Fig 3 - uploaded by Pamela Ann Boss
Content may be subject to copyright.
Normal Raman and SERS spectra of the Ag/TP-TCE system . Spectra obtained using 785 nm excitation at 62.8 mW power and a 60 s acquisition time. (a) Spectra of Ag/TP exposed to TCE as a function of temperature (bottom to top: 25, 20, 15, 10, and 5 @BULLET C). Gas flow rate varied between 9 and 12 ml min −1 . The spectral features of the coating have been subtracted out. (b) Normal Raman spectrum of neat TCE.
Source publication
Preliminary results for a volatile organic compound (VOC) sensor based on surface enhanced Raman spectroscopy (SERS) are described. The sensor is comprised of a SERS substrate mounted on a thermoelectric cooler (TEC). The SERS substrate is chemically modified with a thiol coating that prevents oxidation of the roughened silver surface and attracts...
Contexts in source publication
Context 1
... in the presence of TCE, PCE, and chloroform. The temperature response data was obtained by injecting a 0.5 ml aliquot of neat solvent into the 150 ml sam- ple chamber and varying the temperature of the TEC. The solvent vapors diffuse through the silicone tub- ing and the nitrogen carrier gas transports the solvent vapors to the TEC-SERS module. Fig. 3b shows the normal Raman spectrum obtained for TCE. shows the difference spectra obtained for Ag/TP and TCE as a function of temperature. At 25 • C, weak TCE peaks at 644.8 and 411.5 cm −1 are ...
Context 2
... the temperature is lowered, the intensity of these TCE peaks increases and additional TCE peaks ap- pear in the difference spectra. At 15 • C, TCE peaks at 312.7, 479.2, and 850.2 cm −1 appear, Fig. 3a. At 5 • C, the TCE peak at 1245.5 cm −1 appears. Shifts in the TP peaks are observed when TCE is present in the gas stream. These shifts could be indicative of in- teractions between the coating and TCE. Earlier, An- gel [21] demonstrated that carbon tetrachloride could be concentrated on a diamond substrate mounted on a cold finger ...
Context 3
... An- gel [21] demonstrated that carbon tetrachloride could be concentrated on a diamond substrate mounted on a cold finger and detected by normal Raman spec- troscopy. However, TCE could not be detected using this approach because much lower temperatures were required to freeze TCE on the diamond substrate. As shown by the results summarized in Fig. 3, this is not true when a coated SERS substrate is used that has an affinity for chlorinated solvents. Similar results were obtained for chloroform and PCE. Fig. 4a shows the difference spectra obtained for Ag/TP and CHCl 3 as a function of tempera- ture. At 25 • C, weak chloroform peaks at 394.4 and 681.3 cm −1 are observed in the ...
Context 4
... the peaks due to 1-propanethiol significantly overlap with the peaks due to the chlo- rinated solvents. Comparing Figs. 2 and 3b, it can be seen that there is minimal overlap between TCE and TP. Consequently, not only does the coating need to exhibit an affinity for the analyte, but it must also have a SERS spectrum that minimally interferes with the Raman spectrum of the analyte. ...
Context 5
... the spectral data summarized in Figs. 3-5, it can be seen that the spectral features (i.e. peak positions as well as intensity and shape) of the chlorinated solvent peaks in the SERS difference spectra are similar to those in the Raman spectra of the neat solvents. This facilitates speciation. The results summarized in Figs. 3-5 indicate that the magnitude of the measured VOC response is dependent upon the chemical natures of the coating and the VOC, the tem- perature of the SERS substrate, and the gas flow rate. Also, the same SERS substrate was used to generate the data shown in Figs. 3-5 over a one-month period. During that one-month period, the substrate ...
Citations
... These analytical techniques encompass various methods, such as spectroscopy and inductively coupled plasma-mass spectrometry (ICP-MS) [28], laser-induced breakdown spectroscopy, portable modular biological mass spectrometry (MoBiMS) [29], proton transfer reaction-mass spectrometry (PTR-MS) [30,31], and membrane inlet-mass spectrometry (MI-MS) [32]. While these traditional techniques are used for monitoring both atmospheric organic and inorganic volatile compounds, as well as volatile organohalogen compounds (VOHCs) in the gaseous phase [29,[33][34][35][36][37]. However, their scope of application is constrained due to inherent limitations such as poor quantification capacity, limited detection range, intricate and costly procedures, and the need for highly skilled personnel [29,38]. ...
Background
In recent decades, there has been an increasing global preoccupation with atmospheric volatile organic compounds (VOCs). Given the significant impact of VOCs as pollutants and essential precursors of ozone (O3) in urban and industrial areas, it is imperative to identify and quantify the sources of their emissions to facilitate the development and implementation of effective environmental control strategies.
