Nm For Detection Research Articles

Development of SERS Active Nanoprobe for Selective Adsorption and Detection of Alzheimer's Disease Biomarkers Based on Molecular Docking.

Development of SERS-based Raman nanoprobes can detect the misfolding of Amyloid beta (Aβ) 42 peptides, making them a viable diagnostic technique for Alzheimer's disease (AD). The detection and imaging of amyloid peptides and fibrils are expected to help in the early identification of AD. Here, we propose a fast, easy-to-use, and simple scheme based on the selective adsorption of Aβ42 molecules on SERS active gold nanoprobe (RB-AuNPs) of diameter 29 ± 3 nm for Detection of Alzheimer's Disease Biomarkers. Binding with the peptides results in a spectrum shift, which correlates with the target peptide. We also demonstrated the possibility of using silver nanoparticles (AgNPs) as precursors for the preparation of a SERS active nanoprobe with carbocyanine (CC) dye and AgNPs known as silver nanoprobe (CC-AgNPs) of diameter 25 ± 4 nm. RB-AuNPs probe binding with the peptides results in a spectrum shift, which correlates with the target peptide. Arginine peak appears after the conjugation confirms the binding of Aβ 42 with the nanoprobe. Tyrosine peaks appear after conjugated Aβ42 with CC-AgNPs providing binding of the peptide with the probe. The nanoprobe produced a strong, stable SERS signal. Further molecular docking was utilized to analyse the interaction and propose a structural hypothesis for the process of binding the nanoprobe to Aβ42 and Tau protein. This peptide-probe interaction provides a general enhancement factor and the molecular structure of the misfolded peptides. Secondary structural information may be obtained at the molecular level for specific residues owing to isotope shifts in the Raman spectra. Conjugation of the nanoprobe with Aβ42 selectively detected AD in bodily fluids. The proposed nanoprobes can be easily applied to the detection of Aβ plaques in blood, saliva, and sweat samples.

Phyllantin Extraction Using Imidazolium Ionic Liquids with Chloride and Bromide Anion by Microwaved Assisted Extraction Method

Phyllanthin is known to have therapeutic properties such as immunomodulator, nephroprotective, and anticancer. Phyllanthin is a lignan compound that is commonly found in plants of the Phyllanthus genus, one of which is green meniran (Phyllanthus niruri). Solvent Ionic Liquid (IL) is one of the alternative solvents that are widely used for the extraction of compounds from a plant. The purpose of this study were to compare the extraction yield of philanthine compounds from meniran herbs using IL solvent by Microwave Assisted Extraction (MAE) with methanol by maceration method, and to determine the IL solvent that could produce the highest phyllanthin content. Optimization were carried out using the independent variables IL solvent concentration (0.25 M, 0.75 M, and 1.25 M) and sample-solvent mixture (1:10, 1:12, and 1:14). The variable modeling is designed using Response Surface Methodology that produced 9 runs of combination of solvent concentration and sample-solvent mixture ratio. The phyllanthin assay was using High Performance Liquid Chromatography (HPLC) with ethanol-water mixture (66:34) as mobile phase and wavelength at 229 nm for detection. The optimum extraction conditions showed the best results for imidazolium chloride IL at 1st run with a concentration of 0.75 M, the sample-solvent mixture of 1:14 and phyllanthin content of 0.1783 mg/g while imidazolium bromide IL at 7th run with a concentration of 0.75 M and the sample-solvent mixture of 1:12 and phyllanthin content of 0.23 mg/g. However, the methanol maceration method could only extract phyllanthin as much as 0.1319 mg/g. Based on these results, the use of IL-MAE was more effective than the methanol maceration method due to higher phyllantin extract.

High Performance Liquid Chromatography Method Development and Validation for Separation of Liothyronine Sodium Related Substances Using a Quality by Design Approach

The application of the Quality by Design (QbD) principles in developing a novel high performance liquid chromatography (HPLC) method for the analysis of liothyronine sodium related substances for finished product using Fusion QbD® software is explored. The effect of various chromatographic parameters including, column stationary phase, initial hold time and gradient time on separations were systematically investigated. Results show that optimal separations of these compounds in a standard solution can be achieved using a X Bridge C18 column (150 mm × 4.6 μm, 5m), maintained at sample temperature 15°C by using pH 2.0 buffer solution as mobile phase-A and methanol as mobile phase-B with a flow rate of 1.0 ml/min at 225 nm of detection and a gradient time of 38 minutes. The injection volume is 200 μl. Pre-validation studies of the method were performed and all the parameters met the acceptance criteria. The results are demonstrated that optimized method is selective, linear, precise, repeatable and accurate.

