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A CoNi-based metal-organic framework (CoNi-MOF) nanosheet array is synthesized by the treatment of a CoNi layered double hydroxide nanosheet array on Ni foam with 3,5-diaminobenzoic acid. The CoNi-MOF nanosheet array with amino and carboxyl groups can be used to capture the human chorionic gonadotropin (HCG) primary antibody (HCG Ab1). Nile Blue decorated ZnNi-MOF (NB@ZnNi-MOF) spheres immobilized with HCG secondary antibodies (HCG Ab2) are used for signal amplification. When HCG exists in an analytical sample, a sandwich structure is formed and an electrochemical signal is produced. The analytical signal generated during the detection is caused by the conversion of Co(ii) and Co(iii) in the CoNi-MOF nanosheet array. The Nile Blue of the NB@ZnNi-MOF sphere, as a kind of redox-active species, is responsible for the electrochemical signal amplification in the immunosensor. On the basis of the above advantages, the HCG immunosensor exhibits a lower limit of detection (1.85 × 10-3 mIU mL-1) and a wide linear range from 0.005 mIU mL-1 to 250 mIU mL-1. Additionally, this immunosensor is used to quantitatively detect HCG in human blood serum and shows good correlations with the standard enzyme-linked immunosorbent assay (ELISA), providing a high value on clinical diagnosis.

Optical biosensor for the detection of formaldehyde has been developed based on the transparent enzymatic stacked membranes system on the glass substrate, and employing optical absorption transducer with H+ ion-selective Nile Blue chromoionophore (NBCM) dye-doped methacrylic acrylic (MB28) copolymer membrane as the optode membrane. Alcohol oxidase (AOx) enzymes were entrapped within the biocompatible sol–gel matrix and deposited on top of the pH optode membrane. As the uppermost catalytic membrane catalyzes the oxidative conversion of formaldehyde to formic acid and hydrogen peroxide, the immobilized NBCM undergoes protonation reaction and forms HNBCM+, the dark blue ion-chromoionophore complex via H+ ion transfer reaction within the soft and flexible MB28 polymeric membrane. This rendered the enzymatic optode membrane absorbed a high yellow light intensity from the light source and exhibited maximum absorption peaks at 610 and 660 nm. Optical evaluation of formaldehyde by means on UV–vis absorption transduction of the enzymatic stacked membranes demonstrated rapid response time of 10 min with high sensitivity, good linearity and high reproducibility across a wide formaldehyde concentration range of 1 × 10−3–1 × 103 mM (R2 = 0.9913), and limit of detection (LOD) at 1 × 10−3 mM, which could be useful for formaldehyde assay in industrial, agricultural, environmental, food and beverages as well as medical samples. The formaldehyde concentration in snapper fish, pomfret fish and threadfin fish samples determined by the proposed optical enzymatic biosensor were very much close to the formaldehyde concentration values determined by the UV–vis spectrophotometric NASH standard method based on the statistical t-test. This suggests that the optical biosensor can be used as a reliable method for quantitative determination of formaldehyde levels in food samples.

Surface-enhanced Raman scattering (SERS) is one of the most effective methods for applications in optical sensors and chemical analysis. However, control of the optimal conditions of substrates and the selection of chemical probes are two major challenges which have yet to be solved. In this work, using a simple seeded growth method, nanoparticles with different sizes and shapes were produced. The SERS enhancement factor for each nanoparticle size and shape obtained was evaluated based on three different analytes, methylene blue, Nile blue A and Rhodamine B. We found a maximum enhancement factor on the order of 106 for the case of silver nanorods and Rhodamine B. Considering the SERS performance for silver nanospheres, we observed a systematic increase in the sequence methylene blue-Nile blue A-Rhodamine B. The reason behind the enhanced efficiency is that the maximum of the surface plasmon resonance band of Rhodamine B is the closest to the Raman excitation wavelength. The study also demonstrates that a decrease in size of spherical nanoparticles can lead to an increased enhancement, resulting from a larger surface area for a smaller particle size. Compared with silver nanospheres, silver nanorods yielded a better SERS enhancement factor, as a result of shape anisotropy which significantly enhance the local field hotspots. For low concentration, the intensity of Raman bands increases linearly with increasing dye concentration, which could be useful for applications involving chemical sensors.

Thiophenols as high toxic environmental pollutants are poisonous for animals and aquatic organisms. Therefore, it is indispensable to monitor thiophenols in the environment. Herein, a novel near-infrared fluorescent probe was developed for the detection of thiophenols, which was easily prepared by one-step coupling of 2,4-dinitrobenzenesulfonyl chloride with Nile blue. The probe showed a significant near infrared (∼675 nm) fluorescence “turn-on” response to thiophenols with some good features including chromogenic reaction, high sensitivity and selectivity, fast response, near-infrared emission along with low detection limit (1.8 nM). The probe was employed to rapidly and visually determine thiophenols in several industrial wastewaters with good recoveries (90–110%). Moreover, this probe has been demonstrated good capability for imaging thiophenol in HeLa cells.

Finding specific small molecule probes of a biological target is extremely desired but remains a big challenge. We reported herein a highly selective fluorescent probe derivatized from the nile blue fluorophore, NBL-SS, for thioredoxin (Trx), a ubiquitous redox-regulating protein essentially involved in cell growth, differentiation, and death. NBL-SS displayed multiple favorable properties, such as red emission, fast response, and high fluorescence signal, which enabled the probe to readily image Trx functions in live cells and in vivo. The fluorophore-dependent selectivity indicates that manipulation of weak interactions between probes and their target biomacromolecules could further improve the probes' specificity. In addition, our discovery, i.e., the preference reduction of simple disulfide bonds by Trx over glutathione, also advances the development of disulfide cleavage-based probes, prodrugs, and theranostic agents.

Nanoparticles can be applied to the hair follicles, which can serve as reservoirs for triggered drug release. A valid measurement method for the determination of the pH within the hair follicle in vivo has not been shown yet. Here, melamine formaldehyde particles up to 9 µm in size were applied on 40 freshly plucked scalp hairs of eight individuals to determine the pH along the hair shaft down to the root area of the hair. For fluorescent pH indicators, pyranine and Nile blue were incorporated into the particles. Measurements were conducted using confocal laser scanning microscopy. A pH decay gradient could be found from the hair sheath towards the external hair shaft (p = 0.012) with pH values at the hair sheath of 6.63 ± 0.09, at the hair sheath end at 6.33 ± 0.11, and at the external hair shaft at 6.17 ± 0.09 (mean ± SE). The pH difference between the hair sheath end and the external hair shaft was found to be significant (p = 0.036). The results might be comparable with the pH within the hair follicle in vivo indicating a pH increase towards the hair root.

