Biogenic Synthesis of Tunable CoreâShell C-CaIn2O4, Interface

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A Biogenic Synthesis of Tunable Core-Shell C-CaIn2O4, InterfaceBonding, Conductive Network Channels, and Tailored Dielectric Properties Barkha Tiwari, Shanker Ram, and P. Banerji ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b03197 • Publication Date (Web): 16 Oct 2018 Downloaded from http://pubs.acs.org on October 16, 2018

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A Biogenic Synthesis of Tunable Core-Shell C-CaIn2O4, Interface-Bonding, Conductive Network Channels, and Tailored Dielectric Properties B. Tiwari1, S. Ram, and P. Banerji Materials Science Centre Indian Institute of Technology, Kharagpur, 721302, India ABSTRACT A green aloe-vera gel contains small tissues (as capillaries), which easily upload Ca2+/In3+ species (upon adding in a solution) so as to form a hybrid complex and conduct a local carbothermic reaction (on heating) in the capillaries, forming a nanohybrid C-CaIn2O4  small core-shells of a tunable carbon-shell of a few molecular layers. Thin C-CaIn2O4 plates (15-20 nm thickness) thus were grown preferentially in (200) facets in a tetragonal crystal structure on a mixed gel was burnt in camphor in air. The shell thickness was thermally etched down,  = 3  0.5 nm, by post heating at 400-600 C in air. It finely tailors dielectric properties on account of interfaces, conducting networks, multiple surfaces, and O2- vacancies/twins (induced in a deoxidizing carbon) with effectively enhanced ‘e-h+’ ion-pairs useful for supercapacitors and other devices. In a proposed model, the CaIn2O4 bonds over C-sp2 via O2- in polygons in a network of a 2D-interface Ca2+/In3+OC (  0.5 nm), which when heating exists ( 1% mass) well up to 600 °C in air. A regular monolayer is very critical of feeding a huge dielectric permittivity εr(s) ~ 6.9x106 on a moderate conductivity dc  0.8x10-4 S-cm-1 at frequency   0. After relaxing rapidly, a fairly steady εr =7.6x103 lasts of yet a usefully large value over   102 Hz. A wide plateau spans in a steady ac ~ 0.8x10-4 S-cm-1 over   103 Hz, before it booting-up progressively by nearly two orders on higher  in a frequency modulated ionic-conductor. The ‘e-h+’ pairs in a conductive network govern the conduction process over uneven and dynamic potential wells. A network as disrupts in thicker shells no longer feeds such large εr values. Keywords: Biogenic synthesis, Carbon modified CaIn2O4, Dielectrics, Hybrid nanostructures, Conducive network channels *Corresponding author e-mail: [email protected]

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INTRODUCTION Calcium indate (CaIn2O4) is a mixed-valence oxide semiconductor of a wide band-gap, Eg = 3.9 eV,1 of a spinel family AB2O4, where a divalent cation A can be replaced by a monovalent and/or trivalent (B) cation, with B = In or other IIIB group elements, rare-earths, or transition metals.2-5 As a result, it can markedly tailor its dynamic charge carriers (also spins) when made in effectively small sizes (large surfaces) binding over a synergic surface charge/spin layer of unpaired electrons in a robust core-shell, as useful for developing supercapacitors,6-8 spintronics,3,4 ferroics,2-5 opticalenergy storage,1,9 and photocatalysis9,10 of tailored surface properties. In a normal spinel,2-5 a CaIn2O4 lattice grows in double layers of InO69- polygons in a two-dimensional (2D) triangular layer separated via a single layer of Ca2+ and O2- ions. A nascent C-sp2 as promptly coordinating to metal oxides via O2-, it can feed a 2D microscopic C-O layer over them of oxide polygons in a specific pattern of their local structures. A sample C-CaIn2O4 thus contains an inbuilt Ca2+/In3+-C-O interface of a thin charge layer so as it serves as a ‘conductive through channel’ of small core-shells (capacitors). Further, the ‘C-O’ moieties cross-link the core-shells (which can be made of valuable shapes) in a network (or self-assemblies) in a ‘hierarchical superstructure’, what is it has renewed interest nowadays in decoding C(sp2) surface-modified oxides with tailored electronic, magnetic and optical properties useful for multifunctional applications.11-15 CaIn2O4 actively degrades methylene blue dye (MBD) under visible light irradiation of a wide range well up to 580 nm.16,17 MBD adsorbs and mineralizes on its facets. R3+-doped CaIn2O4 (R = Er, Ho, Tm, Pr, Nd and/or Yb) feeds an efficient up-energy conversion of green-light emitter in an ideal host of a phosphor.9,18,19 Further, Ding et al.10 observed promisingly enhanced photocatalytic activity in a CaIn2O4-graphene (G) composite in producing H2 at a high rate 62.5 mol-h-1 by splitting H2O in CH3OH on irradiating visible light. It promotes separating ‘e-h+’ ion-pairs so as to dissociate H2O on its surfaces. Thermochemical reactions in charge carriers in a liquid bath offer a simple way of grafting a thin microscopic GO/G layer on nascent facets of oxide semiconductors of 0-2D nanostructures,10,13-15,20,21 what is it is very crucial in finely tuning the interface-binding, hierarchical structure and tailored properties in a hybrid nanocomposite of small core-shells. For example, Ding et al.10 used a solvothermal reaction of CaIn2O4 and GO in ethanol in an autoclave at 180 C for 12 h, where a reducing GO  G grows onto the CaIn2O4 in a thin 2D-layer up to a few molecular thickness. Further, a natural gel of aloe-vera22-27 is shown to uniformly upload and trap 2


