Immuno-CoPS (conducting paper strips) for futuristic cost-effective cancer diagnostics

The fabrication of cost-effective, rapid and specific paper based point-of-care (POC) diagnostics based on the principles of bio-recognition is currently at the vanguard of biomedical research, as it is playing a key role in early diagnosis and treatment, resulting in the inhibition of infection and reducing the mortality rate. In the present report, we demonstrate that biomolecules can be directly attached to a paper matrix covalently, by suitable modification of the paper matrices. A high conductivity is achieved and the porosity can be tailored and has been utilized for the quantitative estimation of bio-analytes. We prove the feasibility of our approach for the detection of cancer biomarkers in a wide detection range

Chemical potential shift and gap-state formation in SrTiO3−δ_{3-\delta} revealed by photoemission spectroscopy

In this study, we report on investigations of the electronic structure of SrTiO$_3$ annealed at temperature ranging between 550 and 840$^\circ$C in an ultrahigh vacuum. Annealing induced oxygen vacancies (O$_{vac}$) impart considerable changes in the electronic structure of SrTiO$_3$. Using core-level photoemission spectroscopy, we have studied the chemical potential shift ($\Delta\mu$) as a function of annealing temperature. The result shows that the chemical potential monotonously increases with electron doping in SrTiO$_{3-\delta}$. The monotonous increase of the chemical potential rules out the existence of electronic phase separation in the sample. Using valence band photoemission, we have demonstrated the formation of a low density of states at the near Fermi level electronic spectrum of SrTiO$_{3-\delta}$. The gap-states were observed by spectral weight transfer over a large energy scale of the stoichiometric band gap of SrTiO$_3$ system leading finally to an insulator - metal transition. We have interpreted our results from the point of structural distortions induced by oxygen vacancies.Comment: 7 pages, 6 figures, 1 tabl

Magnetization studies on superconducting MgB2_2 - lower and upper critical fields and critical current density

Magnetization studies have been carried out on superconducting MgB$_2$ (T$_c$=37K) in the temperature range of 2-50K and in magnetic field up to 5 Tesla. From these measurements, values of the lower critical field H$_c1$(0), upper critical field H$_c2$(0) at zero K are estimated to be ~300 Oe and ~12.5 Tesla, respectively, which yield a value of ~26 for the Ginzburg-Landau parameter, k. Magnetization hysteresis loops have been obtained at various temperatures from which the magnetization critical current density is estimated using Bean's critical state model.Comment: 7 pages, 6 figures, to be publihed in Solid State Communications (2001) [in press

Vacuum thermal deposition of crystalline, uniform and stoichiometric CdS thin films in ambient H2S atmosphere

Crystalline, uniform and stoichiometric thin films of CdS have been fabricated on soda lime glass (SLG) substrates using vacuum thermal deposition method in the presence of hydrogen sulphide (H2S) atmosphere. The consequence of ambient H2S on the growth, quality and structure-property relationship of vacuum deposited CdS thin films has been investigated. The deposited films have been characterized by XRD, SEM with EDX analysis, AFM, XPS and optical spectroscopy. The physical characterization of as-deposited CdS films reveals that the films deposited in controlled H2S ambient are more crystalline, highly uniform and stoichiometric in comparison to films deposited without H2S atmosphere

Neutron structural studies on the superconducting (Nd1-xCax)(Ba1.6La0.4)Cu3Oz system

We have investigated the influence of Ca ions substitution on the structural and superconducting properties of (Nd1-xCax)(Ba1.6La0.4)Cu3Oz system. Magnetization, X-ray diffraction and neutron diffraction studies have been carried out on a series of compounds with x = 0.0 to 0.6. The superconducting transition temperature Tc, determined from magnetization measurements increases with increasing Ca2+ substitution. Neutron diffraction studies reveal that these compounds crystallize in a tetragonal structure (space group P4/mmm). A detailed analysis of the neutron diffraction data reveals that Ca and La ions are intermixed at the nominal Ba and Nd sites. While a major fraction of Ca ions occupy the usual Nd site, a small fraction occupies the Ba site. Consequently, the corresponding amount of La substitutes at the nominal Nd site. The intermixing of Ca and La sites randomizes the chain site oxygens leading to a tetragonal structure despite an oxygen content close to 7.0 for all the Ca doped samples. Further increase of Ca content lead to change in its co-ordination from six-fold to eight-fold at x >= 0.4.Comment: 13 Pages, 5 Figure

Neutron Structural Studies on the Superconducting (Nd₁₋ₓCax)(Ba₁.₆La₀.₄)Cu₃Oz System

We have investigated the influence of Ca ion substitution on the structural and superconducting properties of (Nd1−xCax)(Ba1.6La0.4)Cu3Oz system. Magnetization, x-ray diffraction, and neutron diffraction studies have been carried out on a series of compounds with x=0.0-0.6. The superconducting transition temperature Tc, determined from magnetization measurements, increases with increasing Ca2+ substitution. Neutron diffraction studies reveal that these compounds crystallize in a tetragonal structure (space group P4/mmm). A detailed analysis of the neutron diffraction data reveals that Ca and La ions are intermixed at the nominal Ba and Nd sites. While a major fraction of Ca ions occupy the usual Nd site, a small fraction occupies the Ba site. Consequently, the corresponding amount of La substitutes at the nominal Nd site. The intermixing of Ca and La sites randomizes the chain site oxygens leading to a tetragonal structure despite an oxygen content close to 7.0 for all the Ca doped samples. Further increase in Ca content leads to change in its coordination from sixfold to eightfold at x\u3e=0.4

Revelation of graphene-Au for direct write deposition and characterization

Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties

Valence band and core-level analysis of highly luminescent ZnO nanocrystals for designing ultrafast optical sensors

Highly luminescent ZnO:Na nanocrystals of size ~2 nm were synthesized using a improved sol-lyophilization process. The surface analysis such as survey scan, core-level and valence band spectra of ZnO:Na nanocrystals were studied using x-ray photoelectron spectroscopy (XPS) to establish the presence of Na+ ions. The observed increase in band gap from 3.30 (bulk) to 4.16 eV (nano), is attributed to the quantum confinement of the motion of electron and holes in all three directions. The photoluminescence and decay measurements have complemented and supported our study to design an efficient and ultrafast responsive optical sensing device.Comment: 10 Pages, 5 Figure