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12157 KiB

Open AccessArticle

Optimizing Melamine Resin Microspheres with Excess Formaldehyde for the SERS Substrate

by Lu Shen, Junfu Zhu, Yuqing Guo, Zhirong Zhu, Xiaogang Wang and Zhixian Hao

Nanomaterials 2017, 7(9), 263; https://doi.org/10.3390/nano7090263 - 06 Sep 2017

Cited by 4 | Viewed by 5085

Influence of the excess monomer within the synthetic reaction solution of melamine resin microspheres (MFMSs) on the surface-enhanced Raman spectroscopy (SERS) enhancement from Rhodamine 6G (R6G) was investigated, where the R6G was adsorbed on the silver nanoparticles (AgNPs) that were loaded on the [...] Read more.

Influence of the excess monomer within the synthetic reaction solution of melamine resin microspheres (MFMSs) on the surface-enhanced Raman spectroscopy (SERS) enhancement from Rhodamine 6G (R6G) was investigated, where the R6G was adsorbed on the silver nanoparticles (AgNPs) that were loaded on the MFMSs. Surface characteristics of the MFMSs were modified by the excess monomer (i.e., the excessive melamine or formaldehyde) through its terminal overreaction, which can be simply controlled by some of the synthetic reaction conditions, thus further allowing us to optimize the assembly of the loaded AgNPs for the SERS detection. These SERS substrates incorporating the optimized MFMSs with the excess formaldehyde can also be used for tracing analyses of more environmental and food contaminants. Full article

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

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2061 KiB

Open AccessArticle

Hollow Au–Ag Alloy Nanorices and Their Optical Properties

by Keke Yu, Xiaonan Sun, Liang Pan, Ting Liu, Anping Liu, Guo Chen and Yingzhou Huang

Nanomaterials 2017, 7(9), 255; https://doi.org/10.3390/nano7090255 - 04 Sep 2017

Cited by 15 | Viewed by 4562

Abstract

Hollow noble metal nanoparticles have excellent performance not only in surface catalysis but also in optics. In this work, the hollow Au–Ag alloy nanorices are fabricated by the galvanic replacement reaction. The dark-field spectrum points out that there is a big difference in [...] Read more.

Hollow noble metal nanoparticles have excellent performance not only in surface catalysis but also in optics. In this work, the hollow Au–Ag alloy nanorices are fabricated by the galvanic replacement reaction. The dark-field spectrum points out that there is a big difference in the optical properties between the pure Ag nanorices and the hollow alloy nanorices that exhibit highly tunable localized surface plasmon resonances (LSPR) and that possess larger radiative damping, which is also indicated by the finite element method. Furthermore, the surface enhanced Raman scattering (SERS) and oxidation test indicate that hollow Au–Ag alloy nanorices show good anti-oxidation and have broad application prospects in surface-plasmon-related fields. Full article

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

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3380 KiB

Open AccessArticle

Characterization and Discrimination of Gram-Positive Bacteria Using Raman Spectroscopy with the Aid of Principal Component Analysis

by Alia Colniță, Nicoleta Elena Dina, Nicolae Leopold, Dan Cristian Vodnar, Diana Bogdan, Sebastian Alin Porav and Leontin David

Nanomaterials 2017, 7(9), 248; https://doi.org/10.3390/nano7090248 - 01 Sep 2017

Cited by 34 | Viewed by 5811

Abstract

Raman scattering and its particular effect, surface-enhanced Raman scattering (SERS), are whole-organism fingerprinting spectroscopic techniques that gain more and more popularity in bacterial detection. In this work, two relevant Gram-positive bacteria species, Lactobacillus casei (L. casei) and Listeria monocytogenes (L. [...] Read more.

Raman scattering and its particular effect, surface-enhanced Raman scattering (SERS), are whole-organism fingerprinting spectroscopic techniques that gain more and more popularity in bacterial detection. In this work, two relevant Gram-positive bacteria species, Lactobacillus casei (L. casei) and Listeria monocytogenes (L. monocytogenes) were characterized based on their Raman and SERS spectral fingerprints. The SERS spectra were used to identify the biochemical structures of the bacterial cell wall. Two synthesis methods of the SERS-active nanomaterials were used and the recorded spectra were analyzed. L. casei and L. monocytogenes were successfully discriminated by applying Principal Component Analysis (PCA) to their specific spectral data. Full article

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

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4871 KiB

Open AccessArticle

Charge Transfer Effect on Raman and Surface Enhanced Raman Spectroscopy of Furfural Molecules

by Fu Wan, Haiyang Shi, Weigen Chen, Zhaoliang Gu, Lingling Du, Pinyi Wang, Jianxin Wang and Yingzhou Huang

Nanomaterials 2017, 7(8), 210; https://doi.org/10.3390/nano7080210 - 02 Aug 2017

Cited by 30 | Viewed by 6194

Abstract

The detection of furfural in transformer oil through surface enhanced Raman spectroscopy (SERS) is one of the most promising online monitoring techniques in the process of transformer aging. In this work, the Raman of individual furfural molecules and SERS of furfural-M_x (M [...] Read more.