Development and validation of HPLC method for simultaneous determination of Ketotifen Fumarate and Salbutamol Sulfate in bulk and tablets dosage forms

The aim of the study was to develop and validate a new, rapid, sensitive, simple, accurate and reproducible HPLC method for simultaneous determination of ketotifen fumarate and salbutamol sulfate. Simultaneous HPLC method was developed using RP-C18 stainless steel analytical column 4.6×150 mm C18.Acetonitrile and phosphate buffer pH 4 (30 : 70) were used as mobile phase and wavelength was adjusted to 276 nm for detection of drugs. Developed method was validated for its specificity, accuracy, precision, linearity and robustness. Method was also applied to quantify drugs in commercial tablets. Chromatogram obtained by newly developed method for simultaneous determination of two anti-asthmatic drugs, having well distinguished peaks for both drugs. Retention time of ketotifen fumarate and salbutamol sulfate were 2.69 minutes and 9.47 minutes respectively. Total run time for both anti-asthmatic drugs was 12 minutes. Limit of quantification for ketotifen fumarate and salbutamol sulfate was 1 ng/ml and 1.50 ng/ml respectively. Limit of detection of ketotifen fumarate and salbutamol sulfate was 3.03 and 4.54 respectively. A simple, easy, precise and new method was developed for simultaneous quantification of frequently used anti-asthmatic drugs. Developed method may prove effective and beneficial in determination of ketotifen fumarate and salbutamol sulfate in bulk and other pharmaceutical dosage forms.

Synthesis of Water-Soluble Cadmium Selenide/Zinc Sulfide Quantum Dots on Functionalized Multiwalled Carbon Nanotubes for Efficient Covalent Synergism in Determining Environmental Hazardous Phenolic Compounds

Increasing pollution and ecological imbalance have accentuated the need to develop sensors through an efficient technique. Typically, the core–shell nanocrystals of cadmium selenide/zinc sulfide (CdSe/ZnS) with functionalized multiwalled carbon nanotubes (f-MWCNTs) are used for developing an efficient electrochemical sensor that simultaneously detects 4-aminophenol (4-AP) and 4-nitrophenol (4-NP). The composite network formed by CdSe/ZnS quantum dots with the f-MWCNTs (CdSe/ZnS QDs @ f-MWCNT) behaves as an excellent electrocatalyst and provides a transportation pathway by engendering the electron–hole pair. The sensor exhibits low detection limit values of 34.8 and 17.7 nM for detection of 4-AP and 4-NP, respectively. The sensor also showed excellent sensitivity at a linear working range of 0.149–510 μM concentration for both the analytes. Additionally, the study also shows the potential for commercial feasibility of the as-prepared sensor by acquiring a satisfactory recovery percentage of the analytes in real-time biological and environmental sample analyses.

Vplyv prídavku baktérií mliečneho kvasenia na mikrobiotu a výskyt mykotoxínov v ražných silážach

In the rye silages (control and with additive) microbiota isolation and identification (total count of bacteria, coliform bacteria, enterococci, lactic acid bacteria and microscopic filamentous fungi) and occurrence of mycotoxins were evaluated. Total count of bacteria on Plate count agar at 30 °C for 48-72 hours, coliform bacteria on McConkey agar at 37 °C for 24-48 hours, enterococci on Enterococcus selective agar at 37 °C for 48-72 hours, lactic acid bacteria on De Man, Rogosa and Sharpe agar, Mayeux, Sandine and Elliker and All Purpose TWEEN® agar 37 °C for 48-72 hours in microaerophilic condition and microscopic filamentous fungi on Malt extract agar at 25 °C for 7 days were evaluated and identified with mass spectrometry. The most isolated family from both types of silage was Lactobacillaceae. The most isolated species from the control group was Lentilactobacillus buchneri (22%) and lowest number of isolated species was Mucor spp. The most isolated species from silage with additive was Lactobacillus gasseri (16%). The ELISA method (enzyme-linked immunosorbent assay) with using reader at wavelength 650 nm for detection and quantification of mycotoxins (total aflatoxins, total ochratoxins, total fumonisins, deoxynivalenol, zearalenone and T-2/HT-2 toxin) was used. The rye silages of control and with additive were characterized by occurrence of all analyzed mycotoxins, whereas deoxynivalenol was mycotoxin with the highest concentration. The rye silages with additive had significantly lower content of total aflatoxins compared to the control, while significantly higher concentration of total ochratoxins, deoxynivalenol, zearalenone and T-2/HT-2 toxin was determined.

