Combination of inverted pyramidal nanovoid with silver nanoparticles to obtain further enhancement and its detection for ricin.

We have obtained the surface-enhanced Raman scattering substrate by depositing silver nanoparticles on the surface of the inverted pyramidal nanovoid in order to improve the enhance effects. Experimental results showed that the combined substrate exhibited greater enhancement than the nanovoid substrate or nanoparticles. In order to test the SERS activity of the combined substrates, Rh6G and ricin toxin were used as Raman probes. Finite element method was employed to simulate electric field and induced charge distribution of the substrates, which have been used to explore the interaction between nanoparticles and nanovoid as well as mechanism of the great enhancement.

Preparation of tetrapod-like nanostructure array and used as the surface-enhanced Raman scattering substrates.

Nanostructure surface composed of tetrapod-like structure with the period of about 2 microm has been made by simple nanoprinted method, the collodion was poured directly on the surface of the template and tore off after it became solidification, and then a layer of gold was sputtered on the collodion surface. The electric field distributions of the tetrapod-like structure with different size and period have been simulated using finite element method. Surface-enhanced Raman spectra mapping image gotten from the substrates illustrated the uniform enhancement property of it. The diluted aqueous solution of Rhodamine 6G (50 nM) was used to test the enhanced property of substrates for trace detection and good quality spectra has been gotten. The spectra of melamine with the concentration of 1 mg/L (7.9 microM) on the substrates were gotten to show the enhanced ability for molecule with small Raman scattering cross section.

[Using PAA template to fabricate SERS substrate and the SERS detection of melamine].

The authors have got silver film with orderly arranged nanoparticles as the surface-enhanced Raman spectra (SERS) substrates using porous anodic alumina templates (PAA). A silver film (99.99%) with the thickness of several millimeters was thermally evaporated onto the PAA templates and the SERS substrate was got after removing the PAA templates in hydrochloric acid. SERS spectra of pyridine (0.01 mol x L(-1)) were measured on Renishaw 2000 Ramanscope with a He-Ne (632.8 nm) laser as an excitation source in backscattering geometry, and the average enhancement factors were more than 10(5). The authors compared SERS spectra of pyridine from the SERS substrates and from Ag film evaporated directly on glass slide, and the former was 30 times stronger than the latter. The authors got different SERS spectra of pyridine while changing the excitation laser power. It was found that the relationship between the peak intensity of SERS spectra and the excitation laser power was linear as the normal Raman spectrum. We used the substrates to detect melamine, 2.5 mg x L(-1) melamine solution could be recognized al though excitation laser power was below 1 mW.

A novel method for fabricating the surface-enhanced Raman scattering substrates and its enhanced properties.

We have got large area surface-enhanced Raman scattering (SERS) substrates with uniform high enhancement factors by the so-called moulage method for the first time. A silver film (99.99%) with several millimeters thickness was thermally evaporated on the porous anodic alumina templates and the SERS substrate was got after moving off the templates. Surface-enhanced Raman scattering spectra of pyridine (0.01 Mol/L) were measured under 632.8 nm excitation. The experimental enhancement factors were more than 10(5) and S/N(p-p) around 100 was obtained. We have compared the SERS spectra of pyridine collected from different locations on the same SERS substrate and different substrates, which illustrate the well uniform enhance properties and the reproducibility of this method, respectively. The comparison of the SERS spectra, obtained from the SERS substrates and Ag film evaporated directly on glass slide, have proved that the electromagnetic coupling between two adjacent nanoparticles was important to the SERS effect. We also used rhodamine 6G as the probe molecules and found that the different molecules were very sensitive to the morphology of the SERS substrates.

[Raman imaging based on morphological model for human breast cancer tissues].

Raman Mapping spectra were collected on the samples of the normal human breast duct epithelia and the infiltrating duct carcinoma with the excitation wavelength of 633 nm and fitted with the morphological model which was presented before by the author. The normalized coefficients were calculated and used to make Raman images. Examining these images, the authors find that they show quite clearly the distribution of the chemicals which the basis spectrum was mainly derived from and that the DNA coefficient image also indicates the positions and scales of the cell nucleus, while the bright DNA area is bigger and brighter for the infiltrating duct carcinoma than for the normal breast dust epithelia, suggesting the cell nucleus in cancer tissue are larger than those in normal tissue. The correlation coefficient images were also made on these mapping spectra and examined in comparison with these model images, and it was showed that the model images have higher resolution and sensitivity although they are very similar. This work is helpful to understanding the morphological basis of the breast tissue Raman spectra and to developing the Raman diagnostic method for breast tumor.

