The isolation and characterization of exosomes

Unstable detection environment is one of the biggest interferences for in situ surface-enhanced Raman spectroscopy (SERS) using in real-time monitoring of toxic pollutants, leading to unreliable results. To address this problem, we have designed and prepared a cavity-based particle-in-quasicavity (PIQC) architecture composed of hierarchical ZnO/Ag nanosheets and nanoprotrusions for improving the in situ SERS performance under a liquid environment. Benefitting from the special cascaded optical field mode, the PIQC ZnO/Ag exhibits excellent in situ SERS detectability, with 10-18 M of limit of detection for rhodamine 6G and 12.8% of signal relative standard deviation value. Furthermore, by means of a microfluidic chip, this PIQC structure is proved to have the quantitative analysis feasibility and realizes real-time monitoring of the 3,3',4,4'-tetrachlorobiphenyl, a representative global environmental hazard, under the flowing environment. The strategy in this paper provides a brand new idea to promote the application of in situ SERS in contaminant monitoring and is also instructive for light control in other optical fields.

Hierarchical Particle-In-Quasicavity Architecture for Ultratrace In Situ Raman Sensing and Its Application in Real-Time Monitoring of Toxic Pollutants

Au@ZIF-8 SERS paper for food spoilage detection.

Metal-organic frameworks (MOFs), built from organic linkers and metal ions/clusters, have emerged as highly promising materials for wide applications. Combining highly porous crystalline MOFs with the surface-enhanced Raman scattering (SERS) technique can achieve unprecedented advantages of high selectivity, high sensitivity, and expedience in analysis and detection. In this critical review, the aim is to present a comprehensive review of recent advances in understanding of the roles of MOFs in MOF-SERS systems, particularly their structure-to-property correlation. Key examples are selected from representative literature to illustrate critical concepts and the MOF-based property-dependent applications are particularly emphasized. Finally, the barriers, future trends, and prospects for further advances in MOF-SERS platforms are also discussed.

Understanding the Role of Metal–Organic Frameworks in Surface‐Enhanced Raman Scattering Application

Endowed with rich terminal groups, good electrical conductivity, and controllable structure, transition metal carbides/nitrides (MXenes) have attracted extensive attention for potential application in gas sensor, but long‐standing challenges of the MXenes (titanium carbide as the representative) are their limited selectivity and sensitivity. Herein, a high‐active double transition‐metal titanium molybdenum carbide (Mo2TiC2Tx) with superstrong surface adsorption (−3.12 eV) for NO2 gas molecule is proposed, and it is further coupled with molybdenum disulfide (MoS2) by interface modulation to construct an edge‐enriched heterostructure. Due to the synergistic effect of strong adsorption, rich adsorption sites, and coupling interface of Mo2TiC2Tx/MoS2 composite, the as‐fabricated Mo2TiC2Tx/MoS2 gas sensor exhibits an outstanding response toward NO2 with high selectivity against various interference gases, which is well supported by density functional theory calculations. Meanwhile, the sensor exhibits a sensitivity of 7.36% ppm−1, detection limit of 2.5 ppb, and reversibility at room temperature. A portable, wireless NO2 monitoring system is demonstrated for gas leakage searching and dangerous warning based on Mo2TiC2Tx/MoS2 gas sensor. This work facilitates the gas sensing application of MXenes, and provides an avenue for the development of wireless sensing system in environmental monitoring and safety assurance.

Edge‐Enriched Mo2TiC2Tx/MoS2 Heterostructure with Coupling Interface for Selective NO2 Monitoring

A novel kind of array-assisted surface-enhanced Raman spectroscopy (SERS) microfluidic chip (ArraySERS chip) is demonstrated for gas sensing, which has the advantages of both ultrahigh sensitivity and multiplex sensing ability. On the one hand, the introduction of a microstructured triangular array can greatly increase the multiple collision probability between gas molecules and sensing interfaces in the channel. Compared with traditional gas sensors using sealed boxes, where gaseous molecules move only by diffusion, the ArraySERS chip exhibits significantly improved sensitivity. On the other hand, a composite nanoparticle is fabricated as a SERS probe for reading out the fingerprint spectral data, which consists of metal-organic framework (MOF) materials [Zeolitic Imidazolate framework-8 (ZIF-8)] and Au@Ag nanocubes, as well as cysteamine (CA) that serves as the gas-capturing agent. The experimental results show that such a structure of the SERS probe can further increase the sensing ability because of better adsorption of ZIF-8 for gas and the lower SERS background of CA itself. In addition, the simultaneous detection of multiplex gases was easily performed according to their own intrinsic SERS signals. Taking aldehyde gas as a model of a typical air pollutant, trace and multicomponent detection was realized using the ArraySERS chip. The limit of detection value was as low as 1 ppb, which is 2 magnitudes lower than that obtained by traditional methods. This strategy can be well extended for the detection of universal gases and help unleash the potential of existing gas sensors, especially for samples at low concentrations in air.

