Quantum dots are known to confine electrons within their structure. Whenever they periodically aggregate into arrays and cooperative interactions arise, novel quantum properties suitable for ...technological applications show up. Control over the potential barriers existing between neighboring quantum dots is therefore essential to alter their mutual crosstalk. Here we show that precise engineering of the barrier width can be experimentally achieved on surfaces by a single atom substitution in a haloaromatic compound, which in turn tunes the confinement properties through the degree of quantum dot intercoupling. We achieved this by generating self-assembled molecular nanoporous networks that confine the two-dimensional electron gas present at the surface. Indeed, these extended arrays form up on bulk surface and thin silver films alike, maintaining their overall interdot coupling. These findings pave the way to reach full control over two-dimensional electron gases by means of self-assembled molecular networks.Arrays of quantum dots can exhibit a variety of quantum properties, being sensitive to their spacing. Here, the authors fine tune interdot coupling using hexagonal molecular networks in which the dots are separated by single or double haloaromatic compounds, structurally identical but for a single atom.
The ability to confine light down to atomic scales is critical for the development of applications in optoelectronics and optical sensing as well as for the exploration of nanoscale quantum ...phenomena. Plasmons in metallic nanostructures with just a few atomic layers in thickness can achieve this type of confinement, although fabrication imperfections down to the subnanometer scale hinder actual developments. Here, narrow plasmons are demonstrated in atomically thin crystalline silver nanostructures fabricated by prepatterning silicon substrates and epitaxially depositing silver films of just a few atomic layers in thickness. Specifically, a silicon wafer is lithographically patterned to introduce on‐demand lateral shapes, chemically process the sample to obtain an atomically flat silicon surface, and epitaxially deposit silver to obtain ultrathin crystalline metal films with the designated morphologies. Structures fabricated by following this procedure allow for an unprecedented control over optical field confinement in the near‐infrared spectral region, which is here illustrated by the observation of fundamental and higher‐order plasmons featuring extreme spatial confinement and high‐quality factors that reflect the crystallinity of the metal. The present study constitutes a substantial improvement in the degree of spatial confinement and quality factor that should facilitate the design and exploitation of atomic‐scale nanoplasmonic devices for optoelectronics, sensing, and quantum‐physics applications.
Ultrathin crystalline silver structures of <3 nm in thickness are fabricated by lighographically prepatterning a silicon wafer and subsequently depositing a few atomic layers of metal under ultrahigh vacuum conditions. The method has great flexibility regarding the size and morphology of the structures, which are demonstrated to sustain plasmon resonances with quality factors as high as ten.
Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed ...to explore these pathways from the root's vascular bundle to soil microbial communities. Using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging and¹³C‐phospho‐ and neutral lipid fatty acids, we traced in‐situ flows of recently photoassimilated C of¹³CO₂‐exposed wheat (Triticum aestivum) through arbuscular mycorrhiza (AM) into root‐ and hyphae‐associated soil microbial communities. Intraradical hyphae of AM fungi were significantly¹³C‐enriched compared to other root‐cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co‐location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of¹³C‐photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots. Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes.
Improper disposal of heavy metal-contaminated iron ore tailings poses a significant risk to the surrounding environments. Adding compost and growing ryegrass could be a cost-effective long-term ...solution for remediation of iron ore tailings. We conducted a glasshouse study to investigate the impact of compost amendment (0, 50, 75 and 100% w/w) on growth and accumulation of heavy metals (Cu, Fe, Mn, Pb, Ni and Zn) and As in shoots of perennial ryegrass (Lolium perenne L.) grown in two iron ore tailings (Site A and Site B mines, Pilbara, Western Australia). Ryegrass was harvested 45 and 60 days after sowing. Site A iron ore tailings had total concentrations (mg kg−1) of Fe (449,000), Mn (6900), Zn (109), Co (16) and As (7.3). Site B mine tailings had total concentrations (mg kg−1) of Fe (457,000), Ni (21), Zn (109) and As (45). Both tailings had low cation exchange capacity, organic matter, air porosity and near-neutral pH, but varied in particle size distribution (Site A–clay loam and Site B–sandy loam). Ryegrass germination was higher in the extract of Site B than Site A tailings. Increasing compost-to-tailings ratio increased dry shoot biomass at 45 days. The heavy metal/metalloid concentrations in shoots significantly decreased with increasing compost-to-tailings ratio, except for Cu and Zn. The bioconcentration factor (BCF) of heavy metals (metal concentration in shoot/total metal concentration in substrate) significantly decreased with an increasing proportion of compost in growth substrate. The BCF was >1 for Zn and Cu, and <1 for other heavy metals. A high concentration of organic matter in compost treatments likely contributed to the enhanced mobilisation of Cu and Zn for plant uptake. In contrast, compost stabilised other metals/metalloids in the tailings to decrease their uptake by ryegrass and maintain plant growth despite relatively high Mn, Fe, As and Pb concentrations in iron ore tailings.
