Silicon Transport Research Articles

Chemical determination of silica in seagrass leaves reveals two operational silica pools in Zostera marina

Silicon is a major driver of global primary productivity and CO2 sequestration, and is a beneficial element for the growth and environmental stress mitigation of many terrestrial and aquatic plants. However, only a few studies have examined the occurrence of silicon in seagrasses, and its function within seagrass ecosystems and the role of seagrasses in silicon cycling remain largely unexplored. This study uses for the first time two methods, the wet-alkaline digestion and the hydrofluoric acid digestion, to quantify silicon content in seagrass leaves using the species Zostera marina and elaborates on the potential role of silicon in seagrass biogeochemistry and ecology, as well as the role of seagrass ecosystems as a silicon reservoir. The results revealed that seagrass leaves contained 0.26% silicon:dry-weight, which is accumulated in two forms of silica: a labile form digested with the alkaline method and a resistant form digested only with acid digestion. These findings support chemical digestions for silicon quantification in seagrass leaves and provide new insights into the impact of seagrasses on the marine silicon cycle. Labile silica will be recycled upon leaf degradation, benefiting siliceous organisms, while refractory silica will contribute to the ecosystem’s buried silica stock and coupled carbon sequestration. In the Bay of Brest (France), the seagrass silicon reservoir was estimated at 0.18 ± 0.07 g Si m⁻2, similar to that of benthic diatoms, underscoring the potential role of seagrasses in silicon biogeochemistry in the land–ocean continuum, where they might act as a buffer for silicon transport to the ocean.

Efficient spectrally-resolved electron transport for thermal property prediction

Predicting thermal conductivity from the transport of electrons is a complex challenge which must be addressed for the design and production of nano- and microscale devices. In this work, we describe our progress in simulating thermal electron transport in silicon for the purposes of thermal conductivity prediction. We describe a new approach to solve the Boltzmann transport equation for electrons, using the self-adjoint angular flux formulation coupled with a novel approach in computing electron temperature and Fermi energy which does not require the combination of linear “inner” and nonlinear “outer” iterations. The electron Boltzmann transport equation is discretized in space by the continuous finite element method, and in angle by discrete ordinates, using the Multiphysics Object Oriented Simulation Environment, implemented in the radiation transport code Griffin. We rely on density functional theory calculations to provide material properties such as electron density of states, energy, wavevector, mean free path, and more. Our method couples the discrete electron groups through temperature and Fermi energy, to simulate thermal electron transport (in the absence of electric fields) for the prediction of thermal conductivity, thermal and electrical flux, and heat capacity. We show effective thermal conductivity and temperature results for different sized 2D slabs of Si at 300 K, which agree with other studies in the literature. Additionally, we report Fermi energy and efficiency of this method using the generalized minimal residual method.

Silicon uptake and transport mechanisms in plants: processes, applications and challenges in sustainable plant management.

Silicon (Si) is an abundant element in the earth's crustessential for plant growth and development. Recentstudies silicon's potential for improving plant resilience to numerous biotic stressors, notably fungal diseases. This review seeks to offer a comprehensive understanding of the processes and advantages of silicon-induced systemic resistance in plants, with a special focus on its interactions with fungal pathogens. Furthermore, we investigate the effect of silicon on plant physiological and biochemical changes, such as enhanced lignification, strengthening of physical barriers, and activation of antioxidant systems. Additionally, we examine the influence of silicon on microbial populations within the rhizosphere and its effects on mycorrhizal associations. Lastly, we discuss the potential applications and challenges of integrating silicon-based strategies in sustainable plant disease management. This review provides valuable insights into using silicon as a novel approach to enhance plant systemic resistance against fungal pathogens, offering prospects for developing eco-friendly and efficient agricultural practices.

Transcriptomic analysis reveals the mechanism underlying salinity-induced morphological changes in Skeletonema subsalsum.

