Editorial

4 pages, 186 KiB

Open AccessEditorial

Special Issue: Application of SERS for Nanomaterials

by Ronald L. Birke

Nanomaterials 2021, 11(12), 3300; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11123300 - 06 Dec 2021

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Surface-enhanced Raman scattering (SERS) is now a relatively mature field of spectroscopy, with it having been almost 50 years since its first experimental demonstration [...] Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

Research

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15 pages, 3950 KiB

Open AccessFeature PaperArticle

Highly Sensitive and Stable Copper-Based SERS Chips Prepared by a Chemical Reduction Method

by Pei Dai, Haochen Li, Xianzhi Huang, Nan Wang and Lihua Zhu

Nanomaterials 2021, 11(10), 2770; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11102770 - 19 Oct 2021

Cited by 17 | Viewed by 2411

Abstract

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction [...] Read more.

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10–8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10–11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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14 pages, 2520 KiB

Open AccessFeature PaperArticle

Surface-Enhanced Raman Scattering Activity of ZrO₂ Nanoparticles: Effect of Tetragonal and Monoclinic Phases

by Mingyue Yi, Yu Zhang, Jiawen Xu, Dingyuan Deng, Zhu Mao, Xiangchun Meng, Xiumin Shi and Bing Zhao

Nanomaterials 2021, 11(9), 2162; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092162 - 24 Aug 2021

Cited by 6 | Viewed by 2645

Abstract

The effect of the ZrO₂ crystal form on surface-enhanced Raman scattering (SERS) activity was studied. The ratio of the tetragonal (T) and monoclinic (M) phases of ZrO₂ nanoparticles (ZrO₂ NPs) was controlled by regulating the ratio of two types of [...] Read more.

The effect of the ZrO₂ crystal form on surface-enhanced Raman scattering (SERS) activity was studied. The ratio of the tetragonal (T) and monoclinic (M) phases of ZrO₂ nanoparticles (ZrO₂ NPs) was controlled by regulating the ratio of two types of additives in the hydrothermal synthesis method. The SERS intensity of 4-mercaptobenzoic acid (4–MBA) was gradually enhanced by changing the M and T phase ratio in ZrO₂ NPs. The degree of charge transfer (CT) in the enhanced 4–MBA molecule was greater than 0.5, indicating that CT was the main contributor to SERS. The intensity of SERS was strongest when the ratio of the T crystal phase in ZrO₂ was 99.7%, and the enhancement factor reached 2.21 × 10⁴. More importantly, the proposed study indicated that the T and M phases of the ZrO₂ NPs affected the SERS enhancement. This study provides a new approach for developing high-quality SERS substrates and improving the transmission efficiency of molecular sensors. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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26 pages, 4574 KiB

Open AccessArticle

DFT and TD-DFT Investigation of a Charge Transfer Surface Resonance Raman Model of N3 Dye Bound to a Small TiO₂ Nanoparticle

by Ronald L. Birke and John R. Lombardi

Nanomaterials 2021, 11(6), 1491; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11061491 - 04 Jun 2021

Cited by 6 | Viewed by 2788

Abstract

Raman spectroscopy is an important method for studying the configuration of Ru bipyridyl dyes on TiO₂. We studied the [Ru(II)(4,4′-COOH-2,2′-bpy)2(NCS)2)] dye (N3) adsorbed on a (TiO₂)5 nanoparticle using Density Functional Theory, DFT, to optimize the geometry of the complex [...] Read more.

Raman spectroscopy is an important method for studying the configuration of Ru bipyridyl dyes on TiO₂. We studied the [Ru(II)(4,4′-COOH-2,2′-bpy)2(NCS)2)] dye (N3) adsorbed on a (TiO₂)5 nanoparticle using Density Functional Theory, DFT, to optimize the geometry of the complex and to simulate normal Raman scattering, NRS, for the isolated N3 and the N3–(TiO₂)5 complex. Two configurations of N3 are found on the surface both anchored with a carboxylate bridging bidentate linkage but one with the two NCS ligands directed away from the surface and one with one NSC tilted away and the other NCS interacting with the surface. Both configurations also had another –COOH group hydrogen bonded to a Ti-O dangling bond. These configurations can be distinguished from each other by Raman bands at 2104 and 2165 cm⁻¹. The former configuration has more intense Normal Raman Scattering, NRS, on TiO₂ surfaces and was studied with Time-Dependent Density Functional Theory, TD-DFT, frequency-dependent Raman simulations. Pre-resonance Raman spectra were simulated for a Metal to Ligand Charge Transfer, MLCT, excited state and for a long-distance CT transition from N3 directly to (TiO₂)5. Enhancement factors for the MLCT and long-distance CT processes are around 1 × 103 and 2 × 102, respectively. A Herzberg–Teller intensity borrowing mechanism is implicated in the latter and provides a possible mechanism for the photo-injection of electrons to titania surfaces. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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13 pages, 2184 KiB

