In situ monitoring of protein adsorption on a nanoparticulated gold film by attenuated total reflection surface-enhanced infrared absorption spectroscopy

In situ surface enhanced infrared absorption spectroscopy (SEIRAS) with an attenuated total reflection (ATR) configuration has been used to monitor the adsorption kinetics of bovine hemoglobin (BHb) on a Au nanoparticle (NP) film. The IR absorbance for BHb molecules on a gold nanoparticle film deposited on a Si hemispherical optical window is about 58 times higher than that on a bare Si optical window and the detection sensitivity has been improved by 3 orders of magnitude. From the IR signal as a function of adsorption time, the adsorption kinetics and thermodynamics can be explored in situ. It is found that both the electrostatic interaction and the coordination bonds between BHb residues and Au NP film surface affect the adsorption kinetics. The maximum adsorption can be obtained in solution pH 7.0 (close to the isoelectric point of the protein) due to the electrostatic interaction among proteins. In addition, the isotherm of BHb adsorption follows well the Freundlich adsorption model.     

In situ monitoring of pH titration by Raman spectroscopy

Molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman technique was chosen because it allows the identification of compounds in different states, and it can give information about the molecular geometry from the analysis of the vibrational spectra. The effect of pH on organic compounds can give information about the ionisation of molecule species. In this study the ionisation steps of salicylic acid and paracetamol have been studied by means of potentiometry coupled with Raman spectroscopy at 30.0 °C in a solution of ionic strength 0.96 mol dm^?3 (KNO₃) and 0.04 mol dm^?3 (HNO₃). The protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the three different species in the Raman spectra of aqueous salicylic acid have been identified satisfactorily, characterised, and determined by numeric treatment of the data using a multiwavelength curve-fitting program and confirmed with the observed spectral information.     

In situ monitoring of the DNA hybridization by attenuated total reflection surface-enhanced infrared absorption spectroscopy

In situ monitoring of DNA hybridization kinetics is achieved via an attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) technique using a sandwich assay structure. The synergistic enhancement effect gives this ATR-SEIRAS-based detection strategy promise to be a convenient and unique platform for bioanalysis.     

Studies of thermal decay of electropolymerized polypyrrole using in situ surface-enhanced Raman spectroscopy

In this work, the thermal degradation of polypyrrole (PPy) films was investigated by using in situ surface-enhanced Raman spectroscopy (SERS) for the first time. The results indicate that the decay of PPy in conductivity can be ascribed to the loss in oxidation degree and to the shorter conjugation length of PPy upon heating samples from 25 to 75 °C. Continuously raising the temperature of the sample from 75 to 125 °C results in serious decay. The oxidation degree of PPy is significantly decreased correspondingly. However, the peak assigned to the CC backbone stretching becomes broader due to the thermal decomposition of PPy. At temperatures of samples higher than 125 °C, PPy films lose their conducting properties and no characteristic peaks of oxidized PPy related to the oxidation degrees can be observed. Moreover, the peak of the CC backbone stretching completely disappear due to the complete decomposition of PPy.     

In-situ monitoring of nitrile-bearing pesticide residues by background-free surface-enhanced Raman spectroscopy

In-situ monitoring of pesticide residues during crop growth or/and in related products is of great significance in avoiding the abuse of pesticides but remains challenging thus far. In this report, we proposed a background-free surface-enhanced Raman spectroscopy（bf-SERS） platform to non-destructively track the nitrile-bearing pesticide residues in soybean leaves with high sensitivity and selectivity. The outstanding feature of the assay stems from the dramatic Raman enhancement effect of the 50...     

Detection of bacteria by surface-enhanced Raman spectroscopy

The detection and identification of dilute bacterial samples by surface-enhanced Raman spectroscopy has been explored by mixing aqueous suspensions of bacteria with a suspension of nanocolloidal silver particles. An estimate of the detection limit of E. coli was obtained by varying the concentration of bacteria. By correcting the Raman spectra for the broad librational OH band of water, reproducible spectra were obtained for E. coli concentrations as low as approximately 10³ cfu/mL. To aid in the assignment of Raman bands, spectra for E. coli in D₂O are also reported. Figure Light scattering apparatus used to detect bacteria     

Real-time monitoring of microwave-promoted organometallic ligand-substitution reactions using in situ Raman spectroscopy

An apparatus has been developed for real-time monitoring of organometallic reactions under microwave irradiation using in situ Raman spectroscopy and its application for monitoring ligand substitution reactions of Mo(CO)6 demonstrated.     