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metal ions (on adding in a dilute solution) in its small tissues at a molecular scale, forming an emulsion - a synergic liquid precursor. Upon heating, the species trapped in the small tissues (serve as small autoclaves) react in small reaction channels so as to ultimately grow in a stable oxide phase (e.g. In2O3,23 ZnO,24 Fe3O4,25 CoFe2O4,26 and Dy3+:Y2O327) of small 0  2D crystallites of tailored shapes at low temperature in ambient air. Biogenic cells had been exploited as small templates and a soft reductant in producing biogenic gold and silver of tailored shapes and properties out of a supersaturated metal-salt-gel complex.28 In this investigation, we illustrate a simple biogenic synthesis of a grafted C-CaIn2O4 of small core-shells and self-assemblies in a “second level hierarchical structure” by using an eco-friendly hydrothermal reaction of Ca2+/In3+ species in small tissues of a fresh aloe-vera gel followed by a self-propagating combustion of a derived mixture in camphor (a fuel) in open air. Part of hot carbon soot, which releases as a Ca2+/In3+-bio-complex disintegrates and burns in air, locally bonds over the resulting CaIn2O4 in a specific pattern of a grafted C(sp2) surface-layer via the O2- in synergic surface reactions. A hybrid C-CaIn2O4 thus forms in a single-pot reaction from a precursor gel, what is it contains long polymer cells (mainly polysaccharides, enzymes, vitamins, and polyphenols),22-28 so as to serve as a sacrificial template and a surfactant to help CaIn2O4 growing in small plates/bars, and feed a synergic C-sp2 network in the small C-CaIn2O4 core-shells. X-ray diffraction (XRD), microstructure, and phonon bands in a GO-like conjoint-network delineate the features. Uniquely, a markedly enhanced dielectric permittivity (r) develops on a moderate electrical conductivity (ac) in multiple relaxation bands in a conductive network. Critical core-shells control the features in a complex function of microwave frequencies at room temperature. EXPERIMENTAL DETAILS Synthesis of a Biogenic C-CaIn2O4 of Small Core-shells A biogenic C-CaIn2O4 was made as small core-shells in a hydrothermal reaction of analytical pure Ca(CH3COO)2 and In(CH3COO)3 in small tissues in a green aloe-vera gel as follows. A fresh gel was extracted from inner parts of green aloe-vera leaves (from a garden at IIT-Kharagpur) and any immiscible fleshes were washed away by using a specific filter (made of steel) of 50-100 m pores. The two salts were uploaded in the gel one-by-one via solutions in deionized water in avoiding any phase-separation while those mixing in a homogeneous precursor. In a typical experiment, an