RP-HPLC method development and validation for simultaneous estimation of efonidipine hydrochloride ethanolate and telmisartan in their synthetic mixture

A Novel, selective, accurate and rapid Reversed Phase High Performance Liquid Chromatographic (RPHPLC) method for the analysis of Efonidipine Hydrochloride Ethanolate and Telmisartan in binary mixture has been developed and validated. The chromatographic system consisted of a Phenomenex Kinetex ® 5µ C18 Size: 150 * 4.6mm column and the separation was achieved by using ambient temperature with a mobile phase containing mobile Phase Acetonitrile:25mM Phosphate Buffer pH 4.9 (45:55). The samples were monitored at 253 nm for detection at a flow rate of 1.0 mL/min and the retention time was about 7.77 and 4.10 mins for Efonidipine Hydrochloride Ehanolate and Telmisartan respectively. The calibration curve was linear over the concentration range 5-30 and 10-60 ?g/mL for Efonidipine Hydrochloride Ehanolate and Telmisartan respectively. The proposed method is accurate in the range of 99.75% - 100.10% recovery and precise (%RSD of intraday variation and % RSD of inter day variation were found to be within the acceptance criteria). Therefore, this method can be used as a more convenient and efficient option for the analysis of Efonidipine Hydrochloride Ehanolate and Telmisartan in Quality control laboratory.

Near-infrared reflection at 780 nm for detection of early proximal caries in posterior permanent teeth in vitro.

Objectives:The aim of this in vitro study was to evaluate the diagnostic potential of near-infrared reflection at 780 nm (NIRR780nm) for early proximal caries detection on the occlusal, buccal and oral surfaces of molars and premolars under simulated, clinically relevant conditions. The findings were validated by micro-computed tomography (µCT).Methods:Bitewing radiography (BWR) was used as a comparative diagnostic method. 250 sound or decayed permanent teeth were examined using NIRR780nm and BWR. The NIRR780nm findings were evaluated using yes/no decisions depending on the presence of caries lesions, as the enamel-dentin junction was not detectable in the majority of samples. All NIRR780nm, BWR and µCT findings were obtained twice by two trained examiners. NIRR780nm images were evaluated both occlusally alone and combined occlusally, lingually and buccally. All findings were presented in a cross-table. Sensitivity, specificity and area under the curve (AUC) values were calculated. Reliability assessment was performed using κ statistics.Results:Underestimation of caries was observed for NIRR780nm in 26.0% of all surfaces and for BWR in 32.8% of all surfaces. Overestimation was 10.0% for NIRR780nm and 0.4% for BWR. Trilateral NIRR780nm assessment exhibited an overall accuracy of 67.2 %, an underestimation of 13.6% and an overestimation of 19.2%. Trilateral NIRR780nm exhibited 63.0% sensitivity and 69.6% specificity, while BWR exhibited 26.7% sensitivity but 100% specificity for proximal caries detection.Conclusion:NIRR780nm is not suitable for reliable detection of early proximal caries, even with the application of an ideal setup and optimized in vitro conditions.

A novel carbon ceramic electrode modified by Fe3O4 magnetic nanoparticles coated with aptamer-immobilized polydopamine: An effective label-free aptasensor for sensitive detection of diclofenac

Addressed herein, Fe3O4 magnetic nanoparticles were prepared through a typical method. Dopamine molecules polymerized into polydopamine in an optimum pH and coated the surface of the Fe3O4 magnetic nanoparticles (polydopamine@Fe3O4). The as-prepared material was applied for modification of a fabricated carbon ceramic electrode by covalent bond. Fourier transform infrared spectroscopy technique confirmed the formation of Fe3O4 and polydopamine@Fe3O4. A diclofenac single-strand DNA amino functionalized aptamer was immobilized on the surface of the polydopamine@Fe3O4 modified carbon ceramic electrode. The “aptamer-polydopamine@Fe3O4-CCE” was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The fabricated label-free aptasensor was successfully applied for detecting ultra-trace amounts of sodium diclofenac in human blood serum using differential pulse voltammetry method in a signal-off strategy. The limit of detection was estimated about 0.11 nM for detection of diclofenac with significant repeatability and stability at the concentration range of 0.5 to 400 nM.

