SERS Sensor Research Articles

Development of Exhaled Breath Diagnosis Sensors for Rapid Identification of COVID-19 Patients

The novel coronavirus pneumonia, a global pandemic disease named as coronavirus disease 2019, has caused enormous losses on the health and economies of people all over the world, while there is still a lack of quick and sensitive diagnostic method and effective therapy. Developing rapid diagnostic method for coronavirus disease 2019 has become exceptional urgent. Herein we report a rapid diagnostic method for the novel coronavirus through monitoring the volatile biomarkers in human exhaled breath. The breath volatile biomarkers are derived from the metabolism of novel coronavirus, including acetoin, 2,4,6-trimethylpyridine, 3-methyl tridecane, tetradecane, isooctyl alcohol, pentadecane, hexadecane, 1-methylene-1H-indene. By comparing the types and concentrations of the volatile biomarkers in human exhaled breath combined with SERS sensor, we could distinguish between the healthy person and the patients with coronavirus disease 2019. This work confirms that various volatile organic compounds metabolized by novel coronavirus can be employed for rapidly screening of patients with coronavirus disease 2019, and has broad application prospects in the prevention and control of the epidemic.

Bio-inspired Ag nanovilli-based sandwich-type SERS aptasensor for ultrasensitive and selective detection of 25-hydroxy vitamin D3

Vitamin D has been identified as an essential biomarker for various diseases such as rheumatoid arthritis, cancer, and cardiovascular diseases. Recently, many reports have demonstrated a potential link between vitamin D and systemic infections, including coronavirus disease 2019. The villi of the small intestine increase the surface area of the intestinal walls, demonstrating exceptionally efficient absorption of nutrients in the lumen and adding digestive secretions. In this study, based on the villi structure, we developed a bio-inspired silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor for the ultrasensitive and selective detection of 25-hydroxy vitamin D3. The densely packed nanovilli structure enhanced the Raman signal, forming hotspots owing to its large surface area. Using experiments and electromagnetic simulations, we optimized the nanovilli structure as a SERS sensor. The sandwich-type aptasensor was designed using an aptamer and 4-Phenyl-1,2,4-triazoline-3,5-dione-methylene blue complex. The nanovilli-based aptasensor could sensitively detect various concentrations of 25-hydroxy vitamin D3, ranging from those found in deficient to excess conditions. The detection limit of the nanovilli-based sandwich-type aptasensor for 25-hydroxy vitamin D3 was 0.001 ng/mL, which is much lower than the deficiency concentration, and was detectable even in the human serum. In addition, our proposed sensor exhibited good repeatability (17.76%) and reproducibility (7.47%). Moreover, the nanovilli-based sandwich-type SERS aptasensor could selectively distinguish 25-hydroxy vitamin D3 from other vitamins. The silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor opens a new avenue for the development of a bio-inspired vitamin-sensing platform.

Human ACE2-Functionalized Gold “Virus-Trap” Nanostructures for Accurate Capture of SARS-CoV-2 and Single-Virus SERS Detection

HighlightsExtremely sensitive and prompt COVID-19 SERS biosensor to detect SARS-CoV-2 virus in the contaminated water at single-virus level.SERS sensor features a low detection limit of 80 copies mL−1 for the simulated contaminated water by SARS-CoV-2 virus as short as 5 min.ACE2-modified SERS sensor with machine-learning and identification standard enable rapid detection of novel yet-unknown coronaviruses.

