Functionalization of SiO2 Surfaces for Si Monolayer Doping with Minimal Carbon Contamination

Development and inter-laboratory validation of analytical methods for glufosinate and its two metabolites in foods of plant origin

Glufosinate is widely used to control various weeds. Glufosinate and its main metabolites have become the focus of attention because of their high water solubility and persistence in aquatic systems. Quantification of the agrochemical product and its metabolite residues is essential for the safety of agricultural products. In this study, a highly specific, simple method was developed to directly determine glufosinate and its metabolite residues in 21 plant origin foods by liquid chromatography with tandem mass spectrometry (LC-MS/MS), and it was validated on 11 foods in five laboratories. Finally, the repeatability limit, reproducibility limit, and uncertainty of the method were calculated based on these validated data and used to support the more accurate detection results. Four different chromatographic columns were used to analyze three target compounds, and the anionic polar pesticide column showed the optimum separation and peak shape. Composition of the mobile phase, extraction solvent, and the clean-up procedure were optimized. The developed method was validated on 21 plant origin foods. The average recoveries were 74-115% for all matrices. The validation results of five laboratories showed this method had a good repeatability (RSDr < 9.5%) and reproducibility (RSDR < 18.9%). The method validation parameters met the requirements of guidance established by the European Union (EU) and China for pesticide residue analysis. This methodology can be used for a routine monitoring that performs well for glufosinate and its metabolite residues.

Laser-Triggered Bottom-Up Transcription of Chemical Information: Toward Patterned Graphene/MoS2 Heterostructures

Efficiently assembling heterostructures with desired interface properties, stability, and facile patternability is challenging yet crucial to modern device fabrication. Here, we demonstrate an interface coupling concept to bottom-up construct covalently linked graphene/MoS₂ heterostructures in a spatially defined manner. The covalent heterostructure domains are selectively created in analogy to the traditional printmaking technique, enabling graphic patterns at the bottom MoS₂ layer to be precisely transferred to the top graphene layer. This bottom-up connection and transcription of chemical information is achieved simply via laser beam irradiation. Our approach opens up a new paradigm for heterostructure construction and integration. It enables the efficient generation and real-time visualization of spatially well-resolved covalent graphene/MoS₂ heterostructures, facilitating further design and integration of patterned heterostructures into new generations of high-performance devices.

Carbon-Doping as Efficient Strategy for Improving Photocatalytic Activity of Polysilicon Supported Pd in Hydrogen Evolution from Formic Acid

Interest in cost-effective materials pushes researchers to the inexpensive and abundant semiconductors to use photons' energy for generating electrons and holes required for photocatalytic transformations. At the same time, polysilicon is one of the economic semiconductors with a disadvantage of high bandgap which could be solved by carbon-doping. We employed this strategy to the synthesis of carbon-doped polysilicon by a new approach starting from citric acid and methyltrimethoxysilane. The nanocomposite obtained was utterly characterized, and compared with bare polysilicon; increased UV-Vis absorbance and shift to higher wavelengths were the most notable characteristics of the synthesized catalyst. The carbon-doped polysilicon was modified with Pd nanoparticles to obtain a new heterogeneous photocatalyst for the formic acid degradation. The decomposition of formic acid was photocatalyzed by the obtained nanocomposite with a hydrogen production turnover frequency of up to 690 h-1. Moreover, it was demonstrated that the catalyst is stable and recyclable.

Ultradoping Boron on Si(100) via Solvothermal Chemistry*

Ultradoping introduces unprecedented dopant levels into Si, which transforms its electronic behavior and enables its use as a next-generation electronic material. Commercialization of ultradoping is currently limited by gas-phase ultra-high vacuum requirements. Solvothermal chemistry is amenable to scale-up. However, an integral part of ultradoping is a direct chemical bond between dopants and Si, and solvothermal dopant-Si surface reactions are not well-developed. This work provides the first quantified demonstration of achieving ultradoping concentrations of boron (∼1e14 cm² ) by using a solvothermal process. Surface characterizations indicate the catalyst cross-reacted, which led to multiple surface products and caused ambiguity in experimental confirmation of direct surface attachment. Density functional theory computations elucidate that the reaction results in direct B-Si surface bonds. This proof-of-principle work lays groundwork for emerging solvothermal ultradoping processes.

Robust Amphiphobic Few-Layer Black Phosphorus Nanosheet with Improved Stability

Few-layer black phosphorus (FL-BP) has been intensively studied due to its attractive properties and great potential in electronic and optoelectronic applications. However, the intrinsic instability of FL-BP greatly limits its practical application. In this study, the amphiphobic FL-BP is achieved by functionalization of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFDTS) on the surface of FL-BP. The obtained PFDTS coated FL-BP (FL-BP/PFDTS) demonstrates enhanced stability, which is not observed during significant degradation for 2 months in high moisture content environment (95% humidity). Particularly, attributing to the surface amphiphobicity, FL-BP/PFDTS exhibits strong surface water repellency in the presence of oleic acid (as the contaminant), while other passivation coating layers (such as hydrophilic or hydrophobic coating) become hydrophilicity under such conditions. Owing to this advantage, the obtained FL-BP/PFDTS demonstrates enhanced stability in high moisture content environment for 2 months, even though the surface is contaminated by oil liquid or other organic solvents (such as oleic acid, CH2Cl2, and N-methyl-2-pyrrolidone). The passivation of FL-BP by amphiphobic coating provides an effective approach for FL-BP stabilization toward future applications.