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In(CH3COO)3 solution of 200 mL (taken in a 0.25 mol-L-1 concentration as per its poor solubility) was added drop-wise into a 225 mL gel by an ultrasonic stirring in a beaker at room temperature. Then, the mixture was boiled at 60-70 C in air so as it undergoes to a hydrothermal reaction and condenses its volume to nearly 25% in an In3+-bio-complex gel. A stoichiometric Ca(CH3COO)2 was admixed into it drop-wise to 25 mL (of a 1.0 mol-L-1 solution) in a similar process. Finally, a solution so obtained was dried slowly at 80-90 C in air, wherein its initial color had changed slowly from a greenish to a reddish-brownish in the Ca2+/In3+ species react in the aloe-vera gel forming a biogenic-complex. A hybrid phase C-CaIn2O4 was emerged only upon the organics had been burnt-out in a self-propagating combustion in camphor (a fuel) in open air. When pulverized in camphor (1:1 mass ratio) and dispersed in a thin layer (1-2 mm thickness) in a petit disc, it burns uniformly (on igniting) in the camphor, so as the carbon releases readily in soot in air. Any residual carbon that still lasts in a hybrid C-CaIn2O4 can be etched-out selectively by a controlled thermal annealing over 400-600 °C for 1-2 h in a flowing air. Analyses of C-CaIn2O4 Structure and Properties The XRD patterns were scanned over 20 to 80° of diffraction angle 2 by using an X-ray diffractometer (X’pertPRO PANalytical), with an X-ray beam of CuKα of λ = 0.15410 nm wavelength, in analyzing C-CaIn2O4 made of small crystallites. The data were collected at small 2intervals of 0.01° in resolving the weak peaks. Size, morphology and surface C-CaIn2O4 topology were studied with field emission scanning electron microscopy (FESEM) using a ZEISS EVO 60 FESEM at 5-20 kV acceleration voltages. High resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) and lattice images were studied of the samples mounted on a carbon coated Cu-grid, using an analytical TEM (FEI - TECNAI G2 20STWIN) operating at 200 kV. The C-sp2, as breeds a 2D-network on coherent CaIn2O4 facets, exhibits multiple D and G-bands over 1200 to 1800 cm-1 as studied by exciting the Raman spectra with a 514.5 nm Ar+-ion laser. A thermogravimetric (TG) analysis using a TG machine (TA Instruments, model TGA Q50) displays a hot C-sp2 releases successively on heating the sample over 200-700 °C in O2 gas. Dielectric and electrical properties were studied of C-CaIn2O4 pellets over 1 to 1x106 Hz frequencies at room temperature, using a LCR meter.15 To make a dense pellet, a powder C-CaIn2O4 was compacted in a 10 mm diameter (ℓ = 2.515 mm thickness) in a mold at a 200 kg/cm2 pressure and heated in microwave at 250 °C for 30 min. 4


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RESULTS AND DISCUSSION Model Reactions and Formalism of Forming Small C-CaIn2O4 Core-shells A green aloe-vera (Figure 1a) has unique biological and toxicological properties in a long history of uses as cosmetics, anti-inflammatory, wound/burn cures, ultraviolet radiation protector, antiprotozoal, among many others.22,24 Upon milling in a juicer, its green leaves (cut as small pieces) release a nectar having two major products  latex and gel dispersed in ample of water ( 95 wt%) of a cream color (Figure 1b). A nectar (cleaned free from any fleshes) we used here easily uploads Ca2+/In3+ species as a liquid carrier forming a bio-complex as follows. The Ca2+/In3+ species (while mixing in a solution) adsorb on the head-groups (usually polysaccharides in the gel22,26), travel into small tissues in the gel, and ultimately grow in an emulsion - a greenish color (Figure 1c), or a reddish-brown color (Figure 1d) on it dried in air. As a mineralizer and a complexing agent, the nectar leads to grow a Ca2+/In3+ bio-complex by hydrothermal reactions and polycondensation inside the small tissues. A charge transfer reaction18,29 proceeds in the transient colors in a dynamic process in microscopic stages over a time scale in a hydrothermal Ca2+/In3+ reaction in the small columns (tissues). A digital photo (Figure 1e) displays how a dried gel (dispersed in a fuel) burns in a flame and yields a stable C-CaIn2O4 on the byproduct species burns out in air. Hot carbon soot releasing in this process adsorbs and binds over the growing CaIn2O4 in tunable core-shells. An inbuilt shell in this way is uniquely stable so as it is burnt-out selectively in steps on tempering at 400-600 C in air. As it stacking on CaIn2O4 in layers it is what it is thinned down (on heating) successively in the stacking energy. A blackish initial sample color thus vanishes gradually on heating at these temperatures. A whitish color turns-up as soon as a layer thins down to a single molecular thickness,   05 nm. An optical micrograph of an aloe-vera gel (dried on a glass plate) in Figure 1f reveals cellular fibrils, 10-25 m lengths and an average 1 m diameter. It contains mostly polysaccharides, fatsoluble vitamins, minerals, enzymes, polyphenols, and organic acids.22,26 More than 60% mass is made-up of polysaccharides - a major phase. In a model reaction scheme, polysaccharides react with Ca2+/In3+ species {Figure 1(g, h)} on their reactive surfaces with H-bonding via ‘OH’ headgroups (marked in ‘’ signs) lying along their chains in a cellular structure. As a molecular template, the ‘OH’ head-groups thus order Ca2+/In3+ species in a skeleton of polysaccharides of cellular chains. The process follows hydrolysis, polymerization and polycondensation of reaction 5



