Mapping surface soil organic carbon density of cultivated land using machine learning in Zhengzhou.

Research on soil organic carbon (SOC) is crucial for improving soil carbon sinks and achieving the "double-carbon" goal. This study introduces ten auxiliary variables based on the data from a 2021 land quality survey in Zhengzhou and a multi-objective regional geochemical survey. It uses geostatistical ordinary kriging (OK) interpolation, as well as classical machine learning (ML) models, including random forest (RF) and support vector machine (SVM), to map soil organic carbon density (SOCD) in the topsoil layer (0 - 20 cm) of cultivated land.

Positively Charged Hollow Co Nanoshells by Kirkendall Effect Stabilized by Electron Sink for Alkaline Water Dissociation.

While cobalt (Co) exhibits a comparable energy barrier for H adsorption/desorption to platinum in theory, it is generally not suitable for alkaline hydrogen evolution reaction (HER) because of unfavorable water dissociation. Here, the Kirkendall effect is adopted to fabricate positive-charged hollow metal Co (PHCo) nanoshells that are stabilized by MoO and chainmail carbon as the electron sink. Compared to the zero-valent Co, the PHCo accelerates the water dissociation and changes the rate-determining step from Volmer to Heyrovsky process.

In-situ Surface-Enhanced Raman Spectroscopy Reveals a Mars-van Krevelen-Type Gas Sensing Mechanism in Au@SnO Nanoparticle-Based Chemiresistors.

Molecular-level understandings of gas sensing mechanisms of oxide-based chemiresistors are significant for designing high-performance gas sensors; however, the mechanisms are still controversial due to the lack of direct experimental evidence. This work demonstrates efficient in situ surface-enhanced Raman spectroscopy (SERS) tracing of the highly representative SnO-ethanol gas sensing using Au@SnO nanoparticles (NPs), where the Au core and SnO shell provide SERS activity and a gas sensing response, respectively. The in situ SERS evidence suggests that the sensing follows a Mars-van Krevelen mechanism rather than the prevailing adsorbed oxygen (AO) model.

Engineered Au@CuO Nanoparticles for Wide-Range Quantitation of Sulfur Ions by Surface-Enhanced Raman Spectroscopy.

Efficient detection of sulfide ions (S), especially in a wide quantitative range, is of significance but faces challenges. This work strategizes and fabricates Au@CuO nanoparticles for quantitative surface-enhanced Raman spectroscopy (SERS) detection of the S ions based on the S concentration-dependent ion-solid interactions. We have achieved fast and quantitative S detection in a wide range from 5 ppb to 64,000 ppm (saturation concentration of the S source).

Efficient SERS Response of Porous-ZnO-Covered Gold Nanoarray Chips to Trace Benzene-Volatile Organic Compounds.

Fast and sensitive detection of gaseous volatile organic compounds (VOCs), based on surface-enhanced Raman spectroscopy (SERS), is still a challenge due to their weak interaction with plasmonic metals and overly small Raman scattering cross sections. Herein, we propose a simple strategy to achieve the SERS-based highly efficient detection of trace benzene-VOCs (B-VOCs) based on a composite chip. The composite chip is designed and fabricated via covering the porous zinc oxide on gold nanoarrays by a one-step solution growth method.

High-Density-Nanotips-Composed 3D Hierarchical Au/CuS Hybrids for Sensitive, Signal-Reproducible, and Substrate-Recyclable SERS Detection.

Surface-enhanced Raman scattering (SERS) provides an unprecedented opportunity for fingerprinting identification and trace-level detection in chemistry, biomedicine, materials, and so on. Although great efforts have been devoted to fabricating sensitive plasmonic nanomaterials, it is still challenging to batch-produce a SERS substrate with high sensitivity, good reproducibility, and perfect recyclability. Here, we describe a facile fabrication of three-dimensional (3D) hierarchical Au/CuS nanocomposites, in which high-density Au nanotips enable highly SERS-active sensing, and the well-defined microflower (MF) geometry produces perfect signal reproducibility (RSD < 5%) for large laser spot excitations (>50 μm2), which is particularly suitable for practical on-site detection with a handheld Raman spectrometer.