The present work focuses the investigation on fluorescence quenching of nile blue (NB) in presence of various substituted uracil molecules. UV–Visible absorption studies signify the possibility of ground state complex formation between NB and uracil molecules. The increase in concentration of quencher molecules greatly influences the emission spectra of NB. The bimolecular quenching rate constant (kq) were calculated and found to depend on the position and electronic properties of substituent in quencher molecules. Fluorescence quenching experiments were performed at different temperature to calculate the thermodynamic parameters. The fluorescence lifetime measurements show that the quenching process proceeds through static quenching. The mechanism of fluorescence quenching includes the possibility of proton transfer. The bond dissociation enthalpy (BDE) reveals the release of H from the quencher molecules. The quencher molecules possess antioxidant activity and identified using deoxyribose degradation assay. The position of substituent and its electronic property are key features to address the antioxidant activity of uracil molecules.

We report on the improved stability and yield of silver nanorods with well controlled aspect ratios synthesized using a modified seed mediated approach conducted at room temperature. It is found that the longitudinal surface plasmon resonance of these nanoparticles can be tuned in the spectral range 400–700 nm by varying the concentration of seed particles. The surface enhanced Raman scattering (SERS) activity of these nanorods with varying aspect ratios was tested with four dye molecules viz., crystal violet, malachite green, nile blue chloride and rhodamine-6G, using visible and near-infrared laser excitation sources viz., 514.4 and 784.8 nm, respectively. The mechanism of enhancement for the dye molecules adsorbed on these nanorods was investigated in detail. A maximum enhancement factor in the order of 108 was obtained when factors such as the peak wavelength corresponding to the plasmon of the nanorods, the absorption of dye and the excitation line were in close approximation. The linearity obtained in the calibration curves drawn for intense Raman peaks in the SERS spectra of different dye molecules indicated that these substrates are suitable for applications such as biosensing. Keywords: Silver nanorods, Seed mediated synthesis, Surface enhanced Raman scattering, Crystal violet, Malachite green, Nile blue chloride, Rhodamine 6G

An efficient SERS substrate composed of gold nanocone arrays with abundant sharp tips directly grown on 3D porous Ni foam (AuNCA@Ni foam) was developed for sensitive detection of aromatic dyes. The AuNCA@Ni foam was prepared by a facile galvanic replacement reaction between Ni foam and HAuCl4 in the presence of cetyltrimethylammonium bromide (CTAB). The concentration of CTAB played an important role in determining the morphology of the product. Without CTAB or replacing CTAB with other surfactants, no AuNCA could be obtained. Thanks to the abundant uniform sharp tips and 3D porous structure, the AuNCA@Ni foam displayed much stronger SERS enhancement ability and higher reproducibility for aromatic dye detection compared with substrates prepared in the absence of CTAB or in the presence of other surfactants. Moreover, the AuNCA@Ni foam with the robust integrated structure also avoided the tedious operation of assembly and centrifugation. The SERS application of the AuNCA@Ni foam was tested by the detection of aromatic dyes crystal violet (CV) and Nile blue (NB), which achieved a detection limit (LOD) of 0.03 nM and 0.5 nM in standard solution, respectively, and an LOD of 3 nM for determining CV in real water samples.

In this work, a sensitive three-signal assay of perfluorooctanesulfonic acid (PFOS) was proposed. In pH 3.3 Britton–Robinson (BR) buffer solution, perfluorooctane sulfonate anions can react with Nile blue A (NBA) through electrostatic attraction and hydrophobic force to form 1 : 1 ion-association complexes resulting in intensity changes in the fluorescence, UV-vis absorption and resonance light scattering (RLS). There was found to be a certain relationship between the three signal changes dependent upon the concentration of PFOS. The change of absorption of NBA is proportional to the logarithm of the concentration of PFOS in the range of 0.1–4.0 μmol L−1 with a limit of detection (LOD) of 14.8 nmol L−1, and RLS intensity change is proportional to the concentration of PFOS in the range of 2.0–12.0 μmol L−1 with a LOD of 119.5 nmol L−1 and the change in the fluorescence is proportional to the logarithm of the concentration of PFOS in the range of 0.05–4.0 μmol L−1 with a LOD of 3.2 nmol L−1. Scanning electron microscopy (SEM) and zeta potential measurements were recorded in order to study the mechanism. This simple, sensitive and cost-effective fluorescence method was successfully applied in the determination of PFOS in real water samples with RSD values of ≤2.14%.

Cationic dyes are widely used colorants in textile and other related industries. These dyes are highly toxic for marine life and make a major fraction of the industrial effluents. In this study, we report the synthesis of ester derivative of calix[4]arene (EDC) impregnated polymer inclusion membrane (PIM) and employed it for the transfer of cationic dyes between two aqueous phases. EDC forms inclusion complex with cationic dyes having 1:1 M ratio as revealed by the Job’s plot, the log/log plot, and the Benesi-Hildebrand methods while using methylene blue (MB) as a model cationic dye. EDC was used as carrier with cellulose triacetate (CTA) as a base polymer, and 2-nitrophenyl octyl ether (2-NPOE) as a plasticizer for the synthesis of EDC-PIM. Membranes were characterized by Fourier Transform Infrared spectroscopy (FT-IR), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), and Barrett-Joyner-Halenda (BJH) analysis. The extraction performance of the synthesized PIM was optimized by varying different external parameters including pH of the donor and the acceptor phases, temperature, stirring speed, and concentration of EDC and dye while using MB as a model cationic dye. More than 90% extraction was achieved under optimized conditions which is 4.5-fold more than EDC-free-PIM. The extraction efficiency of the EDC-PIM remained similar after ten consecutive cycles that demonstrates its reusability potential in context of economical industrial applications. Finally, the synthesized EDC-PIM was used for selective extraction of other cationic dyes (basic red and nile blue) at the optimized conditions from the real industrial effluents. The extraction efficiency of the EDC-PIM was reproducible in all cases. The reusability and robustness of the EDC-PIM makes it an excellent candidate for retrieving cationic dyes from the industrial effluents.