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species in the form of a hydrogel. As depicted in Figure 1i, a molecular complex as scaffolds about its chain on due reactions it traps the Ca2+/In3+ in a polymeric cell (on the chains spiral and join in groups in this shape) and keeps them order via O2- in a stable phase CaIn2O4, what is it bonds over C-sp2 as a surface layer. In this experiment, the Ca2+, In3+ and O2- species have a hydrothermal reaction in the cells of a complex gel on heating in air. A spinel CaIn2O4 grows as Ca2+/In3+ order via O2- in InO69- bilayers separating by CaO46- mono-layers in a joint network (Figure 1j). Both kinds of the polygons can feed over a C-sp2 network via ‘C-O’ bonds as a C-CaInO4 core-shell (Figure 1k). Different charge-densities in the ionic-cadges render the local charges flow via rather conducting surface channels of unpaired C-sp2 electrons (spins), resulting in markedly tailored e-h+ transport-prosperities in a stable hybrid phase as follows. X-ray Diffraction and Phonons in Small C-CaIn2O4 Core-shells The C-CaIn2O4 has preferentially grown in small core-shells of (200) facets in a tailored XRD of a well-known CaIn2O4 tetragonal (t) crystal structure (141/amd space group30). For example, a typical XRD (Figure 2a) from an annealed C-CaIn2O4 at 600 C for 2 h in air (sample-3) reveals markedly tailored peak positions and intensities relative to those (Figure 2b) of a bulk CaIn2O4 prepared in a solid state reaction30). A normalized value Ip = 100 of a maximum peak intensity arises in (200) peak at interplanar spacing d200 = 0.3015 nm instead of (211) peak at 0.2674 nm in the bulk sample, which has only a weak (200) peak (Ip = 3.4) at 0.3107 nm. Figure 2c displays a cross-section of CaO46- and InO69- polygons in a ratio 1:2 with nearly 35% O2- vacancies in an ionic ratio 1:2:4 in a CaIn2O4 lattice. The HRTEM images confer a preferentially grown C-CaIn2O4 of thin plates in (200) planes bound in a (311) surface (sharing the second most intense XRD peak at 0.1869 nm) in support of a biogenic template. In Table 1 are given dhkl, Ip and (hkl) values observed in XRD peaks in the sample-3. The dhkl values calculated by average lattice parameters a = 0.6021 nm and c = 0.9932 nm reproduce the observed values within an error 0.0005 nm in the major peaks. A compressive surface C-sp2 layer lowers CaIn2O4 lattice volume Vt = 0.3601 nm3 (density t = 6.155 g-cm3) over a bulk value Vt = 0.3800 nm3 (t = 5.833 g-cm3). The XRD (Figure 2a) contains a few weak peaks of an orthorhombic (o) phase (roughly 5-10%) in a lower o = 5.646 g-cm3 (Vo = 0.3924 nm3) than the t-phase, or a known o-CaIn2O4 of o = 6.33 g-cm3 (Vo = 0.3500 nm3).30,31 A polymorphic t  o turns-up on releasing a bonded surface layer.