Isocratic high-performance liquid chromatography (HPLC) for simultaneous quantification of curcumin and piperine in a microparticle formulation containing Curcuma longa and Piper nigrum

Poor bioavailability has been reported as a major challenge in the development of curcumin as a pharmaceutical agent. However, co-administration of curcumin with piperine has been shown to improve curcumin bioavailability. Therefore, to assure product control quality, an analytical method needs to be developed for the determination of curcumin and piperine content in a dosage form formulation. The objective of this study was to develop a simple isocratic reversed-phase HPLC (RP-HPLC) method to simultaneously quantify curcumin and piperine content in solid dispersion based microparticle formulation containing Curcuma longa and Piper nigrum extracts. The method was validated according to the International Council for Harmonization (ICH) guideline. Chromatographic separation of three curcuminoids and piperine could be achieved using acetonitrile-methanol-water of 65:5:35 %, at a flow rate of 1 mL/min and a wavelength of 353 nm for detection. Resolution (Rs) of 3.57 and 1.68 for piperine and curcumin, respectively, a theoretical plate number (N) > 8000 and a tailing factor (T) < 1.5 indicate a satisfactory separation of the compounds. The calibration curve was linear from 1.25-15 μg/mL and 2.5–30 μg/mL for piperine and curcumin, respectively, with the correlation coefficient of >0.999. The intra-day/inter-day accuracy and precision demonstrated a recovery of 99.54–101.50%/99.38–99.89% and 100.78–102.51%/101.15–102.47% with a Relative Standard Deviation (RSD) of 0.53–0.95%/0.13–1.44 % and 0.28–1.62%/0.46–1.14% for piperine/curcumin. The limit of detection (LOD) were 0.27 and 0.42 μg/mL, for piperine and curcumin, which reveals an adequate sensitivity. A solid dispersion based microparticle formulation containing C. longa and P. nigrum extracts confirmed the validity of the developed method as a recovery of 91.14% and 99.14% for piperine and curcumin, respectively. In conclusion, all the tested parameters confirm the precision, accuracy, and reliability of the method for the simultaneous analysis of curcumin and piperine within a microparticle formulation containing C. longa and P. nigrum extracts.

DEVELOPMENT AND VALIDATION OF RAPID STABILITY-INDICATING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY METHOD FOR THE DETERMINATION OF LINAGLIPTIN AND EMPAGLIFLOZIN IN PURE AND DOSAGE FORMS

Objective: A new, simple, rapid, sensitive, and accurate stability-indicating high-performance liquid chromatography (HPLC) method was developed and validated for the quantitative determination of linagliptin (LNG) and empagliflozin (EMP) in pure and tablet dosage forms.&#x0D; Methods: An isocratic HPLC method, using a C18 reversed-phase column (150 mm×4.6 mm i.d., particle size 5 μm) with an isocratic binary mobile phase consisting of phosphate buffer and acetonitrile (65:35, v/v), was investigated to separate the drug from its stress degradation products. The flow rate was 1.0 mL/min at ambient temperature and photodiode array detector is used at 226 nm for detection. The developed method was validated for system suitability, linearity, accuracy, precision, limits of detection and quantitation, specificity, stability, and robustness.&#x0D; Results: The retention time of LNG and EMP was found to be 3.276±0.002 and 6.966±0.0006 min, respectively. The calibration curve was found to be linear with the equation y=158926.39X+11.139, with a correlation coefficient of R2=0.9991 for LNG and y=22688.45X+4.259, with a correlation coefficient of R2=0.9994 for EMP over a concentration range of 2.5–7.5 μg/mL and 5.0–15 μg/mL for LNG and EMP, respectively. The limits of detection were 0.29 and 0.48 μg/mL for LNG and EMP, respectively, and the limits of quantification were 0.89 and 1.5 μg/mL for LNG and EMP, respectively. The recovery values of this method are 101.11% and 101.48% for LNG and EMP, respectively, and the reproducibility is within 0.070 and 0.277 for LNG and EMP, respectively.&#x0D; Conclusion: The proposed method is a rapid stability-indicating HPLC method that can be applied for the determination of LNG and EMP in pure and tablet dosage forms.