Toward Defect-Free Doping by Self-Assembled Molecular Monolayers: The Evolution of Interstitial Carbon-Related Defects in Phosphorus-Doped Silicon

Self-assembled molecular monolayer (SAMM) doping on semiconductors has been widely appraised for its advantages of doping nanoelectronic devices for applications in the complementary metal-oxide-semiconductor transistor (CMOS) industry. However, defects introduced by SAMM-doping will limit the performance of the devices. Previously, we have found that SAMM-doping can bring carbon impurities into the silicon substrate and these unwanted carbon impurities can deactivate phosphorus dopants by forming an interstitial carbon (C_i)-substitutional phosphorus (C_i-P_s) complex. Herein, to develop a defect-free SAMM-doping process, the generation and annihilation of C_i-related defects are investigated by extending the thermal annealing time from 2 to 10 min using secondary ion mass spectrometry and deep-level transient spectroscopy. The results show that the concentration of C_i-related carbon defects is lower after a longer time of thermal annealing, although a longer annealing time actually introduces a higher concentration of carbon impurities into Si. This observation indicates that interstitial carbon evolves into substitutional carbon (C_s) that is electrically inactive during the thermal annealing process. A defect-free SAMM-doping process may be developed by an appropriate post-annealing process.

Nanostructured bulk Si for thermoelectrics synthesized by surface diffusion/sintering doping

Nanostructured bulk silicon (bulk nano-Si) has attracted attention as an advanced thermoelectric (TE) material due to its abundance and low toxicity. However, oxidization will occur easily when bulk nano-Si is synthesized by a conventional method, which deteriorates the TE performance. Various methods to prevent such oxidation have been proposed but they need specific techniques and are thus expensive. Here, we propose a simple and cost-effective method named Surface Diffusion/Sintering Doping (SDSD) to synthesize bulk nano-Si for TEs. SDSD utilizes Si nanoparticles whose surface is coated with a native thin oxide layer. SDSD is composed of two steps, (1) a molecular precursor containing a doping element is added onto the oxide layer of Si nanoparticles and (2) the nanoparticles are sintered into a bulk state. During sintering, the doping element diffuses through the oxide layer forming conductive paths, which results in a high carrier concentration as well as high mobility. Furthermore, owing to the nanostructures, low lattice thermal conductivity (κ_lat) is also achieved, which is an ideal situation for TEs. In this study, we show that P-doped bulk nano-Si synthesized by SDSD shows good TE performance due to its high carrier concentration, high carrier mobility, and low κ_lat. Since SDSD takes advantage of oxidization, it is cost-effective and suitable for mass production to synthesize bulk nano-Si for TEs.

Nanostructured bulk silicon (bulk nano-Si) has attracted attention as an advanced thermoelectric (TE) material due to its abundance and low toxicity.

Diversification of Device Platforms by Molecular Layers: Hybrid Sensing Platforms, Monolayer Doping, and Modeling

Inorganic materials such as semiconductors, oxides, and metals are ubiquitous in a wide range of device technologies owing to the outstanding robustness and mature processing technologies available for such materials. However, while the important contribution of inorganic materials to the advancement of device technologies has been well established for decades, organic-inorganic hybrid device systems, which merge molecular functionalities with inorganic platforms, represent a newer domain that is rapidly evolving at an increasing pace. Such devices benefit from the great versatility and flexibility of the organic building blocks merged with the robustness of the inorganic platforms. Given the overwhelming wealth of literature covering various approaches for modifying and using inorganic devices, this feature article selectively highlights some of the advances made in the context of the diversification of devices by surface chemistry. Particular attention is given to oxide-semiconductor systems and metallic surfaces modified with organic monolayers. The inorganic device components, such as semiconductors, metals, and oxides, are modified by organic monolayers, which may serve as either active, static, or sacrificial components. We portray research directions within the broader field of organic-inorganic hybrid device systems that can be viewed as specific examples of the potential of such hybrid device systems given their comprehensive capabilities of design and diversification. Monolayer doping techniques where sacrificial organic monolayers are introduced into semiconducting elements are reviewed as a specific case, together with associated requirements for nanosystems, devices, and sensors for controlling doping levels and doping profiles on the nanometric scale. Another series of examples of the flexibility provided by the marriage of organic functional monolayers and inorganic device components are represented by a new class of biosensors, where the organic layer functionality is exploited in a functioning device for sensing. Considerations for relying on oxide-terminated semiconductors rather than the pristine semiconductor material as a platform both for processing and sensing are discussed. Finally, we cover aspects related to the use of various theoretical and computational approaches to model organic-inorganic systems. The main objectives of the topics covered here are (i) to present the advances made in each respective domain and (ii) to provide a comprehensive view of the potential uses of organic monolayers and self-assembly processes in the rapidly evolving field of molecular-inorganic hybrid device platforms and processing methodologies. The directions highlighted here provide a perspective on a future, not yet fully realized, integrated approach where organic monolayers are combined with inorganic platforms in order to obtain versatile, robust, and flexible systems with enhanced capabilities.