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As a shell thinning down,   3 nm, the Vt gradually restores (Table 2), with due shifts (also tailored intensities) of the XRD peaks (Figure 2 and Figure S1) over lower 2-values in an as-burnt C-CaIn2O4 sample-1 was heated at 400-600 C in air. A magnified view of XRD in Figure 3(a, b, c) displays how (200) and (103) peaks modify their intensities and shift over lower 2-values in the CCaIn2O4 growing (on heating) preferentially in (200) planes in a thin plate (Figure 3d). A thermal anneal causes (i) a C-sp2 surface layer desorb-off gradually, (ii) a hot C-sp2 reorder on adjoined CaIn2O4 facets, (iii) a bare CaIn2O4 to be growing-up slowly, and (iv) a surface CaIn2O4 alloying in a local reaction with C-sp2 at the above temperatures. Thus, a depressed d200 = 0.3001 nm in (200) peak in the sample-1 (t = 6.256 g-cm3) successively restores to 0.3005 nm in a 400 C-annealed sample-2 (t = 6.215 g-cm3), or 0.3015 nm in a 600 C-annealed sample-3 (t = 6.155 g-cm3). The other (103) peak shifts similarly as an initial  ~ 3.0 nm (sample-1) is decreased to 1-2 nm in the sample-2, or  0.5 nm in the sample-3. As given in Table 2, a C-sp2 shell is depressing the CaIn2O4 along its c-axis in a reduced tetragonality, with c/a = 1.6450 in the sample-1, which is restored to 1.6474 in the sample-2, or 1.6496 in the sample-3, as it thins down on the core. A bulk CaIn2O4 has a far lower c/a = 1.5838 (t = 5.833 g-cm3). The c/a value, as controlling an angle  (62.2 in a bulk CaIn2O4) at (103) plane inclines on (200) plane in a crystal, facilitates C-CaIn2O4 growing-up in (200) facets by reducing  = 61.3  61.2 (samples-1-3) in a way a residual strain releasing over the adjoined facets. In Figure 3d, (200) peak intensity I200/I103 is thus progressively grown by as much as 3.3 times an initial value 1.62 (sample-1). Assuming an X-ray beam incident at an angle on a (200) zone axis, a thin C-CaIn2O4 plate preferentially grown in this way shares a concurrently enhanced XRD cross-section of (200) surfaces in Figure 3e. A model CaIn2O4 contracts in Figure 1k over its In-O and Ca-O bonds on co-bridging to C-sp2 via C-O bonds on its facets in a 2D-network. It yields a microstratin  = 0.85 % in the sample-1, which is cured successively to be 0.65 % in the sample-2, or 0.43% in the sample-3. Asymmetric broadening () in the XRD peaks is used to evaluate  in the Williamson-Hall plot,32  = cos (Dsin)-1. An average crystallite size D = 15 nm thus obtained in the sample-1 is grown a merely to 16 nm in the sample-2, or 20 nm in the sample-3, as the surface layer was successively heatedout in air. Evidently, the shell acts as a ‘compressive layer’ and a ‘grain-growth inhibitor’ in the small C-CaIn2O4 core-shells. Otherwise, small crystallites often expand in volume in a high Gibbsfree-energy above the equilibrium bulk value.5,33 7



