VNF-2) were successfully anchored onto silica nanoparticles (SiO2 NPs) through direct adsorption (SiO2@VNF-1) and covalent post-grafting (SiO2@VNF-2). SiO2 NPs with different sizes (15 ± 3 and 123 ± 7 nm) and surface chemistry (pHpzc in the range of 5-9) were used, offering a wide range of possibilities to fabricate tailor-made photochromic materials. The characterization of VNF-based SiO2 NPs confirmed the efficient VNF immobilization and the integrity of both organic and inorganic components. The photochromic behavior of these new nanoparticles indicates that silica surface acidity and the type of VNF immobilization strategy (adsorption vs. covalent grafting) were crucial factors for the occurrence of photochromism in the VNF-based SiO2 NPs. Upon UV (λ = 365 nm) or sunlight exposure for 1 min, only the SiO2@VNF-1 nanomaterials prepared by direct VNF adsorption onto SiO2 NPs with pHpzc ≈ 6.0 showed direct and reversible photochromic properties, developing fast (in seconds) and intense salmon and violet coloration, with high values of total color difference () and optical densities (ΔOD = 0.14-0.25). In contrast, all nanomaterials prepared by covalent grafting of VNF-2 onto SiO2 NPs (SiO2@VNF-2) did not exhibit photochromism. In the case of the photochromic SiO2@VNF-1 NPs, the decoloration process followed a bi-exponential decay with fast rate constants (k1 = 1.6 × 10-1-1.6 min-1 and k2 = 9.1 × 10-3-1.3 × 10-1 min-1), which were responsible for the loss of coloration in less than 10 min. Furthermore, they presented very good resistance to fatigue, showing reversibility between the colored/uncolored states without significant loss of their performance for at least 8 successive UV/dark cycles.

Correction: Towards a fine-tuning of surface chemistry in aligned carbon nanotubes induced by nitrogen plasma discharge post-treatment: a combined microscopic and spectroscopic study

Correction for ‘Towards a fine-tuning of surface chemistry in aligned carbon nanotubes induced by nitrogen plasma discharge post-treatment: a combined microscopic and spectroscopic study’ by Laith Hussein et al., RSC Adv., 2016, 6, 13088–13100.

Towards a fine-tuning of surface chemistry in aligned carbon nanotubes induced by nitrogen plasma discharge post-treatment: a combined microscopic and spectroscopic study

The selective control of surface chemistry in individual nanotubes inside the VACNT arrays using a dry process without damaging their structure is a key challenge in developing active materials for many electronic, photonic and catalytic applications.