The detection of furfural in transformer oil through surface enhanced Raman spectroscopy (SERS) is one of the most promising online monitoring techniques in the process of transformer aging. In this work, the Raman of individual furfural molecules and SERS of furfural-M_x (M = Ag, Au, Cu) complexes are investigated through density functional theory (DFT). In the Raman spectrum of individual furfural molecules, the vibration mode of each Raman peak is figured out, and the deviation from experimental data is analyzed by surface charge distribution. In the SERS of furfural-M_x complexes, the influence of atom number and species on SERS chemical enhancement factors (EFs) are studied, and are further analyzed by charge transfer effect. Our studies strengthen the understanding of charge transfer effect in the SERS of furfural molecules, which is important in the online monitoring of the transformer aging process through SERS. Full article

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

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1783 KiB

Open AccessCommunication

A Simple and Highly Sensitive Thymine Sensor for Mercury Ion Detection Based on Surface Enhanced Raman Spectroscopy and the Mechanism Study

by Hao Yang, Sui-Bo Ye, Yu Fu, Weihong Zhang, Fangyan Xie, Li Gong, Ping-Ping Fang, Jian Chen and Yexiang Tong

Nanomaterials 2017, 7(7), 192; https://doi.org/10.3390/nano7070192 - 24 Jul 2017

Cited by 13 | Viewed by 4698

Abstract

Mercury ion (Hg²⁺) is recognized as one of the most toxic metal ions for the environment and for human health. Techniques utilized in the detection of Hg²⁺ are an important factor. Herein, a simple thymine was successfully employed as the [...] Read more.

Mercury ion (Hg²⁺) is recognized as one of the most toxic metal ions for the environment and for human health. Techniques utilized in the detection of Hg²⁺ are an important factor. Herein, a simple thymine was successfully employed as the surface enhanced Raman spectroscopy sensor for Hg²⁺ ion detection. The limit of detection (LOD) of the developed sensor is better than 0.1 nM (0.02 ppb). This sensor can also selectively distinguish Hg²⁺ ions over 7 types of alkali, heavy metal and transition-metal ions. Moreover, the LOD of the sensor can even achieve 1 ppb in practical application in the nature system, which is half the maximum allowable level (10 nM, 2 ppb) stipulated in the US Environmental Protection Agency standard. Further investigation of the thymine-Hg²⁺-thymine coordination mechanism provides a possible means of detecting other metal ions by replacing the metal ion-specific ligands. This work paves the way for the detection of toxic metal ions and environmental problems. Full article

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

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3077 KiB

Open AccessArticle

Controllable Charge Transfer in Ag-TiO₂ Composite Structure for SERS Application

by Yaxin Wang, Chao Yan, Lei Chen, Yongjun Zhang and Jinghai Yang

Nanomaterials 2017, 7(7), 159; https://doi.org/10.3390/nano7070159 - 28 Jun 2017

Cited by 42 | Viewed by 5314

Abstract

The nanocaps array of TiO₂/Ag bilayer with different Ag thicknesses and co-sputtering TiO₂-Ag monolayer with different TiO₂ contents were fabricated on a two-dimensional colloidal array substrate for the investigation of Surface enhanced Raman scattering (SERS) properties. For the [...] Read more.

The nanocaps array of TiO₂/Ag bilayer with different Ag thicknesses and co-sputtering TiO₂-Ag monolayer with different TiO₂ contents were fabricated on a two-dimensional colloidal array substrate for the investigation of Surface enhanced Raman scattering (SERS) properties. For the TiO₂/Ag bilayer, when the Ag thickness increased, SERS intensity decreased. Meanwhile, a significant enhancement was observed when the sublayer Ag was 10 nm compared to the pure Ag monolayer, which was ascribed to the metal-semiconductor synergistic effect that electromagnetic mechanism (EM) provided by roughness surface and charge-transfer (CT) enhancement mechanism from TiO₂-Ag composite components. In comparison to the TiO₂/Ag bilayer, the co-sputtered TiO₂-Ag monolayer decreased the aggregation of Ag particles and led to the formation of small Ag particles, which showed that TiO₂ could effectively inhibit the aggregation and growth of Ag nanoparticles. Full article