Diatom cell walls are diverse and unique, providing the basis for species identification and supporting the ecological and economic value of diatoms. However, these important structures sometimes change in response to environmental fluctuations, especially under salt adaptation. Although studies have shown that salinity induces morphological plasticity changes in diatom cell walls, most research has focused on physiological responses rather than molecular mechanisms. In this study, Skeletonema subsalsum was cultured under four salinity conditions (0, 3, 6, 12). Through morphological and physiological methods, we found that salinity increased the cell diameter, protrusion lengths, distance between adjacent cells (DBCs), and nanopore size, while reducing cell height and silicification degree. To further investigate the mechanism underlying morphological changes in S. subsalsum, complementary transcriptome analysis was performed. In total, 20,138 differentially expressed genes (DEGs) were identified among the four treatments. Among them, 231 DEGs were screened and found to be closely associated with morphological changes, of which 107 were downregulated and 124 were upregulated. The findings demonstrated that elevated salinity inhibited silicon transport and deposition via downregulating the expression of DEGs involved in functions including chitin metabolism, putrescine metabolism, and vesicle transport, resulting in reduced silicon content and cell height. Increased salinity promoted the expression of DEGs related to microtubules (MTs), actin, and ubiquitin, which synchronously induced morphological changes. These findings provide a more comprehensive understanding of the salt tolerance of algae and a foundation for future studies on cell wall morphogenesis.

Silicon isotopes reveal the impact of fjordic processes on the transport of reactive silicon from glaciers to coastal regions

Accelerated mass loss from the Greenland Ice Sheet leads to retreating glaciers and enhanced freshwater runoff to adjacent coastal regions, potentially providing additional essential nutrients, such as silicon, to downstream primary producers. However, the role of fjordic sediments in modulating the supply of silicon from glacial environments to marine ecosystems remains poorly constrained, particularly for the quantification of silicon fluxes from the sediments into overlying waters in high-latitude fjordic systems. In this study, we use the concentration and stable isotopic composition of dissolved silicon in pore waters and core-top waters, and amorphous silica phases (such as glacially-derived amorphous silica) in sediments and suspended particulate matter, collected from two fjords in the southwest Greenland margin to address this knowledge gap. We combine downcore observations with core incubations and isotope mass balance approaches to assess the benthic flux of dissolved silicon and deconvolve potential contributors to this flux during early diagenesis. Our results suggest that molecular diffusion only accounts for a portion of benthic dissolved silicon transport. Relative to surrounding continental shelves and highly-productive open ocean waters, the estimated benthic dissolved silicon flux at our sites is smaller in magnitude, supporting the role of fjords as a ‘trap’ for reactive silicon in high-latitude systems.

Composition and transport of silicon in rivers of the Bohai rim with implications for the coastal environment

The transportation of silicon (Si) by rivers to the sea plays a vital role as an external source of Si budget for coastal environments, impacting the carbon cycle in the ocean. Nevertheless, the transport of reactive silica (RSi) from small rivers to the coastal sea has been frequently disregarded in scientific investigations. This research focused on 24 rivers situated along the Bohai Sea (BS) Rim, encompassing small rivers (SR) and the largest river in the region, the Yellow River (YR), to analyze their concentrations and fluxes of dissolved silicate (DSi), biogenic silica (BSi) and other amorphous forms of Si. The findings indicated seasonal variations in DSi concentrations, with higher levels observed during the flood season. Annually, approximately 105 × 103 t DSi and 200 × 103 t BSi were transported to the BS, with SR and YR contributing equally to the total riverine BSi flux. The smaller rivers were found to increase the BSi fraction of RSi due to elevated biological fixation. The ratios of average DSi and BSi fluxes to the river watershed area of SR were 3.5 and 6 times higher, respectively, compared to those of YR. SR play a critical role in the terrestrial Si export in the BS Rim. Human activities have led to significant deviations in the Si ratios to nitrogen and phosphorus in these rivers from the Redfield-Brzezinski ratio. This discrepancy could impact the phytoplankton community, primary production, and the environment of the BS. The study highlights the substantial contribution of SR to coastal environments, particularly in semi-closed marine environments like the BS.