The Effects of Psi Morphology on the Detection Efficiency of the Au-Nps Hot Spot SERS Sensors

This work is related to the investigation of the effects of porous silicon (PSi) morphologies on the performance of plasmonic gold nanoparticles (Au-NPs) hot spot SERS sensors for the detection of amoxicillin molecules. Two Si wafers with different resistivity values of 10 and 100 Ω.cm were used to synthesize a PSi layer of pores- and mud-like structures, respectively, by pulsed photo chemical etching process. The hot spot SERS sensors were synthesized by incorporating the Au-NPs within the PSi morphologies of pores- and mud- like structures which are characterized by high density of nucleation sites. Plasmonic Au- NPs with different sizes and hot spot regions were incorporated into the porous structures by the ion reduction process. It was recognized that the PSi morphologies have a considerable influence on the fabrication process of the detection sensors and, consequently, on the detection process. The plasmonic Au-NPs hot spot SERS sensor based on the PSi morphology of the mud-like structures shows higher sensitivity than that of pores-like structures, even at very low concentrations of amoxicillin solutions.

One-Step Rapid Synthesis of Al-Based Ag Dendrites for Highly Active and Cost Effective SERS Plasmonic Substrates

Highly active Al-based Ag dendrites SERS plasmonic substrates have been rapidly synthesized by the one-step galvanic displacement reaction without the use of any surfactants and templates. The as-prepared SERS substrates were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. XRD measurements confirmed the metallic nature of the formed Ag dendrites. None of the organic additives were used in the synthesis process, which ensures the substrates surfaces are completely clean and avoiding the introduction of organic contaminants. The innovative rough bionic substrates yield a final silver dendritic structure that offers large specific surface area and high-density hotspots. Using malachite green as a model target, the Al-based Ag dendrites SERS substrates exhibited acceptable reproducibility (relative standard deviation of 23.8%) and high enhancement capacities (pushed the detection limit down to 10 pM). Importantly, these Ag dendrites could potentially be employed as highly active and cost effective flexible SERS sensors for label-free ultrasensitive detection of biomolecules.

Highly Sensitive SERS Detection of Neonicotinoid Pesticides. Complete Raman Spectral Assignment of Clothianidin and Imidacloprid.

The use of surface enhanced Raman spectroscopy in the development of low cost, portable sensor devices that can be used in the field for nitroguanidine neonicotinoid insecticide detection is appealing. However, a key challenge to achieving this goal is the lack of detailed analysis and vibrational assignment for the most popular neonicotinoids. To make progress toward this goal, this paper presents an analysis of the bulk Raman and SERS spectra of two neonicotinoids, namely clothianidin and imidacloprid. Combined with first-principles simulations, this allowed assignment of all Raman spectral modes for both molecules. To our knowledge, this is the first report of SERS analysis and vibrational assignment of clothianidin, and a comprehensive assignment and analysis is provided for imidacloprid. Silver nanostructured surfaces were fabricated for qualitative SERS analysis, which provides the characteristic spectra of the target molecules and demonstrates the ability of SERS to sense these molecules at concentrations of 1 ng/mL. These concentrations are on par with high-end chromatographic-mass spectroscopy laboratory methods. These SERS sensors thus allow for the selective and sensitive detection of neonicotinoids and provide complementary qualitative data for the molecules. Furthermore, this technique can be adapted to portable devices for remote sensing applications. Further work focuses on integrating our device with an electronics platform for truly portable residue detection.

Rapid fabrication of three-dimensional flower-like gold microstructures on flexible substrate for SERS applications.

In this work, hierarchical flower-like gold microstructures (HFGMs) are synthesized on a flexible PET film substrate by electrochemical deposition method as a SERS sensor without surfactant or directing agent. The effects of deposition current and electrolyte concentration on morphology and SERS performance are discussed to find the optimal preparation conditions. SERS activity of samples with different morphologies was investigated by comparing experiments and the mechanism was discussed. It shows the HFGMs with 3D nanoflakes and nanosheet tips present outstanding SERS activity with ultrasensitive detection limits. The lowest concentration of R6G that can be detected is 10-10 M, and the characteristic signals of thiram can be detected as low as 0.1 ppm. The HFGMs substrate show great potential of application in trace detection by SERS.