The interaction of DNA with six water soluble benzo[a]phenoxazinium chlorides mono- or di-substituted with 3-chloropropyl groups at the O and N of 2- and 9-positions, along with methyl, hydroxyl and amine terminal groups at 5-positions, was investigated by photophysical techniques. The results indicated that almost all compounds intercalated in DNA base pairs at phosphate to dye ratio higher than 5. At lower values of this ratio, electrostatic binding mode with DNA was observed. Groove binding was detected mainly for the benzo[a]phenoxazinium dye with NH2.HBr terminal. The set of six benzo[a]phenoxazinium chlorides proved successful to label the migrating DNA in agarose gel electrophoresis assays. These finding proves the ability of these benzo[a]phenoxazinium dyes to strongly interact with DNA., Thanks are due to Fundação para a Ciência e a Tecnologia (FCT, Portugal) and FEDER (European Fund for Regional Development)/COMPETE-QREN-EU for financial support to Research Centres CQ/UM [PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302)] and CFUM [PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711)]. The Postdoctoral grant to B. R. Raju (SFRH/BPD/62881/2009) is also acknowledged to FCT, POPHQREN, FSE.

An aptamer-based sensitive method was developed here for detection of multiple foodborne pathogens in food matrix by surface-enhanced Raman scattering (SERS) technology. Polydimethylsiloxane (PDMS) film was first prepared and then coated with gold nanoparticles (AuNP) to act as an active substrate for the enhancement of Raman scattering. The as-prepared Au-PDMS film was functionalized with specific pathogen aptamers (Apt) to capture the targets. In addition, aptamers functionalized AuNP integrated with Raman reporters (4-Mercaptobenzoic acid (4-MBA)/Nile blue A (NBA)) were fabricated as pathogen-specific SERS probes. In this scheme, pathogens were first captured by Apt-Au-PDMS film and then bind with SERS probes to allow the formation of a sandwich assay to complete the sensor module for the detection of multiple pathogens. With Vibrio parahaemolyticus and Salmonella typhimurium as model targets, this protocol can selectively detect 18 cfu/mL and 27 cfu/mL, respectively. Furthermore, this platform can be successfully applied to detect pathogens in seafood samples with recoveries ranging from 82.9% to 95.1%.

Rapid and sensitive detection of botulinum neurotoxins (BoNTs) is important for immediate treatment with proper antitoxins. However, it is difficult to detect BoNTs at the acute phase of infection, owing to its rarity and ambiguous symptoms. To resolve this problem, we developed a surface-enhanced Raman scattering (SERS)-based immunoassay technique for the rapid and sensitive detection of BoNTs. Magnetic beads and SERS nanotags as capture substrates and detection probes, respectively, and Nile Blue A (NBA) and malachite green isothiocyanate (MGITC) as Raman reporter molecules were used for the detection of two different types of BoNTs (types A and B), respectively. The corresponding limits of detection (LODs) were determined as 5.7 ng/mL (type A) and 1.3 ng/mL (type B). Total assay time, including that for immunoreaction, washing, and detection, was less than 2 h.

Separation and detection of hemoglobin (Hb) and glycated hemoglobin fractions (HbA1c, HbAld1+2, HbAle, HbAld3a, HbAla+b, HbA2, and HbAld3b) was performed using an electrochemical AC field modulated separation channel (EMSC) coupled with a sensor probe. The sensor was fabricated based on immobilization of a redox mediator on the poly(2,2′:5′,5″-terthiophene-3′-p-benzoic acid, pTTBA) and N,S-doped porous carbon (NSPC) nanocomposite. The different types of catalytic redox mediators such as Nile Blue (NB), toluidine blue O (TBO), and Neutral Red (NR) were evaluated to achieve the efficient detection. Of these, the NB-based sensor showed the best analytical signal for Hb and HbA1c, thus it was characterized using various electrochemical and surface analysis methods. After that, the sensor was coupled with the EMSC to achieve the separation detection of the Hb family. The frequency and amplitude of the AC electrical field applied onto the EMSC walls were the main driving forces for the separation and sensitive detection of the analytes. Under optimized conditions, linear dynamic ranges for Hb and HbA1c among their fractions were obtained between 1.0 × 10−6 to 3.5 mM and 3.0 × 10−6 to 0.6 mM with the detection limit of 8.1 × 10−7 ± 3.0 × 10−8 and 9.2 × 10−7 ± 5 × 10−8 mM, respectively. Interference effects of other biomolecules were also investigated and the clinical applicability of the device was evaluated by the determination of total Hb and % HbA1c in real human blood samples.

Electrochemical atomic force microscopy tip-enhanced Raman spectroscopy (EC-AFM-TERS) was employed for the first time to observe nanoscale spatial variations in the formal potential, E0′, of a surface-bound redox couple. TERS cyclic voltammograms (TERS CVs) of single Nile Blue (NB) molecules were acquired at different locations spaced 5–10 nm apart on an indium tin oxide (ITO) electrode. Analysis of TERS CVs at different coverages was used to verify the observation of single-molecule electrochemistry. The resulting TERS CVs were fit to the Laviron model for surface-bound electroactive species to quantitatively extract the formal potential E0′ at each spatial location. Histograms of single-molecule E0′ at each coverage indicate that the electrochemical behavior of the cationic oxidized species is less sensitive to local environment than the neutral reduced species. This information is not accessible using purely electrochemical methods or ensemble spectroelectrochemical measurements. We anticipate that qua...

Electrocatalytic activities of graphene nanosheets/Nile blue nanocomposite, synthesized and adsorbed simultaneously on the glassy carbon (GCGNsNB) electrode, are investigated. The nanocomposite was characterized by ATRFTIR, FESEM and voltammetry. Activity of the electrode toward reduction of H2O2 and oxidation of NO2− was studied electrochemically. Values of 1.95 and 0.730 mM are found for the MichaelisMenten constant of the electrode toward H2O2 and NO2−, respectively. Wide dynamic response ranges were observed for the electrode, with DLs of 0.22 μM H2O2 and 1.1 μM NO2−. Effect of interferences was studied. The sensor was successfully tested for H2O2 and NO2− contents in real samples, respectively.

A novel multi-wavelength nonaqueous capillary electrophoresis (MW-NACE) technique based on wavelength-dependent laser-induced fluorescence (LIF) detection was investigated for the simultaneous screening of various synthetic organic dyes. Multi-wavelength excitation light sources were utilized to excite different organic dyes [e.g., 543 nm for crystal violet (CV), methyl violet B (MVB), methyl violet B base (MBB), rhodamine 6G (R6G), and rhodamine B base (RBB); 635 nm for nile blue A (NBA) and methylene blue (MB)] simultaneously. Using a nonaqueous buffer system composed of 15 mM sodium borate and 835 mM acetic acid in 100% ethanol (pH=5.4), all dyes were analyzed within 15 min with excellent resolution (R≥4.0) under an electric field of 500 V/cm. Calibration curves showed excellent linearity with square of correlation coefficients (r(2)) greater than 0.9908 over wide dynamic ranges of 0.4-50 μM for CV, 0.8-50 μM for MVB, 1.5-50 μM for MBB, 0.08-5 nM for R6G, 0.06-10 μM for MB, 0.02-10 μM for NBA, and 0.13-10 pM for RBB. The detection limits (S/N=3) of 40 fM to 0.5 μM were 10-200,000 times lower than those of previous detection methods. While adjacent peaks were not well distinguished with baseline separation in a single capillary, the devised technique was faster and more sensitive than conventional aqueous and nonaqueous CE approaches, thereby enabling the quantitative analysis of various dyes based on wavelength-dependent fluorescence detection with different excitation wavelengths.