Open AccessArticle

SERS-Based Aptasensor for Rapid Quantitative Detection of SARS-CoV-2

by Elena Zavyalova, Oganes Ambartsumyan, Gleb Zhdanov, Dmitry Gribanyov, Vladimir Gushchin, Artem Tkachuk, Elena Rudakova, Maria Nikiforova, Nadezhda Kuznetsova, Liubov Popova, Bakhtiyar Verdiev, Artem Alatyrev, Elena Burtseva, Anna Ignatieva, Anna Iliukhina, Inna Dolzhikova, Alexander Arutyunyan, Alexandra Gambaryan and Vladimir Kukushkin

Nanomaterials 2021, 11(6), 1394; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11061394 - 25 May 2021

Cited by 64 | Viewed by 5344

Abstract

During the COVID-19 pandemic, the development of sensitive and rapid techniques for detection of viruses have become vital. Surface-enhanced Raman scattering (SERS) is an appropriate tool for new techniques due to its high sensitivity. SERS materials modified with short-structured oligonucleotides (DNA aptamers) provide [...] Read more.

During the COVID-19 pandemic, the development of sensitive and rapid techniques for detection of viruses have become vital. Surface-enhanced Raman scattering (SERS) is an appropriate tool for new techniques due to its high sensitivity. SERS materials modified with short-structured oligonucleotides (DNA aptamers) provide specificity for SERS biosensors. Existing SERS-based aptasensors for rapid virus detection are either inapplicable for quantitative determination or have sophisticated and expensive construction and implementation. In this paper, we provide a SERS-aptasensor based on colloidal solutions which combines rapidity and specificity in quantitative determination of SARS-CoV-2 virus, discriminating it from the other respiratory viruses. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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14 pages, 4419 KiB

Open AccessArticle

Charge-Transfer Induced by the Oxygen Vacancy Defects in the Ag/MoO₃ Composite System

by Qi Chu, Jingmeng Li, Sila Jin, Shuang Guo, Eungyeong Park, Jiku Wang, Lei Chen and Young Mee Jung

Nanomaterials 2021, 11(5), 1292; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11051292 - 14 May 2021

Cited by 17 | Viewed by 2446

Abstract

In this paper, an Ag/MoO₃ composite system was cosputtered by Ar plasma bombardment on a polystyrene (PS) colloidal microsphere array. The MoO₃ formed by this method contained abundant oxygen vacancy defects, which provided a channel for charge transfer in the system [...] Read more.

In this paper, an Ag/MoO₃ composite system was cosputtered by Ar plasma bombardment on a polystyrene (PS) colloidal microsphere array. The MoO₃ formed by this method contained abundant oxygen vacancy defects, which provided a channel for charge transfer in the system and compensated for the wide band gap of MoO₃. Various characterization methods strongly demonstrated the existence of oxygen vacancy defects and detected the properties of oxygen vacancies. 4-Aminothiophenol (p-aminothiophenol, PATP) was used as a candidate surface-enhanced Raman scattering (SERS) probe molecule to evaluate the contribution of the oxygen vacancy defects in the Ag/MoO₃ composite system. Interestingly, oxygen vacancy defects are a kind of charge channel, and their powerful effect is fully reflected in their SERS spectra. Increasing the number of charge channels and increasing the utilization rate of the channels caused the frequency of SERS characteristic peaks to shift. This interesting phenomenon opens up a new horizon for the study of SERS in oxygen-containing semiconductors and provides a powerful reference for the study of PATP. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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12 pages, 3385 KiB

