Raman Spectroscopy System Research Articles

Comparison of Line-Focused and Point-Focused Raman Mineral Analysis in Planetary Exploration

Raman spectroscopy plays a critical role in planetary exploration by providing detailed analysis of mineralogical and chemical compositions. However, the conventional point-focused Raman systems, while precise, are limited by their time-consuming nature, which hampers efficiency in space missions. This study compares a line-focused Raman spectroscopy system equipped with a cylindrical mirror array to a traditional point-focused system by testing various lunar-analogue minerals. The results demonstrate that the line-focused mode significantly reduces mineral detection time while covering larger sample surface areas, albeit with a slightly higher detection limit compared to the point-focused mode. Both modes exhibit similar capabilities in mineral identification and compositional analysis, with the line-focused system offering a more practical solution for rapid, high-throughput analysis in large-scale planetary geological surveys. These findings suggest that the line-focused Raman system could be a valuable tool in accelerating geochemical data collection during future deep space exploration missions.

Autofluorescence imaging guided needle-type Raman spectroscopy system for breast tumor margin assessment.

A trajectory-tracked, near-infrared autofluorescence imaging guided, biochemical signature-projected needle-type Raman spectroscopy (TNBN-RS) system integrated on a medical cart was developed for rapid wide-field breast tissue stratification. A wide-field (10 × 10 cm2) near-infrared autofluorescence (NIRAF) imaging subsystem was developed for gross stratification of breast tissue types based on higher NIRAF intensity associated with breast cancer, followed by projection of NIRAF-identified breast tumor margins onto the tissue of interest with a compact projector. Raman spectra were further acquired from the NIRAF projected regions for confirmed margin assessment using a needle-type Raman probe equipped with color camera-based probe trajectory tracking. The trajectory of the Raman probe and the accompanying RS biochemical signature-based margin assessment were instantly projected. A unique field of view (FOV) calibration method was proposed to calibrate the TNBN-RS FOVs, resulting in a projection accuracy of <2 mm. A graphical user interface (GUI) was developed in C# for system control, real-time processing and display of NIRAF images, Raman spectra, and projection of their results. The performance of the TNBN-RS system was validated on an ex vivo breast tissue, demonstrating its potential for rapid intraoperative breast tumor margin assessment.

Application of Raman spectroscopy for analyzing the behavior of gases in sandstone reservoirs

The behavior of gases within subsurface pores determines the oil and gas recovery and CO2 storage in the region. In this study, we report a novel method based on Raman spectroscopy for observing the distributions of CH4 and CO2 gases in the pores of sandstone reservoirs. First, we designed a pressure-cell to inject gases into a sample. Then, CH4 and CO2 gases were injected into the sample using the pressure-cell placed on the Raman spectroscopy system sample stage. Quartz and feldspar were the predominant minerals in the sample. The CH4-occupied pores exhibited a Raman peak at 2917 cm−1. Two-dimensional (2D) and three-dimensional (3D) mapping of the pores depicted the geometry of the CH4 gas-filled pores. After injecting CO2 gas, we observed an intensity peak at 1388 cm−1; we obtained 2D and 3D maps of the CO2 gas-filled pores based on this peak value. This study demonstrates the potential use of Raman spectroscopy as a visualization tool to reveal the pore geometry of sandstone reservoirs and determine the distribution of gases within such reservoirs. Our study can serve as a foundation for understanding the behavior of gases in subsurface reservoirs, improving oil and gas prospecting and exploration, and assessing CO2 storage..

In-situ imaging and time-resolved investigation of local pH in electrocatalytic CO2 reduction

Local pH near the catalyst surface exerts a substantial influence on both catalytic selectivity and activity in electrocatalytic CO2 reduction (CO2RR). While the investigation of local pH remains challenging in the aspect of in-situ imaging and monitoring. In this study, a novel lateral-type surface-enhanced Raman spectroscopy (L-SERS) system with a wide pH testing range from acidic to alkaline, is developed for the in-situ observation of local pH distributions with high spatial and temporal resolution during CO2RR. Excellent in-situ imaging of local pH near the catalyst surface is obtained, showing good consistency with simulation results. Besides, the gradual pH elevation and stabilization can be monitored via this time-resolved local pH investigation. This study presents a direct visualization of local pH distribution and variation at the Nernst layer during CO2RR, providing direct evidence in local pH for the feasibility of acidic electrolyte and offering theoretical guidance for optimizing CO2RR conditions.

