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Gold Nanocrystal-built Films for SERS-based Detection of Trace Organochlorine Pesticides
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
Xia Zhou, Hongwen Zhang, Weiping Cai
It is well known that the SERS-based detection is an ultrasensitive technique and has a lot of potential applications in fields such as biological sensing [11–13], environmental monitoring [14, 15], food safety [16, 17], biomedical science [18–20], and molecular imaging [21], etc. The fabrication of the SERS substrates or chips, with both stable structure and strong SERS effect or activity, is of importance in the SERS-based detection technique. Mostly, the SERS chips are made of the noble metals with nanostructure. The edges/corners and sharp tips on the chips are the most important enhancement structures [22–24]. Such structures can amplify the Raman signals since they not only can serve as the “super electromagnetic intensifiers” (like nano-antennas) or the “hot spots” but also are the preferential adsorption sites of some target molecules [25]. Therefore, the fabrication of the noble metal substrates, with the large number density of edges/corners and sharp tips, is an important way to obtain the high activity of SERS chips.
Nanoscale Spectroscopy for Defense and National Security
Published in Sarhan M. Musa, Nanoscale Spectroscopy with Applications, 2018
Aditi Deshpande, Mohit Agarwal, Suman Shrestha, George C. Giakos
Surface-enhanced Raman spectroscopy (SERS) is a technique to greatly enhance Raman scattering using surface phenomenon of the material such as SPR by “Raman-active” molecules adsorbed or layered on rough metallic surfaces. Various kinds of surface phenomenon (occurring due to the special properties of the surface molecules) enhance the Raman scattering up to 1010 times; this level of signal intensity makes it possible to detect even single molecules. SERS greatly improves the selectivity and sensitivity of Raman spectroscopy [14]. There are two main kinds of processes that modify the surface behavior and enhance spectroscopy—electromagnetic and chemical—the primary one being the electromagnetic enhancement that is due to the roughness and the increased electrical activity of the metallic surface specially designed for SERS. Localized surface plasmons are created when the light is incident on the surface of the material being used. For SERS, we mostly use light of wavelength in the visible or NIR range. If the frequency of the plasmon oscillations is in resonance with the incident light, the Raman scattering is the strongest, that is, when SPR occurs. Also, these oscillations must be in a plane normal to the plane of incidence, that is, perpendicular to the surface, for scattering to occur. This SPR perpendicular to the surface is induced/enhanced by using rough metallic surfaces or, even better, nanoparticles. Surfaces composed of nanostructured materials offers the incident light a large change in the vibrational state and greatly intensifies Raman scattering by increasing SPR.
Biosensing Based on Surface- Enhanced Raman Spectroscopy
Published in Li Jun, Wu Nianqiang, Biosensors Based on Nanomaterials and Nanodevices, 2017
Logan Liu Gang, Zheng Wenwei, Zhang Pingping, Chen Fanqing (Frank)
Raman scattering, first demonstrated by C.V. Raman in 1928, occurs because of the inelastic scattering of light from molecules or atoms [26,27]. Then, in the mid-1970s, the explosion of activity in the field of surface-enhanced Raman scattering (SERS) started. The first measurement of a surface Raman spectrum from pyridine adsorbed on an electrochemically roughened silver electrode was reported by Fleischmann, Hendra, and McQuillan in 1974 [24], which stemmed from their pioneering work on applying Raman spectroscopy to the in situ study of electrode surfaces [28,29]. Till now, SERS has been developed to be a useful technique in a wide variety of research fields due to its significantly increased Raman signals from molecules, which have been attached to nanometer-sized plasmonic structures. To better understand and use SERS, the mechanism and theoretical modeling of SERS are first discussed. Before discussing the mechanism of SERS, we briefly recall the “surface plasmon resonance,” which is one of the main physics behind SERS.