Abnormally Weak Surface-Enhanced Raman Scattering Activity of Tip-Rich Au Nanostars: The Role of Interfacial Defects.

Designing and regulating the geometry of a given plasmonic metal (Au, Ag, .) has become one of the most efficient approaches to achieve highly active surface-enhanced Raman spectroscopy (SERS) substrates, but this work demonstrates that plain efforts on this may not be enough. Here, we report that the often-neglected inner crystal defects also have huge impacts on the SERS activity, through a case of Au nanostars (NSs) with good SERS geometry but rich in defects.

Optimal Excitation Wavelength for Surface-Enhanced Raman Spectroscopy: The Role of Chemical Interface Damping.

The optimal excitation wavelength (OEW) for surface-enhanced Raman spectroscopy (SERS) is generally close to that of the local surface plasmon resonance (LSPR). In some cases, however, the OEW is significantly longer than that of the observed LSPR. Its origin is still unclear and controversial.

Quantitative Surface-Enhanced Raman Spectroscopy for Field Detections Based on Structurally Homogeneous Silver-Coated Silicon Nanocone Arrays.

Practical application of surface-enhanced Raman spectroscopy (SERS) is greatly limited by the inaccurate quantitative analyses due to the measuring parameter's fluctuations induced by different operators, different Raman spectrometers, and different test sites and moments, especially during the field tests. Herein, we develop a strategy of quantitative SERS for field detection via designing structurally homogeneous and ordered Ag-coated Si nanocone arrays. Such an array is fabricated as SERS chips by depositing Ag on the template etching-induced Si nanocone array.

Ultrasensitive surface-enhanced Raman spectroscopy detection of gaseous sulfur-mustard simulant based on thin oxide-coated gold nanocone arrays.

Surface Enhanced Raman Spectroscopy (SERS) could be a powerful technique for detecting trace gaseous sulfur-mustard, but it is still challenging due to the difficulty in efficiently capturing sulfur-mustard molecules by normal SERS substrates. Here, a chemically trapping strategy is presented for such detection via coating an ultrathin metal-oxide sensing layer on a SERS substrate. In the strategy, a SERS substrate Au-wrapped Si nanocone array is designed and fabricated by Si wafer-based organic template-etching and appropriate Au deposition, and coated with an ultrathin CuO for chemically capturing sulfur-mustard molecules.

Ultrathin Hexagonal PbO Nanosheets Induced by Laser Ablation in Water for Chemically Trapping Surface-Enhanced Raman Spectroscopy Chips and Detection of Trace Gaseous HS.

Lead oxide (PbO) nanosheets are of significance in the design of functional devices. However, facile, green, and fast fabrication of ultrathin and homogenous PbO nanosheets with a chemically clean surface is still desirable. Herein, a simple and chemically clean route is developed for fabricating such nanosheets via laser ablation of a lead target in water for a short time and then ambient aging.

Conductometric Response-Triggered Surface-Enhanced Raman Spectroscopy for Accurate Gas Recognition and Monitoring Based on Oxide-wrapped Metal Nanoparticles.

Accurate and efficient gas monitoring is still a challenge because the existing sensing techniques mostly lack specific identification of gases or hardly meet the requirement of real-time readout. Herein, we present a strategy of conductometric response-triggered surface-enhanced Raman spectroscopy (SERS) for such gas monitoring, via designing and using ultrathin oxide-wrapped plasmonic metal nanoparticles (NPs). The oxide wrapping layer can interact with and capture target gaseous molecules and produce the conductometric response, while the plasmonic metal NPs possess strong SERS activity.

Ultrathin layer solid transformation-enabled-surface enhanced Raman spectroscopy for trace harmful small gaseous molecule detection.

Detection of trace harmful small gaseous molecules (h-SGMs), based on surface enhanced Raman spectroscopy (SERS), has been expected to be a useful strategy but is challenging due to the extremely small Raman cross section (RCS) and weak metal affinity of the h-SGMs. Here, a new strategy, ultrathin layer solid transformation-enabled (ULSTE)-SERS, is proposed. It uses the chemical reaction between the target h-SGM and an ultrathin layer of solid sensing matter coated on a plasmonic metal SERS substrate.