Feasibility study on non-destructive detection of microplastic content in flour based on portable Raman spectroscopy system combined with mixed variable selection method

Microplastics, as emerging environmental pollutants, have garnered considerable attention due to their contamination of both the environment and food. Microplastics can infiltrate the human food chain through multiple pathways, potentially posing health risks to humans. Currently, non-destructive testing of microplastics in food is considered challenging. This study aims to investigate the feasibility of employing a portable Raman spectroscopy system for non-destructive detection of microplastic content (polystyrene, PS; polyethylene, PE) in flour. In this study, a portable spectrometer was used to collect flour spectra of different abundances of microplastics. To enhance the predictive performance of the partial least squares (PLS) model, a mixed variable selection strategy that combined the wavelength interval selection method (Synergy interval partial least squares, siPLS) and the wavelength point selection method (Least absolute shrinkage and selection operator, LASSO; Multiple feature-spaces ensemble by least absolute shrinkage and selection operator, MFE-LASSO) was proposed. Four regression models (PLS, siPLS, siPLS-LASSO, siPLS-MFE-LASSO) were developed and compared for detecting PS and PE content in flour. The siPLS-MFE-LASSO model exhibited the best generalization performance in the prediction set, and was considered to have the best generalization performance (PS: RP2 = 0.9889, RMSEP=0.0344 %; PE: RP2 = 0.9878, RMSEP=0.0361 %). In conclusion, this study has demonstrated the potential of using a portable Raman spectrometer in conjunction with a mixed variable selection algorithm for non-destructive detection of PS and PE content in flour, providing more possibilities for non-destructive detection of microplastic content in food.

High-Sensitivity and In Situ Multi-Component Detection of Gases Based on Multiple-Reflection-Cavity-Enhanced Raman Spectroscopy.

Raman spectroscopy with the advantages of the in situ and simultaneous detection of multi-components has been widely used in the identification and quantitative detection of gas. As a type of scattering spectroscopy, the detection sensitivity of Raman spectroscopy is relatively lower, mainly due to the low signal collection efficiency. This paper presents the design and assembly of a multi-channel cavity-enhanced Raman spectroscopy system, optimizing the structure of the sample pool to reduce the loss of the laser and increase the excitation intensity of the Raman signals. Moreover, three channels are used to collect Raman signals to increase the signal collection efficiency for improving the detection sensitivity. The results showed that the limits of detection for the CH4, H2, CO2, O2, and N2 gases were calculated to be 3.1, 34.9, 17.9, 27, and 35.2 ppm, respectively. The established calibration curves showed that the correlation coefficients were all greater than 0.999, indicating an excellent linear correlation and high level of reliability. Meanwhile, under long-time integration detection, the Raman signals of CH4, H2, and CO2 could be clearly distinguished at the concentrations of 10, 10, and 50 ppm, respectively. The results indicated that the designed Raman system possesses broad application prospects in complex field environments.

Performance evaluation of a hyphenated laser spectroscopy system with conventional methods for microplastic analysis

Microplastics are one of the concerning environmental pollutants because of their ubiquity. Their capability to adsorb other environmental pollutants increases the risk even further. Existing identification approaches for microplastic characterization for polymer class and their surface-adsorbed heavy metal detection require the utilization of multiple resources and expertise. The article discusses the applicability of a custom-made hyphenated Laser Induced Breakdown Spectroscopy (LIBS)—Raman spectroscopic system in characterizing microplastics by comparing the analytical performance with conventional methods such as Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy, confocal Raman spectroscopy, and Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDS). Raman analysis identified polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) plastics, which is confirmed by confocal Raman and FTIR study of the same. LIBS study of microplastics detected heavy metals such as Al, Ni, Co, and Zn, along with Ca and Mg trace elements. The cross-examination with EDS validates these trace elements' presence on the microplastics' surface. The results of the reported LIBS-Raman analysis and its validity evaluated using conventional gold-standard methods show the applicability of the proposed methodology in characterizing microplastics from environmental resources with less or no sample preparation in short time.

Wavelength-swept spontaneous Raman spectroscopy system improves fiber-based collection efficiency for whole brain tissue classification.