Luminescent PbS and PbS/CdS Quantum Dots with Hybrid Coatings as Nanotags for Authentication of Petroleum Products

There is an urgent need to tag some valuable liquid products, such as petroleum products, for authentication. However, it is a challenging task because of the strong autofluorescence of liquid petroleum products in the visible range and the chemically active and harsh medium. Therefore, strongly luminescent, near-infrared (NIR) fluorophores with long-term stability are needed. The use of NIR quantum dots (QDs), such as lead chalcogenides, seems to be the best approach; however, most widely used coatings do not provide enough stability, and QDs are quenched in a short time in liquid petroleum products. Here, we report for the first time the synthesis of highly luminescent, ultrasmall, NIR-emitting PbS and PbS/CdS QDs with a hybrid coating consisting of oleylamine (OLA), 1-dodecanethiol (DT), and poly(methacrylic acid) (PMAA), adopting a simple, greener synthetic method. The photoluminescence (PL) emission wavelengths of these QDs were tuned between 700 and 1100 nm for detection with low-cost, widely used silicon detectors, which allows easy translation of such QDs as luminescent nanotags to serve as a means for the authentication of goods, such as petroleum. In the nanoparticle design, a thin layer of a CdS shell deposited by a cation-exchange process was adopted to enhance the emission intensity and stability of PbS QDs. The influence of postsynthetic ligand exchange of OLA with DT on the stability is also shown. PMAA in the coating provided a significant blue shift in the peak maxima, enhanced the luminescence intensity, and, most importantly, improved the long-term stability of QDs, especially in liquid petroleum products (oil, gasoline, and diesel). Such stability and size tunability was utilized to create binary barcodes. Hence, these QDs are shown as promising luminescent nanotags for liquid petroleum products. The development of such stable QD-based nanotags offers an invaluable use of nanotechnology for optical barcode generation.

Turn-on detection of MicroRNA155 based on simple UCNPs-DNA-AuNPs luminescence energy transfer probe and duplex-specific nuclease signal amplification.

A novel luminescence energy transfer (LET) probe for detection of tumor related microRNAs using NaGdF4:Yb,Er@NaYF4 upconversion nanoparticles (UCNPs) as energy donors and gold nanoparticles (AuNPs) as energy acceptors was developed. Using the double modified complementary DNA sequences of microRNA155 (miRNA155) as a bridge, NaGdF4:Yb,Er@NaYF4 UCNPs and AuNPs were conjugated to form NaGdF4:Yb,Er@NaYF4 UCNPs-DNA-AuNPs nanocomplexes (UCNPs-DNA-AuNPs) probe. The energy transfer would occur when the distance between donor and acceptor gets closer. In the presence of target miRNA155, DNA-RNA heteroduplexes appeared as product, but the luminescence intensity was not changed obviously. In the existence of duplex-specific nuclease (DSN), DSN could hydrolyze the DNA strand of DNA-RNA heteroduplexes, the bridge linked NaGdF4:Yb,Er@NaYF4 UCNPs and AuNPs was destroyed, which induced that the quenched luminescence intensity was recovered and RNA was released. The released miRNA155 could react with another UCNPs-DNA-AuNPs probe to form DNA-RNA heteroduplexes again. This cyclic reaction generates an amplification of luminescence signal for quantitative detection of miRNA155. Under the illumination of 980 nm laser, the concentration ranges from 0.1 nM to 15 nM and the detection of limits was 0.045 nM for detection of miRNA155. Moreover, the UCNPs-DNA-AuNPs probe was used in quantify miRNA155 in cell lysates with satisfactory results.

Designing an "Off-On" Fluorescence Sensor Based on Cluster-Based CaII-Metal-Organic Frameworks for Detection of l-Cysteine in Biological Fluids.