便携式SERS传感器的近岸海水中PAHs检测

便携式SERS传感器的近岸海水中PAHs检测

Nanostructured GaN sensors for Surface Enhanced Raman Spectroscopy

The aim of this communication is to describe the range of applications of GaN-based platforms for trace detection and identification of biological and chemical agents using SERS technique. The methods of nano-structuring of GaN surface for SERS application are briefly described. The results of employing SERS method for analysis of Fentanyl and Bacillus Atrophaeus spores is demonstrated. The arguments are summarized which show the universal feature of GaN-based platforms as SERS sensor.

Thermo-responsive molecularly imprinted sensor based on the surface-enhanced Raman scattering for selective detection of R6G in the water.

In this study, a novel SERS sensor was successfully prepared by combining a molecular imprinted technique (MIT) with a SERS technique to improve the selectivity of the traditional SERS technique. Moreover, a thermo-sensitive technique was also introduced to confer stimuli-responsive properties to the materials. In a typical procedure, the Ag nanoparticles (NPs) were reduced on the surface of ZnO nanorods (NRs), and the ZnO/Ag heterostructures were used as the SERS substrates. Subsequently, a layer of thermo-sensitive imprinted polymer was coated on the surface of ZnO/Ag heterostructures to prepare the thermoresponsive ZnO/Ag/molecularly imprinted polymers (ZOA-TMIPs) by precipitation polymerization. Moreover, it was proven that the ZOA-TMIPs were regenerable and exhibited good reusability. The results proved that the materials in this study can be effectively used for residual organic dye detection in water.

Surface modification of Au and Ag plasmonic thin films via diazonium chemistry: Evaluation of structure and properties

Plasmon-active noble metals nanostructures based on Ag and Au thin films become widely applied in the field of plasmonics and related sensing technologies. For improvement of the metal interaction with different media, metals surface can be functionalized in order to increase/decrease hydrophilicity, lipophilicity or introduce/change the surface charge. In this paper, the surface functionalization of plasmon-active Au and Ag films using arenediazonium tosylates was described. The surface functionalization was performed in the aqueous medium by the spontaneous and electrically induced mechanisms. Functionalized surfaces were characterized by the Raman and UV–vis spectroscopies, AFM nanomechanical mapping, SEM (EDX), XPS, CVA, zeta- potential, and water contact angle measurement techniques. It was founded that the key difference between reactivity of gold and silver films is distributional behavior of grafted organic functional groups: silver has higher tendency to form clustered, island-like structure while gold is covered more homogeneously. Spontaneous modification forms approximately monomolecular thick films of organic compounds and can be used in the field of SPR or SERS sensors. Electrochemically induced activation produces thick polyphenylene layer on the metal surface and can find application in the field of tunable plasmonic devices or plasmon-based lasers.

Influence of the Particle Shape and Density of Self-Assembled Gold Nanoparticle Sensors on LSPR and SERS

A low-cost methodology to prepare highly sensitive sensors is reported with different nanoparticles for LSPR and SERS measurements. The LSPR and SERS sensor was self-assembled as an array of polystyrene-capped gold nanoparticles (Au NPs), produced by drop-coating a Au NP suspension on a glass surface followed by plasma etching of the polystyrene. The procedure was applied to different sizes and shapes of Au NPs, primarily 60 nm gold nanospheres and 80 nm gold nanoraspberries, created with precise control on the packing density of the array. The LSPR sensitivity and figure of merit (FOM) for the arrays of gold nanoraspberries were found to be almost 2-fold better than for the nanospheres and had a shorter penetration depth, a consequence of their small-sized surface asperities. The average measured SERS enhancement factor (EF) for the raspberries was also higher than for spheres and control over the EF was achieved using different packing densities which allowed control of the interparticle coupling enhanc...