Enhanced heat transport in amorphous silicon via microstructure modulation

Amorphous materials are extensively utilized in electronic devices due to their exceptional optoelectronic properties. However, the disorder nature of their structure leads to a low thermal conductivity, which hampers effective thermal management of electronic devices. Understanding the correlation between microstructures and thermal transport in amorphous materials is crucial for modulating their thermal conductivity (TC). In this work, we performed molecular dynamics simulations in conjunction with an accurate machine learning potential to generate various amorphous Si (a-Si) structures through an atomic deposition procedure. The results demonstrate that increasing the substrate temperature during deposition procedure or conducting high-temperature secondary annealing significantly improves the short-range and mid-range ordering of a-Si. This improved structural ordering reduces atomic stresses and consequently boosts the TC of a-Si by more than 40 %. The spectral TC analysis reveals that elevated substrate temperature and annealing temperature primarily improve the TC of modes below 8 THz, corresponding to propagation and diffusion modes. Our work provides not only a strategy to tune the TC of amorphous materials via the deposition process, but also a deeper understanding of heat transport mechanisms in these materials.

Effect of Trap-Assisted Tunneling on Carrier Transport in Silicon Oxide/Polycrystalline Silicon

Effect of Trap-Assisted Tunneling on Carrier Transport in Silicon Oxide/Polycrystalline Silicon

Silicon transport and its “homeostasis” in rice

Silicon transport and its “homeostasis” in rice

Hot-hole transport and noise phenomena in silicon at cryogenic temperatures from first principles

Hot-hole transport and noise phenomena in silicon at cryogenic temperatures from first principles

How Human Activities Are Disrupting the Silicon Cycle

Dissolved silicon is an essential nutrient for the growth of various ocean organisms that need it to build their skeletons. Most of the dissolved silicon that sustains these organisms comes from the breakdown of silicon-containing rocks on land. In recent decades, human activities have greatly disturbed the transport of silicon from land to ocean. For example, dams built to generate electricity can interrupt the transport of dissolved silicon and starve downstream areas. Fertilizers and other human pollution add large amounts of non-silicon nutrients to rivers, lakes, and reservoirs, which can stimulate organisms to grow and use up silicon before it reaches the ocean. In addition, consequences of climate change can also impact the silicon cycle. In this article, we explain how human activities have disturbed the silicon cycle and discuss how climate change may affect it in the future.

Gene Duplication, Shifting Selection, and Dosage Balance of Silicon Transporter Proteins in Marine and Freshwater Diatoms.

Numerous factors shape the evolution of protein-coding genes, including shifts in the strength or type of selection following gene duplications or changes in the environment. Diatoms and other silicifying organisms use a family of silicon transporters (SITs) to import dissolved silicon from the environment. Freshwaters contain higher silicon levels than oceans, and marine diatoms have more efficient uptake kinetics and less silicon in their cell walls, making them better competitors for a scarce resource. We compiled SITs from 37 diatom genomes to characterize shifts in selection following gene duplications and marine-freshwater transitions. A deep gene duplication, which coincided with a whole-genome duplication, gave rise to two gene lineages. One of them (SIT1-2) is present in multiple copies in most species and is known to actively import silicon. These SITs have evolved under strong purifying selection that was relaxed in freshwater taxa. Episodic diversifying selection was detected but not associated with gene duplications or habitat shifts. In contrast, genes in the second SIT lineage (SIT3) were present in just half the species, the result of multiple losses. Despite conservation of SIT3 in some lineages for the past 90-100 million years, repeated losses, relaxed selection, and low expression highlighted the dispensability of SIT3, consistent with a model of deterioration and eventual loss due to relaxed selection on SIT3 expression. The extensive but relatively balanced history of duplications and losses, together with paralog-specific expression patterns, suggest diatoms continuously balance gene dosage and expression dynamics to optimize silicon transport across major environmental gradients.

Theoretical study on structural, electronic, transport and thermoelectric properties of Si/Ge doped graphene

First-principles simulations are used in this study to show the structural, electronic, transport, and thermoelectric features of silicon and germanium-doped monolayer graphene. We employed a supercell of 2 × 2 × 1 graphene that contains 8 C atoms. One C atom was substituted by Si/Ge at a doping concentration of 12.5 %. The results obtained show that the band gap of pure graphene may be effectively opened and converted into a direct bandgap semiconductor material by replacing the C atom with Si/Ge atoms. Phonon dispersion provides a representation of the dynamical stability of all three structures. Graphene's thermal conductivity is also decreased when heteroatoms are added. Additionally, the Seebeck coefficient, the power factor, the electrical conductivity, and the figure of merit of pure, silicon, and germanium-doped graphene were investigated. This study offers a theoretical basis for using a heteroatom-doping process to improve the performance of graphene's electronic, transport, and thermoelectric characteristics.