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•Physical chemical properties of iron ore tailings improved with addition of 75% w/w compost.•Growth of perennial ryegrass increased many-fold at 75% w/w compost addition to iron ore tailings.•Shoot content of Cu and Zn in perennial ryegrass was elevated with increasing proportion of compost.•Bioconcentration factors decreased with increased proportion of compost added to tailings.
Purpose
Biochar, the by-product of thermal decomposition of organic materials in an oxygen-limited environment, is increasingly being investigated due to its potential benefits for soil health, crop ...yield, carbon (C) sequestration, and greenhouse gas (GHG) mitigation.
Materials and methods
In this review, we discuss the potential role of biochar for improving crop yields and decreasing the emission of greenhouse gases, along with the potential risks involved with biochar application and strategies to avoid these risks.
Results and discussion
Biochar soil amendment improves crop productivity mainly by increasing nutrient use efficiency and water holding capacity. However, improvements to crop production are often recorded in highly degraded and nutrient-poor soils, while its application to fertile and healthy soils does not always increase crop yield. Since biochars are produced from a variety of feedstocks, certain contaminants can be present. Heavy metals in biochar may affect plant growth as well as rhizosphere microbial and faunal communities and functions. Biochar manufacturers should get certification that their products meet International Biochar Initiative (IBI) quality standards (basic utility properties, toxicant assessment, advanced analysis, and soil enhancement properties).
Conclusions
The long-term effects of biochar on soil functions and its fate in different soil types require immediate attention. Biochar may change the soil biological community composition and abundance and retain the pesticides applied. As a consequence, weed control in biochar-amended soils may be difficult as preemergence herbicides may become less effective.
The explosive popularity of small-cell and Internet of Everything devices has tremendously increased traffic loads. This increase has revolutionised the current network into 5G technology, which ...demands increased capacity, high data rate and ultra-low latency. Two of the research focus areas for meeting these demands are exploring the spectrum resource and maximising the utilisation of its bands. However, the scarcity of the spectrum resource creates a serious challenge in achieving an efficient management scheme. This work aims to conduct an in-depth survey on recent spectrum sharing (SS) technologies towards 5G development and recent 5G-enabling technologies. SS techniques are classified, and SS surveys and related studies on SS techniques relevant to 5G networks are reviewed. The surveys and studies are categorised into one of the main SS techniques on the basis of network architecture, spectrum allocation behaviour and spectrum access method. Moreover, a detailed survey on cognitive radio (CR) technology in SS related to 5G implementation is performed. For a complete survey, discussions are conducted on the issues and challenges in the current implementation of SS and CR, and the means to support efficient 5G advancement are provided.
The objective of this current study was to analyze the biochemical compositions of three Malaysian
Channa spp. fish. The proximate analysis revealed that the protein content of
Channa lucius,
Channa ...micropeltes and
Channa striatus was 19.9%, 22.1%, 23.0% (% of dry weight), respectively. The total lipid content was generally high, ranging from 5.7% to 11.9% and crude ash ranged from 1.0% to 1.8%. The major amino acids were glutamic acid, aspartic acid and lysine, ranging from 9.7% to 21.7%, and the most abundant fatty acid in
Channa spp. was C16:0, ranging from 25.6% to 30.4%. The other major fatty acids detected were C22:6, C18:1 and C18:0. The level of arachidonic acid (C20:4) was unusually high in