Raman spectroscopy is a valuable technique for tissue identification, but its conventional implementation is hindered by low efficiency due to scattering. Addressing this limitation, we are further developing the wavelength-swept Raman spectroscopy approach. We aim to enhance Raman signal detection by employing a laser capable of sweeping over a wide wavelength range to sequentially excite tissue with different wavelengths, paired with a photodetector featuring a fixed narrow-bandpass filter for collecting the Raman signal at a specific wavelength. We experimentally validate our technique using a fiber-based swept-source Raman spectroscopy setup. In addition, simulations are conducted to assess the efficacy of our approach in comparison with conventional spectrometer-based Raman spectroscopy. Our simulations reveal that the wavelength-swept configuration leads to a significantly stronger signal compared with conventional spectrometer-based Raman spectroscopy. Experimentally, our setup demonstrates an improvement of at least 200× in photon detection compared with the spectrometer-based setup. Furthermore, data acquired from different regions of a fixed monkey brain using our technique achieves 99% accuracy in classification via -nearest neighbor analysis. Our study showcases the potential of wavelength-swept Raman spectroscopy for tissue identification, particularly in highly scattering media, such as the brain. The developed technique offers enhanced signal detection capabilities, paving the way for future in vivo applications in tissue characterization.

Investigating the Secrets of Stonehenge with Raman Spectroscopy: Provenance of the Ancient Altar Stone

Abstract In-field compositional analysis of large prehistoric relics, such as the Altar Stone at Stonehenge (England), is limited due to the size of the relics and difficulty in obtaining samples that can be analyzed in a laboratory. In this study, a portable Raman spectroscopy system was used to analyze the Altar Stone to help determine its origin and classification, which appears to differ from other bluestones at Stonehenge. While the study is ongoing and the definitive origin of the Altar Stone is not yet known, this study demonstrates the applicability of a portable Raman spectroscopy system in the compositional analysis of large samples in the field.

In situ single-cell spontaneous Raman spectroscopy differentiates tumor-associated macrophages

The analysis of in situ single cells in tissue is crucial for the study of tumors. However, simultaneous analysis of multiple biomolecules for single cells by fluorescence immunohistochemistry is challenging. Spontaneous Raman spectroscopy provides biochemical fingerprints of individual cells in a label-free and nondestructive manner, yet it is not well applied to single cells in tissue. Here, we develop an in situ single-cell spontaneous Raman spectroscopy (SRS) system that can localize a single cell in tissue with fluorescence imaging, while obtaining the single-cell Raman spectra for molecular analysis. Our system is verified by measuring the standard polystyrene beads of different sizes. Measurements of in situ single macrophages in clinical cancerous and para-cancerous tissues are then performed. By using discriminant analysis, it is shown that CD68+ macrophages in cancerous and para-cancerous tissues are classified with an accuracy of 98.3 %. The molecular content of single macrophages in tissue is analyzed by using multivariate curve resolution-alternating least squares method. We find that the lipid content of tumor-associated macrophages in cancerous tissues is higher while both the contents of protein and nucleic acid are lower than those in para-cancerous tissues, which is challenging to achieve by conventional immunohistochemistry. Our in situ single-cell SRS system has the capability for the obtaining of molecular information of a localized single cell in tissue, which may find potential applications for clinical cancer diagnosis.

Technical note: Characterization of a single-beam gradient force aerosol optical tweezer for droplet trapping, phase transition monitoring, and morphology studies

Abstract. Single particle analysis is essential for a better understanding of the particle transformation process and to predict its environmental impact. In this study, we developed an aerosol optical tweezer (AOT) Raman spectroscopy system to investigate the phase state and morphology of suspended aerosol droplets in real time. The system comprises four modules: optical trapping, reaction, illumination and imaging, and detection. The optical trapping module utilizes a 532 nm laser and a 100 × oil immersion objective to stably trap aerosol droplets within 30 s. The reaction module allows us to adjust relative humidity (RH) and introduce reaction gases into the droplet levitation chamber, facilitating experiments to study liquid–liquid phase transitions. The illumination and imaging module employs a high-speed camera to monitor the trapped droplets, while the detector module records Raman scattering light. We trapped sodium chloride (NaCl) and 3-methyl glutaric acid (3-MGA) mixed droplets to examine RH-dependent morphology changes. Liquid–liquid phase separation (LLPS) occurred when RH was decreased. Additionally, we introduced ozone and limonene/pinene to generate secondary organic aerosol (SOA) particles in situ, which collided with the trapped droplet and dissolved in it. To determine the trapped droplet's characteristics, we utilized an open-source program based on Mie theory to retrieve diameter and refractive index from the observed whispering gallery modes (WGMs) in Raman spectra. It is found that mixed droplets formed core–shell morphology when RH was decreased, and the RH dependence of the droplets' phase transitions generated by different SOA precursors varied. Our AOT system serves as an essential experimental platform for in situ assessment of morphology and phase state during dynamic atmospheric processes.