Cadmium accumulation in brown rice (Oryza sativa L.) depends on environmental factors and nutrient transport: A three-year field study

Cadmium (Cd) accumulation in brown rice is a complex process in agroecosystems and is influenced by multiple factors, such as climate, soil properties, and nutrient transport. However, during the Cd transport process (soil-root-straw-brown rice), it remains unclear how Cd concentration in brown rice (BCd) is causal relationship to environmental factors and nutrient transport. The differences in precipitation, soil properties, nutrient transport, and Cd transport were studied through a three-year fixed-point field trial and linked them to the standard of Cd and nutrient absorption and transport processes. The results showed that the available Cd concentration (ACd), and BCd in 2020 were lower than those in 2019 and 2021, but monthly precipitation (MP) was higher in 2020 than in 2019 and 2021. The MP and niche metrics were significantly negatively associated with ACd and BCd. However, the relationship between the form and location of different nutrient elements and Cd in roots, Cd in straws, and BCd also varied during the transport of nutrient elements and Cd from soil to root to straw to brown rice. Structural equation modelling analysis showed that nitrogen (N 15.5 %), phosphorus (P 14.1 %), silicon (Si 4.2 %), and iron (Fe 7.6 %) transport were more closely related to BCd than to potassium (K), calcium (Ca), magnesium (Mg), and manganese (Mn). The increase in MP significantly inhibited the increase in BCd, whereas the MP led to a decrease in BCd by affecting the transport of N and Fe. Among them, Si, Fe, and BCd had indirect causal relationships, whereas N, P, and BCd had direct causal relationships. Particularly, P is a crucial nutrient in reducing BCd in the Cd transport process. Our results highlight a strong causal relationship between environmental factors and nutrient transport and BCd, and provide a theoretical basis for fertiliser application in Cd-contaminated agroecosystems.

Scattering of e$$^\pm $$ by silicon atoms and transport coefficients in mixtures of inert gas with silicon vapor

Scattering of e$$^\pm $$ by silicon atoms and transport coefficients in mixtures of inert gas with silicon vapor

Comparison of the performances between the gray and non-gray media approaches of thermal transport in silicon-tin

We have compared the performances of the gray and non–gray media approaches of thermal transport in Silicon – Tin using Monte Carlo Simulation. The Boltzmann Transport Equation (BTE) for phonons was used to describe the heat flow and ballistic conduction in semiconducting alloy systems. In this work, we have attempted solving the BTE using Monte Carlo (MC) simulation Computational domains for both gray and non-gray media approaches are modeled and the geometry and dimensions of unit cell and sub-cells in the domain are determined. In addition, the computational performances of the gray and non-gray media approaches are compared. The results revealed that when compared to non- gray approach, the gray media approach has more errors in the sub-cells. The maximum relative error is about 3.5%. The results also show that the non–gray media approach of thermal transport in Silicon – Tin exhibited numerical predictions with a very close match to experimental data.

Thermal transport properties of nanoporous silicon with significant specific surface area

This paper studies thermal transport in nanoporous silicon with a significant specific surface area. First, the equilibrium molecular dynamics approach was used to obtain the dependence of thermal conductivity on a specific surface area. Then, a modified phonon transport kinetic theory-based approach was developed to analyze thermal conductivity. Two models were used to evaluate the phonon mean free path in the porous materials. The first model assumes that the dependence of the mean free path only relies on the specific surface area, and the second one also considers the mean free path variation with the porosity. Both approaches approximate molecular dynamics data well for the smaller porosity values. However, the first model fails for highly porous matrixes, while the second one matches well with molecular dynamics simulations across all considered ranges of the porosities. This work illustrates that the phonon mean free path dependence with the porosity/volume fraction of composite materials is essential for describing thermal transport in systems with significant surface-to-volume ratio.

