Modification of Oxide Surfaces with Functional Organic Molecules, Nanoparticles, and Hetero-Oxide Layers

The research work described in this thesis is concerned with the modification of oxide surfaces, as reflected by its title. The surfaces and their modification have been studied using a range of experimental surface characterization tools, in particular x-ray photoelectron spectroscopy (XPS), fluorescence microscopy, scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy. A large part of the thesis is related to the modification of oxide or metal surfaces with nanoparticles. In particular, three different immobilization schemes for the coupling of molecularly imprinted polymer (MIP) nanoparticles to silicon oxide (SiO2) and gold surfaces were designed and characterized at every step. The first method reports the immobilization of MIPs using a photo-coupling agent in combination with an aminosilane compound. The second method explores an epoxysilane-based coupling agent to directly anchor the nucleophilic core-shell MIP nanoparticle to the surface. Both methods were proven to be non-destructive towards the specific binding sites of the MIP nanoparticles. The third scheme offers the immobilization of nucleophilic core-shell nanoparticles on model gold surfaces using self-assembled monolayers of 11-mercaptoundecanoic acid activated by carbodiimide/N-hydroxysuccinimide. All three coupling methods are quite versatile and can be used in biosensors to couple functional nano-objects with transducer surfaces. In addition to these investigation directly aimed at the immobilization of nanopartciles, more fundamentally oriented studies were carried out on the modification of the rutile TiO2(110) surface with silane molecules to obtain a detailed understanding of adsorption mechanism and geometry of these silanes. The deposition of a different type of nanopartciles, block copolymer reverse micelles loaded gold nanoparticles, on a titanium dioxide surface was tested using electrospray deposition. The study demonstrates that electrospray deposition is a viable method for depositing metal single-size metal nanoparticles onto a surface in vacuum, thereby retaining the clean vacuum conditions. Furthermore, it was shown that the removal of the block copolymer shell after deposition can be achieved both by atomic oxygen and an oxygen plasma, with the atomic oxygen being somewhat more efficient. Overall, it was demonstrated that a TiO2 surface decorated with narrow sized gold nanoparticles could be created, a result of importance in the catalysis domain. The last part of the thesis is concerned with the true in-situ investigation of growth of hetero-oxide layers on oxide surfaces from metal precursors. Tetraethyl orthosilicate (TEOS) was used as precursor for the chemical vapor deposition of silicon oxide on rutile TiO2(110). The growth was monitored in real time using ambient pressure XPS (APXPS), which revealed the dissociative adsorption with the formation of new species in the presence of a TEOS gas phase reservoir. Annealing results in the formation of SiO2 and of a mixed titanium/silicon oxide. Furthermore, tetrakis(dimethylamino)titanium was employed in the atomic layer deposition (ALD) of TiO2 on RuO2. The APXPS results showed evidence was for side reactions beyond the idealized scheme of ALD

A study of causes of perinatal mortality in tertiary center in Bundelkhand region

Background: The distribution of causes of death in population suggests a great potential for prevention. So the aim of study is to evaluate the cause of perinatal death in tertiary center of Bundelkhand region in M.L.B. medical college Jhansi, Uttar Pradesh (India).Methods: A retrospective study was done over a period of last one year from June 2013 to May 2014, which included total 2691 deliveries out of which 184 perinatal deaths occurred, hence perinatal mortality rate was 68.37 per 1000 birth and causes of perinatal deaths was identified and analysed.Results: Out of 68.37% perinatal mortality, majority of perinatal deaths (54.3%) occurred due to preterm low birth weight with or without associated other factors, 8.6% due to congenital anomalies, more than 38% perinatal death due to maternal factor antepartum haemorrhage, eclampsia, obstructed labour, malpresentation, medical problem in pregnancy.Conclusions: Early identification of mothers at risk of pregnancy complications through antenatal care screening, teaching pregnant women to recognize signs of pregnancy complications, timely access to obstetric care, monitoring of labour for fetal distress, and proper newborn resuscitation may reduce some of the categories of deaths. There should also be increased awareness among paediatrics and obstetrics about coordinated approach to bring down perinatal mortality.