Array-Assisted SERS Microfluidic Chips for Highly Sensitive and Multiplex Gas Sensing

Gas sensors lie at the heart of various fields ranging from medical to environmental sciences, and the demand of gas sensors is instantly expanding. However, in the face of complex gas samples, how to maintain high sensitivity while performing multiplex detection still puzzles the researchers. Here, by introducing Ti3C2Tx MXene into a microfluidic gas sensor with a three-dimensional (3D) transferable SERS substrate, a powerful gas sensor having both multiplex detecting ability and high sensitivity is demonstrated. The employ of MXene endows the sensor with a universal high adsorption efficiency for various gases while the generation of in situ gas vortices in the sophisticated nanomicro structure extends the molecule residence time in SERS-active area, both leading to the increased sensitivity. In the proof-of-concept experiment, a limit of detection (LOD) of 10-50 ppb was achieved for three typical volatile organic compounds (VOCs) according to the intrinsic SERS signals of gas molecules. Besides, the well-designed periodic 3D structure solves the general repeatability problem of SERS substrates. In addition, the detailed composition of gas mixture was revealed using classic least-square analysis (CLS) with an average accuracy of 90.6%. Further, a chromatic barcode was developed based on the results of CLS to read out the complex composition of samples visually.

Ti3C2Tx MXene-Loaded 3D Substrate toward On-Chip Multi-Gas Sensing with Surface-Enhanced Raman Spectroscopy (SERS) Barcode Readout.

Human mucin-1 (MUC1) has attracted considerable attention owing to its overexpression in diverse malignancies Here, for the rapid and efficient detection of MUC1, we present a SERS-colorimetric dual-mode aptasensor, by integrating SERS probes with magnetic separation, which has several distinctive advantages Using such a dual-mode aptasensor, the colorimetric functionality is distinguishable by the naked eye, providing a fast and straightforward screening ability for the detection of MUC1 Moreover, SERS-based detection greatly improves the detection sensitivity, reaching a limit of detection of 01 U/mL In addition, the combination of SERS and colorimetric method holds the advantages of these two techniques and thereby increases the reliability and efficiency of MUC1 detection On the one hand, the magnetic nanobeads functionalized with MUC1-specific aptamer were utilized as an efficient capturing substrate for separating MUC1 from biological complex medium On the other hand, the gold-silver core-shell nanoparticles modified with Raman reporters and the complementary sequences of MUC1 were used as the signal indicator, which could simultaneously report the SERS signal and colorimetric change This strategy can achieve a good detection range and realize MUC1 analysis in real patients’ samples Thus, we anticipate that this kind of aptasensor would provide promising potential applications in the diagnosis and prognosis of cancers

A SERS-colorimetric dual-mode aptasensor for the detection of cancer biomarker MUC1

Peroxidase-like recyclable SERS probe for the detection and elimination of cationic dyes in pond water

Surface-enhanced Raman spectroscopy (SERS) is a promising technology for wearable sensors due to its fingerprint spectrum and high detection sensitivity. However, since SERS-activity is sensitive to both the distribution of "hotspots" and excitation angle, it is profoundly challenging to develop a wearable SERS sensor with high stability under various deformations during movements. Herein, inspired by omnidirectional light-harvesting of the compound eye of Xenos Peckii, a wearable SERS sensor is developed using omnidirectional plasmonic nanovoids array (OPNA), which is prepared by assembling a monolayer of metal nanoparticles into the artificial plasmonic compound-eye (APC). Specifically, APC is an interconnected frame containing omnidirectional "pockets" and acts as an "armour", not only rendering a broadband and omnidirectional enhancement of "hotspots" in the delicate nanoparticles array, but also maintaining an integrity of the "hotspots" against external mechanical deformations. Furthermore, an asymmetry super-hydrophilic pattern is fabricated on the surface of OPNA, endowing the hydrophobic OPNA with the ability to spontaneously extract and concentrate the analytes from sweat. Such an armored SERS sensor can enable the wearable and in situ analysis with high sensitivity and stability, exhibiting great potential in point-of-care analysis.

Kuo Yang

Papers

Array-Assisted SERS Microfluidic Chips for Highly Sensitive and Multiplex Gas Sensing

Ti3C2Tx MXene-Loaded 3D Substrate toward On-Chip Multi-Gas Sensing with Surface-Enhanced Raman Spectroscopy (SERS) Barcode Readout.

A SERS-colorimetric dual-mode aptasensor for the detection of cancer biomarker MUC1

Peroxidase-like recyclable SERS probe for the detection and elimination of cationic dyes in pond water

Wearable SERS Sensor Based on Omnidirectional Plasmonic Nanovoids Array with Ultra-High Sensitivity and Stability.