A poly(Nile blue) modified glassy carbon electrode (PNBMGCE) was fabricated by electropolymerisation of Nile blue (NB) monomer using cyclic voltammetry (CV) and was used for the determination of paracetamol (ACOP), tramadol (TRA) and caffeine (CAF). The electrochemical investigations showed that PNB - film formed on the surface of glassy carbon electrode (GCE) improved the electroactive surface area and displayed a remarkable increase in the peak current and a substantial decrease in over potential of ACOP, TRA and CAF when compared to bare GCE. The dependence of peak current and potential on pH, sweep rate and concentration were also investigated at the surface of PNBMGCE. It showed good sensitivity and selectivity in a wide linear range from 2.0 x 10(-7) to 1.62 x 10(-5) M, 1.0 x 10(-6) to 3.1 x 10(-4) M and 8.0 x 10(-7) to 2.0 x 10(-5) M, with detection limits of 0.08, 0.5 and 0.1 mu M, for ACOP, TRA and CAF, respectively. The PNBMGCE was also successfully applied for the determination of ACOP, TRA and CAF in pharmaceutical dosage forms. (C) 2016 Elsevier B.V. All rights reserved.

Covalent immobilization of redox-active dyes is an important strategy to evaluate structure-activity relationships in nanoscale electrochemistry by using optical readouts such as surface-enhanced Raman scattering (SERS). Here we investigate the role of the tether length in the SERS spectroelectrochemistry of surface-attached Nile Blue. Differential pulse voltammetry and a potential-dependent SERS derivative analysis reveal that the Nile Blue molecules adopt a different orientation with respect to the electrode surface as the number of carbons in a carboxylic acid-terminated alkanethiol monolayer is varied, which leads to unique SERS spectroelectrochemical behaviors. We use the relative molecular orientations and spectral characteristics to propose a model in which tethers shorter than the length of the molecule limit molecular motion under electrochemical perturbation, but tethers longer than the length of the molecule allow dye intercalation into the hydrophobic self-assembled monolayer, producing an unexpected decrease in the SERS intensity when the molecule is in the oxidized form.

Over the last decade several research groups have accomplished the fabrication of 2D periodic and 3D nanocage like structures on different materials using diverse lithographic approaches. Herein, we present the detailed studies on the fabrication of femtosecond (fs) laser‐induced periodic/ripple‐like surface structures on nickel (Ni) substrate in distilled water whereas 3D-like (nanocages) features on Ni substrates in acetone by tailoring the laser processing parameters (pulse energy). The morphological studies of simultaneously obtained Ni nanoparticles (NPs)/nanostructures (NSs) in distilled water/acetone were meticulously studied using transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM). The fabricated Ni periodic/3D-like structures were gold (Au) plated using thermal evaporation technique and subsequently utilized as surface enhanced Raman scattering (SERS) active sensors for detecting the traces of various analyte molecules such as malachite green (MG) and Nile blue (NB). The grooved Ni-Au substrates allowed us to detect extremely low concentrations of MG (500 pM) and NB (5 nM) and, significantly, utilizing a simple, portable Raman spectrometer. Moreover, the substrates have demonstrated superior reproducibility as well as multi-utility nature with a relative standard deviation (RSD) of

Selenocysteine (Sec) is a primary kind of reactive selenium species in cells, and its vital roles in physiological processes have been characterized. Therefore, the highly effective method for sensing Sec in metabolic processes and selenium-rich food must be developed. This study presents a new fluorescent probe, namely, GSH-NB@AuNPs, for highly selective detection of selenol based on the fluorescence quenching quality on the surface of gold nanoparticles (AuNPs). The probe consists of glutathione (GSH) and Nile blue (NB) moieties assembled on AuNPs. The probe exhibits excellent sensitivity and selectivity for Sec and is applied in imaging endogenous and exogenous Sec in living cells through confocal fluorescence microscopy. The proposed probe provides a promising and powerful method for detecting selenol in foodstuff (such as selenium-rich rice and tea) with the detection limit of 9.5 nM.

International audience; We describe a novel protocol for a one-step, seed-less, organic solvent- and surfactant-free synthesis of optically dense aqueous colloids of gold nanoflowers (AuNF), with tunable absorption wavelength between 620 and 800 nm. We demonstrate that simple variation of the ratio of two reagents allows the plasmonic band position to be tuned to any desired wavelength ± 5 nm, namely to those of the laser sources commonly used for SERS spectroscopy. The AuNF size distribution was sufficiently narrow, comparable to that known with seed-mediated synthesis. The AuNF have been validated as efficient aggregation-free substrates for surface-enhanced Raman scattering (SERS) spectroscopy using two common fluorescent dyes, Nile Blue and Crystal Violet, both thiol-free. Their fluorescence was quenched and SERS signal intensity was a linear function of the dye concentration, from nanomolar to micromolar range. Easy to prepare and to use, these AuNF appear as a particularly user-friendly and efficient way to obtain plasmonic substrates for SERS in the red and deep red spectral range.

Metallic silver nanowires with high yield were synthesized using a modified seed mediated approach at room temperature. Ribbon-like nanostructures were obtained when the concentration of NaOH was lower and further increase of NaOH transformed it into long nanowires. These nanowires possess high aspect ratio, with length and diameter ~6.5 μm and 17 nm respectively. The surface enhanced Raman scattering activity of these nanowires was tested with three different probe molecules viz., crystal violet, malachite green and nile blue chloride using visible (514.4 nm) and near-infrared (784.8 nm) excitation lines. The minimum detection limits for crystal violet and nile blue chloride molecules were found to be down to 10−7 M with good linear responses, as evidenced by values of correlation coefficients, indicating their potential for a variety of applications such as sensing. Principal component analysis was performed with the surface enhanced Raman spectra in order to discriminate the dye molecules and their mixture, simultaneously. The first two principal components, which provided 69.80 and 27.93% of the total data variance, could be conveniently represented as a two dimensional PCA score plot. The score plot showed clear clustering of probe molecules and their mixture. The relative contribution of wavenumbers to each of the two principal components was identified by plotting the PCA loading matrix. These results further promote possibilities of quantification of multiplexed SERS detection and analysis.

