Paritosh Mohanty

Porous covalent electron-rich organonitridic frameworks as highly selective sorbents for methane and carbon dioxide

Carbon dioxide capture from point sources like coal-fired power plants is considered to be a solution for stabilizing the CO(2) level in the atmosphere to avoid global warming. Methane is an important energy source that is often highly diluted by nitrogen in natural gas. For the separation of CO(2) and CH(4) from N(2) in flue gas and natural gas, respectively, sorbents with high and reversible gas uptake, high gas selectivity, good chemical and thermal stability, and low cost are desired. Here we report the synthesis and CO(2), CH(4), and N(2) adsorption properties of hierarchically porous electron-rich covalent organonitridic frameworks (PECONFs). These were prepared by simple condensation reactions between inexpensive, commercially available nitridic and electron-rich aromatic building units. The PECONF materials exhibit high and reversible CO(2) and CH(4) uptake and exceptional selectivities of these gases over N(2). The materials do not oxidize in air up to temperature of 400 °C.

Synthesis of periodic mesoporous coesite.

Periodic mesoporous coesite was obtained by a modified nanocasting process from a periodic mesoporous silica SBA-16/C composite at a pressure of 12 GPa and 350 degrees C.

Metal oxide nanostructures incorporated/immobilized paper matrices and their applications: a review

Metal oxide nanostructures of TiO2, ZnO, Fe2O3/Fe3O4, Bi2O3, CeO2, ITO, SiO2, MoO2, and WO3 have shown great potential for applications in various fields such as piezoelectric, magnetic, gas sensors, and dye sensitized solar cells due to their unique optical, electronic, conductivity, catalytic and antimicrobial properties. However, recovery and reuse of these nanostructures pose big threats from cost and environmental perspectives. Thus, various substrates have been employed for incorporating or immobilizing them but finding suitable substrate is still a big challenge. Paper, being a natural biopolymer, has been used recently to incorporate/immobilize various metal oxide nanostructures. The metal oxide nanostructures are normally adhered to the cellulose matrices through weak interactions such as van der Waals force and hence, usually have retention related issues. This was circumvented to a great extent by using suitable linkers, binders, or retention aids for the incorporation/immobilization of the nanostructures in paper matrices. Although these reagents improve retention, as well as some of the properties, they ultimately add cost to the final product. Additionally, these retention aids and linkers hinder accessibility of active surface sites of metal oxide nanostructures for their various applications. Very recently our group developed an in situ single step hydrothermal method to immobilize metal oxide nanostructures such as TiO2, ZnO, and Bi2O3 without using any binder, linker or retention aid. In this review a comprehensive account of the development of methodology for incorporation/immobilization of metal oxide nanostructures is discussed. Furthermore, how the immobilization of nanostructures evolved without using any binder, linker or retention aid is thoroughly discussed based on the chemistry of the cellulose and metal oxides. Applications of nanostructure immobilized paper matrices are highlighted and critical challenges are discussed along with directions for future research.

ZnO-modified cellulose fiber sheets for antibody immobilization.

Cellulose fiber sheets impregnated with saccharide capped-ZnO nanoparticles were used as bioactive materials for antibody immobilization. First, ZnO nanoparticles were synthesized in the presence of glucose (monosaccharide), sucrose (disaccharide) as well as alginic acid and starch (polysaccharides). The pine cellulose fibers were then modified by the obtained saccharide capped nanoparticles and further incorporated into the sheets. The presence of ZnO significantly improved the immobilization of the antibodies on the surface of the sheets. After rewetting the alginic acid-ZnO modified sheets with saline solution, the retention of antibodies was about 95%. A high degree of the immobilization of biomolecules is an important feature for possible fabrications of bioactive- or biosensing-papers and we successfully tested the sheets on the detection of blood types using (A, B, and D blood antibodies). The ZnO nanoparticles affected also the other properties of the sheets. The ZnO-modified fiber sheets showed higher values of tensile index (strength), smoothness and opacity, while the value of porosity was substantially lower than that of the unmodified sheet. The presence of ZnO nanoparticles provided also the antimicrobial activity to the sheets. They showed a strong activity against bacteria (Escherichia coli and Staphylococcus aureus) and strong resistance to the attack of cellulase producing fungus Gloeophyllum trabeum.

Periodic Mesoporous Organosilica Nanorice

A periodic mesoporous organosilica (PMO) with nanorice morphology was successfully synthesized by a template assisted sol–gel method using a chain-type precursor. The PMO is composed of D and T sites in the ratio 1:2. The obtained mesoporous nanorice has a surface area of 753 m2 g−1, one-dimensional channels, and a narrow pore size distribution centered at 4.3 nm. The nanorice particles have a length of ca. 600 nm and width of ca. 200 nm.

