Electronic and optical properties of strain-locked metallic Ti2O3 films

Lahneman D.J.,Kim H.,Jiang H.,Mathews S.A.,Lock E.,Prestigiacomo J.,Qazilbash M.M.,Rohde C.,Piqué A. 한국물리학회 2023 Current Applied Physics Vol.47 No.-

We successfully grow corundum structured Ti2O3 films on c-plane sapphire substrates using pulsed laser deposition. Temperature dependent resistivity measurements show that a metal to insulator transition (MIT) is suppressed, showing conducting behavior at all temperatures. Samples still show an increase in resistivity as temperature is decreased, a characteristic indicative of a semiconducting phase. Our films exhibit grain size on the order of 30 nm which induce a strain consistent with nanoparticle Ti2O3 showing a (c/a) ratio of 2.7. The imposed strain causes an increase in the c-axis length as the temperature is decreased, and thereby suppresses the transition to an insulating phase. Our optical data agrees with this result, showing the lack of a band gap and the electronic structure consistent with bulk high temperature metallic Ti2O3 with the a1g - eπg interband transition shifted down to 0.7 eV from its bulk insulating value of ~1 eV.

Evaluation of the Extension Programme of Njala University College Sierra Leone

( Mathew L. S. Gboku ),( A. A. Jibowo ) 한국농촌경제연구원 1988 Journal of Rural Development Vol.11 No.1

The purpose of the study was to evaluate the effectiveness of the extension programme of Njala University College. Operationally, the study assessed the farmers` adoption level of the agricultural innovations introduced to them, determined their socio-economic characteristics and how these were related to the adoption behavior of the programme participants. Two hundred farmers drawn randomly from six chiefdoms were involved in the study. Data analysis revealed that there was a positively significant relationship between innovation adoption by the participants and farm size, years of schooling, decision making type, cosmopoliteness, land tenure, aspiration to change farm size and number of farm enterprises, number of information sources used and awareness of agricultural innovations. The programme strategy, that is, the trickle down adoption through the non-participants had not been appreciably noticeable in terms of technology transfer from the former to the latter. The participants` farm size, income, social participation, extension contact, number of information sources used, awareness of agricultural innovations, and posititve attitudes toward the extension programme were significantly higher than those of the non-participants. The non-participants within the programme area, however, experienced the programme`s spill-over effect more than those non-participants outside the programme area. Lack of credit, shortage of extension agents, and limited number of tractors were discovered as some of the problems confronting the farmers. The study concluded with the following recommendations; a) a review of the extension strategy to extend activities to those farmers who have not benefitted from the programme, b) encouraging group action among farmers, c) re-emphasizing extension contact by increasing the strength of the present field staff and d) assisting farmers in getting credit and the timely supply of inputs such as fertilizers and improved seeds.

Hydrophobically modified spherical MCM-41 as nanovalve system for controlled drug delivery

Mathew, A.,Parambadath, S.,Park, S.S.,Ha, C.S. Elsevier 2014 Microporous and mesoporous materials Vol.200 No.-

Spherical MCM-41 nanovalve having hydrophobically modified pore channels was synthesized via surfactant assisted sol-gel methodology and post modification process. The spherical MCM-41 has been tailored as a smart pH responsive drug carrier system by the insertion of N-3-(trimethoxysilyl)propyl aniline (TMSPA) at the pore opening before extracting the surfactant and further with phenyltrimethoxysilane (PTMS) to impart hydrophobicity on the inner surfaces of the pore channels. The surfactant extracted MCM-41 exhibits excellent textural properties such as very high specific surface area (1307 m<SUP>2</SUP>g<SUP>-1</SUP>), pore diameter (24 A) and pore volume (0.65 cm<SUP>3</SUP>g<SUP>-1</SUP>). The transmission electron microscope (TEM) and scanning electron microscope (SEM) images of mesosphere reflect the highly uniform and mono-dispersed spherical morphology having a particle size of 500nm. 5-Fluorouracil (5-Fu) and famotidine have been loaded into the hydrophobically modified channels followed with β-cyclodextrin (β-CD) as the gatekeeper to make the material as a pH responsive drug delivery system. The drug delivery has been carried out under in vitro condition at pH 4 and the amount of drug released from the nanovalve system was monitored by UV-Vis spectroscopy under regular intervals. The hydrophobically modified nanovalve was found to have delayed drug release of both 5-Fu and famotidine in comparison to the drug delivery from the nanovalve having unmodified pore channels synthesized from spherical MCM-41 under similar experimental conditions. The significance of functionalization as well as capping has been verified by the comparison of drug delivery behaviors among hydrophobically modified, unmodified, β-CD capped and uncapped nanocontainers.