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A joint C-CaIn2O4 network reveals a wide group of Raman bands (C=C stretching) in Figure 4(a, b, c). A single D-band known of 1329 cm-1 in graphene34 is split in three distinct bands overlapping one another at 1345, 1400 and 1480 cm-1 in the sample-1; likely in three major C-sp2 networks exist on CaIn2O4 facets  most likely (200), (213), and (311) as shown in HRTEM images of small C-CaIn2O4 plates. Nevertheless, only a single G-band (of 1591 cm-1 in graphene34) spans in an average frequency of 1618 cm-1 (a merely enhanced to 1620 cm-1 in the sample-2, or 1625 cm-1 in the sample-3) in a C-CaIn2O4 network oscillating coherently in GO-type polygons. Also C-Fe3O4 core-shells keep only a single G-band (~1590 cm-1) even on varying -values.35 As part of the C-sp2 releasing on heating the samples-2, 3, the multiple D-bands reorder in the ‘phonon C-sp2 density of states’ over 50-80 cm-1 lower values on CaIn2O4 facets. Further, a band is grown at 1255 cm-1 in the sample-2, or 1285 cm-1 in the sample-3; likely InO6  InO3 tripods convert on hot CaIn2O4 facets in reacting to C-sp2 species. Part of hot C-sp2 induces an ‘alloyed In2O3–C surface’ of CaIn2O4 that is what it finely tailors the electronic properties as will be described later. As shown in Figure 4(d-g), a tripod ‘InO3’ can breed a stable network with C-sp2, C-O and C=O species in different ways. As boroxol rings ‘B3O6’ of B2O3 (of the In2O3 group IIIB), an indoxol ring ‘In3O6’ of three ‘InO3’ tripods in a hexagon (Figure 4g) accounts in a group of three In-O stretching bands of reasonably smaller frequencies, 1200-1400 cm-1 (as per a larger In3+ mass than B3+), over that of 1240,1365 and 1495 cm-1 in B2O3.5,36 A weak C=O stretching band lasts at 1730 cm-1 in a functionalized CaIn2O4-CO surface layer unless heating it out at  600C in open air. Microstructure in small C-CaIn2O4 Core-shells The C-CaIn2O4 stands well stable in small core-shells in open air. Only a small mass-loss,  0.8 %, is marked over 100-300 C (step-1) in TG-DTG curves {Figure S2(a, b)} in free carbon/functional groups (C=O, COOH, or CHO at surfaces5,15) burn out as gases on heating a sample-1 in a carrier O2 - 40% N2 gas. Also any adsorbed gases in fine pores/surfaces (as shown in N2 adsorptiondesorption in Figure S3) release in this regime. The carbon binding to CaIn2O4 as a shell is quite stable so as it releases in successive steps 2  4 over 300-680 C, with total 4.2% mass–loss, before a local transformation, InO6  InO3 + 3/2O2, incurs in bared facets (on the carbon releases) with ~ 0.3 % mass-loss over 680-800C (step-5). In the models (Figure S2(c-e), a C-CaIn2O4 surface layer bridging via C-O bonds is releasing in a sequence of its average -value, stacking energy, and interface-bonding on the oxide facets. In a critically hot surface, a network modifies in InO3-C and 8


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In3O6-C polygons {Figure S2(d, e)}. Ultimately, any residual carbon releases in a prominent DTG peak at 670 K in a network dissociates rapidly (step-4), and a resulting In2O3 evaporates in a weak DTG peak at 780 C (step-5). Uniquely, a hybrid C-CaIn2O4 grown in situ in small core-shells here in a biogenic process has a high degree of stability. Otherwise, a bare GO releases its 30% mass over 150-300 C in N2 gas.6 An elemental mapping studied with energy dispersive X-ray (EDX) spectra of the samples confers a duly uniform Ca2+, In3+ and O2- distribution in a due 1:2:4 ratio, as given in Figure S4 for a master sample-1. FESEM images in Figure 5a display how tiny C-CaIn2O4 embedding in a ‘hierarchical composite structure’ of well-separated films (15-20 nm thickness) in this sample-1. As soon as the carbon films burnt out at 400 C in air, a bared C-CaIn2O4 appears in plates/prisms (w = 20-40 nm widths and  = 10- 20 nm depth) binding over a refined carbon layer in a bright peripheral ( = 1-2 nm) in Figure 5(b, c). A refined C-CaIn2O4 in this way has a more intact C-sp2 binding via C-O bonds in a regular 2D-network. On heating, it cross-links via C-O bonds into small chains (Figure 5d). A closer view of such entities in HRTEM in Figure 5(e, f) displays small CaIn2O4 prisms (w = 8-10 nm) binding over a carbon shell ( < 1 nm). Figure 5g displays a carbon film embedding C-CaIn2O4 in a dispersed phase. An exfoliated GO film (150-250 nm wide and 300600 nm long) in Figure 5h looks transparent in a few nanometers thickness, with a SAED of two halos of radii r1 = 0.3575 nm and r2 = 0.2105 nm from its (002) and (101) crystallographic planes. In a due O2- inclusion in a GO network, it is markedly stretched over d002 = 0.3356 nm and d101 = 0.2034 nm in a pure graphite.30 A C-sp2 network expands in bonding to O2- on metal oxides as observed in softer phonons of Raman bands. Figure 6a displays HRTEM images of C-CaIn2O4 (sample-3) binding one another via distinct In-C-O interfaces ( ~ 0.8 nm) in a ‘microscopic network’. A lattice image (Figure 6b) from one of its plates A confers it is grown as a single crystal in (200) planes, d200 = 0.3010, with a visible shell of a magnified view in Figure 6c. It exhibits a SAED (Figure 6d) of (004) arrays, d004 = 0.2485 nm, using an electron beam incident along a [200] axis  the (004) planes. A few twins (T) are marked at off-positions of the regular spots, likely in O2- vacancies created in a redox C-sp2 reaction at  400 C in air. Further, as reported in C-coated ferrites5 and gold,37 a C-CaIn2O4 interface exhibits diffraction fringes as briefed in Figure S5. Both the surface binding and Ts play a critical role in finely tuning the dielectric properties as follows. 9