Raman spectra of naphthalene under shock compression

The Hugoniot data of naphthalene under shock compression were measured by using a two-stage gas gun, and the D-u line was obtained at an impact pressure of 13.7 GPa: D = 2.102 (±0.09) + 1.865 (±0.066) up. Furthermore, the Raman spectra of naphthalene were acquired under impact pressures of 2.33 GPa and 3.55 GPa by utilizing a transient Raman spectroscopy system. Seven intramolecular vibration modes were observed, and the corresponding Raman peaks shifted blue with the increase of impact pressure. However, no anomalous phenomena such as peak splitting or disappearance were detected, indicating that the stability of naphthalene within the applied pressure range and the frequency shift of shock-compressed naphthalene obviously depend on the density rather than the pressure.

In situ monitoring of loading and elution processes of cryoprotectants at the single-cell level with Raman spectroscopy

BackgroundThe analysis of cell membrane permeability plays a crucial role in improving the procedures of cell cryopreservation, which will affect the specific parameter settings in loading, removal and cooling processes. However, existing studies have mostly focused on deriving permeability parameters through osmotic theoretical models and cell volume response analysis, and there is still a lack of the direct experimental evidence and analysis at the single-cell level regarding the migration of cryoprotectants. ResultsIn this work, a side perfusion microfluidics chips combined with Raman spectroscopy system was built to monitor in situ the Raman spectroscopy of extracellular and intracellular solution during loading and elution process with different cryoprotectant solution systems (single and dual component). And it was found that loading a high concentration cryoprotectant solution system through a single elution cycle may result in significant residual protective agent, which can be mitigated by employing a multi-component formula but multiple elution operations are still necessary. Furthermore, the collected spectral signals were marked and analyzed to was perform preliminary relative quantitative analysis. The results showed that the intracellular concentration changes can be accurately quantified by the Raman spectrum and are closely related to the extracellular solution concentration changes. Significance and noveltyBy using the method of small flow perfusion (≤20 μL/min) in the side microfluidic chip after the gravity sedimentation of cells, the continuous loading and elution process of different cryoprotectants on chip and the spectral acquisition can be realized. The intracellular and extracellular concentrations can be quantified in situ based on the ratio of spectral peak intensities. These results indicate that spectroscopic analysis can be used to effectively monitor intracellular cryoprotectant residues.

Combined Mutual Learning Net for Raman Spectral Microbial Strain Identification.

Infectious diseases pose a significant threat to global health, yet traditional microbiological identification methods suffer from drawbacks, such as high costs and long processing times. Raman spectroscopy, a label-free and noninvasive technique, provides rich chemical information and has tremendous potential in fast microbial diagnoses. Here, we propose a novel Combined Mutual Learning Net that precisely identifies microbial subspecies. It demonstrated an average identification accuracy of 87.96% in an open-access data set with thirty microbial strains, representing a 5.76% improvement. 50% of the microbial subspecies accuracies were elevated by 1% to 46%, especially for E. coli 2 improved from 31% to 77%. Furthermore, it achieved a remarkable subspecies accuracy of 92.4% in the custom-built fiber-optical tweezers Raman spectroscopy system, which collects Raman spectra at a single-cell level. This advancement demonstrates the effectiveness of this method in microbial subspecies identification, offering a promising solution for microbiology diagnosis.

Swept-source Raman spectroscopy of chemical and biological materials.

