Details of the topological state transition induced by gradually increased disorder in photonic Chern insulators.

Using two well-defined empirical parameters, we numerically investigate the details of the disorder-induced topological state transition (TST) in photonic Chern insulators composed of two-dimensional magnetic photonic crystals (MPCs). The TST undergoes a gradual process, accompanied with some interesting phenomena as the disorder of rod positions in MPCs increases gradually. This kind of TST is determined by the competition among the topologically protected edge state, disorder-induced wave localizations and bulk states in the system. More interestingly, the disorder-induced wave localizations almost have no influence on the one-way propagation of the original photonic topological states (PTSs), and the unidirectional nature of the PTSs at the edge area can survive even when the bulk states arise at stronger disorders. Our results provide detailed demonstrations for the deep understanding of fundamental physics underlying topology and disorder and are also of practical significance in device fabrication with PTSs.

3D aluminum/silver hierarchical nanostructure with large areas of dense hot spots for surface-enhanced raman scattering.

Plasmonic nanomaterials possessing large-volume, high-density hot spots with high field enhancement are highly desirable for ultrasensitive surface-enhanced Raman scattering (SERS) sensing. However, many as-prepared plasmonic nanomaterials are limited in available dense hot spots and in sample size, which greatly hinder their wide applications in SERS devices. Here, we develop a two-step physical deposition protocol and successfully fabricate 3D hierarchical nanostructures with highly dense hot spots across a large scale (6 × 6 cm2 ). The nanopatterned aluminum film was first prepared by thermal evaporation process, which can provide 3D quasi-periodic cloud-like nanostructure arrays suitable for noble metal deposition; then a large number of silver nanoparticles with controllable shape and size were decorated onto the alumina layer surfaces by laser molecular beam epitaxy, which can realize large-area accessible dense hot spots. The optimized 3D-structured SERS substrate exhibits high-quality detection performance with excellent reproducibility (13.1 and 17.1%), whose LOD of rhodamine 6G molecules was 10-9 M. Furthermore, the as-prepared 3D aluminum/silver SERS substrate was applied in detection of melamine with the concentration down to 10-7 M and direct detection of melamine in infant formula solution with the concentration as low 10 mg/L. Such method to realize large-area hierarchical nanostructures can greatly simplify the fabrication procedure for 3D SERS platforms, and should be of technological significance in mass production of SERS-based sensors.

Bioscaffold arrays decorated with Ag nanoparticles as a SERS substrate for direct detection of melamine in infant formula.

Three-dimensional (3D) plasmonic structures have been intensively investigated as high performance surface enhanced Raman scattering (SERS) substrates. Here, we demonstrate a 3D biomimetic SERS substrate prepared by deposition of silver nanoparticles (Ag NPs) on the bioscaffold arrays of cicada wings using laser molecular beam epitaxy. This deposition method can offer a large number of nanoparticles with average diameter of ∼10 nm and nanogaps of sub-10 nm on the surface of chitin nanopillars to generate a high density of hotspots. The prepared 3D Ag/cicada SERS substrate shows a limit of detection (LOD) for Rhodamine 6G as low as 10-7 M, high enhancement factor of 1.09 × 105, and excellent signal uniformity of 6.8%. Moreover, the molecular fingerprints of melamine in infant formula can be directly extracted with an LOD as low as 10 mg L-1, without the need for functional modification. The prepared SERS-active substrate, due to its low cost, high-throughput, and good detection performance, can be widely used in applications such as food safety and environmental monitoring.

Recognizing nucleosides with transverse electronic transport via perpendicular direction of base planes for DNA sequencing.

Putting the four DNA nucleosides in the middle of gold [111] nanoelectrodes with base planes parallel to the electrode surface layer, we study the transverse electronic transport properties of four nucleosides along the direction of electrodes. First, the optimal distance of the electrodes is released. The results show that the optimal electrode distance to study transverse electronic transport characteristics of DNA nucleosides is about 0.68 nm. Second, we theoretically calculate the conductance and current of the four nucleosides via perpendicular direction of base planes in the bias range of [-2, 2] V by exploiting the first principle theory. According to the calculated results, we propose three methods to recognize the nucleoside type in practice application.

High-resolution separation of graphene oxide by capillary electrophoresis.