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Dielectrics and Conductivity in Small C-CaIn2O4 Core-shells A hybrid C-CaIn2O4 (a molecular network of 2D-triangular CaO-In2O3 layers2-5) tailors its dielectric features over its basic oxides of an insulator CaO (Eg = 7.1 eV and dielectric permittivity r(∞) = 11.8)38 and a semiconductor In2O3 (Eg = 2.75 eV and r(∞) = 4.1)39 as binding the C-sp2 over its top oxide layers - a tunable core-shell structure. Small core-shells C-CaIn2O4 not only store surface charge carriers in multiple 2D-layers, but also feed ionic vacancies, Ts, and interstitial species in the core, tailoring dynamics of the charge carriers (Ca2+, In3+, O2- and dopants) in three microscopic domains  core, interface, and shell. Localized e-/h+ charges thus stay in multilayers (an antenna) as a ‘supercapacitor’. An interface tunnels an e-/h+-conduction as a ‘microscopic through channel’, what is it promotes both r() and ac() in an interfacial polarization over those of the space charges in a local field induced charge reordering at varied frequencies (), up to 106 Hz in this work. A value r() = ԑ'-jԑ''  Csℓ ÷ εoA was measured from a C-CaIn2O4 pellet of capacitance Cs and contact area A = 0.785 cm2 (ℓ = 2.515 mm), where ε′ and ε″ are its real and imaginary parts, and ԑo = 8.854x10-12 F/m is the free space permittivity. Figure 7(a, b, c) plots a static ԑr(s) value as large as 6.9x106 as   0 (band-1) on account of a molecularly thin shell (sample-3), which decays rapidly at higher -values ending-up a fairly steady r(∞) ~ 8x103 at  > 102 Hz (bands-2  5). The r(∞) drops by two orders on a thicker shell,  = 2-3 nm (sample-1), in a different process in three bands-1, 2 and 3  5. As given in Table 3, the r(∞) stands to be 1 to 3 orders larger from those of CaO,38 In2O3,39 or a spinel MgAl2O4 (ԑr  14 at   106 Hz).40 Unfortunately, no data is available on CaIn2O4 to make a direct comparison of the values. At small   10 Hz, the surface charges rapidly polarize over the core (space charges) in a fairly enhanced ԑr value at a 106 scale. On higher frequencies, an electro-coupling to the core weakens in a ‘joint-oscillation’ in the fields, so only a bulk ԑr value prevails in slowly relaxing electric-dipoles. A local field induced electron-hopping in mobile charges between the electrodes gives a residual ԑr value in the bands-3  5. A core-shell C-CaIn2O4 promptly tunes  and  values in multiple frequency bands in the samples-1-3 (Figures S6 and S7). In the sample-1, the  values exhibit a prominent peak at a critical frequency c = 5.6x105 Hz, while only a diffused peak arises in the  values at c = 1.4x105 Hz, in a tailored shell controlled dynamics of charge carriers. These features result in a conductive network of small core-shells. A maximum ԑr value (bands-1, 2) 10