Mars-van-Krevelen mechanism-based blackening of nano-sized white semiconducting oxides for synergetic solar photo-thermocatalytic degradation of dye pollutants.

Blackening (or enhancing the optical absorption in the visible region) of nano-sized white semiconducting oxides (N-WSOs) is of significant importance for solar utilization. Here, we present a novel Mars-van-Krevelen mechanism-based method for blackening the N-WSOs via facile one-step heating of the N-WSOs with alcohols. Taking n-butanol-induced blackening of TiO (anatase) as an example, the pristine TiO NP powders can be successfully blackened to form black TiO (B-TiO) via heating with n-butanol at 300 °C for 20 min.

Rapid and ultrasensitive surface-enhanced Raman spectroscopy detection of mercury ions with gold film supported organometallic nanobelts.

Rapid, ultrasensitive and reliable detection of mercury ions (Hg) by surface enhanced Raman spectroscopy (SERS) is of importance, but is restricted by the extremely low Raman cross section of the Hg. Here, we report a facile methodology that can realize such detection based on the organometallic Cu(CHNS)Cl · 0.5HO nanobelts and SERS.

Ultrathin and Isotropic Metal Sulfide Wrapping on Plasmonic Metal Nanoparticles for Surface Enhanced Ram Scattering-Based Detection of Trace Heavy-Metal Ions.

A facile and general strategy is presented for homogenous and ultrathin metal sulfide wrapping on plasmonic metal (PM) nanoparticles (NPs) based on a thiourea-induced isotropic shell growth. This strategy is typically implemented just via adding the thiourea into pre-formed PM colloidal solutions containing target metal ions. The validity of this strategy is demonstrated by taking the wrapped NPs with Au core and CuS shell or Au@CuS NPs as an example.

Large Area α-CuS Particle-Stacked Nanorod Arrays by Laser Ablation in Liquid and Their Strong Structurally Enhanced and Stable Visible Photoelectric Performances.

A flexible route is developed for fabrication of large area α-CuS nanorod arrays (NRAs) on the basis of one-step laser ablation of a copper foil in CS liquid. It has been demonstrated that the obtained products are the high-temperature phase α-CuS and consist of the nanorods vertically standing on the Cu foil, exhibiting the array. The nanorods were about 1 μm in length and around 100 nm in thickness and built by stacking the nearly spherical and ⟨110⟩-oriented nanoparticles (NPs) up.

Ultrathin Oxide Layer-Wrapped Noble Metal Nanoparticles via Colloidal Electrostatic Self-Assembly for Efficient and Reusable Surface Enhanced Raman Scattering Substrates.

Controllable and flexible fabrication of ultrathin and uniform oxide layer-wrapped noble metal nanoparticles (NPs) has been expected. Here a new strategy is presented for them based on colloidal electrostatic attraction and self-assembly on the metal NPs via one-step laser ablation of noble metal targets in the hydrolysis-induced hydroxide sol solutions at room temperature. The Au NPs, with several tens of nanometers in size, are taken as core part and TiO as shell-layer to demonstrate the validity of the presented strategy.

Nanoscaled Amorphous TiO Hollow Spheres: TiCl Liquid Droplet-Based Hydrolysis Fabrication and Strong Hollow Structure-Enhanced Surface-Enhanced Raman Scattering Effects.

A very simple route is developed for fast fabrication of nanosized amorphous titanium dioxide (TiO) hollow spheres (THPs) just via dropping the pure four titanium chloride (TiCl) liquid droplets into deionized water at around room temperature. The THPs, at around 80 nm in mean diameter, can be formed within a few seconds after dropping TiCl droplets into water. The shell layers of the obtained THPs are amorphous and porous in structure with a porosity of 58-80% and show a linear increase in thickness with the size of THPs.

Ultrathin tin oxide layer-wrapped gold nanoparticles induced by laser ablation in solutions and their enhanced performances.

A simple and flexible method of preparing an ultrathin semiconducting oxide layer-wrapped gold nanoparticles (NPs) is presented. The method is a single-step procedure based on laser ablation in a precursor solution. The spherical Au NPs (<20nm in mean size) wrapped with a SnO layer of approximately 2nm in thickness are formed after the laser ablation of a gold target in SnCl solutions with concentrations of 0.