Graphene‐on‐Silicon Hybrid Field‐Effect Transistors

AbstractThe combination of graphene and silicon in hybrid electronic devices has attracted increasing attention over the last decade. Here, a unique technology of graphene‐on‐silicon heterostructures as solution‐gated transistors for bioelectronics applications is presented. The proposed graphene‐on‐silicon field‐effect transistors (GoSFETs) are fabricated by exploiting various conformations of channel doping and dimensions. The fabricated devices demonstrate hybrid behavior with features specific to both graphene and silicon, which are rationalized via a comprehensive physics‐based compact model which is purposely implemented and validated against measured data. The developed theory corroborates that the device hybrid behavior can be explained in terms of two independent silicon and graphene carrier transport channels, which are, however, strongly electrostatically coupled. Although GoSFET transconductance and carrier mobility are found to be lower than in conventional silicon or graphene field‐effect transistors, it is observed that the combination of both materials within the hybrid channel contributes uniquely to the electrical response. Specifically, it is found that the graphene sheet acts as a shield for the silicon channel, giving rise to a nonuniform potential distribution along it, which impacts the transport, especially at the subthreshold region, due to non‐negligible diffusion current.

Control of dephasing in spin qubits during coherent transport in silicon

One of the key pathways toward scalability of spin-based quantum computing systems lies in achieving long-range interactions between electrons and increasing their interconnectivity. Coherent spin transport is one of the most promising strategies to achieve this architectural advantage. Experimental results have previously demonstrated high-fidelity transportation of spin qubits between two quantum dots in silicon and identified possible sources of error. In this theoretical study, we investigate these errors and analyze the impact of tunnel coupling, magnetic field, and spin-orbit effects on the spin transfer process. The interplay between these effects gives rise to double dot configurations that include regimes of enhanced decoherence that should be avoided for quantum information processing. These conclusions permit us to extrapolate previous experimental conclusions and rationalize the future design of large-scale quantum processors.

Benthic diatoms modify riverine silicon export to a marine zone in a hypertidal estuarine environment

Riverine dissolved silicon (DSi) and biogenic silica (BSi) are modulated along the estuarine gradient by several biotic and abiotic processes governed by physical forcings. An important area controlling silicon transport in alluvial estuaries with large intertidal mudflats is the benthic diatom-dominated biofilm system. Here, the hypertidal Severn Estuary, UK, has been used as a case study to improve our understanding of silicon transport in these benthic-dominated systems. We present the first time-series dataset of Si concentrations in the Severn. River and tidal hydrodynamics drove spatio-temporal changes in DSi. The longitudinal profile of DSi followed the classical view of dilution with downstream transport. Despite low riverine supply of BSi and low siliceous-phytoplankton production, relatively high BSi concentrations were measured in the Severn Estuary (maximum of 14.9 mg/L), which accounted for over 70% of the total bioavailable silicon present and were characterised by isotopically heavy waters (δ30Si of + 0.9 to + 1.1‰). Benthic biofilms (microphytobenthos) on the intertidal mudflats contained significant biomass (measured as chlorophyll a concentration with a maximum of 116.8 ± 16.2 µg/g dw. sed) with high productivity, driven by their photoprotective adaptions to these harsh intertidal environments, contributing to isotopically heavy mudflat water (δ30Si of + 1.19 to + 2.03‰), and resulting in high benthic BSi content in the spring (0.74 ± 0.03%) and summer (0.76 ± 0.05%). The fast-flowing tidal currents resulted in high bottom shear stress which likely exceeded the erosion thresholds of the biofilms, transporting the sediment-BSi matrix into the water column. Suspended particulate matter (SPM) and BSi remained tightly coupled in the estuarine water column (bioflocculation), and experienced the series of erosion–deposition events, burial/dissolution and export out of the estuary. Our novel observations improve understanding of the complex processes governing Si transport in hypertidal, benthic-dominated estuaries, and highlights the importance of tightly coupled benthic-pelagic systems in influencing the terrestrial silicon export to a marine zone.