A new optical urea biosensor based on urease (Urs) physically attached to a pH optode made from Nile Blue (NB) chromoionophore-doped kappa-carrageenan (KC) membrane is described in this paper. The immobilized Urs on the biosensor surface catalyzed the hydrolytic decomposition of urea into ammonium hydroxide, a pH changed to a more basic condition, and resulted in a colour change of the pH sensor membrane from blue to violet, which can be quantified reflectometrically using a fibre optic reflectance spectrophotometer. A linear relationship was perceived between the reflectance intensity of the KC membrane-based biosensor and the urea concentration in the range of 0.001–100 mM with the detection limit calculated at 0.001 mM. The response time of the urea biosensor was 10 min, and no significant discrepancy was noted for the results obtained from the direct analysis of urine samples by both the reflectance catalytic biosensor and the UV–vis spectrophotometric standard method based on the p -dimethylaminobenzaldehyde (DMAB) reagent.

The development of rapid, sensitive methods for α-fetoprotein and telomerase is significant because their blood concentrations are related to hepatocellular carcinoma. Therefore, the determination of α-fetoprotein and telomerase may allow the detection of liver cancer. A novel method for the high-yield synthesis of gold-silica alloy core-shell nanoparticles is reported. Gold-silica core-shells prepared by a convenient reduction provided good stability, served as immobilization carriers for the antibodies, and facilitated electron transfer. A simple label-free, three-dimensional hierarchical plasmonic nanoarchitecture was designed for the sensitive surface-enhanced Raman scattering determination of α-fetoprotein and telomerase. The active groups of the gold-silica nanoparticles allowed 4-mercaptobenzoic acid and Nile blue to absorb antibodies and generate a signal. Gold-silica@4-mercaptobenzoic acid and gold-silica@Nile blue were employed in the surface-enhanced Raman scattering immunosensor. When ...

The Nile blue has been used as a photosensitizer with Arabinose as a reductant in photogalvanic cell for optimum conversion efficiency and storage capacity. Reduction cost of the photogalvanic cell for commercial utility. The generated photopotential and photocurrent are 816.0 mV and 330.0 uA respectively. The maximum power of the cell is 269.30 uW where as the observed power at power point is 91.28 uW. The observed conversion efficiency is 0.6095% and the fill factor 0.2566 has been experimentally found out at the power point of the photogalvanic cell, whereas the absolute value is 1.00. The photogalvanic cell so developed can work for 120.0 minutes in dark if it is irradiated for 200.0 minutes that is the storage capacity of photogalvanic cell is 60.00%. The effects of different parameters on the electrical output of the photogalvanic cell have been observed. A mechanism has also been proposed for the photogeneration of electrical energy.

The pursuit of techniques with a high time resolution together with molecular signature information at the electrochemical interfaces has never stopped in order to explicitly monitor and understand the dynamic electrochemical processes. Here, we developed a transient electrochemical surface-enhanced Raman spectroscopy (TEC-SERS) to monitor the structural evolution of surface species at a time resolution that equals the transient electrochemical methods (e.g., cyclic voltammetry and chronoamperometry), so that the Raman signal with the molecular signature information and the electrochemical current signal can be precisely correlated. The technique was employed to study the redox process of nile blue on Ag surfaces. We revealed an interesting two-rate constant process and a peculiar increase of the absolute intensity during the reduction of nile blue on the Ag surface, which both related to the dissociation of nile blue aggregates and the follow-up reduction. Therefore, we were able to uncover the processes that are impossible to observe by conventional steady state SERS methods. The ability to provide a time resolution shorter than the charging time of the double layer capacitance with molecular fingerprint information has unprecedented significance for investigation of both reversible and irreversible electrochemical processes.

In this study, development of an electrochemical DNA biosensor based on a hepatitis C virus probe was introduced using an electrochemically pre-treated pencil graphite electrode (PPGE) as a transducer and Nile blue (NB) as an electroactive indicator. At first, the electrochemical behaviour of NB on the PPGE was investigated. Then, elucidating the specific interaction of NB with each of the nucleotides of DNA, the interactions of NB with oligonucleotides containing only one base type were studied. In this study, four 18-mer oligonucleotides of poly A, poly T, poly C, and poly G were used as probe and were used as related complementary/non-complementary sequences in the hybridization section. The extent of hybridization was evaluated based on the difference between DPV signals of NB accumulated on the probe–PPGE and NB accumulated on the probe–target–PPGE. Then, the developed biosensor was applied successively for the detection of short sequences of Hepatitis C 3a virus (14 pic). The hybridization between the probe (14 pic) and its complementary sequence (C2Comp) as the target was studied. Some hybridization experiments with non-complementary oligonucleotides also showed that the suggested DNA sensor responds selectively to the target. Diagnostic performance of the developed biosensor was described and the detection limit was found to be 1.1 nM with a relative standard deviation of 3.5 % in the 0.1-M Tris–HCl buffer solution (pH 7.0) containing 20 mM NaCl.

Super-resolution surface-enhanced Raman scattering (SERS) is used to investigate local surface potentials on plasmonic gold and silver colloidal aggregates using the redox-active reporter molecule, Nile Blue A. This molecule is electrochemically modulated between an oxidized emissive state and a reduced dark state. The diffraction-limited SERS emission from Nile Blue on the surface of a single plasmonic nanoparticle aggregate is fit to a two-dimensional Gaussian to track the position of the emission centroid as a function of applied potential. Potential-dependent centroid positions are observed, consistent with molecules experiencing site-specific oxidation and reduction potentials on the nanoparticle electrode surface. Correlated structural analysis performed with scanning electron microscopy reveals that molecules residing in nanoparticle junction regions, or SERS hot spots, appear to be reduced and oxidized at the most negative applied potentials as the potential is cycled.

Nile blue/graphene (NB-GNs) nanocomposite was synthesized for the first time via a green and effective one-step electrochemical method, allowing to reduce graphene oxide (GO) and NB on the glassy carbon electrode (GCE) simultaneously and construct GCE-GNs-NB poly composite. The composite was characterized by scanning electron microscopy (SEM), UV–Vis spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical results obtained in the absence of any redox probe, where NB was active, allowed to trace step-by-step addition of the NB-GNs nanocomposite onto the GCE electrode surface, supporting formation of the GCE-GNs-NB poly composite. The electrocatalytic activity of the as-prepared GCE-GNs-NB poly towards O 2 reduction was studied in neutral medium. The results revealed excellent electrocatalytic performance for two-electron reduction of oxygen, suggesting its potential application as metal-free electrocatalysts for O 2 reduction reaction. Application of the GCE-GNs-NB poly in electrochemical biosensing was demonstrated by immobilization of glucose oxidase (GOx) on the surface of GCE-GNs-NB poly , and then, using it for sensing of glucose. The biosensor exhibited a linear response, from 0.2 to 2.0 mM glucose, with a low detection limit, 2.1 μM, and high sensitivity, 67.0 μA mM −1 cm − 2 , obtained by cyclic voltammetry method. The proposed biosensor was successfully tested for determination of glucose in blood serum samples.