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

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1657 KiB

Open AccessArticle

Highly Sensitive Magnetic-SERS Dual-Function Silica Nanoprobes for Effective On-Site Organic Chemical Detection

by Cheolhwan Jeong, Hyung-Mo Kim, So Yeon Park, Myeong Geun Cha, Sung-Jun Park, San Kyeong, Xuan-Hung Pham, Eunil Hahm, Yuna Ha, Dae Hong Jeong, Bong-Hyun Jun and Yoon-Sik Lee

Nanomaterials 2017, 7(6), 146; https://doi.org/10.3390/nano7060146 - 13 Jun 2017

Cited by 10 | Viewed by 5171

Abstract

We report magnetic silver nanoshells (M-AgNSs) that have both magnetic and SERS properties for SERS-based detection. The M-AgNSs are composed of hundreds of Fe₃O₄ nanoparticles for rapid accumulation and bumpy silver shell for sensitive SERS detection by near-infrared laser excitation. [...] Read more.

We report magnetic silver nanoshells (M-AgNSs) that have both magnetic and SERS properties for SERS-based detection. The M-AgNSs are composed of hundreds of Fe₃O₄ nanoparticles for rapid accumulation and bumpy silver shell for sensitive SERS detection by near-infrared laser excitation. The intensity of the SERS signal from the M-AgNSs was strong enough to provide single particle-level detection. We obtained much stronger SERS signal intensity from the aggregated M-AgNSs than from the non-aggregated AgNSs. 4-Fluorothiophenol was detected at concentrations as low as 1 nM, which corresponds to 0.16 ppb. The limit of detection for tetramethylthiuram disulfide was 10 μM, which corresponds to 3 ppm. The M-AgNSs can be used to detect trace amounts of organic molecules using a portable Raman system. Full article

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

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3139 KiB

Open AccessArticle

Melanin-Associated Synthesis of SERS-Active Nanostructures and the Application for Monitoring of Intracellular Melanogenesis

by Haixin Dong, Zhiming Liu, Huiqing Zhong, Hui Yang, Yan Zhou, Yuqing Hou, Jia Long, Jin Lin and Zhouyi Guo

Nanomaterials 2017, 7(3), 70; https://doi.org/10.3390/nano7030070 - 20 Mar 2017

Cited by 11 | Viewed by 5455

Abstract

Melanin plays an indispensable role in the human body. It serves as a biological reducer for the green synthesis of precious metal nanoparticles. Melanin–Ag nanocomposites were successfully produced which exhibited very strong surface-enhanced Raman scattering (SERS) effect because of the reducibility property of [...] Read more.

Melanin plays an indispensable role in the human body. It serves as a biological reducer for the green synthesis of precious metal nanoparticles. Melanin–Ag nanocomposites were successfully produced which exhibited very strong surface-enhanced Raman scattering (SERS) effect because of the reducibility property of melanin. A melanin–Ag composite structure was synthesized in situ in melanin cells, and SERS technique was performed for the rapid imaging and quantitative assay of intracellular melanin. This imaging technique was also used to successfully trace the formation and secretion of intracellular melanin after stimulation with melanin-stimulating hormones. Based on the self-reducing property of melanin, the proposed SERS imaging method can provide potentially powerful analytical detection tools to study the biological functions of melanin and to prevent and cure melanin-related diseases. Full article

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

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Review

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5872 KiB

Open AccessReview

Review of SERS Substrates for Chemical Sensing

by Pamela A. Mosier-Boss

Nanomaterials 2017, 7(6), 142; https://doi.org/10.3390/nano7060142 - 08 Jun 2017

Cited by 469 | Viewed by 22229

Abstract

The SERS effect was initially discovered in the 1970s. Early research focused on understanding the phenomenon and increasing enhancement to achieve single molecule detection. From the mid-1980s to early 1990s, research started to move away from obtaining a fundamental understanding of the phenomenon [...] Read more.

The SERS effect was initially discovered in the 1970s. Early research focused on understanding the phenomenon and increasing enhancement to achieve single molecule detection. From the mid-1980s to early 1990s, research started to move away from obtaining a fundamental understanding of the phenomenon to the exploration of analytical applications. At the same time, significant developments occurred in the field of photonics that led to the advent of inexpensive, robust, compact, field-deployable Raman systems. The 1990s also saw rapid development in nanoscience. This convergence of technologies (photonics and nanoscience) has led to accelerated development of SERS substrates to detect a wide range of chemical and biological analytes. It would be a monumental task to discuss all the different kinds of SERS substrates that have been explored. Likewise, it would be impossible to discuss the use of SERS for both chemical and biological detection. Instead, a review of the most common metallic (Ag, Cu, and Au) SERS substrates for chemical detection only is discussed, as well as SERS substrates that are commercially available. Other issues with SERS for chemical detection have been selectivity, reversibility, and reusability of the substrates. How these issues have been addressed is also discussed in this review. Full article

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

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