Effects of antenatal corticosteroids administration on fetoplacental circulation in preterm pregnancies with intrauterine growth restriction and its correlation with perinatal outcome

Background: Antenatal corticosteroid administration in preterm pregnancies is recommended to promote fetal lung maturation. Studies have reported temporary reduction in fetal heart rate, breathing and movements following maternal corticosteroid administration. Authors studied effect of maternal corticosteroid administration on fetoplacental circulation in preterm pregnancies with IUGR and its correlation with perinatal outcome.Methods: Observational study included 77 preterm singleton pregnant women with IUGR. Color doppler day 0 (before betamethasone) of umbilical artery of 77 cases done. All received two doses of 12 mg of betamethasone intramuscularly 24 hours apart. Umbilical artery doppler on day 2 (24 to 48 hours of 1st dose of betamethasone) and day 4 (72 to 96 hours of 1st dose of betamethasone) done. Pulsatility index (PI) of umbilical artery on doppler and Neonatal details of all women noted.Results: On day 2 doppler, 56 (73%) women (Group A) showed decrease in umbilical artery PI while 21 (27%) women (Group B) did not show decrease in umbilical artery PI. Mean umbilical artery PI of 77 cases on day 0 and day 2 were 1.73±0.73 and 1.54±0.76 respectively (p<0.001). Mean Umbilical artery PI values of undelivered 60 cases on day 0, day 2 and day 4 were 1.55±0.61, 1.33±0.55 and 1.47±0.63 respectively (p<0.001). Group B neonates had poorer Apgar scores, higher neonatal complication, longer hospital stay, lesser umbilical pH at birth and higher perinatal mortality rate than Group A neonates.Conclusions: Significant reduction in mean umbilical artery PI observed on day 2 following betamethasone administration (p<0.001), which was maintained till 4th day after 1st dose of betamethasone (p<0.05). Women who showed improvement in umbilical artery pulsatility index following betamethasone administration had a better perinatal outcome as compared to women who did not

Covalent immobilization of molecularly imprinted polymer nanoparticles using an epoxy silane.

AbstractMolecularly imprinted polymers (MIPs) can be used as antibody mimics to develop robust chemical sensors. One challenging problem in using MIPs for sensor development is the lack of reliable conjugation chemistry that allows MIPs to be fixed on transducer surface. In this work, we study the use of epoxy silane to immobilize MIP nanoparticles on model transducer surfaces without impairing the function of the immobilized nanoparticles. The MIP nanoparticles with a core–shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model transducer surface is functionalized with a self-assembled monolayer of epoxy silane, which reacts with the core–shell MIP particles to enable straightforward immobilization. The whole process is characterized by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show that the MIP particles are immobilized uniformly on surface. The photoelectron spectroscopy results further confirm the action of each functionalization step. The molecular selectivity of the MIP-functionalized surface is verified by radioligand binding analysis. The particle immobilization approach described here has a general applicability for constructing selective chemical sensors in different formats

Controlled short-linkage assembly of functional nano-objects

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In situ characterization of the deposition of anatase TiO2 on rutile TiO2(110)

Growing additional TiO2 thin films on TiO2 substrates in ultrahigh vacuum (UHV)-compatible chambers have many applications for sample preparation, such as smoothing surface morphologies, templating, and covering impurities. However, there has been little study into how to control the morphology of TiO2 films deposited onto TiO2 substrates, especially using atomic layer deposition (ALD) precursors. Here, the authors show the growth of a TiO2 film on a rutile TiO2(110) surface using titanium tetraisopropoxide (TTIP) and water as the precursors at pressures well below those used in common ALD reactors. X-ray absorption spectroscopy suggests that the relatively low sample temperature (175 °C) results in an anatase film despite the rutile template of the substrate. Using ambient pressure x-ray photoelectron spectroscopy, the adsorption of TTIP was found to be self-limiting, even at room temperature. No molecular water was found to adsorb on the surface. The deposited thickness suggests that an alternate chemical vapor deposition growth mechanism may be dominating the growth process. This study highlights the possibility that metal oxide film deposition from molecular precursors is an option for sample preparations in common UHV-compatible chambers

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Measurement of the W gamma Production Cross Section in Proton-Proton Collisions at root s=13 TeV and Constraints on Effective Field Theory Coefficients

A fiducial cross section for W gamma production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb(-1) of data collected using the CMS detector at the LHC. The W -> e nu and mu nu decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.Peer reviewe