Ion-imprinted mesoporous silica hybrids for selective recognition of target metal ions

Moorthy, M.S.,Tapaswi, P.K.,Park, S.S.,Mathew, A.,Cho, H.J.,Ha, C.S. Elsevier 2013 Microporous and mesoporous materials Vol.180 No.-

A novel ion-imprinted functional ligand derivative bearing periodic mesoporous organosilica (IIPMO) was obtained using a sol-gel process from a chemically synthesized organopolysilane precursor with a metal template (Co<SUP>2+</SUP> ion) imprinted ligand centre with tetraethylorthosilicate (TEOS) and cetyltrimethylammoniumbromide (CTAB) as a structural directing surfactant under basic conditions. The imprinted metal template was easily leached out from the hybrid materials during an acid treatment, which resulted in a template-free ion-imprinted network in the PMO pore wall framework with an unaltered particle size and morphology. The ion-imprinted hybrid PMO materials were characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, solid-state <SUP>29</SUP>Si and <SUP>13</SUP>C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy, N<SUB>2</SUB> adsorption-desorption analysis and elemental analysis. Furthermore, the removal of the imprinted metal template was confirmed by inductively coupled plasma-atomic emission spectroscopy. The selective rebinding ability of the template ions on the ion-imprinted PMO hybrid adsorbents was examined using a cobalt nitrate solution. The rebinding results showed that the selective efficiency of Co<SUP>2+</SUP> ions on the IIPMOs were 10.1, 7.4 and 9.3 for Cu<SUP>2+</SUP>, Cd<SUP>2+</SUP> and Zn<SUP>2+</SUP>, respectively.

Highly efficient and selective adsorption of In³⁺ on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

Barnabas, M.J.,Parambadath, S.,Mathew, A.,Park, S.S.,Vinu, A.,Ha, C.S. Academic Press 2016 Journal of solid state chemistry Vol.233 No.-

<P>A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In3+ ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In3+ intake. The structure and properties of Zn/Al-LDH and In3+ adsorbed Zn/Al-LDH (In-Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N-2-sorption/desorption, UV-vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In3+ adsorption and quite stable even after the adsorption process. The selective adsorption of In3+ on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn2+, Co2+, Ni2+, Cd2+, Pb2+, and Cu2+. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In3+ from large volumes of aqueous solutions. (C) 2015 Elsevier Inc. All rights reserved.</P>

Periodic mesoporous organosilica (PMO) containing bridged succinamic acid groups as a nanocarrier for sulfamerazine, sulfadiazine and famotidine: Adsorption and release study

Parambadath, S.,Mathew, A.,Barnabas, M.J.,Rao, K.M.,Ha, C.S. Elsevier 2016 Microporous and mesoporous materials Vol.225 No.-

<P>Periodic mesoporous organosilica (PMO) with a bridged amine framework and a pendant succinamic acid group (SA-PMO-5) was synthesised using a sol gel and post modification process. The bridged amino functionality was introduced to the pore wall of the PMO (MA-PMO-5) using a silsesquioxane precursor, N,N-bis[3-(triethoxysilyl)propyl]amine (BTMSA), along with tetramethyl orthosilicate (TMOS). The succinamic acid functionality was tailored by the ring opening reaction of succinic anhydride with the bridged amine. The physico-chemical properties of SA-PMO-5 were determined by a range of spectroscopic analyses. X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that the MA-PMO-5 and SA-PMO-5 possessed mesoscopically ordered, hexagonal symmetry as well as well-defined morphologies. The N-2 sorption experiment showed the MA-PMO-5 and SA-PMO-5 had a large surface area (704 and 623 m(2) g(-1)), acceptable pore diameter (3.2 and 2.4 nm) and pore volume (0.56 and 0.47 cm(3) g(-1)) to accommodate the guest molecules inside the pore channels. Organic functionalisation was determined successfully by Fourier transform infrared spectroscopy and C-13 cross-polarisation magic angle spinning (CP-MAS) NMR spectroscopy. Si-29 MAS NMR spectral analysis revealed the silicon environment of the final material. Sulfamerazine (SMR), sulfadiazine (SDZ) and famotidine (FAMO) adsorption as well as the release properties from the MA-PMO-5 and SA-PMO-5 were investigated at pH 4 and 7.4. The high adsorption and delayed release properties exhibited by SA-PMO-5 were attributed to the strong interaction between succinamic acid functionality with the drug molecules. (C) 2015 Elsevier Inc. All rights reserved.</P>

SILICON QUANTUM DOTS GROWTH IN SiNx DIELECTRIC: A REVIEW

A. K. PANCHAL,D. K. RAI,M. MATHEW,C. S. SOLANKI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2009 NANO Vol.4 No.5

This paper reviews research works carried out on silicon quantum dots (Si-QDs) embedded in the silicon nitride (SiNx) dielectric matrix films with different fabrication techniques and different characteristics. The advantages of SiNx as a dielectric compared to silicon dioxide (SiO2) for Si-QDs from a device point of view are discussed. Various fabrication techniques along with different optimized deposition conditions are summarized. The typical results of structural characteristics of the films with Raman spectroscopy and Transmission Electron Microscopy (TEM) are discussed. The origin of photoluminescence (PL) from the films and the chemical compositional analysis such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Secondary Ion Mass Spectroscopy (SIMS) analysis of the films are also made available in brief. The charge conduction mechanism in the films with metal–insulator–semiconductor (MIS) structure, with their electrical characterization like capacitance–voltage (C–V) and current–voltage (I–V) measurements are presented.