Real-time monitoring of microwave-promoted Suzuki coupling reactions using in situ Raman spectroscopy

The progress of microwave-promoted Suzuki reactions has been monitored using an in situ Raman spectroscopy apparatus assembled from commercially available components. It was possible to see if any reaction occurred and, if so, when it reached completion. In addition, the monitoring technique has given us an insight into the reaction, confirming that, when run in aqueous media, the coupling is in competition with the rapid deboronation of the boronic acid.     

Swellable polymer films containing Au nanoparticles for point-of-care therapeutic drug monitoring using surface-enhanced Raman spectroscopy

Large (10 × 10 cm) sheets of surface-enhanced Raman spectroscopy (SERS) active polymer have been prepared by stabilising metal nanoparticle aggregates within dry hydroxyethylcellulose (HEC) films. In these films the aggregates are protected by the polymer matrix during storage but in use they are released when aqueous analyte droplets cause the films to swell to their gel form. The fact that these “Poly-SERS” films can be prepared in bulk but then cut to size and stored in air before use means that they provide a cost effective and convenient method for routine SERS analysis. Here we have tested both Ag and Au Poly-SERS films for use in point-of-care monitoring of therapeutic drugs, using phenytoin as the test compound. Phenytoin in water could readily be detected using Ag Poly-SERS films but dissolving the compound in phosphate buffered saline (PBS) to mimic body fluid samples caused loss of the drug signal due to competition for metal surface sites from Cl⁻ ions in the buffer solution. However, with Au Poly-SERS films there was no detectable interference from Cl⁻ and these materials allowed phenytoin to be detected at 1.8 mg L⁻¹, even in PBS. The target range of detection of phenytoin in therapeutic drug monitoring is 10–20 mg L⁻¹. With the Au Poly-SERS films, the absolute signal generated by a given concentration of phenytoin was lower for the films than for the parent colloid but the SERS signals were still high enough to be used for therapeutic monitoring, so the cost in sensitivity for moving from simple aqueous colloids to films is not so large that it outweighs the advantages which the films bring for practical applications, in particular their ease of use and long shelf life.     

In situ generation of palladium nanoparticles: ligand-free palladium catalyzed ultrafast Suzuki-Miyaura cross-coupling reaction in aqueous phase at room temperature

An ultrafast and highly efficient ligand-free Suzuki-Miyaura cross-coupling reaction between aryl bromides/iodides and arylboronic acids using palladium chloride as catalyst in PEG400/H₂O in air at room temperature has been developed. TEM showed that palladium nanoparticles were generated in situ from PdCl₂/PEG400/H₂O without use of other reductants. The catalyst system can be recycled to reuse three times with good yields.     

In situ resonance Raman spectroscopy of polyazulene on aluminum

Polyazulene (PAz) has been electrochemically deposited on different electrode substrates. The films were characterized with Raman and UV-vis spectroscopy. The spectroelectrochemical studies were performed in situ during p- and n-doping (electrochemical oxidation and reduction, respectively). The focus of this work was mainly on the charging and discharging reactions of PAz on Al substrates. The results were compared to the corresponding results obtained from PAz on Pt substrates. Three different excitation wavelengths (514, 633, and 780 nm) were used in the Raman experiments and the resonance enhancement effect was observed when changing the wavelength of the excitation line. The vibrational behavior of PAz deposited on Al was very similar to that of PAz deposited on Pt during p-doping. Furthermore, it was found that the vibrational responses during p- and n-doping are different indicating that the electronic structure of PAz is not the same during positive and negative charging. It was concluded that PAz is not reversibly n-doped on Al. The n-doping on Pt was shown to be more reversible. In this paper, the important correlation between UV-vis and Raman spectroscopy is discussed as well as the correlation between doping-induced infrared active bands and Raman bands of neutral PAz.     