Raman spectroscopy has been used as a powerful tool for chemical analysis, enabling the noninvasive acquisition of molecular fingerprints from various samples. Raman spectroscopy has proven to be valuable in numerous fields, including pharmaceutical, materials science, and biomedicine. Active research and development efforts are currently underway to bring this analytical instrument into the field, enabling in situ Raman measurements for a wider range of applications. Dispersive Raman spectroscopy using a fixed, narrowband source is a common method for acquiring Raman spectra. However, dispersive Raman spectroscopy requires a bulky spectrometer, which limits its field applicability. Therefore, there has been a tremendous need to develop a portable and sensitive Raman system. We developed a compact swept-source Raman (SS-Raman) spectroscopy system and proposed a signal processing method to mitigate hardware limitations. We demonstrated the capabilities of the SS-Raman spectroscopy by acquiring Raman spectra from both chemical and biological samples. These spectra were then compared with Raman spectra obtained using a conventional dispersive Raman spectroscopy system. The SS-Raman spectroscopy system used a wavelength-swept source laser (822 to 842nm), a bandpass filter with a bandwidth of 1.5nm, and a low-noise silicon photoreceiver. Raman spectra were acquired from various chemical samples, including phenylalanine, hydroxyapatite, glucose, and acetaminophen. A comparative analysis with the conventional dispersive Raman spectroscopy was conducted by calculating the correlation coefficients between the spectra from the SS-Raman spectroscopy and those from the conventional system. Furthermore, Raman mapping was obtained from cross-sections of swine tissue, demonstrating the applicability of the SS-Raman spectroscopy in biological samples. We developed a compact SS-Raman system and validated its performance by acquiring Raman spectra from both chemical and biological materials. Our straightforward signal processing method enhanced the quality of the Raman spectra without incurring high costs. Raman spectra in the range of 900 to were observed for phenylalanine, hydroxyapatite, glucose, and acetaminophen. The results were validated with correlation coefficients of 0.88, 0.84, 0.87, and 0.73, respectively, compared with those obtained from dispersive Raman spectroscopy. Furthermore, we performed scans across the cross-section of swine tissue to generate a biological tissue mapping plot, providing information about the composition of swine tissue. We demonstrate the capabilities of the proposed compact SS-Raman spectroscopy system by obtaining Raman spectra of chemical and biological materials, utilizing straightforward signal processing. We anticipate that the SS-Raman spectroscopy will be utilized in various fields, including biomedical and chemical applications.

Measurement report: Water diffusion in single suspended phase-separated aerosols

Abstract. Water diffusion is a typical thermodynamic process in ambient aerosols that plays pivotal roles in their physicochemical properties and atmospheric lifetime and influences the climate and human health. A fair amount of aerosols become phase-separated after experiencing atmospheric aging processes such as efflorescence, amorphization, and liquid–liquid phase separation. However, detecting the hygroscopicity of heterogeneous aerosols is quite intractable. Here, for the first time, we directly characterized the water diffusion in single suspended phase-separated aerosols via a self-constructed laser tweezer Raman spectroscopy (LTRS) system. The H2O–D2O isotope exchange was harnessed to trace the water diffusion in single laser-levitated homogenous/heterogeneous microdroplets. The time-resolved cavity-enhanced Raman spectra of the microdroplets were used to detect the diffusion process in real time. Two archetypes of phase-separated aerosols, i.e., partially engulfed and core–shell, were studied. Moreover, we quantified the dynamic water diffusion process by experimentally measuring the diffusion coefficients. The results showed that compared with the homogenous aerosols, water diffusion limitations existed in the phase-separated aerosols. The incomplete diffusion may stem from the formation of certain hydrated molecule clusters. This work provides possible implications for the evolutions, especially the gas–particle partition, of the actual phase-separated atmospheric aerosols.

Electro-optical properties of a graphene device on a tip-enhanced Raman spectroscopy system.

This paper investigates the impact of graphene on tip-enhanced Raman spectroscopy (TERS) by developing an electromagnetic characterization of the TERS-graphene device system. The study focuses on the interaction between the tip, the gate voltage, and the sample, specifically examining the electromagnetic effects in the system. Employing a finite element method (FEM)-based simulation model, we meticulously dissect the electric field distribution and the Raman amplification when graphene is introduced into the system. Our findings reveal that including graphene results in a marginal reduction in Raman amplification and a negligible variation in the induced charges within the system. To reinforce our simulations, we employ a simplified capacitor model, which corroborates our results, showcasing negligible induced charges and validating the obtained capacitance values. In this manuscript, we also explore the influence of the setup on the electro-optical properties of graphene, revealing a slight variation in conductivity despite strong changes in chemical potential. Overall, this work contributes to understanding TERS's electromagnetic aspects in the presence of graphene.