Green synthesis of mono and bimetallic alloy nanoparticles of gold and silver using aqueous extract of Chlorella acidophile for potential applications in sensors
Published in Preparative Biochemistry & Biotechnology, 2021
Sujin Jeba Kumar Thangaswamy, Mushtaq A. Mir, Arumugam Muthu
SERS enables chemical identification of molecules that attach to the surface of noble metals with SPR occurring in the NIR and visible region of the spectrum.[54,55]A strong signal indicated by a more prominent peak at 1340 cm−1was detected in Au–Ag NPs, while as the same peak was less pronounced in monometallic Au NPs (Figure 6). In contrast, there was no Raman signal in case of Ag NPs when excited at 633 nm laser light. These results suggest that there is enhanced Raman signal of Au when it is in form alloy with Ag. SERS has a great potential toward sensing chemicals and biomolecules, and thus integrating enormous sensitivity and precision.[56,57] A strong extinction and scattering spectra can be produced as result of localized SPR excitation and consequently the SERS signal. Usually, multiple folds can amplify a weak effect. The electromagnetic enhancement effect exhibited by SERS is due to electric field amplification. It happens as a result of the molecules that act as a probe in association with the coupling action among plasmon band of substrates and the laser line of excitation.[58] The bimetallic Au–Ag particles presented a much stronger SERS signal than monometallic Au alone, indicating that existence of Au in bimetallic or alloy form with Ag with improved properties.
Effects on surface-enhanced Raman scattering from copper nanoparticles synthesized by laser ablation
Published in Radiation Effects and Defects in Solids, 2020
Rajesh Rawat, Archana Tiwari, Manish Kumar Singh, R. K. Mandal, A. P. Pathak, Ajay Tripathi
Surface enhanced Raman scattering (SERS) is a highly sensitive vibrational spectroscopy which utilized LSPR property of noble metal NPs to increase the intensity of Raman signal of probe molecules having low inherent Raman signal (4). Because of its highly sensitive and non-destructive nature, SERS has been widely used in various fields such as environmental monitoring, medical sciences, explosive detection and so on (9–12). Mostly Ag and Au NPs or combination of both are widely used candidates for observing SERS phenomena. This is because of their strong LSPR appearance and the stability in time (13,14). Owing to similar LSPR in the visible region, Cu NPs are not preferred in the first choice. This is due to the highly reactive nature of Cu with the ambient atmosphere which hampers its SERS quality. Although, there are several reports of Cu NPs being used as an SERS substrate (1,4), still these lack a proper understanding to comprehend the factors that affect the efficiency of SERS such as effects of size, shape and the method of preparation of Cu NPs. Since Cu is cheaper than Au and Ag and is rich in the earth's crust, we present Cu as a reliable candidate as new SERS substrate with greater stability which can replace these noble metals in wide range of applications.
Controlling steady-state second harmonic signal via linear and nonlinear Fano resonances
Published in Journal of Modern Optics, 2020
Mehmet Günay, Zafer Artvin, Alpan Bek, Mehmet Emre Tasgin
Metal nanoparticles (MNPs) trap incident radiation into nm-size hot spots as localized surface plasmon (LSP) oscillations. Intensity of the hot spot (near field) can be times of the one for the incident field (1, 2) or even further (3). This phenomenon enables several technical applications based on the enhancement of linear and nonlinear responses. For instance, a fluorescent molecule in the vicinity of the hot spot becomes detectable (4, 5), which would not be possible with a weak intensity incident field. Localization also strengthens the nonlinear properties of molecules positioned in the vicinity of the hot spots. Signal from a Raman-reporter molecule can be enhanced remarkably (6). Such a great increase in the signal results from the localization of both the incident and the produced (Raman) fields (7). In this way, surface enhanced Raman scattering (SERS) enables detection of Raman signal even from a single molecule. Similarly, nonlinear processes like second harmonic generation (SHG) (8, 9) and four wave-mixing (FWM) (10, 11) are also enhanced.