Uniform phenolic resin microspheres were prepared by the polycondensation of 3-aminophenol and formaldehyde. On the surface of the 3-aminophenol resin microspheres, silver nanoparticles were synthesized in situ and immobilized by simple heating. The composite was employed as a substrate for surface-enhanced Raman scattering (SERS). The SERS enhancement factor was evaluated using 4-mercaptobenzoic acid and Nile blue A as signal molecules. A highly sensitive SERS immunoassay that combined labeled antibody conjugated silver nanoparticle modified 3-aminophenol resin microspheres and coating antibody conjugated magnetic nanoparticles was fabricated to determine carcinoembryonic antigen. A linear relationship was obtained between the Raman intensity and the concentration of carcinoembryonic antigen. The limit of detection was 1.2 picograms per milliliter at a signal-to-noise ratio of three. This is believed to be the first report of a SERS immunoassay using silver nanoparticle modified 3-aminophenol resin micro...

Recently, growing concern has been paid to the sensitive and selective determination hypochlorite because of its crucial roles in our daily life. In this paper, a simple, sensitive, selective spectrofluorimetric method was applied to detect the hypochlorite. Upon reaction of the probe with ClO − , a fluorescence quenching was observed. The method was shown to be highly selective for ClO − , and exhibited real time response as well as linear relationship to ClO − concentration, and hypochlorite could be detected at low micromolar levels in aqueous solution. The linear response range of hypochlorite ( R 2 = 0.9994) was from 0.13 to 25 µmol/L. The detection limit (3 σ / k ) was 0.04 µmol/L, which was lower than that of previously mentioned. The accuracy and reliability of the method was further ensured by recovery studies via a standard-addition method, with percentage recoveries in the ranges of 95.0–104.8%, 96.3–102.6% and 97.8–102.5, respectively. Additionally, the quenching mechanism was discussed. Judging from temperature, fluorescence lifetime, UV–visible absorbance spectra, quenching mechanism was proved static quenching. This method was finally used to detect the hypochlorite in local water samples.

A Nile blue-based chemodosimeter was newly synthesized. It can detect Hg(2+) in aqueous solution based on desulfurization reaction. Upon its addition into aqueous Hg(2+) ion solution, it exhibited a considerable blue-shift in its absorption and obvious fluorescence quenching. The detection mechanism was proved by mass spectrometry analysis and Gaussian calculations. Detection at an emission of 685 nm was extremely sensitive, with a detection limit of 2.5 × 10(-9) mol/L. The fluorescent images in living cells and zebrafish demonstrate its potential for studying the accumulation of mercury species in organism.

Springer New York LLC, A new indirect ultrasonic-assisted cloud point extraction (UA-CPE) method has been developed for the determination of trace sulfite species by means of spectrophotometry. The method is based on either directly imide–bisulfite adducts formation or ion-pairing complexation of enolate–bisulfite adducts produced by the oxidation of pyrogallol with sulfite at pH 10 with 3-amino-7-diethylamino-8,9-benzo-2-phenoxazine chloride (Nile blue A) and CPE of ion-pairing complex formed from aqueous solution using Triton X-114. Under the optimized conditions, the calibration graphs with and without bromide were highly linear in the ranges of 6–180 and 7.5–180 ?g L?1 with changing sensitivity. The limits of detection and quantification (LOD and LOQ) (3?blank/m and 10?blank/m) with bromide was 1.75 and 5.83 ?g L?1 (n = 6) and the precision, the relative standard deviations (RSDs), for determination of 25, 75, and 150 ?g L?1 of sulfite was in range of 2.40–5.20 % (n = 10). The method showed good selectivity, and was successfully applied to the speciative determination of trace sulfite in selected beverages with and without alcohol. The results were compared with those of the standard 5,5?-dithio-bis(2-nitrobenzoic acid (DTNB) method, and the two paired t test was used to determine whether the results obtained by the two methods differ significantly. © 2015, Springer Science+Business Media New York., Altunay, N.; Faculty of Science, Department of Chemistry, University of CumhuriyetTurkey

Royal Society of Chemistry, A new micellar-mediated, cloud-point extraction (CPE) method has been developed for the quantification of trace levels of fluoride by means of spectrophotometry. The method is based on the selective ion association of stable anionic complexes, Sn(OH)F2- or Sn(OH)F32- of fluoride with Sn(ii) in presence of cationic dye (Nile blue A) at pH 5.0, and its extraction to the micellar-rich phase of nonionic surfactant polyoxyethylene (7.5) nonylphenyl ether (PONPE 7.5) as the extracting agent. Afterwards, the ternary complex formed was spectrophotometrically detected at 638 nm after preconcentration with CPE. Under optimized conditions, the calibration curves were rectilinear in the ranges of 5-25 and 25-360 ?g L-1 in the linear region with changing sensitivity. The limits of detection and quantification (LOD and LOQ) (3?blank/m and 10?blank/m) was 1.45 and 4.83 ?g L-1, respectively, and the precision (as RSD) for determination of 15, 75, and 150 ?g L-1 of fluoride was in the range of 2.35-4.65%. The validity of the method was checked through recovery experiments, independent analysis by potentiometry and analysis of the standard reference material SRM 2695. The developed method was successfully applied to the accurate, sensitive and reliable quantification of total acid hydrolyzed fluoride present in selected beverage and food samples. © 2015 The Royal Society of Chemistry., Altunay, N.; University of Cumhuriyet, Faculty of Sciences, Department of ChemistryTurkey

SERS optrodes were used to "fish" aqueous drops from superhydrophobic surfaces. The technique led to an improvement of 2-3 orders of magnitude in the lowest detectable amount of the Raman probe nile blue A, reaching 25 fg (34 attomoles). Further tests run on samples containing pesticide revealed that 20 pg of triazophos could be clearly detected from a single drop.