[Quantities analysis of the infrared diffuse reflection spectrum of hydrocarbon source rocks by OSC-iPLS].

In many cases, the scattering can be an overpowering contributor to the spectrum, sometimes accounting for most of the variance in the data. Although the degree of scattering is dependent on the wavelength of the light that is used and the particle size and refractive index of the sample, the scattering is not uniform throughout the spectrum. In order to remove the effects of scattering and noise on multivariate calibration of IR spectral signals, orthogonal signal correction (OSC) was used as a method to preprocess the infrared spectra of the hydrocarbon source rocks to be quantitatively determined, thus to establish the calibration model of hydrocarbon source rocks before and after pretreatment by inetval partial least square (iPLS). Pretreatment was smoother and more orderly array. This indicated that the major information in hydrocarbon source rocks spectra could be reserved while part of noise was removed by OSC method. In this study, pretreatment calibration model was obtained, the model's correlation coefficient is 0.994 04 and RMSE is 0.635 2, but with no pretreatment the calibration model's correlation coefficient is 0.770 9 and RMSE is 3.925 7.

[Raman spectra studies of MBE-grown n-GaAs/SI-GaAs films].

n-GaAs films doped with Si were grown by MBE on semi-insulated GaAs (100) substrates. The films with different doping concents were characterized by Raman spectra at room temperature. It is obviously that the Raman peaks shifted. Some peaks were enhanced and some were weakened. This is attributed to the fact that the higher the doping contents, the highertge lattice mismatch. And the lattice misfit induced the imperfection in epitaxy layers. This experimental result coincides with the theory.

[Study of electroreflectance spectrum and Franz-Keldysh effect at metal-GaAs interfaces].

Electronic properties (electric field, Fermi level pinning and density of interface states) of Au-GaAs, Al-GaAs and Ni-GaAs interfaces were studied by optical methods. These interfaces were fabricated by depositing metals (Ni, Au and Al) on specialized surface-intrinsic-n+ (SIN+) GaAs samples. Electroreflectance (ER) was used to study the electric fields and Fermi level pinnings of metal-GaAs interfaces. Fourier transformation (FT) of ER spectra was used to analyze these interfacial properties. Assuming that only a fraction of the total illuminated area was the effective interface state area, the density of interface states was obtained by measuring the relation between the photovoltage induced by an exciting He-Ne laser beam and the illumination intensity of the laser beam.

[Study on electro-degradation of new conjugated polymer PFO-BT15 light emitting diodes].

In the present paper electroluminescence spectrum and Raman spectrum were used to study electro-degradation of polymer light emitting devices (PLEDs) of PFO-BT15, a new and high-efficiency emitting polymer synthesized by the institute of polymer optoelectronic material & devices (IPOM) in South China University of Technology. The PLEDs with a configuration of ITO glass/PEDOT(120 nm)/PFO-BT15(80 nm)/Ba(4 nm)/Al(200 nm) emitted green light at 550 nm when 5 V dc voltage was applied. Three of those devices were used to study the electro-degradation mechanism of PLEDs. Device A was deposited in vacuum box in dark room to keep sample fresh; Device B was first lighted with current of 1 mA x 0.25 cm(-2) for 200 minutes, then with current of 5 mA x 0.25 cm(-2) for 60 minutes, finally with current of 10 mA x 0.25 cm(-2) for 40 minutes; Device C was lighted with current of 20 mA x 0.25 cm(-2) until the electroluminescence failure. Our experimental results indicate that the degradation speeds highly depend on the current through the devices. The stressed devices show the decrease in electroluminescence efficiency. However, the luminescence spectrum of the stressed device did not change compared with the fresh device, which suggest that the structure of the luminescent polymer did not change with the electro-stress. Raman spectrum was employed to probe the structure changes of the materials used in the device. We found that the PEDOT Raman peak disappeared andthe PFO-BT15 Raman peak still existed in electro-stress device. The results confirmed that it was the breakage of the PEDOT layer instead of degradation of emitting polymer, that led to the final failure of the PLEDs device. This work gives some valuable information for the design and development of highly stable organic light-emitting device.

[DWT-iPLS applied in the infrared diffuse reflection spectrum of hydrocarbon source rocks].

