02073nas a2200181 4500008004100000022001400041245013100055210006900186260000900255300001600264490000700280520138700287100001801674700002301692700002201715700002301737856013101760 2023 eng d a1463-907600aInvestigation of Al2O3 induced variations in the structural parameters in strontium borosilicate glasses using solid state NMR0 aInvestigation of Al2O3 induced variations in the structural para cMAY  a13550-135590 v253 a

The physical properties of oxide glasses are crucially dependent on the atomistic structural speciation. In this study, we investigate the variation in the local ordering in the glass network of strontium borosilicate glasses (34.82 SrO, 51.84 B2O3, 13.34 SiO2 in mol%) with a progressive substitution of B2O3 by Al2O3 and estimate the structural parameters: the oxygen packing fraction, and the average network coordination number. The coordination of the network forming cations at various glass compositions is determined using B-11, Al-27, and Si-29 solid-state nuclear magnetic resonance (SSNMR). The SSNMR reveals that at the higher substitution of B2O3 by Al2O3 in the glass composition, the coordination network of Al3+ exists predominantly in the 4 coordinated state, the network forming B3+ cations transform from a tetrahedral BO4 to a trigonal BO3 structure, and the Q(4) form of silicates is dominant. The average coordination number and the oxygen packing fraction were calculated using the parameters obtained from the SSNMR results, and it is observed that the average coordination number decreases, and the oxygen packing fraction increases on incorporating Al. It is interesting to note that some of the thermophysical properties of these compositions closely follow the pattern shown by the average coordination number and the oxygen packing fraction.

1 aIllath, Kavya1 aOjha, Prasanta, K.1 aRath, Sangram, K.1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/investigation-al2o3-induced-variations-structural-parameters-strontium-borosilicate-glasses02819nas a2200241 4500008004100000022001400041245009100055210006900146260000900215300001400224490000700238520200900245653002302254653003102277653002302308653001702331653002002348100002702368700002202395700002002417700002302437856011702460 2024 eng d a1543-838400aIn situ monitoring of competitive coformer exchange reaction by 1H MAS solid-state NMR0 aIn situ monitoring of competitive coformer exchange reaction by  cFEB  a1479-14890 v213 a

In a competitive coformer exchange reaction, a recent topic of interest in pharmaceutical research, the coformer in a pharmaceutical cocrystal is exchanged with another coformer that is expected to form a cocrystal that is more stable. There will be a competition between coformers to form the most stable product through the formation of hydrogen bonds. This will cause destabilization of the pharmaceutical products during processing or storage. Therefore, it is important to develop a mechanistic understanding of this transformation by monitoring each and every step of the reaction, employing a technique such as H-1 nuclear magnetic resonance (NMR). In this study, an in situ monitoring of a coformer exchange reaction is carried out by H-1 magic angle spinning (MAS) solid-state NMR (SSNMR) at a spinning frequency of 60 kHz. The changes in caffeine maleic acid cocrystals on addition of glutaric acid and caffeine glutaric cocrystals on addition of maleic acid were monitored. In all of the reactions, it has been observed that caffeine glutaric acid Form I is formed. When glutaric acid was added to 2:1 caffeine maleic acid, the formation of metastable 1:1 caffeine glutaric acid Form I was observed at the start of the experiment, indicating that the centrifugal pressure is enough for the formation. The difference in the end product of the reactions with a similar reaction pathway of 1:1 and 2:1 reactant stoichiometry indicates that a complete replacement of maleic acid has occurred only in the 1:1 stoichiometry of the reactants. The polymorphic transition of caffeine glutaric acid Form II to Form I at higher temperatures was a crucial reason that triggered the exchange of glutaric acid with maleic acid in the reaction of caffeine glutaric acid and maleic acid. Our results are novel since the new reaction pathways in competitive coformer exchange reactions enabled understanding the remarkable role of stoichiometry, polymorphism, temperature, and centrifugal pressure.

10acaffeine cocrystal10acoformer exchange reaction10ain situ monitoring10apolymorphism10aSolid-state NMR1 aHareendran, Chaithanya1 aAlsirawan, Bashir1 aParadkar, Anant1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/situ-monitoring-competitive-coformer-exchange-reaction-1h-mas-solid-state-nmr02106nas a2200229 4500008004100000022001400041245008600055210006900141260000900210300001400219490000700233520136100240653001601601653001701617653002701634653001901661653001501680100002701695700002601722700002301748856010501771 2024 eng d a1543-838400aInsights into the structure of sucralfate by advanced solid- and liquid-state NMR0 aInsights into the structure of sucralfate by advanced solid and  cFEB  a1390-14010 v213 a

Sucralfate, which is a sucrose octasulfate aluminum complex, is an active pharmaceutical ingredient (API) falling in the category of cytoprotective agents which are very effective for gastric and duodenal ulcers. On interaction with stomach acid, it ionizes into aluminum and sucrose octasulfate ions to form a protective layer over the ulcerated region inhibiting further attack from acid. The mechanism of action of sucralfate in the context of its structure is not well understood. Considering that at least two forms of this API are available in the market, there are no reports on the various forms of sucralfate and differences in their pharmacological action. We characterized the two forms of sucralfate using multinuclear, multidimensional solid-state NMR, and the results show significant structural differences between them arising from variation in the aluminum environment and the level of hydration. The impact of structural differences on pharmacological action was examined by studying acid-induced Al release by Al-27 liquid-state NMR. The sucralfate, European pharmaceutical standard, Form I, undergoes faster disruption in acid compared to Form II. The difference is explained on the basis of structural differences in the two forms which gives significant insights into the action of sucralfate in relation to its structure.