In this work, glassy carbon electrode (GCE) surface was modified by drop-coating graphene oxide (GO) and nile blue (NB) to form GO/NB/GCE. By using a one-step coreduction treatment under cyclic voltammetry (CV) scanning, gold nanoparticles (AuNPs) were electrodeposited onto GO/NB/GCE surface, simultaneously generating reduced GO (rGO). AuNPs from the prepared rGO/NB/AuNPs/GCE was combined with 5′-SH-terminated aptamer of dopamine (DA) via Au-S coupling to fabricate aptamer-rGO/NB/AuNPs/GCE system. DA specifically combined with its aptamer modified on rGO/NB/AuNPs/GCE surface. CV, electrochemical impedance spectroscopy, square wave voltammetry responses of this system as the working electrode were measured. With the addition of DA, the peak current intensities located at −0.45 V (INB) and 0.15 V (IDA) showed gradually decreased and increased changes, respectively. There was a good linear (R2 = 0.9922) relationship between lg(IDA/INB) and the logarithm of DA concentration (lgCDA) in the CDA range from 10 nM to 0.2 mM, showing a low detection limit of 1 nM. This system as a novel, sensitive and label-free aptasensor was used for ratiometric electrochemical sensing of DA. Experimental results verified that this aptasensor possessed high stability, selectivity and sensitivity towards DA detection, over potential interferents. This aptasensor efficiently determined DA in real biological samples, together with high detection recoveries of 97.0–104.0%.

Fluorescence-based immonoassays are widely used in several areas, ranging from basic biomedical research to disease diagnostics. A variety of new probes have been developed recently to address some limitations in typical assays performed with organic dyes. Ideally, new fluorescence tags that allow quantification with a low limit of detection are highly desired. In this work, the surface-enhanced fluorescence (SEF) phenomenon was explored in the development of tags for Immunoglobulin-M (IgM) detection. Shell-isolated gold nanoparticles (Au-SHINs) with 100 nm core size and a 10 nm silica shell were synthesized. These particles contain an outermost thin fluorescent layer of nile blue (NB) that was further coated by another 5 nm of silica (SEF tags). The outer silica shell was then functionalized with antibodies to allow the detection of IgM as in typical immunological sandwich assays. IgM concentrations down to the 10 ng mL−1 mark were successfully detected. A linear dependence between the average fluorescence intensity and the IgM concentration was found.

Hydrogen sulfide has recently been identified as a biologically responsive species. The design and synthesis of fluorescence probes, which are constructed with Nile-red or Nile-blue fluorophores and a fluorescence-controllable dinitrophenyl group, for hydrogen sulfide are reported in this paper. The Nile-red-dinitrophenyl-ether-group-based probe (1a) is essentially non-fluorescent because of the inhibition of the photo-induced electron-transfer process; when the dinitrobenzene moiety is removed by nucleophilic substitution with the hydrosulfide anion, probe 1a is converted into hydroxy Nile red, eliciting a H2S-induced fluorescence turn-on signal. Furthermore, probe 1a has high selectivity and sensitivity for the hydrosulfide anion, and its potential for biological applications was confirmed by using it for real-time fluorescence imaging of hydrogen sulfide in live HeLa cells. The Nile-blue-dinitrobenzene-based probe (1b) has gradually diminishing brightness in the red-emission channel with increased hydrogen-sulfide concentration. Thus, this paper reports a comparative study of Nile-red and Nile-blue-based hydrogen-sulfide probes.

Reduced graphene oxide-CdS quantum dots (rGO-CdS QDs) nanocomposite was synthesized with a one-pot and facile solvothermal strategy and characterized with X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The nanocomposite modified with electropolymerized Nile blue (NB) had high electrocatalytic and photoelectrocatalytic activity toward NADH oxidation with lowering 700 mV of overvoltage compared to bare GCE. The linear response up to 200 µM was obtained for photoamperometric determination of NADH and the detection limit was 1 µM (S/N=3). Furthermore, with covalence immobilizing of glucose dehydrogenase onto the nanocomposite, the electrochemical and photoelectrochemical ability of the proposed system toward glucose biosensing was also investigated.

The electrochemical behaviour of levodopa (LD) has been investigated at multiwalled carbon nanotube (MWCNT) and poly(Nile blue-A) (PNB) modified glassy carbon electrodes (GCE). MWCNT/PNB modified electrodes were prepared by NB potential cycling electropolymerisation in 0.1 M phosphate buffer solution (PB), pH 6.0, followed by MWCNT deposition, and PNB/MWCNT/GCE by coating in the inverse order. The oxidation behaviour of LD was investigated in 0.1 M PB at pH values between 5.0 and 8.0. Quantitative determination of LD by differential pulse and square wave voltammetry was carried out in 0.1 M PB at pH 6.0. Analytical parameters were compared with the literature.

A K + ion-sensitive optical sensor based on Nile Blue (chromoionophore ETH5294) incorporated into poly(n-butyl acrylate) [poly(nBA)] microspheres was successfully developed. A combination of acrylic spheres and optical reflectometry had enhanced the sensing performance of the optical K + ion sensor, as the former provides large surface area for better loading capacity and higher reaction rate, while the latter offers simple and rapid measurements. The sensing mechanism involves ion-exchange reaction, which occurs at the surface of the microspheres where influx of K + ions and efflux of H + ions take place. The sensor response was a result of the total deprotonation of chromoionophore immobilized within poly(nBA) microspheres in response to the formation of K + ion–ionophore complex. The change of the response in the presence of K + ions was studied via reflectance spectroscopy using an optical fibre probe. The K + ion sensor based on these microspheres exhibited sensitivity slope of 43.15 ΔIntensity/decade ( R 2 = 0.961) in a range 0.01–1000 mM of KCl with a lower detection limit of 0.01 mM. Sensor response time was 10 min with good reproducibility (relative standard deviation, %RSD = 5.71). Analysis of urine samples for K + ions gave 87–115% recovery and the results were comparable with established method for K + ions analysis. Leaching tests and life time study revealed that acrylic microspheres worked well as an immobilization matrix for hydrophobic chromoionophore.

A surface enhanced Raman scattering (SERS) substrate, capable of extracting small amounts of organic species from surfaces of different types of materials with variable roughness, has been fabricated. The substrate consists of Ag NPs encapsulated in poly(vinyl alcohol) (PVA) hydrogels, commonly known as PVA "slime". Unlike traditional SERS substrates, such as colloidal suspensions, the resulting PVA slime SERS substrate presents good viscoelasticity, allowing it to conform to the surface of various materials of arbitrary roughness. Surfaces of different materials, including sandpapers, cotton, metal, and wood, previously contaminated with nile blue A (NBA) were analyzed with the PVA slime SERS substrate. Limits of detection (LOD) as low as 100 ppb (0.79 ng in a total amount on an area of ∼3 cm(2)) were achieved for all surfaces tested. Pesticides and Sudan red III on the glass surface have also been detected, with a LOD of 1.6 ng per ∼3 cm(2).