Infrared spectroscopy is useful to monitor the quality of products on-line, or to quality multivariate properties simultaneously. The IR spectrometer satisfies the requirements of users who want to have quantitative product information in real-time because the instrument provides the information promptly and easily. However, Samples that are measured using diffuse reflectance often exhibit significant differences in the spectra due to the non-homogeneous distribution of the particles. In fact, multiple spectral measurements of the same sample can look completely different. In many cases, the scattering can be an overpowering contributor to the spectrum, sometimes accounting for most of the variance in the data. Although the degree of scattering is dependent on the wavelength of the light that is used and the particle size and refractive index of the sample, the scattering is not uniform throughout the spectrum. Typically, this appears as a baseline shift, tilt and sometimes curvature, where the degree of influence is more pronounced at the longer-wavelength end of the spectrum. The diffuse reflection spectrum is unsatisfactory and the calibration may provide unsatisfactory prediction results. So we must use some methods to remove the effects of the scattering for multivariate calibration of IR spectral signals. Discrete wavelet transform (DWT) is a good method to remove the effects of the scattering for multivariate calibration of IR spectral signals. By using DWT on individual signals as a preprocessing method in regression modeling on IR spectra, good compression is achieved with almost no loss of information, the low-frequency varying background and the high-frequency noise be removed simultaneously. In this report, we use the iPLS method to establish the calibration models of hydrocarbon source rocks. iPLS is a new regression method and the authors can get better results by using DTW- iPLS.

[Application of wavelet transform to the infrared diffusion reflectance spectrum of rocks].

The infrared diffuse reflectance spectra of hydrocarbon source rocks with different particle sizes were measured. The result indicated that the absorbency of the raw spectrum decreased with the reduction of particle size, but the relationship turned to be reverse after we pretreated the original spectra by using wavelet transform to eliminate the background and calibrate the baseline drift, both of which were caused by scattering. The reversed relations showed that the spectral lines were influenced deeply by the scattering of the samples. So the particle size of the samples to be measured and the particle size of the model samples must be consistent to reduce the error. The low frequency part of the spectrum filtrated by wavelet transform corresponds to the scattering, and the authors used it to set up a model at the latent absorbance wave number (near 2 820 cm(-1)) to forecast the particle size. By comparing this model with the other model based on the original spectrum the authors found that the pertinence of the anterior model is higher than the latter one and the value reaches 0.999 7. So the authors can accurately forecast and control the distribution of the particle size by this model, which can be used to improve the accuracy in the quantitative analysis of the infrared reflectance spectrum. Also the study validated that both scattering and absorption coefficients are inversely correlated with the particle size.

[A novel fuzzy neural network method for diesel quantitative analysis with near infrared spectroscopy].

To satisfy the requirement of the production control and quality inspection of petrochemical products, a novel fuzzy neural network control method is proposed for determining product composition by near infrared spectroscopy. For the data analysis three different diesel products were selected as samples and six analytical models, such as saturated hydrocarbons, polar compounds, monoaromatics, dicyclic aromatics, tricyclic aromatics and naphthenes, were developed with the proposed fuzzy neural network method. Based on dSPACE, the near infrared spectroscopy system real-time experimental platform has been established to testify and analyze different diesel samples. The experimental results show that the improved performance is superior because of its advantage of quick response and good robustness. The mean squared error (MSE) of calibration and prediction samples is of the order of 10(-6) in the spectral range of 800-2300 nm. The developed method can be used in the research on petrochemical products processing.

[Microscopic raman imaging spectra of realgar and light-induced degradation products in realgar].

Light-induced degradation in realgar was studied by means of Raman spectroscopy. The result substantiated the following reaction: An additional S atom is inserted between the As atoms in the As4S4 molecule because As--As bonds are weaker than As--S bonds. It is likely that the resulting As--S--As molecule is too unstable to exist. Furthermore, an S atom in the As4S5 molecule is released from one of the equivalent As--S--As linkages in As4Ss which becomes the As4S4 molecular of pararealgar. After the As4S5 molecule is divided into an S atom (radical) and the As4S4 (pararealgar type) molecule, the free S atom is re-attached to another As4S4 (realgar type) molecule, reproducing an As4S5 molecule. The reproduced As4S5 molecule is again divided into an S atom (radical) and an As4S4 (pararealgar type) molecule. This cycle whereby realgar is indirectly transformed into pararealgar via the As4S5 molecule is promoted by light and repeated during light exposure.

[Study of human tumor tissues by Raman imaging spectra].

The Raman mapping spectra were collected from the samples of fresh human breast tumor tissues with the excitation wavelength at 633 nm, their correlation coefficients with the reference spectra of chemical DNA, cytoplasm and extra-cellular matrix etc. were calculated, and the images were created based on these correlation coefficients. Examining these images, the authors found that they show approximately the distribution of the corresponding reference chemicals in human tissues and that the DNA spectrum correlation images reflect the DNA distribution quite well because of its much lower correlation with the spectra of other morphological chemicals. This work is helpful in understanding the chemical/morphological basis of the breast tissue Raman spectra and in developing the Raman diagnostic method for breast tumor.