Recently, luminescent metal-organic framework (MOF) materials have attracted considerable attention in fluorescence sensing. In this essay, we prepared a new cluster-based CaII-MOFs {[Ca1.5(μ8-HL1)(DMF)2]·DMF}n (1) with good water dispersibility, excellent photoluminescence properties (FL quantum yield of 20.37%) and great fluorescence stability. Further, it was employed to design as an "off-on" fluorescence sensor for sensitive detection of l-cysteine. This proposed strategy was that fluorescence of CaII-MOFs 1 was quenched for providing a low fluorescence background by the introduction of Pb2+ forming the CaII-MOFs 1/Pb2+ hybrid system. The quenching effect could be ascribed to the static quenching mechanism because of the formation of ground-state complexes and coordination interactions between the free carboxyl of H4L1 ligands of CaII-MOFs 1 and Pb2+. Then, with the addition of l-cysteine into the CaII-MOFs 1/Pb2+ hybrid system, the fluorescence signal was immediately restored. This result was because the Pb2+ was gradually released from the hybrid system by chelation interactions between the -SH groups of l-cysteine and Pb2+. This method received a relative wide linear range varying from 0.05 to 40 μM and a low detection limit of 15 nM for detection of l-cysteine. This proposed strategy was also successfully applied to detect l-cysteine in human serum samples with satisfactory recoveries from 95.9 to 101.5%.

Photochemical Vapor Generation for Colorimetric Speciation of Inorganic Selenium.

Gold nanoparticles (AuNPs) are widely used as optical probes in colorimetric detection, thanks to their high molar extinction coefficient. However, sample matrixes of high salinity or strong acidity/alkalinity often break the electrostatic repulsion of AuNPs suspension, or/and the surface functionality of AuNPs, causing strong and unfavorable interferences. Photochemical vapor generation (PVG) is an efficient technique for the sample matrix separation. Besides, it possesses distinct features of green reducing reagent, reduced interferences from concomitant elements, and direct speciation by the assistance of photocatalyst. Herein, we developed a photochemical vapor generation (PVG) method for the green and direct speciation analysis of inorganic selenium (i.e., Se(IV) and Se(VI)), by colorimetric or visual monitoring of unmodified AuNPs. The generated Se species from PVG were directed into the AuNPs solution for a reaction to take place, which produced a specific new absorption band at 600 nm for detection. The experimental parameters, including the concentration of organic acid, the sample flow rate, the concentration of AuNPs, and the flow rate of carries gas, were optimized in detail. Under optimized conditions, the limits of detection (LOD) for Se(IV) and Se(VI) were 0.007 and 0.006 μg mL-1 by UV-vis detection, respectively. It is worth mentioning that 0.08 μg mL-1 Se can induce an obvious color change, which can be directly observed with the naked eye. Relative standard deviations (RSDs) of 4.5% and 4.3% were obtained from seven replicate measurements of 0.15 μg mL-1 Se(IV) and Se(VI) standard solution, respectively. The developed assay has been successfully applied for the speciation of Se in a dietary supplement sample and environmental water samples including lake water, seawater, simulated water reference materials, and tap water.

The in vivo biosynthesis of antibacterial silver nanoparticles using red pepper (Capsicum annuum L) fruit extract

Green synthesis of nanoparticles using biological organisms is of increased demand by many scientific and economic sectors. Biosynthesis of silver nanoparticles was undertaken using aqueous extract from red fleshly sweet fruits of Capsicum annuum and the antibacterial activity of silver nanoparticles (Ag NPs) was investigated. We tracked color change of pepper extract from orange to deep dark brown after 10 mins of incubation with silver nitrate (1mM) solution. Silver nanoparticles have been characterized using three techniques: UV-Vis spectrophotometry at 415 nm for detection of characteristic optical absorption band of Ag NPs, FTIR spectroscopy; for information about the water-soluble molecules of red pepper fruit that were responsible for the reduction process, and, the crystalline nature and mean size of Ag NPs were studied using X-ray diffraction according to the line width of the plane and the refraction peak has been calculated using the ScherrerÂ’s equation. Elemental analysis showed the presence of strong peak of silver at 3 KV which confirmed the synthesis of silver element. The biosynthesized Ag NPs possessed moderate antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Aramco S4 bacterial isolate with inhibition zones of 2 to 3 mm.

