Helium ion microscopy (HIM) has been used to image mesoporous silica and organosilica for the first time. Images of chiral nematic silica, ethylenesilica, and new benzenesilica reveal the structural organization, pore dimensions and connectivity of these materials on the nanometer length scale.

Naturally occurring biomolecules are sustainable and green precursors for the development of new materials. Within this family of natural materials, cellulose nanocrystals (CNCs) have emerged as one of the most promising materials because of their outstanding physico-chemical properties and the possibility to produce them in large quantities. One key trait of CNCs is their ability to self-assemble into a chiral nematic liquid crystalline phase. In this review, we discuss how templating can be used to transfer the three-dimensional structure of liquid crystalline phases onto solid materials. This is followed by examples that illustrate the fascinating properties and potential applications that arise from the resulting nanostructured materials such as sensing and catalysis. We then summarize efforts to use the liquid crystalline phase of a selection of other biopolymers for templating. While nanocrystalline chitin, having very similar properties to CNCs, has been successfully employed to make a variety of new materials, efforts to template liquid crystal phases of other biomolecules have been met with limited success. However, we discuss virus nanoparticles and collagen as examples to highlight further possibilities for materials research.

Chiral nematic mesoporous organosilica (CNMO) films are functionalized with a mixture of hydrophobic silanes and spiropyran compounds to create freestanding photochromic films that can be used for reversible photo patterning. The mesoporosity and interconnected pore structure of the films imparted by the cellulose nanocrystal template enables a large crosssection of the material to be functionalized. Thus, the materials show intense absorp tion spectra from the tethered spiropyran and rapid color changes when the porous films are irradiated with UV or white light. The spiropyranbound CNMO films behave as reversible sensors where metal binding to the spi ropyran results in visible color changes detectable by the naked eye. These metals can be removed in the presence of ethanol and white light, regener ating the metalfree film. The proofofconcept demonstrated in this paper may help to develop new photochromic displays, security features, and patterns.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201703346. Results and DiscussionEt-CNMO films were synthesized according to the literature procedure [27] using 1,2-bis(trimethoxysilyl)ethane as precursor.

surfactants and inorganic precursors, it has been possible to create mesoporous materials with different symmetries and pore sizes, and diverse compositions. [5,8] For example, using chiral surfactants as a liquid crystal template has created chiral mesoporous materials with twisted helical structures. [13] In 1999, three research groups independently reported on the incorporation of organic groups into mesoporous silica by using (R′O) 3 SiRSi(OR′) 3 precursors in the place of Si(OR) 4 precursors for the sol-gel condensation. [7,9,14] It proved possible to construct periodic mesoporous silica with organic groups directly integrated into the walls of the mesoporous structure. [11,[15][16][17][18][19][20][21][22][23] Sol-gel processing of silicate materials is highly versatile-it can incorporate various types of precursors and can be carried out under a variety of reaction conditions (e.g., variable pH, temperature, concentration, and solvent mixtures). [24] Therefore, mesoporous organosilica materials have attracted increasing interest for applications including catalysis, [1,25] metal scavenging, [26] chromatography, [27] and biomedical applications. [2] Cellulose nanocrystals (CNCs) obtained from sulfuric-acidcatalyzed hydrolysis of biomass are remarkable materials. [28,29] In 1951, Rånby isolated the crystalline regions within plant cellulose microfibers to form colloidal CNCs with nanoscale dimensions. [28] CNCs have impressive mechanical properties that arise from their high crystallinity and large aspect ratios. [30] Remarkably, CNCs also form a chiral nematic liquid crystal in water. [31] This order can be retained upon drying the aqueous suspension to give a colored, iridescent film. [32] The CNCs arrange into a Bouligand structure, where the crystallites themselves are aligned in layers, but twist with a characteristic helical pitch, P. It is the repeating helicoidal structure that leads to diffraction of circularly polarized light from the CNC films. [33] Many researchers are making new materials that take advantage of the unique properties of CNCs. [30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In 2010, we discovered that films of mesoporous silica with chiral nematic structure could be prepared using CNCs as a template. [20] When Si(OR) 4 is condensed with CNCs in water, the resulting composite film contains silica and a chiral nematic assembly of CNCs. CNCs can be removed from the composite materials using pyrolysis, leaving behind thin films of iridescent mesoporous silica with a chiral nematic arrangement of pores inside the glass. These materials are of interest Mesoporous organosilica films with chiral nematic structures are prepared with a bridging urea group and with alkylene bridges, where the length of the alkylene bridge varies from C 1 -C 6 . To synthesize these materials, cellulose nanocrystals (CNCs) are used as liquid crystal templates, which coassemble with the organosilica precursor to give composite materials with a chiral nematic structure of CNCs embedded within. Remova...

A free-base tetraarylporphyrin was synthesized by the [2+2] macrocyclization of a dipyrromethane derivative with 3,4,5-tris(dodecyloxy)benzaldehyde in 61% yield. The free-base porphyrin was metallated with zinc acetate in 94% conversion. The free-base and metallated porphyrins show typical intense Soret bands at 426 and 425 nm, respectively, along with the expected number and intensity of Q-bands. Both porphyrins are also fluorescent and display small Stokes shifts between 13 and 18 nm. Cyclic voltammetry established that each porphyrin underwent two reversible one-electron oxidations at 492 and 725 mV (vs Fc/Fc + (ferrocene reference)) for the free-base porphyrin and at 329 and 589 mV (vs Fc/Fc + ) for the Zn-metalloporphyrin. Electron-transfer rates were also determined to fall between 1.2 Â 10 -3 and 2.4 Â 10 -3 cm s -1 . In addition, spectroelectrochemistry and density functional theory calculations of the oxidized products were carried out to confirm the macrocyclic ring oxidations.Résumé : On a réalisé la synthèse d'une tétraaraylporphyrine sous la forme de base libre avec un rendement de 61 % par macrocyclisation [2+2] d'un dérivé de dipyrrométhane avec du 3,4,5-tris(docécyloxo)benzaldéhyde. On a effectué la métal-lation de la porphyrine à l'état de base libre, avec un rendement de 94 %, par traitement avec de l'acétate de zinc. La base libre et la porphyrine métallée présentent respectivement les bandes typiques intenses de Soret à 426 et à 425 nm ainsi que le nombre et l'intensité attendu des bandes Q. Les deux porphyrines sont aussi fluorescentes et elles présentent de faibles déplacements de Stokes, entre 13 et 18 nm. La voltampérométrie cyclique a permis d'établir que chaque porphyrine subit deux oxydations réversibles à un électron, à 492 et 725 mV (vs Fc/Fc + ) pour la base libre et à 329 et 589 mV (vs Fc/Fc + ) pour la Zn-métalloporphyrine. On a aussi déterminé que les vitesses de transfert d'électron se situent entre 1,2 Â 10 -3 et 2,4 Â 10 -3 cm s -1 . De plus, de la spectroélectrochimie et des calculs d'après la théorie de la fonctionnelle de la densité effectués sur les produits oxydés pour confirmer les oxydations des noyaux macrocycliques.Mots-clés : porphyrinoïdes, électrochimie, chimie d'oxydoréduction, photochimie, calculs de la fonctionnelle de la densité.[Traduit par la Rédaction]