电化学原位表面增强拉曼光谱研究Au@Pd纳米粒子薄膜电极上吸附 CO的斯塔克效应

电化学 Stark效应是指电极溶液界面的吸附物或金属-吸附物之间的化学键的振动频率随电极电势而发生变化的现象.研究该效应,可以更好地理解吸附物与基底的相互作用(如吸附构型、吸附取向和覆盖度等随电位的变化),也可反过来推断电极基底的电子构型及其随电势的变化规律,对理解电化学双电层的结构以及电催化反应的构效关系都很有帮助.多年以来,电极表面吸附 CO的电化学 Stark效应广受关注,是由于 CO为很多小分子氧化的中间产物,研究 CO的谱学行为,可加深对 CO以及其它能产生 CO中间物有机小分子的电催化氧化机理和动力学的理解;另一方面, CO与过渡金属之间普遍存在s给电子以及p反馈电子作用,因此 CO也可作为探针分子,通过考察 COad以及 M–COad的振动频率的变化,可推断相应条件下基底的电子与几何结构等信息.
　　本文使用电化学原位表面增强拉曼技术,在一个大的电势范围内考察了 Au@Pd纳米粒子薄膜电极上饱和吸附 CO的振动光谱行为,以期更好地理解 COad与基底的成键作用与电极电势之间的关系.由于纯 Pd电极表面的拉曼信号太弱,实验使用具有核壳结构的 Au@Pd纳米粒子薄膜作为模型电极,并利用 Au核的拉曼增强特性.宽广的电势范围约–1.5到0.55V vs. NHE,通过使用酸性、中性以及碱性电解质得以实现.实验考察的电势上限由 COad氧化起始电位决定,而下限由强烈氢析干扰测量所限制.结果表明,在检测的电势范围内, C–OM(M指在电极表面的桥式吸附CO和穴位吸附 CO所形成的谱带重叠)和 Pd–COM键的振动频率可以分为三段： dνC–OM/dE在–1.5~–1.2 V范围内是185~207 cm–1/V,在–1.2~–0.15 V是83~84 cm–1/V,在–0.2~0.55 V是43 cm–1/V;而 dνPd–COM/dE在–1.5~–1.2 V范围内是–10~–8 cm–1/V,在–1.2~–0.15 V是–31~–30 cm–1/V,在–0.2~0.55 V是–15 cm–1/V.与同时记录的极化曲线对比,认为在中性和碱性介质中所观察到 dνC–OM/dE在–1.2 V附近的急剧变化与电极表面发生了强烈的析氢反应有关.另外,结合密度泛函理论模型计算,认为共吸附的 H减少了 COad从桥式构型到穴位构型的转变,在酸性介质中这种变化不明显,可能是由于对应的电势较高,桥式吸附的 CO比例越大,桥式向穴位的转变本身相对较少.     

In situ X-ray Raman spectroscopy of LiBH4

X-Ray Raman Spectroscopy (XRS) is used to study the electronic properties of bulk lithium borohydride (LiBH(4)) and LiBH(4) in porous carbon nano-composites (LiBH(4)/C) during dehydrogenation. The lithium (Li), boron (B) and carbon (C) K-edges are studied and compared with calculations of the starting material and intermediate compounds. Comparison of the B and C K-edge XRS spectra of the as-prepared samples with rehydrogenated samples shows that the B and C electronic structure is largely regained after rehydrogenation. Both Li and C K-edge spectra show that during dehydrogenation, part of the Li intercalates into the porous carbon. This study shows that XRS in combination with calculations is a promising tool to study the electronic properties of nano-crystalline light-weight materials for energy storage.     

In situ Raman spectroscopy of surfaces modified by ion soft landing

The design and characterization of a system for in situ Raman analysis of surfaces prepared by ion soft landing (SL) is described. The performance of the new high vacuum compatible, low cost, surface analysis capability is demonstrated with surface enhanced Raman spectroscopy (SERS) of surfaces prepared by soft landing of ions of crystal violet, Rhodamine 6G, methyl orange and copper phthalocyanine. Complementary in situ mass spectrometric information is recorded for the same surfaces using a previously implemented secondary ion mass spectrometer (SIMS). Imaging of the modified surfaces is achieved using 2D Raman imaging as demonstrated for the case of Rhodamine 6G soft landing. The combination of the powerful molecular characterization tools of SERS and SIMS in a single instrument fitted with in-vacuum sample transport capabilities, facilitates in situ analysis of surfaces prepared by ion SL. In particular, information is provided on the charge state of the soft landed species. In the case of crystal violet the SERS data suggest that the positively charged ions being landed retain their charge state on the surface under vacuum. By contrast, in the case of methyl orange which is landed as an anion, the SERS spectra suggest that the SL species has been neutralized.     