C. striatus (19.02%). The levels of DHA in these fish would also explain the use of
Channa spp., especially
C. striatus, which has been used for centuries for reducing pain, inflammation and promote wound healing in Malaysia.
Surfaces are at the frontier of every known solid. They provide versatile supports for functional nanostructures and mediate essential physicochemical processes. Intimately related to two-dimensional ...materials, interfaces and atomically thin films often feature distinct electronic states with respect to the bulk, which is key to many relevant properties, such as catalytic activity, interfacial charge-transfer, and crystal growth mechanisms. To induce novel quantum properties via lateral scattering and confinement, reducing the surface electrons' dimensionality and spread with atomic precision is of particular interest. Both atomic manipulation and supramolecular principles provide access to custom-designed molecular assemblies and superlattices, which tailor the surface electronic landscape and influence fundamental chemical and physical properties at the nanoscale. Here the confinement of surface-state electrons is reviewed, with a focus on their interaction with molecular scaffolds created by molecular manipulation and self-assembly protocols under ultrahigh vacuum conditions. Starting with the quasifree two-dimensional electron gas present at the ( 111 ) -oriented surface planes of noble metals, the intriguing molecule-based structural complexity and versatility is illustrated. Surveyed are low-dimensional confining structures in the form of artificial lattices, molecular nanogratings, or quantum dot arrays, which are constructed upon an appropriate choice of their building constituents. Whenever the realized (metal-)organic networks exhibit long-range order, modified surface band structures with characteristic features emerge, inducing noteworthy physical phenomena such as discretization, quantum coupling or energy, and effective mass renormalization. Such collective electronic states can be additionally modified by positioning guest species at the voids of open nanoarchitectures. The designed scattering potential landscapes can be described with semiempirical models, bringing thus the prospect of total control over surface electron confinement and novel quantum states within reach.
Renewing carbon and re-establishing it again in the soil is one of the valuable means to cope with climate change. There are many technologies for carbon apprehension and storage, but the most ...important one gaining attention is biochar technology. So, to carbonize and return different biological materials back to the farmland, a comprehensive study was proposed to characterize and evaluate the carbon (C) mineralization of biochars produced from different animal manures and crop straws. Six types of biochars were prepared from animal manures (poultry litter, swine and cattle manures) and crop straws (rice, soybean, and corn straws). The biochars were analyzed for chemical characteristics (elemental variables, thermal decomposition, cation exchange capacity, pH, electrical conductivity, specific surface area, and surface functional groups) and an incubation experiment was conducted to evaluate C mineralization from soil biochar mixture. Biochars produced from crop straws resulted to have more C as compared to the biochars produced from animal manures. Concentration of nitrogen was low, while P, K, Ca, and Mg were found reasonably higher in all biochars except swine manure biochar. The plant-derived biochars presented lower CO
emissions when incorporated to soil at 1 and 2% of C. Varying but all the biochars prepared represented an alkaline pH. Biochars prepared from the crop straws resulted to have more C, alkaline in nature, high CEC, low CO
emissions, can sequester C and more suitable to enhance the soil fertility in comparison to biochars produced from other sources.
Graphyne (GY) and graphdiyne (GDY)‐based monolayers represent the next generation 2D carbon‐rich materials with tunable structures and properties surpassing those of graphene. However, the detection ...of band formation in atomically thin GY/GDY analogues has been challenging, as both long‐range order and atomic precision have to be fulfilled in the system. The present work reports direct evidence of band formation in on‐surface synthesized metallated Ag‐GDY sheets with mesoscopic (≈1 µm) regularity. Employing scanning tunneling and angle‐resolved photoemission spectroscopies, energy‐dependent transitions of real‐space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate the observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h‐BN, whereas adsorption‐induced in‐gap electronic states evolve at the synthesis platform with Ag‐GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.
ToC Figure illustrates the emergence of unconventional band structure in mesoscopically (≈1 µm) ordered metallated‐graphdiyne single sheet due to combined frontier molecular orbital and lattice symmetries.
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