[Surface-enhanced Raman spectra of natural tissue and cancerous tissue of lung].

Surface-enhanced Raman spectra of natural tissue and cancerous tissue of lung from 300 to 1700 cm(-1) were measured. In the cancerous tissue of lung, the orderly conformations of amides III and amides I of the main chains in protein such as alpha-helix, beta-corner and no rules curly were damaged seriously; conversely, the extendable vibration of skeleton C-N and skeleton C-C increased. Side chains change became complicated. In general, the content of nucleic acids increases in the cancer tissue of lung. The lengthways conformations of lecithoid chains is out-of-order in the cancerous tissue of lung compared with the natural ones.

[Confocal Raman microspectroscopic study of human breast morphological elements].

Breast tissue sections were examined by means of confocal Raman spectroscopy with an excitation wavelength of 633 nm. Acquired using a microscopic mapping approach with the sample volume of -2 microm3, these spectra were compared with the ones of the commercially available actin, DNA, collagen (type I), triolein etc. Some spectra were distinguished and identified and characterize the morphological elements like cell cytoplasm, extracellular matrix etc. The cell nucleus spectrum was also obtained by K-means cluster analysis. The correlation analysis showed that the spectrum from a morphological element is highly correlated with that from the corresponding purified chemical. The spectroscopic characterization of these morphological elements was then investigated. This study is helpful to understanding the chemical/morphological basis of the Raman spectrum and designing the Raman microspectroscopic model of human breast tissue.

[The measurement of the ratio of primary hydroxyl group to second hydroxyl group in polyether polyol by near infrared spectrum].

The method of near infrared spectrum, combined with derivative spectrum and multiple linear regression was applied to measure the ratio of primary hydroxyl group to second hydroxyl group in polyether polyol. The authors obtained good predictive results by using the method in this experiment. The work is very helpful for the on-line measurement of polyether polyol.

[The three-dimension spectral subtraction fluorescence to check adulteration of diesel oil by 120# solvent naphtha].

The characteristics of a adulterated sample of diesel oil by 120# solvent naphtha were studied with three-dimension spectral subtraction fluorescence technique, and it is shown that the technique could determine quickly whether there is a adulterated sample of 120# solvent naphtha in diesel. At the same time, by measuring the volume of three-dimension spectral subtraction fluorescence graph, the authors found that this total volume is directly related to the concentration of the adulterant present in the sample. The study is important for us to analyse whether there is a adulterated sample of 120# solvent naphtha in diesel, and is of significance for us to maintain the stability of market.

[Study of poly (3,4-ethylene dioxythiophene) : poly (styrene sulfonate) by in-situ resonance Raman spectroscopy].

Poly (3,4-ethylene dioxythiophene) (PEDOT): Poly (styrene sulfonate) (PSS) has attracted a lot of interest for application in organic electronics due to good stability and high electronic conductivity in its doped state. Indeed, thin layers of PEDOT:PSS was regularly used in light emitting diodes (PLEDs) as hole injection and transportation layer. Here, Doping and dedoping states of PEDOT:PSS were studied by absorbance spectra and Raman spectra. A new absorption band centered at 620 nm was observed on dedoped PEDOT:PSS. Consistently, Raman signals of dedoped PEDOT:PSS are resonantly intensified since the Raman excitation wavelength (633 nm) is set in the enhanced absorption band. So it gives a sensitive way to study the doping and dedoping states of PEDOT:PSS. Furthermore, for the encapsulated polymer light-emitting diodes, Raman spectroscopy is a powerful way to study the polymer layers inside the devices.

[The orthogonal polynomial regression method of multi-wavelength radiation thermometry].

For the problem of multi-wavelength radiation thermometry, the traditional data processing methods are the least squares techniques, the multiple linear regression fitting, and the stepwise regression fitting. There are some shortages in these methods, resulting in a certain error between the fitting result and the true temperature of the object surface. A new data processing method of multi-wavelength radiation thermometry--the orthogonal polynomial regression method was brought forward in this article on the base of variable emissivity. The mathematic principle of orthogonal polynomial regression method was expounded and according to the surface emissivities of tungsten, the true temperature of tungsten surface was simulated by the stepwise regression method and the orthogonal polynomial regression method. By comparing the fitting results, the authors found that the orthogonal polynomial regression method has the merit of simple principle and small operation, and the relative error between the fitting result and the surface true temperature is smaller. So the authors can draw the conclusion that using the orthogonal polynomial regression method to process the data of the multi-wavelength radiation thermometry, the fitting result has smaller error, it can fit the true temperature of object faster, and the result is more accurate than the traditional data processing methods.