Synthesis of Stishovite Nanocrystals from Periodic Mesoporous Silica

Faceted stishovite nanocrystals with sizes of 200-400 nm were synthesized at a pressure of 12 GPa and a temperature of 400 degrees C in a multianvil apparatus using mesoporous silica SBA-16 as the precursor.

ZnO nanowire-immobilized paper matrices for visible light-induced antibacterial activity against Escherichia coli

Paper matrices showing antibacterial activity were prepared by immobilizing ZnO nanowires (NWs) of diameter ca. 130–500 nm and length up to 2.5 μm on the surface of cellulose fibers by a single-step hydrothermal method. The antibacterial activity of the paper matrices has been investigated versus the visible light exposure time and ZnO contents (2.0 to 18.0 wt%). A complete inhibition of E. coli growth (i.e. 99.99%) was observed with the ZnO-immobilized paper matrices for 6 to 9 h exposure. A possible growth mechanism for the ZnO NW growth on the surface of the cellulose fibers has been proposed. The immobilization of ZnO NWs in paper matrices was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoluminescence spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy.

Light emission associated with the 5D0 → 7F3 forbidden transition in Eu3+ cations dispersed in an Eu3+:Al2O3 mesoporous structure

Light emission associated with the 5D0 → 7F3 electronic transition in Eu3+ ions dispersed within a mesoporous structure of Al2O3 is reported. It lies in a long band centred at 666 nm with an integrated intensity about 1.75 times that of the more common 5D0 → 7F2 transition at 619 nm. Usually, the 5D0 → 7F3 transition is an electric–dipole, quadruple, or magnetic–dipole forbidden transition. The symmetrically shaped band has a width of 50 nm, which can be compared to values of 20 nm or less found for the same transition in non-porous samples. A model is proposed to explain the results.

Enhanced photoemission in dispersed Eu2O3 nanoparticles in amorphous Al2O3

Dispersed Eu2O3 nanoparticles in amorphous Al2O3 have a strong photoemission in the visible 560 to 720 nm region of the electromagnetic spectrum. Four distinct bandgroups occur with the most intense band in the spectrum at ∼666 nm (contributing as much as 50% integrated intensity It in the four bands). The It value varies in a nonlinear function with Eu3+ concentration, with a maximum value at 1.0 wt% Eu3+, which is as much as 25 times that of other samples in this series. The four bandgroups lie at 587.0, 619.0, 665.5 and 702.0 nm in the spectrum of the 1.0 wt% Eu3+–Al2O3 sample and arise from 5D0 → 7FJ (J = 1 to 4) electronic transitions, respectively, in Eu3+(4f6) cations. The average position of the 666 nm band does not change significantly with Eu3+ content, in the 0.5 to 1.5 wt% range, while the maxima of the other bands vary in a complex manner. It seems that different electron–phonon coupling processes or Eu3+–Eu3+ interactions operate in the different 5D0 → 7FJ transitions which accounts for their different nonlinear spectral responses with Eu3+ concentration. The results are analyzed and discussed in correlation with the microstructure.

Sonochemical synthesis of cyclophosphazene bridged mesoporous organosilicas and their application in methyl orange, congo red and Cr(VI) removal

A rapid sonochemical route was adopted for the synthesis of cyclophosphazene bridged mesoporous organosilicas (CPMOs) by co-condensation of (3-aminopropyl)triethoxysilane (APTES) and phosphonitrilic chloride trimer (PNC) with variable amounts of tetraethyl orthosilicate (TEOS) in the presence of cetyltrimethylammonium bromide (CTABr). The products were formed as early as 15 min, however, the experiments were carried out for 1 h for better condensation and aging. The specific surface areas of the specimens were a function of the APTES to TEOS ratio and varied in the range of 58 to 974 m2 g−1. The pore size distribution of these specimens was centred around 1.4 to 3.7 nm. These CPMOs were employed for the adsorption of organic dyes such as methyl orange (MO) and congo red (CR) as well as Cr(VI) ions. Adsorption studies were carried out in aqueous solution by varying the contact time, initial dye concentration, and temperature. The equilibrium data were fitted using the Langmuir and Freundlich isotherm by linear regression analysis. The kinetic analysis revealed that the overall adsorption process was pseudo-second-order. The maximum adsorption capacities were 523 mg g−1, 320 mg g−1 and 101 mg g−1 for MO, CR and Cr(VI) ions, respectively at 25 °C. The adsorption was a spontaneous exothermic process with negative ΔG and ΔH derived from the thermodynamics studies.