For VO2-based thermochromic smart windows, high luminous transmittance (Tlum) and solar regulation efficiency (ΔTsol) are usually pursued as the most critical issues, which have been discussed in numerous researches. However, environmental durability, which has rarely been considered, is also so vital for practical application because it determines lifetime and cycle times of smart windows. In this paper, we report novel VO2@ZnO core–shell nanoparticles with ultrahigh durability as well as improved thermochromic performance. The VO2@ZnO nanoparticles-based thermochromic film exhibits a robust durability that the ΔTsol keeps 77% (from 19.1% to 14.7%) after 103 hours in a hyperthermal and humid environment, while a relevant property of uncoated VO2 nanoparticles-based film badly deteriorates after 30 h. Meanwhile, compared with the uncoated VO2-based film, the VO2@ZnO-based film demonstrates an 11.0% increase (from 17.2% to 19.1%) in ΔTsol and a 31.1% increase (from 38.9% to 51.0%) in Tlum. Such integrated thermochromic performance expresses good potential for practical application of VO2-based smart windows.Keywords: durability; excellent performance; smart window; thermochromic; vanadium dioxide; VO2@ZnO;

In this work, a novel biomimetic mat consisting of brush-like polyacrylonitrile (PAN)–hydroxyapatite (Hap) composite fibers was successfully prepared by means of a combination of two simple but effective methods – electrospinning technology and vapor hydrothermal treatment. The backbone of the fiber is the PAN fiber with a diameter of 2–3 μm and the lateral branch is the Hap nanowires. In the biomimetic process, calcium phosphate (TCP) worked as the seed and it transferred to the Hap nanowire in situ and pierced the PAN fiber when it was cultured under a high temperature vapor. This mat is an ideal candidate material for decontaminating metal ions in terms of its convenience of recycling and high specific surface area. The as-obtained materials were characterized with X-ray diffractometry (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Moreover, adsorption experiments of the PAN/Hap composite fiber mat for Pb2+ were conducted. The results exhibited that the maximum adsorption quantity of the composite fiber mat for heavy metal Pb2+ was up to 433 mg g−1, and the Pb2+ adsorption process occurs through a two-step mechanism: rapid surface complexation followed by partial dissolution of hydroxyapatite and precipitation of pyromorphite.

Hierarchical VO2(M)–ZnO dandelions with ZnO nanorods grown radially on VO2(M) nanoparticle cores have been successfully fabricated for the first time. In these dandelions, the VO2(M) NPs were prepared by a TiO2 seed-assisted hydrothermal method and the dandelion-like ZnO nanorods were formed over two steps: heteroseed-induced nucleation and the subsequent heteroepitaxial growth processes. The coupled ZnO could increase the chemical stability of VO2(M) at relatively high temperatures. In addition, the VO2(M)–ZnO composite film with decreased phase transition temperature (Tc = 62.6 °C) simultaneously displayed an enhanced visible transmission (Tvis-l = 52.2%) and solar modulating ability (ΔTsol = 9.3%) as compared with the pure VO2(M) film. Besides, the VO2(M)–ZnO dandelions also exhibited improved photocatalytic performance, likely due to the synergistic effect of the VO2(M)–ZnO heterojunction, unique dandelion-like hierarchical structure and high specific surface area. This is the first report of such a single VO2(M)–ZnO dandelions structure with energy saving and environmental protection effects that offer significant potential for creating a multifunctional smart coating.

Novel VO2(M)/SnO2 heterostructured nanorods are prepared by combining the conventional hydrothermal synthesis method and post annealing process. The results reveal that the nanosized SnO2 particles are not only successfully grown on the surface of the VO2 nanorods but also uniformly distribute on VO2 without aggregation. The existence of the SnO2 nanoparticles inhibits the aggregation during the annealing process and widens the band gap of the VO2 crystals from 0.75 to 1.7 eV. The two aspects can both improve the optical properties of the VO2(M)/SnO2 composite film. The visible transmittance is up to 35.7% and the IR modulation at 2500 nm is more than 56%, which were much higher than the pure VO2(M) film. In addition, the SnO2 layer could reduce the width of the hysteresis from 17.8 to 10.7 °C caused by Sn-doping and enhance the sensitivity. We believe that the VO2(M)/SnO2 heterostructured coating is a good candidate for smart windows.

VO2/Al-O core-shell structure (V/AO) was synthesized by a facile method and its application for thermochromic film on smart window was investigated. Comparisons of thermochromic properties and stabilities in different environments between VO2 and annealed V/AO nanoparticles were made. As a result, VO2 nanoparticle was easily oxidized and lost thermochromic property. In contrast, with the protection provided by Al-O-based shell, the VO2 core remained stable at a high temperature (350 °C in air) and in H2O2 solution. Especially, thermochromic films made by annealed V/AO nanoparticles almost kept thermochromic performance in damp heating environment (T=60 °C, RH=90%) for 20 days while VO2 films lost their thermochromic properties after 3 days. Besides, the degradation progress of VO2 and V/AO nanoparticles in damp heating environment was also explored. Results indicate that Al-O-based shell provides a good protection for the VO2 core originated from the compact structure of shell, which effectively prevents oxygen and water from eroding VO2. In summary, the VO2 nanoparticles coated with Al-O-based shell exhibit a great potential in the application of smart window.

•Graphene was directly grown on the surface of biomedical 316 type stainless steel.•Graphene deposition correlated with metallic Ni and Cr3C2 phases on surface.•Graphene promoted the adhesion and collagen secretion of mesenchymal stem cells.We first report on the direct deposition of transfer-free graphene layer on 316 type biomedical stainless steel (316 BSS) by chemical vapor deposition (CVD) method. The growth of graphene on BSS is considered to correlate with the surface Ni metal and Cr3C2 phases on 316 BSS. Further study shows that the graphene depositing layer can effectively promote the initial adhesion and collagen secretion of bone marrow mesenchymal stem cells on BSS surface. This surface modification with graphene may be applicable to other types of biomedical stainless steel as well and hold promise for stainless steel based biomedical applications.The direct deposition of graphene layer on biomedical 316 stainless steel can effectively enhance its surface biological activity.