Methods
A mobile laboratory vehicle equipped with a single-photon ionization–time-of-flight mass spectrometer (SPI–TOFMS) and a navigation system was employed to establish the traceability of VOCs that contribute to the formation of ozone in Suzhou Industrial Park. The method exhibited a favorable detection limit of 0.090 ppbv, accompanied by a mass resolution of 1500 for the instrument and a correlation coefficient ≥ 0.990. A positive matrix factorization (PMF) model was utilized to determine the source appointment of the VOCs.
Results
The study tentatively traced and identified the VOCs emissions source and their contribution to ozone formation in Suzhou. Using the PMF model, the sources of VOCs were profiled: three primary sources of VOCs were identified, namely, vehicular emissions, an industrial solvent, and biofuel combustion. Alkanes groups were found to be the most abundant VOCs species, accounting for 60% of the total VOCs, followed by aromatics and alkenes. Maximum incremental reactivity (MIR) quantifies the impact of photochemical reaction mechanism on the potential ozone formation.
Conclusions
The findings of this study complement existing knowledge on the pollution status of atmospheric VOCs and highlight the correlation with ozone formation potential in Suzhou. The aforementioned sources were identified as the primary factors responsible for the pollution in Suzhou. The successful implementation of SPI–TOFMS has demonstrated a promising methodology that is well-suited for the real-time and online monitoring of VOCs in the atmosphere. In addition, a library for identifying VOC fingerprints from the same plant was established. This library serves as a comprehensive resource for establishing on-site VOC traceability, estimating source apportionment, and evaluating their impact on ozone formation.
... For instance, when heat sinking and fans will not suffice in electronics cooling applications, a TEC can be used as an alternative. Similarly, TECs can be used to cool down components in lasers and volatile organic compound detectors (Mansour et al., 2006;Mosier-Boss & Lieberman, 2003). ...
Thermoelectric coolers are semiconductor heat pumps that can be used in precision temperature control applications. After designing a thermoelectric temperature control system, the primary challenge is tuning and testing control algorithms. For instance, developing proportional-integral-derivative controllers involves tuning gains until the desired characteristic is observed,a tedious, time-consuming process. Furthermore, experimenting with new algorithms not only takes a long time, but may also run the risk of damaging the hardware. We propose a faster-than-real-time temperature control simulation library, called OpenPelt. OpenPelt contains utilities for developing and verifying temperature control algorithms as well as a model of a thermoelectric cooler to act as the plant. OpenPelt also enables exporting simulation results to Fenics to simulate the control system’s impact on three-dimensional heat diffusion models.
... To overcome this drawback, SERS could be an interesting alternative detection technique. Only a few publications in the literature reported SERS experiments for the detection of organic compounds and the detection of VOCs [24][25][26][27][28][29][30][31]. ...
This paper reports on the fabrication and characterization of a plasmonic/sol-gel sensor for the detection of aromatic molecules. The sol-gel film was engineered using polysilsesquioxanes groups to capture the analyte, through π-π interaction, and to concentrate it close to the plasmonic surface, where Raman amplification occurs. Xylene was chosen as an analyte to test the sensor. It belongs to the general class of volatile organic compounds and can be found in water or in the atmosphere as pollutants released from a variety of processes; its detection with SERS is typically challenging, due to its low affinity toward metallic surfaces. The identification of xylene was verified in comparison with that of other aromatic molecules, such as benzene and toluene. Investigations were carried out on solutions of xylene in cyclohexane, using concentrations in the range from 0 to 800 mM, to evaluate the limit of detection (LOD) of about 40 mM.
... [31,32] Similarly, for toluene, the characteristic Raman scattering peaks at 637, 786, and 1210 cm −1 were detected. [33] Detection of these characteristic Raman peaks can differentiate the volatile organic compound (VOC) molecules with similar chemical structure, providing outstanding selectivity of 3D-CMA. ...
Practical sensing applications such as real-time safety alerts and clinical diagnoses require sensor devices to differentiate between various target molecules with high sensitivity and selectivity, yet conventional devices such as oxide-based chemo-resistive sensors and metal-based surface-enhanced Raman spectroscopy (SERS) sensors usually do not satisfy such requirements. Here, a label-free, chemo-resistive/SERS multimodal sensor based on a systematically assembled 3D cross-point multifunctional nanoarchitecture (3D-CMA), which has unusually strong enhancements in both “chemo-resistive” and “SERS” sensing characteristics is introduced. 3D-CMA combines several sensing mechanisms and sensing elements via 3D integration of semiconducting SnO2 nanowire frameworks and dual-functioning Au metallic nanoparticles. It is shown that the multimodal sensor can successfully estimate mixed-gas compositions selectively and quantitatively at the sub-100 ppm level, even for mixtures of gaseous aromatic compounds (nitrobenzene and toluene) with very similar molecular structures. This is enabled by combined chemo-resistive and SERS multimodal sensing providing complementary information.