Surface characterization of carbon fiber reinforced polymers by picosecond laser induced breakdown spectroscopy

Adhesive bonding of composite materials requires reliable monitoring and detection of surface contaminants as part of a vigorous quality control process to assure robust and durable bonded structures. Surface treatment and effective monitoring prior to bonding are essential in order to obtain a surface which is free from contaminants that may lead to inferior bond quality. In this study, the focus is to advance the laser induced breakdown spectroscopy (LIBS) technique by using pulse energies below 100μJ (μLIBS) for the detection of low levels of silicone contaminants in carbon fiber reinforced polymer (CFRP) composites. Various CFRP surface conditions were investigated by LIBS using ∼10ps, 355nm laser pulses with pulse energies below 30μJ. Time-resolved analysis was conducted to optimize the gate delay and gate width for the detection of the C I emission line at 247.9nm to monitor the epoxy resin matrix of CFRP composites and the Si I emission line at 288.2nm for detection of silicone contaminants in CFRP. To study the surface sensitivity to silicone contamination, CFRP surfaces were coated with polydimethylsiloxane (PDMS), the active ingredient in many mold release agents. The presence of PDMS was studied by inspecting the Si I emission lines at 251.6nm and 288.2nm. The measured PDMS areal densities ranged from 0.15 to 2μg/cm2. LIBS measurements were performed before and after laser surface ablation. The results demonstrate the successful detection of PDMS thin layers on CFRP using picosecond μLIBS.

Upconversion-enabled array spectrometer for the mid-infrared, featuring kilohertz spectra acquisition rates.

Mid-infrared spectroscopy is an essential analytical method in science and industry. Unlike in the near-infrared range, grating spectrometers for the mid-infrared are rarely employed, mostly due to the limited availability and performance of suitable line array detectors. In this work, continuous-wave nonlinear-optical upconversion is used to enable mid-infrared spectroscopy. A broad spectral window between 3.7 and 4.7 μm is upconverted to 825 - 867 nm for detection on a silicon-camera-based near-infrared grating spectrometer with a high sensitivity down to sub-picowatt of input power. A theoretical model is presented that accurately describes the upconversion process and the total system behavior. Spectroscopic flame emission measurements demonstrate the applicability towards the analysis of highly dynamic processes.

Recognition unit-free and self-cleaning photoelectrochemical sensing platform on TiO2 nanotube photonic crystals for sensitive and selective detection of dopamine release from mouse brain

For implementing sensitive and selective detection of biological molecules, the biosensors are been designed more and more complicated. The exploration of detection platform in a simple way without loss their sensitivity and selectivity is always a big challenge. Herein, a prototype of recognition biomolecule unit-free photoelectrochemical (PEC) sensing platform with self-cleaning activity is proposed with TiO2 nanotube photonic crystal (TiO2 NTPCs) materials as photoelectrode, and dopamine (DA) molecule as both sensitizer and target analyte. The unique adsorption between DA and TiO2 NTPCs induces the formation of charge transfer complex, which not only expends the optical absorption of TiO2 into visible light region, thus significantly boosts the PEC performance under illumination of visible light, but also implements the selective detection of DA on TiO2 photoelectrode. This simple but efficient PEC analysis platform presents a low detection limit of 0.15nm for detection of DA, which allows to realize the sensitive and selective determination of DA release from the mouse brain for its practical application after coupled with a microdialysis probe. The DA functionalized TiO2 NTPCs PEC sensing platform opens up a new PEC detection model, without using extra-biomolecule auxiliary, just with target molecule naturally adsorbed on the electrode for sensitive and selective detection, and paves a new avenue for biosensors design with minimalism idea.

Design and demonstration of a liquid level fiber sensor based on self-imaging effect

A novel liquid level fiber sensor based on self-imaging properties of the multimode interference (MMI) in no core fiber (NCF) is proposed and demonstrated. Based on the beam propagation method (BPM) simulation, a NCF of optimal length is selected to act as a sensing head and tunable filter in a ring cavity fiber laser. For high liquid level sensing, a height conversion setup based on atmospheric pressure balance principle is designed and the sensitivity is magnified 5 times. A 50cm range of liquid level can be detected by monitoring the peak wavelength shift of output laser. The sensor exhibits an excellent linear response (R2=0.9999) and a sensitive response to different liquid refractive index (RI). The sensitivity of the single mode-no core- single mode (SNS) sensor is 108.8pm/mm and the accuracy is about 1% at the resolution of 0.1nm of detection using an OSA with the liquid RI of 1.4152, which is the highest accuracy for a 50cm liquid level range to our best knowledge.