Portable shifted excitation Raman difference spectroscopy for on‐site soil analysis

Abstract

On-site soil analysis in the framework of precision agriculture is gaining significant importance to achieve improved crop productivity, increased soil health and reduced fertilizer application. In situ sensing techniques can provide the information required for decision support systems immediately on the field, for example, to control fertilization and liming. Shifted excitation Raman difference spectroscopy (SERDS) pilot investigations for on-site soil analysis are presented using a portable SERDS sensor system specifically developed for infield studies. The SERDS sensor includes a dual-wavelength diode laser at 785 nm integrated in an in-house realized turnkey laser system and an optical power of 36 mW at the sample was chosen for our experiments. Outdoor preinvestigations with the device and polystyrene as test sample show the capability of SERDS for qualitative and quantitative analysis under changing daylight conditions. On-site soil analysis is carried out and SERDS extracts Raman signals from disturbing background interference with a 15-fold improvement of the signal-to-background-noise ratio. Beside others, closely neighboured Raman signals of calcite and dolomite are identified and even mixtures of both soil carbonates are discriminated using SERDS. The number of accumulations for generating an averaged SERDS spectrum of soil with a sufficient signal stability and signal-to-background-noise ratio is evaluated to optimize the overall exposure time for such in situ experiments. The presented results demonstrate the large capability of the developed portable SERDS sensor system for on-site soil investigations as promising tool for precision agriculture.

Shifted Excitation Raman Difference Spectroscopy Combined with Wide Area Illumination and Sample Rotation for Wood Species Classification

“…This is due to the fact that the shot noise in the two Raman spectra recorded at the slightly shifted excitation wavelengths is uncorrelated thus leading to increased noise levels in the SERDS spectrum. 88 However, in many practical applications not only the uncorrelated shot noise but also other sources of noise are evident in the recorded Raman spectra. This type of noise can be present as fixed-pattern noise, e.g., originating from varying sensitivities of different detector pixels of the CCD or transmission characteristics of optical filters used in the experimental setup.…”

Detection of microplastic samples based on spatial heterodyne microscopic differential Raman spectroscopy

“…Differential Raman spectroscopy is restored by multiple constraint iterative algorithm 18 . The process of multiple constraint iterative algorithm is as follows.…”

A rapid and nondestructive approach for forensic identification of novel psychoactive substances using shifted‐excitation Raman difference spectroscopy and machine learning

“…[ 24 ] Therefore, the baseline of the spectrum can be aligned by mathematical means such as difference between the two spectra, normalization, reconstruction, and baseline correction, [ 25 ] so as to effectively filter out the interference peaks and obtain a pure Raman spectrum. SERDS has been available for some time since its introduction, but its main application areas are focused on biology, [ 26 ] ores, [ 27 ] and soils, [ 28 ] and we have not yet seen studies on the application of handheld SERDS to the examination of NPS. It is worth noting that, in addition to resistance to strong fluorescence interference, SERDS can also be detected through glass, liquid, envelope paper, and so forth.…”

“…[24] Therefore, the baseline of the spectrum can be aligned by mathematical means such as difference between the two spectra, normalization, reconstruction, and baseline correction, [25] so as to effectively filter out the interference peaks and obtain a pure Raman spectrum. SERDS has been available for some time since its introduction, but its main application areas are focused on biology, [26] ores, [27] and soils, [28] and we…”