... Tang et al. [15] detected polychlorinated biphenyl (PCB) 77 as low as 10 −11 M by a three-dimensional (3D) hybrid SERS substrate fabricated by assembling small Ag nanoparticles (AgNPs) and large Ag spheres onto ZnO nanorods. Mosier-Boss and Lieberman [16] performed a VOC sensing by using the SERS substrate modified with a thiol coating and mounted on a thermoelectric cooler. These methods show that the SERS can be a great potential technique for environmental contaminants in laboratory. ...
The increasingly serious environmental pollution worldwide has posed a great threat to the ecosystem and human health, and yet the development of portable in situ monitoring techniques that are sensitive to gaseous and water pollutants remains incomplete. Herein, we report a highly active surface-enhanced Raman spectroscopy (SERS) substrate fabricated by immobilizing gold nanoparticles (AuNPs) onto a polyvinylidene fluoride (PVDF) membrane for continuous in situ SERS detection of pollutants in water and atmosphere. 4-Mercaptobenzoic acid (4-MBA) was adopted as a probe molecule to evaluate the performance of the substrate, and the results indicate that the polymer-based flexible substrate features high sensitivity, uniformity, and repeatability. The fabricated PVDF/SERS substrate was integrated with a portable Raman spectrometer operating under both passing-by and passing-through modes. The integrated system accomplishes quantitative detection and real-time online monitoring of pH in a liquid environment with a response speed of less than 10 s and the rapid SERS response to gas molecules at a low concentration within 30 s. We also demonstrated the highly sensitive detection for mainstream smoke (MS) and sidestream (SS) of cigarette smoke and verified their differences in the main constituent which contributes to the harmful secondhand smoke in public. The developed portable Raman system has excellent application prospects in online liquid and gas environmental detection.Graphical abstract
... SERS detection of molecules relies on plasmonic metal nanostructures that, upon resonant laser excitation, exhibit intensively enhanced electromagnetic field on their surface, termed "hot spot". When the molecules of interest are adsorbed in the hot spot, they would be excited to emit strong SERS signals to provide vibration fingerprint of the unique molecular structure [13][14][15][16][17][18] . ...
Surface-enhanced Raman spectroscopy (SERS) finds wide applications in the field of organic molecule detection. However, reliable SERS detection of organic molecules and in situ monitoring of organic reactions under natural conditions by metal colloids are still challenging due to the formation of unstable nanoparticle clusters in solution and the low solubility of the organic molecules. Here, we approach the problems by introducing calcium ions to aggregate silver nanoparticles to form stable hot spots and acetone to promote uniform distribution of organic molecules on the nanoparticle surface. Significantly, our method exhibits stable SERS detection of up to 6 types of organic molecules in liquid. With acetone signals as an internal standard, we are able to determine molecule concentrations as well as monitor 3 kinds of organic reactions in situ. Our method shows potential for biomedical analysis, environmental analysis, and organic catalysis research.
... [9] Moreover, Mosier-Boss and Lieberman used a thermoelectric cooler mounted with a roughened silver substrate to detect different vapors including aromatic compounds, methyl t-butyl ether and chloroform. [10] However, the enhancement of SERS signals from the roughened gold or silver substrate was unsatisfactory because of the limited rough region and random "hot spots" on substrates. In addition, Khan reported that a mixed AgPd nanoparticle (NP) substrate could analyze the CO and N 2 O by SERS signals. ...
... In Figure 4e, the effect of the thickness of shell on SERS intensity is compared through the characteristic peak at 1002 cm −1 , which are assigned to the standard Raman spectrum of toluene. [36] As shown in Table S1 (Supporting Information), for other volatile small organic molecules, such as chloroform, [10] methyl t-butyl ether, [10] ethanol, [37] methanol [37] and acetone, [38] there are no characteristic peak at 1002 cm −1 in their normal Raman spectra, indicating the Au@ZIF-8 NP arrays could realize selective detection for toluene vapor depended on the characteristic peak at 1002 cm −1 . www.advancedsciencenews.com www.particle-journal.com ...
... In Figure 4e, the effect of the thickness of shell on SERS intensity is compared through the characteristic peak at 1002 cm −1 , which are assigned to the standard Raman spectrum of toluene. [36] As shown in Table S1 (Supporting Information), for other volatile small organic molecules, such as chloroform, [10] methyl t-butyl ether, [10] ethanol, [37] methanol [37] and acetone, [38] there are no characteristic peak at 1002 cm −1 in their normal Raman spectra, indicating the Au@ZIF-8 NP arrays could realize selective detection for toluene vapor depended on the characteristic peak at 1002 cm −1 . www.advancedsciencenews.com www.particle-journal.com ...