Gold nano-popcorn-based targeted diagnosis, nanotherapy treatment, and in situ monitoring of photothermal therapy response of prostate cancer cells using surface-enhanced Raman spectroscopy

Prostate cancer is the second leading cause of cancer-related death among the American male population, and the cost of treating prostate cancer patients is about $10 billion/year in the United States. Current treatments are mostly ineffective against advanced-stage prostate cancer and are often associated with severe side effects. Driven by these factors, we report a multifunctional, nanotechnology-driven, gold nano-popcorn-based surface-enhanced Raman scattering (SERS) assay for targeted sensing, nanotherapy treatment, and in situ monitoring of photothermal nanotherapy response during the therapy process. Our experimental data show that, in the presence of LNCaP human prostate cancer cells, multifunctional popcorn-shaped gold nanoparticles form several hot spots and provide a significant enhancement of the Raman signal intensity by several orders of magnitude (2.5 × 10(9)). As a result, it can recognize human prostate cancer cells at the 50-cells level. Our results indicate that the localized heating that occurs during near-infrared irradiation can cause irreparable cellular damage to the prostate cancer cells. Our in situ time-dependent results demonstrate for the first time that, by monitoring SERS intensity changes, one can monitor photothermal nanotherapy response during the therapy process. Possible mechanisms and operating principles of our SERS assay are discussed. Ultimately, this nanotechnology-driven assay could have enormous potential applications in rapid, on-site targeted sensing, nanotherapy treatment, and monitoring of the nanotherapy process, which are critical to providing effective treatment of cancer.     

In situ surface-enhanced Raman spectroscopic studies of nafion adsorption on Au and Pt electrodes

Understanding interactions between Nafion (perfluorosulfonic acid) and Pt catalysts is important for the development and deployment of proton exchange membrane fuel cells. However, study of such interactions is challenging and Nafion/Pt interfacial structure remains elusive. In this study, adsorption of Nafion ionomer on Au and Pt surfaces was investigated for the first time by in situ surface-enhanced Raman spectroscopy. The study is made possible by the use of uniform SiO(2)@Au core-shell particle arrays which provides very strong enhancement of Raman scattering. The high surface sensitivity offered by this approach yields insightful information on interfacial Nafion structure. Through spectral comparison of several model compounds, vibration assignments of SERS bands were made. The SER spectra suggest the direct interaction of sulfonate group with the metal surfaces, in accord with cyclic voltammetric results. Comparison of present SERS results with previous IR spectra was briefly made.     

Study on transport of molecules in gel by surface-enhanced Raman spectroscopy

Cellulose - Surface-enhanced Raman spectroscopy (SERS)-based biosensors have recently been extensively developed because of their high sensitivity and nondestructive nature. Conventional SERS...     

Detection of proteins on silica-silver core-shell substrates by surface-enhanced Raman spectroscopy

We have employed the proposed Silica-Silver Core-Shell (SSCS) SERS-active substrates to detect four model proteins: lysozyme (a protein without chromophore), cytochrome c (a protein with chromophore of heme), fluorescein isothiocyanate (FITC)-anti human IgG (labeled with FITC) and atto610-biotin/avidin (recognition with labeled small molecules). SERS spectra of these proteins and Raman labels on the SSCS substrates show both high sensitivity and reproducibility, which are due to electromagnetic SERS enhancement with additional localization field within closely packed Ag nanoparticles decorated on the SiO(2) nanoparticles and the aggregation of SiO(2)@Ag particles. We have found that the SERS intensities of atto610-biotin/avidin adsorbed on the SSCS substrates are about 20 times stronger than those from Ag plating on Au-decorated substrate. Moreover, the broad surface plasmon resonance (SPR) of the proposed substrates will extend SERS applications to more biological molecules with different laser excitations.