10a(27)AlMQMAS10aH-1-H-1 DQSQ10apharmacological action10asolid-stateNMR10asucralfate1 aHareendran, Chaithanya1 aRavindranathan, Sapna1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/insights-structure-sucralfate-advanced-solid-and-liquid-state-nmr01871nas a2200241 4500008004100000022001400041245012500055210006900180260000800249300001400257490000800271520104600279100001801325700002901343700001701372700001901389700001601408700002101424700001801445700001601463700002301479856012701502 2025 eng d a1520-610600aInsights into the Chemical Durability and Structure of ZnO-Incorporated Sodium Borosilicate Glasses from Solid-State NMR0 aInsights into the Chemical Durability and Structure of ZnOIncorp cJUL a7349-73600 v1293 a

ZnO-incorporated NBS glasses have been studied for their application as a matrix for nuclear waste immobilization. However, structural factors affecting chemical durability have not been established. In this study, the structural changes in NBSZn glasses across various Na2O/(B2O3 + ZnO) ratios are explored using multinuclear MAS, MQMAS NMR, and EXAFS techniques. The Na MAS and MQMAS studies reveal remarkable changes in the Na environment after ZnO incorporation, which leads to an increase in chemical durability. Based on the results from NMR and EXAFS, we rationalized the structure of this glass in terms of the modified random network (MRN) model. The glass network comprises a highly polymerized region and alkali percolation channels bordered by nonbridging oxygens from the depolymerized regions. The constriction of these percolation channels increases the chemical durability of the glass. Our findings will help in the advancement of Zn-containing NBS glasses as a promising matrix for nuclear waste immobilization.

1 aIllath, Kavya1 aAnanthanarayanan, Arvind1 aBanerjee, D.1 aMishra, R., K.1 aKumar, Ravi1 aBhattacharya, D.1 aKumar, Sanjay1 aManohar, S.1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/insights-chemical-durability-and-structure-zno-incorporated-sodium-borosilicate-glasses02769nas a2200325 4500008004100000022001400041245011600055210006900171260000800240300001100248490000800259520172100267653001701988653002202005653001902027653001802046653001702064653001902081100002202100700002202122700002302144700002002167700002502187700002702212700001802239700001902257700001902276700001902295856012902314 2025 eng d a0008-622300aIonic liquid driven Refined functionalization of graphene oxide: An insight via combined experiments and theory0 aIonic liquid driven Refined functionalization of graphene oxide  cAUG a1205710 v2433 a

Functionalizing graphene and its derivative, or doping them with heteroatoms can significantly enhance their optoelectronic, photonic and bio-photonic properties; but controlled and tuneable functionalization of GO is still in their infancy. Herein, a series of functionalized graphene oxide (FGO) are synthesized solvothermally by using task specific ionic liquids (ILs) of varying alkyl chain length; 1-alkyl-3-methylimidazolium tetra fluoroborate, [Cnmim]BF4 (n = 2, 4 etc.). ILs are not only used as a solvent but also as source of fluoride ion for functionalization of GO. A drastic decrease in the oxygen containing functional groups of GO upon fluorination is evidenced by FTIR, Raman, XPS, EDX analysis and electrochemical study. Solid state 19F NMR spectroscopy indicates that, fluorination happens exclusively in edge positions, not on basal planes. Band gap of FGOs decreases along with increasing the chain length of ILs. Further, intense blue emission and high photocatalytic efficiency, using crystal violet as model dye are observed for all the FGOs under visible light. The tailored functionalization by varying alkyl chain length of IL has been rationalized by DFT calculations. It has been realized that owing to the ease of dissociation for [Cnmim]BF4 complexes with n >= 10; greater extent of fluorination/functionalization of GO has been observed. Elimination of a non-covalent interaction on increasing the alkyl chain length has been attributed for lower stability of higher chain length IL which in turn renders ease of dissociation. Easy yet controlled functionalization of GO using tuneable ILs can open a new direction in the environment friendly synthesis and applications.

10afluorination10aFunctionalization10agraphene oxide10aionic liquids10aLuminescence10aPhotocatalysis1 aKewat, Heera, Lal1 aDutta, Debangkana1 aAjithkumar, T., G.1 aChavda, Dhruvil1 aSharma, Rahul, Kumar1 aTiwari, Mrityunjay, K.1 aSidiqi, Ubaid1 aManna, Moutusi1 aNigam, Sandeep1 aGhosh, Pushpal uhttps://library.ncl.res.in/content/ionic-liquid-driven-refined-functionalization-graphene-oxide-insight-combined-experiments