Separation and purification of graphene oxide (GO) prepared from chemical oxidation of flake graphite and ultrasonication by capillary electrophoresis (CE) was demonstrated. CE showed the ability to provide high-resolution separations of GO fractionations with baseline separation. The GO fractionations after CE were collected for Raman spectroscopy, atomic force microscopy, and transmission electron microscopy characterizations. GO nanoparticles (unexfoliated GO) or stacked GO sheets migrated toward the anode, while the thin-layer GO sheets migrated toward the cathode. Therefore, CE has to be performed twice with a reversed electric field to achieve a full separation of GO. This separation method was suggested to be based on the surface charge of the GO sheets, and a separation model was proposed. This study might be valuable for fabrication of GO or graphene micro- or nanodevices with controlled thickness.

Effects of Metal Ions on Conductivity and Structure of Single DNA Molecule in Different Environmental Conditions.

We design a novel nano-gap electrode to measure the current of DNA molecule, by which the current-voltage characteristics of individual native DNA, Ag-DNA and Ni-DNA molecules are obtained, respectively. The results show that the voltage gap of Ag- and Ni-DNA is higher than that of native DNA, and the conductance is lower than native DNA in neutral environment. The structure transition from B- to Z-DNA is observed in the presence of high concentrations of nickel ions and Ag-DNA appears chaos state by STM image and U-V spectra characterization. But in alkaline environment, the conductance of Ni-DNA rises and the voltage gap decreases with the increasing of nickel ion concentration denotes that the conductive ability of Ni-DNA is higher than that of native DNA.

[SERS spectra of serum from rash].

The SERS spectra of serums from the healthy persons and rash patients were measured. In the serum of rash, the band of amide I appeared at 1648 cm(-1), while this peak vanished in healthy serums. The relative intensity of 637 cm(-1) assigned to the gauche conformation of C S increased 23% and the band at 725 cm(-1) corresponding to anti-conformation decreases 60%. These indicate that the structure of the protein has changed in serums from the rash patients. The relative intensity at 1449 cm(-1) assigned to the lipids increased nearly one time. The band at 1099 cm(-1) assigned to the Man-D vanished, indicating that the contents of lipids, glucide and protein increased in rash patients. These results may offer a powerful experiment basis for rash diagnosis and biochemistry mechanism study. The multivariae ura statistical methods of principal component analysis (PCA) were also used to analyze the SERS of the serums from healthy persons and rash patients, it can be seen that the regional distribution of rash is wider than healthy volunteers, showing that these serums can be discriminated by PCA.

[SERS spectra of serum from diabetic].

The SERS spectra were measured from normal and the diabetic serum. In the diabetic serum, the band of amide II shifted to 1 585 cm(-1) and the relative intensity increased 14%, while the relative intensity of 593 cm(-1) which belongs to amide VI reduced 33%. For the protein side chain, the band at 1 368 cm(-1) assigned to the "buried" tryptophan shifted to 1 365 cm(-1) of the "exposed" and the relative intensity reduced 59%. The relative intensity of 635 cm(-1) assigned to the gauche conformation of the C-S decrased 15% and the band at 725 cm(-1) increased 58%. These indicate that the structure of the protein changed in the diabetic serum. The relative intensity at 1 449 cm(-1) assigned to the lipids characteristic increased 58%. The relative intensity of the glucide characteristic at 1 331, 1 099 and 740 cm(-1) increased 35%, 100% and 62%, respectively. So it is indicated that the content of lipids, glucide and protein increased in diabetic. These results may offer a powerful experimental basis for diabetes diagnosis and biochemistry mechanism study.

Study on the Electric Conductivity of Ag-Doped DNA in Transverse Direction.

In this article, we reported a novel experiment results on Ag-doped DNA conductor in transverse direction. I-V characteristics were measured and the relative conductances were calculated for different silver ions concentrations. With the increase of the concentration of silver ions, the conductive ability of DNA risen rapidly, the relative conductance of DNA enhanced about three magnitudes and reached a stable value when Ag(+) concentration was up to 0.005 mM. In addition, Raman spectra were carried out to analyse and confirm conduction mechanism.

Raman spectra of single cell from gastrointestinal cancer patients.

AIM: To explore the difference between cancer cells and normal cells, we investigated the Raman spectra of single cells from gastrointestinal cancer patients. METHODS: All samples were obtained from 30 diagnosed as gastrointestinal cancer patients. The flesh tumor specimen is located in the center of tumor tissue, while the normal ones were 5 cm away from the outside tumor section. The imprint was put under the micros-cope and a single cell was chosen for Raman measurement. All spectra were collected at confocal Raman micro-spectroscopy (British Renishaw) with NIR 780 nm laser. RESULTS: We measured the Raman spectra of several cells from gastrointestinal cancer patients. The result shows that there exists the strong line at 1 002 /cm with less half-width assigned to the phenylalanine in several cells. The Raman lines of white cell were lower and less, while those of red cell were not only higher in intensity and more abundant, but also had a particular C-N breathing stretching band of pyrrole ring at 1 620-1 540 /cm. The line at 1 084 /cm assigned to phosphate backbone of DNA became obviously weaker in cancer cell. The Raman spectra of stomach cancer cells were similar to those of normal cells, but the Raman intensity of cancer cells was much lower than that of normal cells, and even some lines disappear. The lines of enteric cancer cells became weaker than spectra above and many lines disappeared, and the cancer cells in different position had different fluorescence intensity. CONCLUSION: The Raman spectra of several cells from cancer patients show that the structural changes of cancer cells happen and many bonds rupture so that the biological function of cells are lost. The results indicate that Raman spectra can offer the experiment basis for the cancer diagnosis and treatment.