Prevalence of rotavirus diarrhea among hospitalized under-five children

Mathew, M. A.,Paulose, A.,Chitralekha, S.,Nair, M. K.,Kang, G.,Kilgore, P. INDIAN PEDIATRIC 2014 Indian pediatrics Vol.51 No.1

Objectives: To estimate the prevalence of rotavirus diarrhea among hospitalized children less than 5 years of age in Kerala State and to determine the circulating strains of rotavirus in Kerala.Design: Multicenter, cross-sectional study.Setting: Eight representative hospitals in Kunnathunadu Thaluk, Ernakulam district, Kerala.Participants: Children in the age group under 5 yearsMethods: Hospitalized children admitted with acute diarrhea were examined and standardized case report form was used to collect demographic, clinical and health outcome. Stool specimens were collected and ELISA testing was done. ELISA rotavirus positive samples were tested by reverse transcription PCR for G and P typing (CMC Vellore).Results: Among the 1827 children, 648 (35.9%) were positive for rotavirus by the Rotaclone ELISA test. The prevalence of rotavirus diarrhea in infants less than 6 months of age was 24.7%; 6-11 months 31.9%; 12-23 months 41.9%; 24-35 months 46.9%; and 33.3% in 36- 59 months. Rotavirus infections were most common during the dry months from January through May. GIP[8] (49.7%) was the most common strain identified followed by G9P[8] (26.4%), G2P[4] (5.5%), G9P[4] (2.6%) and G12P[6] (1.3%).Conclusions: The prevalence of rotavirus diarrhea among hospitalized children less than 5 years is high in Ernakulam district, Kerala State.

Fracture analysis and remaining life prediction of aluminium alloy 2014a plate panels with concentric stiffeners under fatigue loading

A. Ramachandra Murthy,Rakhi Sara Mathew,G.S. Palani,Smitha Gopinath,Nagesh R. Iyer 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

Fracture analysis and remaining life prediction has been carried out for aluminium alloy (Al2014A) plate panels with concentric stiffener by varying sizes and positions under fatigue loading. Tensioncoupon tests and compact tension tests on 2014A have been carried out to evaluate mechanical propertiesand crack growth constants. Domain integral technique has been used to compute the Stress intensity factor(SIF) for various cases. Generalized empirical expressions for SIF have been derived for various positions ofstiffener and size. From the study, it can be concluded that the remaining life for stiffened panel for particularsize and position can be estimated by knowing the remaining life of corresponding unstiffened panel.

Diffusion mediated selective adsorption of Zn²⁺ from artificial seawater by MCM-41

Mathew, A.,Parambadath, S.,Kim, S.Y.,Ha, H.M.,Ha, C.S. Elsevier 2016 Microporous and mesoporous materials Vol.229 No.-

<P>MCM-41 can play a pivotal role as a host material for adsorption applications. In this work, MCM-41 was found to be 100% selective for Zn2+ from artificial seawater containing Ni2+, Li+, Co2+, Cd2+ and Zn2+ as hetero ions. The pristine and Zn2+ ions adsorbed MCM-41 (Zn@MCM-41) were well characterized by various spectroscopic techniques. The selective Zn2+ ion adsorption property of MCM-41 remained intact irrespective of the concentration of Zn2+ ions. The adsorption property of MCM-41 was unaffected by the synthesis strategy of MCM-41. SBA-15 exhibited 85 and 15% mole selectivity for Zn2+ and Cd2+ ions, respectively, under similar experimental conditions. This highlights the unique property of MCM-41 for the selective adsorption of Zn2+ ions from artificial seawater. TEM, FTIR and XPS analysis confirmed the presence of Zn2+ ions in Zn@MCM-41. The protection using methyl group on the outer/both surfaces of MCM-41 (Me-MCM-41/MeS-MCM-41) disclosed the necessity of interaction between silica surface and metal ion for selective adsorption of Zn2+ ions. The detailed investigation of adsorption mechanism postulates that the selective adsorption of Zn2+ ions by MCM-41 was achieved only in the presence of sodium chloride, which is the major component of artificial seawater. An adsorbed amount of 12 mg g(-1) was observed for Zn2+ ions even in presence of Cd2+ ions, while both of the ions possess similar chemical characteristics. (C) 2016 Elsevier Inc. All rights reserved.</P>