Surface‐enhanced Raman scattering (SERS) is an effective technique for detecting toxic gas and volatile organic molecules (VOMs); however, recent SERS‐based gas sensors have disadvantages and lack an effective approach to capture toxic gas and insufficient reproducibility of SERS substrates. Herein, a facile strategy is developed to integrate metal‐organic frameworks with Au nanoparticle (NP) arrays to form Au@ZIF‐8 NP arrays, which can be used as an “optical nose” based on SERS to detect toxic VOMs with good reproducibility and sensitivity. Toluene as a target molecule is recognized at ppm levels by the Au@ZIF‐8 NP arrays in situ. And the analytical enhancement factor of Au@ZIF‐8 NP arrays for toluene is about 1.2 × 10⁵. Importantly, this SERS substrate can also detect the 1‐butanol molecule, which provides an idea for designing a universal VOM sensor. In addition, the coating method of the ZIF‐8 shell can be extended to synthetize various NPs@ZIF‐8 core–shell composites, such as Au nanospheres@ZIF‐8, Au@Ag nanorods@ZIF‐8, PS microspheres@ZIF‐8, and Fe2O3 microellipsoids@ZIF‐8 composites.
... There are three approaches for detecting hazardous molecules in the gas phase: (i) designing metal nanostructures or coating other supplementary layers with hydrophobic or charged ligands, polymer films, 23 or porous films in order to efficiently bind target airborne molecules near the hot-spot area, (ii) introducing external forces to confine target molecules into a tiny hot-spot (e.g. cooling for the condensation of target gaseous molecules, 24,25 evaporating the solvent to dissolve airborne molecules 26 and applying the electric potential for the accumulation of target molecules) 27 and (iii) producing hot-spots via assembly after the collection of target molecules on the surface of each nanostructure. ...
Surface-enhanced Raman scattering(SERS)-based sensors utilize the electromagnetic-field enhancement of the plasmonic substrates with the chemical specificity of the vibrational Raman spectroscopy to identify trace amounts of a wide variety of different target analytes while being minimally affected by photobleaching. However, despite many advantageous features of this method, SERS sensors, particularly for detecting hazardous chemicals, suffer from several limitations such as requirement of the gigantic signal enhancement that is often poorly controllable, subtle change and degradation of the SERS substrate and consecutive fluctuation of the signal, the lack of reliable receptors for capturing targets of interest and the absence of general principles in detecting various chemical in different phases and matrices. To overcome these limitations and find practical use, SERS sensors must 1) acknowledge the characteristics of the matrices of target systems, 2) finely engineer and tune the receptors of the SERS sensor to properly extract the target analyte from the phase, and 3) prepare additional mechanistic modifications to enhance the plasmonic signal. This minireview underlines the difficulties associated with different phases and a wide range of target analytes, and introduces the practical measures undertaken to overcome the respective difficulties in SERS-based detection of hazardous chemicals.
... Self-assembled monolayers (SAMs) prepared from aromatic thiols have attracted significant attention over the last 20 years, 1−11 in particular in view of their potential applications in molecular electronics, 12−15 interface engineering in organic electronics, 16−21 and nanofabrication. 22 Among different kinds of such SAMs, fluorine-decorated and fluorine-substituted aryl thiols 23−27 are especially interesting because of their relevance for optoelectronic devices, 27,28 organic field-effect transistors (OFETs), 29 molecular diodes, 25,30 etc., where these SAMs were mainly used for work function adjustment at the metal electrodes. Significantly, as far as the modified electrodes were used as substrates for the growth of organic semiconductors, both growth mode thereof and performance of the resulting devices were found to be strongly influenced by the structure and morphology of the SAMs. ...
... Self-assembled monolayers (SAMs) prepared from aromatic thiols have attracted significant attention over the last 20 years, 1−11 in particular in view of their potential applications in molecular electronics, 12−15 interface engineering in organic electronics, 16−21 and nanofabrication. 22 Among different kinds of such SAMs, fluorine-decorated and fluorine-substituted aryl thiols 23−27 are especially interesting because of their relevance for optoelectronic devices, 27,28 organic field-effect transistors (OFETs), 29 molecular diodes, 25,30 etc., where these SAMs were mainly used for work function adjustment at the metal electrodes. Significantly, as far as the modified electrodes were used as substrates for the growth of organic semiconductors, both growth mode thereof and performance of the resulting devices were found to be strongly influenced by the structure and morphology of the SAMs. ...