[Raman spectra of cell from breast cancer patients].

Raman spectra of normal and cancer cell from breast cancer patients a represented. It is reported that all of the Ramanlines become weak. The intensities of Raman lines 782 and 1 084 cm(-1) of DNA phosphate group and 1 155 and 1 262 cm(-1) of deoxyribosephosphate decrease. The spectral lines 812 cm(-1) of A-type DNA and 979 and 668 cm(-1) disappear, and the 905 cm(-1) peak is shifted to lower frequency by 6 cm(-1). This means that the phosphate backbone of DNA is destroyed to a certain extent and the fissiparity of cancer cell can't be controlled effectively. In addition, the authors found a kind of Raman line 960 cm(-1) concerning calcificationand sclerosis of cancer cell. The results indicate that Raman spectra may offer the experiment basis for the cancer diagnosis and treatment.

Temperature-dependent Raman spectra of collagen and DNA.

Raman spectra of collagen and DNA were discussed at different temperatures. The temperature-dependence of Raman intensity was obtained in the region from -150 to 200 degrees C. Four denaturation points at 0, 40, 68 and 90 degrees C of collagen and two peaks at 38 and 82 degrees C for DNA were obtained. The wavenumbers of many vibrational modes were found to increase for lower temperature, but the peak at 1302 cm(-1) of collagen and the peak at 1101 cm(-1) of DNA showed the opposite trend. In all of the vibrational modes of DNA, the bases showed the most sensitive to different temperatures and there is a pronounced shift of bands at 70 degrees C, the starting point of denaturation.

[Temperature dependence of collagen by Raman spectra].

Raman spectra of collagen I at different temperature were obtained. There was no change at 1003 cm(-1) line, 1302 cm(-1) line moved to a higher wave number, but other lines moved to lower wave number when temperature increased. In addition, the authors observed the temperature dependence of Raman intensity and four denaturation points at 0, 40, 68 and 90 degrees C respectively. The points at 40 and 68 degrees C are in agreement with the experimental data by DSC and SHG. The point at 0 degrees C might be frozen transition; the point at 90 degrees C might be related to the damage of secondary structure. When heated to 150 degrees C, the Raman intensity of all bands decreased rapidly and many lines disappeared.

[Temperature dependence study of calf thymus DNA by Raman spectra].

In this paper, the authors obtained Raman spectra of DNA in fiber and aqueous solution at different temperatures. These spectra revealed that the vibration of bases and phosphate group were influenced by varying temperature. Adenine was the most sensitive to varying temperature in all of the vibrational modes. The wave numbers of most of the vibrational modes decreased as the temperature increased except for the band at 1101 cm(-1), and the shift of wave numbers mainly concentrated upon the beginning point of denaturation at 70 degrees C. The temperature dependence of Raman intensity was discussed, and two peaks were obtained at 38 and 82 degrees C, respectively. The results obtained by Raman spectra were in agreement with experimental data by DSC at 82 degrees C. The peak at 38 degrees C was related to the biological activity region of DNA function.

[Resonance Raman spectra of single red-cell from human blood].

Resonance Raman spectra of single red-cell from human blood are presented by different laser sources. It is reported that there is 1002 cm(-1) line of insensitive conformation of phenylalanine aromatic ring stretching and 1620 cm(-1) line of C-N breathing stretching band of pyrrole ring, which cause strong and sharp resonance lines when excited by 782 nm laser source. They are weaker and the intensity of other lines of high wave number is large and clear when excited by 514 nm laser source. But the intensity of lines of low wave number is strong and clear when excited by 782 nm laser source. At the same time, the authors got Raman spectra lines at different times after taking blood under the same laser source. When using 782 nm laser source, there is no difference except for 1601 cm(-1). There are a lot of weakened lines and lines shifting about 4-10 cm(-1) toward low wave number. The results indicate that Raman spectra may offer the experimental basis for studying structure, function and variability of single red-cell.