Engineered “hot” core–shell nanostructures for patterned detection of chloramphenicol

In this study, we described a novel method for highly sensitive and specific detection of chloramphenicol (CAP) based on engineered “hot” Au core-Ag shell nanostructures (Au@Ag NSs). Cy5-labeled DNA aptamer was embedded between the Au and Ag layers as a signal generator and target-recognition element, to fabricate uniform Au@Ag NSs with unexpected strong and stable SERS signals. The presented CAP can specifically bind to the DNA aptamer by forming an aptamer-CAP conjugate, and cause greatly decreased SERS signals of Au@Ag NSs. By using this method, we were able to detect as low as 0.19pgmL−1 of CAP with high selectivity, which is much lower than those previously reported biosensors. Compared with the other SERS sensors that attached a dye in the outer layer of nanoparticles, this method exhibits excellent sensitivity and has the potential to significantly improve stability and reproducibility of SERS-based detection techniques.

SE(R)RS devices fabricated by a laser electrodispersion method

A novel laser electrodispersion (LE) technique was employed to deposit gold nanoparticles onto Si and SiO(x) surfaces. The LE technique combines laser ablation with cascade fission of liquid metal micro-drops, which results in the formation of nanoparticles upon rapid cooling. The shape and the size distribution of the Au nanoparticles prepared by LE depend on the nature of the support. Gold nanoparticles were also deposited in the channels of microreactors fabricated by wet etching of Si and used as SE(R)RS sensors. The influence of the nanoparticle surface density as well as of the nature of the substrate on the Raman response was studied. At an appropriate surface density of the deposited nanoparticles a significant enhancement of Raman signal was observed showing the possibility to create efficient SERS substrates. Application of microfluidic devices in surface enhanced Raman spectroscopy (SERS) in continuous-flow mode with sensor regeneration is described.

Raman and surface‐enhanced Raman spectroscopic studies of the 15‐mer DNA thrombin‐binding aptamer

AbstractAptamers are single‐stranded oligonucleotides that selectively bind to their target molecules owing to their ability to form secondary structures and shapes. The 15‐mer (5′‐GGTTGGTGTGGTTGG‐3′) DNA thrombin‐binding aptamer (TBA) binds to thrombin following the formation of a quadruplex structure via the Hoogsten‐type G–G interactions. In the present study, Raman and SERS spectra of TBA and thiolated TBA (used to facilitate covalent bonding to metal nanoparticle) in different conditions are investigated. The spectra of the two analogs exhibit vibrations, such as the C8N7H2 deformation band at ∼1480 cm−1 of the guanine tetrad, that are characteristic of the quadruplex structure in the presence of K+ ions or at low temperature. Interestingly, SERS spectra of the two analogs differ markedly from their respective normal Raman spectra, possibly due to changes in the conformation of the aptamer upon binding, as well as to the specific interaction of individual vibrational modes with the metal surface. In addition, the SERS spectra of the thiolated aptamer show significant changes with different concentrations, which may be due to different orientation of the molecule with respect to the metal surface. This study provides useful information for the development of label‐free aptamer‐based SERS sensors and assays. Copyright © 2009 John Wiley & Sons, Ltd.

Sol-gel Encapsulated Gold-Silica Nanoshell-based SERS Sensors

ABSTRACTWe have used sol-gel methods to immobilize gold-silica nanoshells to create robust SERS based sensors. Using a protocol commonly used to immobilize proteins, biologically friendly SERS sensors for the study of gold binding peptides and proteins have been created. Specifically, by combining tetramethyl orthosilicate (TMOS), methyltrimethoxysilicate (MTMS), phosphate buffer, and gold nanoparticles we have created sol-gels with reduced fluorescence and Raman backgrounds. The resulting substrates have been tested using the Raman scattering response of 4-mercaptonbenzoic acid (4-MBA) to determine porosity and long-term stability of this SERS substrate. Multiple rinse cycles using phosphate buffer showed no significant decline in the SERS response of the substrate up to ten rinse cycles. Future studies will test the feasibility of using such substrates for the detection of biomolecules on the surface of gold.

Fibre-optic SERS sensors with well-defined nanoscale structures

Fibre-optic SERS sensors with well-defined nanoscale structures