Realizing Nanolime Aqueous Dispersion via Ionic Liquid Surface Modification to Consolidate Stone Relics.

After decades of research in the conservation of cultural heritage, nanolime (NL) has emerged as a potential alternative inorganic material to the frequently used organic materials. However, its poor kinetic stability in water has been a major challenge that restricted its penetration depth through cultural relics and resulted in unsatisfactory conservation outcomes. Here, for the first time, we realize NL water dispersion by modification of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) via a sample aqueous solution deposit method. Our findings indicate that the cation of the ionic liquid (IL) binds strongly to the surface of NL particles (IL-NL) by forming hydrogen bonds with Ca(OH)2 facets. The absorption of IL causes an unexpected significant alteration in the morphology of NL particles and results in a drastic reduction in NL's size. More importantly, this absorption endows NL excellent kinetic stability dispersed into water and implements NL water dispersion, which makes a breakthrough in terms of extreme poor kinetic stability of as-synthesized NL and commercial NL in water. The mechanism driving IL-NL water dispersion is explained by Stern theory. In the context of consolidating weathered stone, the presence of IL may delay carbonation of NL but the penetration depth of IL-NL through stone samples is three times deeper than that of as-synthesized and commercial NLs. Additionally, the consolidation strength of IL-NL is similar to that of as-synthesized NL and commercial NL. Moreover, IL-NL has no significant impact on the permeability, pore size, and microstructure of consolidated stone relics. Our research contributes to the field of NL-related materials and will enhance the dissemination and utilization of NL-based materials in the preservation of water-insensitive cultural heritage.

Investigation of the electronic structural and optical properties of CH3NH3HgI3 crystal.

Based on the first-principles density functional theory, the electronic structure and optical properties of CH3NH3HgI3 crystal were investigated by means of generalized gradient approximation (GGA + U) approach. Then, CH3NH3HgI3 crystal was grown successfully by anti-solvent method, and the UV-vis-NIR spectra of crystal grown were investigated. The results indicate that CH3NH3HgI3 belongs to direct band-gap semiconductor with 2.801 eV of band-gap. The energy level of electrons at the top of the valence band and the bottom of the conduction band is mainly formed by Hg and I, while C, N, and H of CH3NH3+ do not participate in forming the electron configuration near the Fermi level. CH3NH3HgI3 was combined by electrostatic interactions with CH3NH3+ and [HgI4]2-. Their electrostatic interactions lead to distortion of [HgI4]2- tetrahedron and cause the increase of band-gap of CH3NH3HgI3. Moreover, steric hindrance effect of CH3NH3+ spurs [HgI4]2- tetrahedron to form 1D chain structure. The result obtained from the UV-vis-NIR spectra of crystal shows that the band-gap of CH3NH3HgI3 crystal is 2.877 eV, which is good coincident with the calculated gap (2.801 eV). Our discussions on the electronic structural and energy band of crystal suggest that CH3NH3HgI3 can be used as an ultraviolet detector material.

Polydopamine-Modified Nanolime with High Kinetic Stability in Water for the Consolidation of Stone Relics.

As a promising inorganic nanomaterial for the conservation of arenaceous sandstone-based relics such as wall painting, ancient building, stone heritage etc., nanolime (NL) has drawn increasing attention in recent years. Usually, NL needs to be dispersed into an alcoholic solution when applied. Nevertheless, a back-migration phenomenon of NL to the surface of the stone and delayed carbonation of NL enabled by alcohol do not guarantee good preservation effects. Dispersing NL into water can avoid the above issues. However, NL water suspension shows extremely poor kinetic stability, greatly restricting the penetration of NL into stone relics as well as bringing unfavorable impacts to the treated stone heritage. Here, we develop a facile method to synthesize polydopamine (PDA)-modified NL (PDA@NL). Characterizations demonstrate that PDA is uniformly distributed on the surface of NL particles though hydrogen bonds. In addition, the presence of PDA reduces the size of NL particles and achieves the highest specific surface area of NL reported to date. More importantly, water suspension of PDA@NL is far more stable than that of pure NL. The kinetic stability mechanism of PDA@NL in water is attributed to the lessened spatial interactions between NL particles, which is realized by the coverage of PDA on the surface of NL particles. Furthermore, the coverage of PDA does not inhibit carbonation. Within 105 h, NL in PDA@NL completes carbonation and obtains 93.7% calcite, which is comparable to that of NL suspension. Permeability tests prove that the PDA@NL suspension penetrates far deeper through stone specimens compared with the NL suspension. Additionally, PDA@NL presents good consolidation performances for stone samples. Our work opens a new direction for the modification of NL that will boost the studies of NL-modified materials as well as the conservation of cultural heritage.

Sesame water-soluble proteins fraction contains endopeptidases and exopeptidases with high activity: A natural source for plant proteases.