In this study, an ultrasensitive surface-enhanced Raman scattering (SERS) detection of alkaline phosphatase (ALP) has been developed, in which nile blue A (NBA) was chosen to replace nitro blue tetrazolium chloride (NBT) in a reactive system of 5-bromo-4-chloro-3-indolyl phosphate (BCIP), NBT, and ALP. In the reactive process, NBA was converted to a low SERS-active molecule, and its SERS intensity at 592 cm−1 decreased when NBA was reduced by 5-bromo-4-chloro-3-indolyl, which converted from BCIP by ALP. The SERS signal of NBA was inversely proportional to the amount of ALP in the reactive system. Based on convenient SERS materials of gold nanoshells absorbed on acupuncture needles, the detectable concentration range of ALP was 1–104 mU L−1 in a reactive system of BCIP, NBA, and ALP.

A novel poly(amido amine)/poly(Nile blue) (PAMAM/PNB)-modified electrode was fabricated by adopting electro-deposition and electro-polymerization method, and the obtained electrode used to sense various biological and clinical substrates of L-dopa, paracetamol, dopamine, gallic acid, butyl hydroxyanisole, ascorbic acid, uric acid, L-tryptophan, vanillin, and riboflavin. The surface and structural morphology of the electrode was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. The electrocatalytic activity of the electrode was observed by cyclic voltammetry (CV) studies using 0.1 M phosphate buffer solution (PBS, pH 7) at a scan rate of 50 mVs−1, and the results indicate the excellent electrocatalytic activity of the newly fabricated electrode against oxidation and reduction reactions of biological analytes. In addition, the modified electrode is revealed to have good stability and reproducibility, and hence it has potential application as a sensor for the determination of various biologically significant compounds in the near future.

We present a convenient precipitation procedure to fabricate ultrasmall fluorescent ion selective nanosensors that operate on the basis of bulk ion exchange sensing principles. The nanosphere matrix is composed of bis(2 ethylhexyl) sebacate (DOS) and a triblock copolymer Pluronic ® F 127 which also functions as a surfactant to stabilize the nanoparticle. The particles can be prepared easily in large quantity without resorting to further complicated purification. Dynamic light scattering shows that these particles have a monodisperse size distribution with an average diameter of ~40 nm suggesting that the nanoparticles are among the smallest ionophore based ion selective nanosensors reported to date. A newly reported oxazinoindoline (Ox) as well as a Nile blue derivative (chromoionophore I) was used as a chromoionophore. Na+ and H+ selective nanospheres were characterized by absorbance and fluorescence spectroscopy. Owing to the very small size of the nanospheres the suspension containing the particles is transparent. In the additional presence of the pH indicator HPTS spectroscopic interrogation of pH and Na+ in the same sample was demonstrated. As an example the nanospheres were used to measure the Na + level in commercial mineral waters and the results showed good agreement with atomic absorption spectroscopy (AAS). © 2013 American Chemical Society.

In the present study, oleic acid (OA) functionalized Fe3O4 magnetic nanoparticles (MN) were synthesized following modified wet method of MN synthesis. The optimum amount of OA required for capping of MN and the amount of bound and unbound/free OA was determined by thermogravimetric analysis (TGA). Further, we have studied the effect of water molecules, associated with MN, on the variation in their induction heating ability under alternating current (AC) magnetic field conditions. We have employed a new approach to achieve dispersion of OA functionalized MN (MN-OA) in aqueous medium using sodium carbonate, which improves their biological applicability. Interactions amongst MN, OA and sodium carbonate were studied by Fourier transform infrared spectroscopy (FT-IR). Intracellular localization of MN-OA was studied in mouse fibrosarcoma cells (WEHI-164) by prussian blue staining and confocal laser scanning microscopy (CLSM) using nile blue A as a fluorescent probe. Results showed MN-OA to be interacting mainly with the cell membrane. Their hyperthermic killing ability was evaluated in WEHI-164 cells by trypan blue method. Cells treated with MN-OA in combination with induction heating showed decreased viability as compared to respective induction heating controls. These results were supported by altered cellular morphology after treatment of MN-OA in combination with induction heating. Further, the magnitude of apoptosis was found to be ~5 folds higher in cells treated with MN-OA in combination with induction heating as compared to untreated control. These results suggest the efficacy of MN-OA in killing of tumor cells by cellular hyperthermia.

The aim of this work is to illustrate the power of recently developed methods for measuring resonance Raman scattering (RRS) spectra of efficient fluorophores (using a standard continuous wave excitation and a charge-coupled device (CCD)-based Raman spectrometer), by applying them to a detailed study of a specific fluorophore: Nile Blue A. A combination of methods are used to measure the RRS properties of Nile Blue A in water (quantum yield (QY) of 4%) and ethanol (QY of 22%) at excitation wavelengths between 514 and 647 nm, thus covering both pre-resonance and RRS conditions. Standard Raman measurements are used in situations where the fluorescence background is small enough to clearly observe the Raman peaks, while the recently introduced polarization-difference RRS and continuously shifted Raman scattering are used closer to (or at) resonance. We show that these relatively straightforward methods allow us to determine the Raman cross-sections of the most intense Raman peaks and provide an accurate measurement of their line-width; even for broadenings as low as � 4c m � 1 . Moreover, the obtained Raman excitation profiles agree well with those derived from the optical absorption by a simple optical transform model. This study demonstrates the possibility of routine RRS measurements using standard Raman spectrometers, as opposed to more complicated time-resolved techniques. Copyright © 2013 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this article.

Nile blue is used extensively in biology as a histological stain and fluorescent probe. Its absorption and emission spectra are strongly solvent dependent, with variations larger than 100 nm. The molecule is charged due to an iminium group, and it is therefore an obvious target for gas-phase ion spectroscopy. Here we report the absorption and emission spectra of the mass-selected bare ions isolated in vacuo, and based on our results we revisit the interpretation of solution-phase spectra. An accelerator mass spectrometer was used for absorption spectroscopy where the absorption is represented by the yield of photofragment ions versus excitation wavelength (action spectroscopy). The luminescence experiments were done with a newly built ion trap setup equipped with an electrospray ion source, and some details on the mass selection technique will be given which have not been described before. In vacuo, the absorption and emission maxima are at 580 +/- 10 nm and 628 +/- 1 nm. These values are somewhat blue-shifted relative to those obtained in most solvents; however, they are much further to the red than those in some of the most non-polar solvents. Furthermore, the Stokes shift in the gas phase (1300 cm(-1)) is much smaller than that in these non-polar solvents but similar to that in polar ones. An explanation based on charge localization by solvent dipoles, or by counterions in some non-polar solvents, can fully account for these findings. Hence in the case of ions, it is nontrivial to establish intrinsic electronic transition energies from solvatochromic shifts alone. Published by AIP Publishing.