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The current measurement of soil properties can be limited in the variable-rate fertilizer application using soil analysis, due to the labor-intensive and time-consuming in the laboratory. Rapid, non-destructive soil detection is highly required to be developed using visible-infrared spectroscopy. Among them, Raman spectroscopy can be used to detect the vibrational properties of molecules, due to the fast, non-invasive, small sample treatment, and free interference from water in various fields. Nevertheless, incident light is also required to induce the Raman scattering, in order to compensate for the information with infrared spectroscopy. Therefore, the Raman scattering measurement can be widely used in the composition and dynamic process of soil minerals, bacteria colonies, and humic fraction in soil sensing. However, it is still lacking on the fluorescence effect of soil in the sensing of soil nutrients, which can weaken the Raman signals and the information extraction for the quantitative analysis. Raman spectroscopy has been introduced into some novel measurement techniques to improve the signal-to-noise ratio in recent years, including the shifted excitation Raman difference spectroscopy (SERDS), confocal Raman microscope, and surface-enhanced Raman spectroscopy (SERS). Meanwhile, both aliphatic and aromatic compounds are Raman active in the quantitative and qualitative detection of soil organic matter (SOM). Moreover, many phosphorous compounds in soil are also Raman active, leading to low prediction accuracy using visible-near infrared spectroscopy. In this review, the research progress was proposed on the Raman spectroscopy in the rapid detection of soil nutrients, together with the technical means in suppressing soil fluorescence interference to obtain high-resolution Raman signals. In the detection of SOM, the fusion of infrared and Raman spectral data significantly improved the prediction accuracy of 43% in the root mean square error (RMSE). In addition, the SERDS technique was used to detect the SOM of 33 soil samples. The reconstructed Raman peaks of soil minerals and organic materials obtained an excellent prediction accuracy of the SOM, with the determination of coefficient R 2=0.82, and the residual prediction deviation RPD=1.81. Raman spectroscopy was used to detect the water-soluble nitrogen in the soil solution, whereas, the SERS was to enhance the Raman peaks. An excellent correlation was obtained between the concentration of water-soluble nitrogen and the SERS data (R²=0.91). Research showed that Raman spectroscopy can be an effective tool to identify the different phosphate species in soil. Wavelet packet decomposition of Raman spectra was used to predict the phosphorus concentration in the phosphate-mixed soil with the SOM leached, where the accuracy of the regression model reached R²=0.94. Since the measurement area of Raman spectroscopy depended mainly on the spot size of the laser that irradiated on the sample surface, the spatial variability of the soil sample can be difficult to focus on the target substance. The effective Raman signal of soil nutrients can be obtained with high spatial resolution while suppressing the interferences from the background light. The combination of SERDS and micro-Raman technologies can be expected to serve as an in-situ measurement of soil nutrients. Reducing the redundant variables is crucial when applying spectral fusion since interpretability and reproducibility of the prediction model are paramount in the sensor development using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Surface Enhanced Raman Scattering（SERS）is a vibration spectroscopy technology，which can directly identify target analytes and has a wide range of applications in chemistry，physics，materials， biomedicine and other fields. Ordered SERS substrate refers to the SERS substrate composed of regularly arranged nanostructures，which has good uniformity and reproducibility. In this review，surface enhanced Raman scattering and SERS substrates are introduced，and the self-assembly method，lithography technology and template-assisted method for preparing ordered SERS substrates are emphatically described. [ABSTRACT FROM AUTHOR]

By combining anodic oxidation with photo-reduction method，a uniform，stable and recyclable surface enhanced Raman scattering （SERS）-active substrate composed of well-ordered Ag nanoparticles decorated on TiO2 nanotube arrays （TiO2NTAs/Ag） is obtained. The composition and structure of the TiO2NTAs/Ag are characterized using X-ray powder diffraction （XRD），X-ray photoelectron spectroscopy （XPS），UV-Vis diffuse reflection spectrum（UV-Vis DRS），surface enhanced Raman scattering spectroscopy （SERS）and scanning electron microscope（SEM）measurements. The SERS response of the TiO2NTAS/Ag array to tetracycline hydrochloride（TC-HCl）is further studied，which exhibits superior sensitivity for SERS detection of TC-HCl，and the detection limit could reach 1 × 10－14 mol/L in water. In addition，the TiO2NTAs/Ag substrate exhibits excellent degradation activity for TC-HCl under light and could be recycled for at least 8 times. It shows a potential application in SERS detection and degradation of organic contaminants in environment. [ABSTRACT FROM AUTHOR]

Graphene is a zero-gap semiconductor with low work function and high leakage current which limit its applications. Doping of nitrogen is one of the ways to tailor the properties of graphene. However, there remain some defects, such as the low nitrogen content and poor controllability. In order to enhance the content of nitrogen and control the bonding characters to embed nitrogen atoms inside the carbon lattice, solid-state sources (melamine) and gas-state sources (methane) were used to prepare nitrogen doped graphene (NG) films. The preparation time, the dosage of melamine and temperature were set as tunable parameters. The morphology of NG, the content of nitrogen (mass fraction of nitrogen atoms) and the bonding characters for the embedding of N atoms were studied. The results indicated that the preparation process of NG films was involved with nucleation, growth and aggregation. Proper temperature (990 °C) was conductive for the improvement of the content of nitrogen. Pyrrolic N was produced at high temperature (＞1 000 °C), while graphitic N was on the opposite. With increasing the dosage of melamine, the content of nitrogen was increased and then decreased with the maximum value of 6.98%. The content of Pyridinic N will be elevated with increasing the amount of melamine. Compared with graphene, NG films were capable of detecting the Raman signals from Rhodamine B molecules even at the concentration as low as 10−5 mol/L. [ABSTRACT FROM AUTHOR]