Recently, the interest in the plant proteases has greatly increased. However, only a few of proteases are isolated from the hugely produced oilseeds for the practical utilizations. In this study, the raw sesame milk prepared from peeled sesame seeds was separated into floating, skim, and precipitate fractions by centrifugation. The predominant aspartic endopeptidases and serine carboxypeptidases, which exerted high synergetic activity at pH 4.5-5 and 50-60 °C, were identified in the skim by the liquid chromatography tandem mass spectrometry, Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis, protease inhibitor assay, trichloroacetic acid-nitrogen soluble index (TCA-NSI), and free amino acid analyses. By incubating the mixture (protein content, 2%) of skim and precipitate at pH 4.5 and 50 °C for 6 h, the TCA-NSI and free amino acids achieved to 38.42% and 3148 mg/L, respectively. Moreover, these proteases efficiently degraded the proteins from soybean, peanut, and bovine milk.

Dual Functionalities of Few-Layered Boron Nitrides in the Design and Implementation of Ca(OH)2 Nanomaterials toward an Efficient Wall Painting Fireproofing and Consolidation.

Preserving ancient wall paintings from damage has become a challenge over the years. Nanosized calcium hydroxide (Ca(OH)2) has been identified as a promising material to preserve wall paintings. However, the synthesis of nanosized Ca(OH)2 is extremely difficult. Here, we demonstrate a breakthrough in wall painting protection enabled by boron nitride nanosheets (BNNSs) through strategic synthesis Ca(OH)2-BNNS nanohybrids using an aqueous method. The BNNS have two significant functionalities in the design and implementation of the Ca(OH)2 nanomaterials. First, the introduction of BNNS results in the successful synthesis of uniform and nanosized Ca(OH)2 (∼80 nm) in the nanohybrids, which can be attributed to the supersaturation-induced "etching-stripping" mechanism. More interestingly and importantly, a unique gradient penetration structure is strategically formed when applying Ca(OH)2-BNNS hybrids on the wall paintings, i.e., the BNNS-rich layer will be at the surface of wall painting, whereas Ca(OH)2 nanomaterials prefer to penetrate deep in to the wall paintings. This gradient structure will allow the BNNS-rich layer to protect the wall paintings from fire, which is the first report to date among the protection materials for wall paintings; at the same time, nanosized Ca(OH)2 shows superior wall painting consolidation strength compared to commercial Ca(OH)2 material. These results endow new applications of the newly emerging two-dimensional nanomaterials for protecting cultural heritage.

Au NPs@MoS2 Sub-Micrometer Sphere-ZnO Nanorod Hybrid Structures for Efficient Photocatalytic Hydrogen Evolution with Excellent Stability.

MoS2 shows promising applications in photocatalytic water splitting, owing to its uniquely optical and electric properties. However, the insufficient light absorption and lack of performance stability are two crucial issues for efficient application of MoS2 nanomaterials. Here, Au nanoparticles (NPs)@MoS2 sub-micrometer sphere-ZnO nanorod (Au NPs@MoS2 -ZnO) hybrid photocatalysts have been successfully synthesized by a facile process combining the hydrothermal method and seed-growth method. Such photocatalysts exhibit high efficiency and excellent stability for hydrogen production via multiple optical-electrical effects. The introduction of Au NPs to MoS2 sub-micrometer spheres forming a core-shell structure demonstrates strong plasmonic absorption enhancement and facilitates exciton separation. The incorporation of ZnO nanorods to the Au NPs@MoS2 hybrids further extends the light absorption to a broader wavelength region and enhances the exciton dissociation. In addition, mutual contacts between Au NPs (or ZnO nanorods) and the MoS2 spheres effectively protect the MoS2 nanosheets from peeling off from the spheres. More importantly, efficiently multiple exciton separations help to restrain the MoS2 nanomaterials from photocorrosion. As a result, the Au@MoS2 -ZnO hybrid structures exhibit an excellent hydrogen gas evolution (3737.4 µmol g-1 ) with improved stability (91.9% of activity remaining) after a long-time test (32 h), which is one of the highest photocatalytic activities to date among the MoS2 based photocatalysts.

Correction: Hybrid nanostructures of metal/two-dimensional nanomaterials for plasmon-enhanced applications.

Correction for 'Hybrid nanostructures of metal/two-dimensional nanomaterials for plasmon-enhanced applications' by Xuanhua Li et al., Chem. Soc. Rev., 2016, 45, 3145-3187.

Hybrid nanostructures of metal/two-dimensional nanomaterials for plasmon-enhanced applications.

Hybrid nanostructures composed of graphene or other two-dimensional (2D) nanomaterials and plasmonic metal components have been extensively studied. The unusual properties of 2D materials are associated with their atomically thin thickness and 2D morphology, and many impressive structures enable the metal nanomaterials to establish various interesting hybrid nanostructures with outstanding plasmonic properties. In addition, the hybrid nanostructures display unique optical characteristics that are derived from the close conjunction of plasmonic optical effects and the unique physicochemical properties of 2D materials. More importantly, the hybrid nanostructures show several plasmonic electrical effects including an improved photogeneration rate, efficient carrier transfer, and a plasmon-induced "hot carrier", playing a significant role in enhancing device performance. They have been widely studied for plasmon-enhanced optical signals, photocatalysis, photodetectors (PDs), and solar cells. In this review, the developments in the field of metal/2D hybrid nanostructures are comprehensively described. Preparation of hybrid nanostructures is first presented according to the 2D material type, as well as the metal nanomaterial morphology. The plasmonic properties and the enabled applications of the hybrid nanostructures are then described. Lastly, possible future research in this promising field is discussed.