Rapid and simultaneous quantitative and discriminative analyses of liquor quality parameters with machine learning-assisted batch Raman spectroscopy: Synergistic instrumental upgrade and chemometric optimization

This study investigates the rapid and simultaneous assessments of two key liquor quality parameters – alcohol content and overall sensory quality – utilizing a batch Raman spectroscopic system and chemometrics, with a commercial baijiu (Chinese liquor) as the subject. An in-house designed motorized 12-cuvette tray facilitated stable and efficient spectral acquisition from 34 production batches of standard baijiu, supplemented by alcohol content-adjusted and overall sensory-disqualified samples, to form two separate datasets for the optimization and evaluation of chemometric approaches based on multivariate analysis and machine learning. The combination of dimension reduction with principal component analysis (PCA) and support vector regression (SVR) with a nonlinear kernel showed superior performances for predicting alcohol content and identifying sensory-disqualified samples. Expanding the alcohol content range of the training set enhanced the quantification capacity of the PCA-SVR model and yielded a relatively accurate alcohol content prediction (±0.15 % v/v) for the tested standard baijiu. The PCA-SVR model built for sensory quality grading achieved an average precision of 93% for identifying disqualified baijiu samples that compositionally resemble standard ones. Based on the synergistic instrumental and chemometric optimization, the proposed machine learning-assisted batch Raman spectroscopic system offers a rapid, reliable, and integrated quality control tool for liquor production.

MEMS-based portable confocal Raman spectroscopy rapid imaging system.

Aiming at the miniaturization and rapid imaging requirements of a portable confocal Raman system, a MEMS-based portable confocal Raman spectroscopy rapid imaging method is proposed in this study. This method combines the dual 2D MEMS mirror scanning method and the grid-by-grid scanning method. The dual 2D MEMS mirror scanning method is used for the miniaturization design of the system, and the grid-by-grid scanning method is used for rapid imaging of Raman spectroscopy. Finally, the rapid imaging and miniaturization design of a portable confocal Raman spectroscopy system are realized. Based on this method, a portable confocal Raman spectroscopy rapid imaging system with an optical probe size of just 98m m×70m m×40m m is constructed. The experimental results show that the imaging speed of the system is 45 times higher than that of the traditional point-scan confocal Raman system, and the imaging speed can be further improved according to the requirements. In addition, the system is used to swiftly identify agate ore, and the material composition distribution image over a 126µm 2×126µm 2 region is obtained in just 16min. This method provides a new solution for the rapid imaging and miniaturization design of the confocal Raman system, as well as a new technical means for rapid detection in deep space exploration, geological exploration, and field detection.

Collision Enhanced Raman Scattering (CERS): An Ultra-High Efficient Raman Enhancement Technique for Hollow Core Photonic Crystal Fiber Based Raman Spectroscopy Gas Analyzer.

Raman enhancement techniques are essential for gas analysis to increase the detection sensitivity of a Raman spectroscopy system. We have developed an efficient Raman enhancement technique called the collision-enhanced Raman scattering (CERS), where the active Raman gas as the analyte is mixed with a buffer gas inside the hollow-core photonic-crystal fiber (HCPCF) of a fiber-enhanced Raman spectroscopy (FERS) system. This results in an enhanced Raman signal from the analyte gas. In this study, we first showed that the intensity of the 587 cm-1 stimulated Raman scattering (SRS) peak of H2 confined in an HCPCF is enhanced by as much as five orders of magnitude by mixing with a buffer gas such as helium or N2. Secondly, we showed that the magnitudes of Raman enhancement depend on the type of buffer gas, with helium being more efficient compared to N2. This makes helium a favorable buffer gas for CERS. Thirdly, we applied CERS for Raman measurements of propene, a metabolically interesting volatile organic compound (VOC) with an association to lung cancer. CERS resulted in a substantial enhancement of propene Raman peaks. In conclusion, the CERS we developed is a simple and efficient Raman-enhancing mechanism for improving gas analysis. It has great potential for application in breath analysis for lung cancer detection.