Open AccessFeature PaperArticle

A SERS Study of Charge Transfer Process in Au Nanorod–MBA@Cu₂O Assemblies: Effect of Length to Diameter Ratio of Au Nanorods

by Lin Guo, Zhu Mao, Sila Jin, Lin Zhu, Junqi Zhao, Bing Zhao and Young Mee Jung

Nanomaterials 2021, 11(4), 867; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11040867 - 29 Mar 2021

Cited by 12 | Viewed by 2364

Abstract

Surface-enhanced Raman scattering (SERS) is a powerful tool in charge transfer (CT) process research. By analyzing the relative intensity of the characteristic bands in the bridging molecules, one can obtain detailed information about the CT between two materials. Herein, we synthesized a series [...] Read more.

Surface-enhanced Raman scattering (SERS) is a powerful tool in charge transfer (CT) process research. By analyzing the relative intensity of the characteristic bands in the bridging molecules, one can obtain detailed information about the CT between two materials. Herein, we synthesized a series of Au nanorods (NRs) with different length-to-diameter ratios (L/Ds) and used these Au NRs to prepare a series of core–shell structures with the same Cu₂O thicknesses to form Au NR–4-mercaptobenzoic acid (MBA)@Cu₂O core–shell structures. Surface plasmon resonance (SPR) absorption bands were adjusted by tuning the L/Ds of Au NR cores in these assemblies. SERS spectra of the core-shell structure were obtained under 633 and 785 nm laser excitations, and on the basis of the differences in the relative band strengths of these SERS spectra detected with the as-synthesized assemblies, we calculated the CT degree of the core–shell structure. We explored whether the Cu₂O conduction band and valence band position and the SPR absorption band position together affect the CT process in the core–shell structure. In this work, we found that the specific surface area of the Au NRs could influence the CT process in Au NR–MBA@Cu₂O core–shell structures, which has rarely been discussed before. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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29 pages, 14653 KiB

Open AccessEditor’s ChoiceArticle

Investigations of Shape, Material and Excitation Wavelength Effects on Field Enhancement in SERS Advanced Tips

by Yaakov Mandelbaum, Raz Mottes, Zeev Zalevsky, David Zitoun and Avi Karsenty

Nanomaterials 2021, 11(1), 237; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11010237 - 18 Jan 2021

Cited by 7 | Viewed by 2697

Abstract

This article, a part of the larger research project of Surface-Enhanced Raman Scattering (SERS), describes an advanced study focusing on the shapes and materials of Tip-Enhanced Raman Scattering (TERS) designated to serve as part of a novel imager device. The initial aim was [...] Read more.

This article, a part of the larger research project of Surface-Enhanced Raman Scattering (SERS), describes an advanced study focusing on the shapes and materials of Tip-Enhanced Raman Scattering (TERS) designated to serve as part of a novel imager device. The initial aim was to define the optimal shape of the “probe”: tip or cavity, round or sharp. The investigations focused on the effect of shape (hemi-sphere, hemispheroid, ellipsoidal cavity, ellipsoidal rod, nano-cone), and the effect of material (Ag, Au, Al) on enhancement, as well as the effect of excitation wavelengths on the electric field. Complementary results were collected: numerical simulations consolidated with analytical models, based on solid assumptions. Preliminary experimental results of fabrication and structural characterization are also presented. Thorough analyses were performed around critical parameters, such as the plasmonic metal—Silver, Aluminium or Gold—using Rakic model, the tip geometry—sphere, spheroid, ellipsoid, nano-cone, nano-shell, rod, cavity—and the geometry of the plasmonic array: cross-talk in multiple nanostructures. These combined outcomes result in an optimized TERS design for a large number of applications. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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11 pages, 1565 KiB

Open AccessArticle

Role of 2‒¹³C Isotopic Glyphosate Adsorption on Silver Nanoparticles Based on Ninhydrin Reaction: A Study Based on Surface—Enhanced Raman Spectroscopy

by Meng-Lei Xu, Yu Gao, Jing Jin, Jin-Feng Xiong, Xiao Xia Han and Bing Zhao

Nanomaterials 2020, 10(12), 2539; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10122539 - 17 Dec 2020

Cited by 7 | Viewed by 2273

Abstract

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to [...] Read more.

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒¹³C‒glyphosate (hereafter: 13–GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by ¹³C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13–GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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