Effect of iron and nanolites on Raman spectra of volcanic glasses:A reassessment of existing strategies to estimate the water content

Global peatlands are a valuable but vulnerable resource. They represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles. Peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties. Pore sizes in undecomposed peat can exceed 5 mm, but significant shrinkage occurs during dewatering, compression and decomposition, reducing pore-sizes. The structure of peat soil consists of pores that are open and connected, dead-ended or isolated. The resulting dual-porosity nature of peat soils affects water flow and solute migration, which influence reactive transport processes and biogeochemical functions. Advective movement of aqueous and colloidal species is restricted to the hydrologically active (or mobile) fraction of the total porosity, i.e. the open and connected pores. Peat may attenuate solute migration through molecular diffusion into the closed and dead-end pores, and for reactive species, also through sorption and degradation reactions. Slow, diffusion-limited solute exchanges between the mobile and immobile regions may give rise to pore-scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils. While new information on the diversity and functionalities of peat microbial communities is rapidly accumulating, the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils. In this paper, we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage, flow and the migration of solutes. This paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils

A chemical threshold controls nanocrystallization and degassing behaviour in basalt magmas

An increasing number of studies are being presented demonstrating that volcanic glasses can be heterogeneous at the nanoscale. These nano-heterogeneities can develop both during viscosity measurements in the laboratory and during magma eruptions. Our multifaceted study identifies here total transition metal oxide content as a crucial compositional factor governing the tendency of basalt melts and glasses towards nanolitization: at both anhydrous and hydrous conditions, an undercooled trachybasalt melt from Mt. Etna readily develops nanocrystals whose formation also hampers viscosity measurements, while a similar but FeO- and TiO2-poorer basalt melt from Stromboli proves far more stable at similar conditions. We therefore outline a procedure to reliably derive pure liquid viscosity without the effect of nanocrystals, additionally discussing how subtle compositional differences may contribute to the different eruptive styles of Mt. Etna and Stromboli

Multiple Routes to Smart Nanostructured Materials from Diatom Microalgae: A Chemical Perspective

Diatoms are unicellular photosynthetic microalgae, ubiquitously diffused in both marine and freshwater environments, which exist worldwide with more than 100 000 species, each with different morphologies and dimensions, but typically ranging from 10 to 200 μm. A special feature of diatoms is their production of siliceous micro- to nanoporous cell walls, the frustules, whose hierarchical organization of silica layers produces extraordinarily intricate pore patterns. Due to the high surface area, mechanical resistance, unique optical features, and biocompatibility, a number of applications of diatom frustules have been investigated in photonics, sensing, optoelectronics, biomedicine, and energy conversion and storage. Current progress in diatom-based nanotechnology relies primarily on the availability of various strategies to isolate frustules, retaining their morphological features, and modify their chemical composition for applications that are not restricted to those of the bare biosilica produced by diatoms. Chemical or biological methods that decorate, integrate, convert, or mimic diatoms' biosilica shells while preserving their structural features represent powerful tools in developing scalable, low-cost routes to a wide variety of nanostructured smart materials. Here, the different approaches to chemical modification as the basis for the description of applications relating to the different materials thus obtained are presented

Biosilica from diatoms microalgae: Smart materials from bio-medicine to photonics

Diatoms microalgae can be regarded as living factories producing nanostructured and mesoporous biosilica shells (frustules) having a highly ordered hierarchical architecture. These unique, morphological, chemical and mechanical properties make diatoms' biosilica a very attractive nanomaterial for a wide variety of applications. Methods of purification of frustules that preserve their nanostructured morphology have been set up as well as in vivo or in vitro chemical modification protocols of the biosilica with functional molecules to generate biohybrid active materials for photonics, sensing, drug delivery and electronics. Herein we describe, with some selected examples, the great variety of applications envisaged for native and modified frustules, highlighting the material scientists' benefit to avail of nature in the construction of highly ordered biohybrid architectures for nanotechnology. New concepts for the biotechnological production of nanomaterials are opened by the use of diatoms as living factories

Mussel Inspired Polydopamine as Silica Fibers Coating for Solid-Phase Microextraction

Commercial solid-phase microextraction fibers are available in a limited number of expensive coatings, which often contain environmentally harmful substances. Consequently, several different approaches have been used in the attempt to develop new sorbents that should possess intrinsic characteristics such as duration, selectivity, stability, and eco-friendliness. Herein we reported a straightforward, green, and easy coating method of silica fibers for solid-phase microextraction with polydopamine (PDA), an adhesive, biocompatible organic polymer that is easily produced by oxidative polymerization of dopamine in mild basic aqueous conditions. After FT-ATR and SEM characterization, the PDA fibers were tested via chromatographic analyses performed on UHPLC system using biphenyl and benzo(a)pyrene as model compounds, and their performances were compared with those of some commercial fibers. The new PDA fiber was finally used for the determination of selected PAHs in soot samples and the results compared with those obtained using the commercial PA fiber. Good reproducibility, extraction stability, and linearity were obtained using the PDA coating, which proved to be a very promising new material for SPME

Supramolecular Biohybrid Construct for Photoconversion Based on a Bacterial Reaction Center Covalently Bound to Cytochrome c by an Organic Light Harvesting Bridge

A supramolecular construct for solar energy conversion is developed by covalently bridging the reaction center (RC) from the photosynthetic bacterium Rhodobacter sphaeroides and cytochrome c (Cyt c) proteins with a tailored organic light harvesting antenna (hCy2). The RC-hCy2-Cyt c biohybrid mimics the working mechanism of biological assemblies located in the bacterial cell membrane to convert sunlight into metabolic energy. hCy2 collects visible light and transfers energy to the RC, increasing the rate of photocycle between a RC and Cyt c that are linked in such a way that enhances proximity without preventing protein mobility. The biohybrid obtained with average 1 RC/10 hCy2/1.5 Cyt c molar ratio features an almost doubled photoactivity versus the pristine RC upon illumination at 660 nm, and similar to 10 times higher photocurrent versus an equimolar mixture of the unbound proteins. Our results represent an interesting insight into photoenzyme chemical manipulation, opening the way to new eco-sustainable systems for biophotovoltaics

Perspectives on applications of nanomaterials from shelled plankton

Biomineralization ubiquitously occurs in plankton, featuring hierarchically nanostructured shells that display several properties that benefit their host survival. Nanostructures' shapes and many of these properties are tunable through in vitro or in vivo modification of microorganisms, making their shells very appealing for applications in materials sciences. Despite the abundance of shell-forming species, research has focused mainly on diatoms and coccolithophores microalgae, with current scientific literature mostly targeting the development of photonic, biomedical and energy storage/conversion devices. This prospective article aims to critically overview potentialities of nanomaterials from biomineralizing plankton, possible outcomes and technological impact relevant to this technology

Ethylenediammine is not detrimental to the photoactivity of the bacterial photosynthetic reaction center

Abstract: The effect of the exposure of the photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides to ethylenediamine (EDA) was investigated by transient absorption spectroscopy and UV–Visible-Near Infrared absorption spectroscopy. We show that EDA is not detrimental to the photoactivity of the protein even at pH close to 12. EDA instead appears to inhibit the secondary quinone binding site with an apparent binding constant of 19.05 mM−1. Graphic abstract: [Figure not available: see fulltext.