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11

observed on a moderate ac ~ 1x10-4 S-cm-1 over   103 Hz in the sample-3 (Figure 8) is reduced by an order on an order of enhanced ac value in an effectively thicker shell in the sample-2. Both the ԑr and ac values collapse as a thicker shell (sample-1) no longer so firmly couple to the core in a regular network. Thus, an interface of only a few atomic layers (conductive channels) is critical in finely tuning these properties in the small core-shells. Two well-separated bands-2 and 3  5 of dielectric-loss (tan = /) appear over frequencies (Figure 9) in a conducting network of C-CaIn2O4 core-shells in the samples-2, 3. A Jonscher’s power law,41 ac = dc + An, where σdc is the dc conductivity (  0), fits the frequency ac plots in Figure 8 in a dispersion parameter A and a dimensionless exponent n. As n  0, it accounts in the interaction in an ideal ‘Debye dielectric’ of dipolar-type, while an ‘ideal ionictype dielectric’ at n  1. Arbitrary values n = 0.358 and A = 1.49x10-5 fit the plot in the sample-1, while n = 0.527 and A = 4.88x10-7 that in the sample-3. A reasonably larger A = 1.09x10-2 on an order of lower n = 0.071 traces a solely modified plot in a slowly increasing ac over frequencies in a primarily dipolar-type ‘Debye dielectric’ on a better conducting network in the sample-2. Thus, a hopping of dynamic charge carriers through uneven potential wells briefs a complex conduction process in a ‘conductive network’ of the small core-shells. The Nyquist plots in Figure 10 confer a conducting C-CaIn2O4 network of the core-shells finely tailoring the impedance resistance Z and Z over frequencies in the multiple bands-1  5 in an elliptical trajectory stretched along the Z-axis. A reasonably large elliptical curve is obtained in the sample-1 in an average larger resistance as per lower ac values (Figure 8a) over the frequencies in Figure 10a. Uniquely, the plot traces a straight line (band-1) at low frequencies up to 10 Hz, before an elliptical curve takes over (primarily in the core resistance) at higher frequencies (bands-2  5) in a progressively induced ac (Figure 8a) in recurring relaxations of the charge carriers. In the Debye theory, we express a complex impendence resistance as,41

z r  z   jz   z  

z s  z , 1 j

(1)

where Zs, Z∞ and  are the static Z-value, Z-value at   ∞, and relaxation time, respectively. From Eq. (1), one can deduce that

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z s  z 2 , 1   

(2)

 z s  z   , and 2 1  

(3)

z   z  2  z 2  z s  z  2 .

(4)

z   z 

z  

Thus, Eq. (4) describes a semicircle of Z versus Z plot in a Debye dipolar relaxation. Three distinct elliptical curves comprise the experimental plot in Figure 10a in a ‘hybrid composite’ of recurrent charge carriers. Multiple semicircles were observed recently in C-LiMnPO415 and CFe3O435 core shells. The recurring relaxation processes are a key factor of promoting the dielectric properties in a network of small core-shells of multiple surfaces. A large elliptical path of the Nyquist plot in the sample-1 is rotated up the Z-axis by an angle  ~ 11, while it has an order of lower radius of its curvature in the samples-2, 3 (Figure 10). A distorted catenary is traced over Z (  8) in three overlapping bands-2 , 3, 4 in the sample-2 has an order of larger ac values in a better conductor. A pretty symmetric ellipse is obtained in a group of two-circles-1, 2 displacing one after other in the sample-3. The first two-ellipses-2, 3 shown as a catenary (sample-2) are merged in a single circle-1, while its part of an ellipse-4 is grown in a circle-2 extending in a linear path (band-5). A merely single semicircle is known with a straight line inclined over   0 (band-1) in few metal-oxides14,42 or alloys43 of small core-shells. In view of dispersing ԑr, tan, ac, and Z/Z values in multiple bands (Figures 7-10), a sample C-CaIn2O4 owes four types of charge carriers (i) space charges of primarily O2-ions/vacancies/twins, (ii) decoupled e/h+ pairs in the conducting channels, (iii) ionic species of multiple valences in the interfaces, and (iv) C-sp2 electrons/spins (as a spintronic conductor). They render frequency driven electronic properties in a complex function of their multiple dynamics and relaxations in three microscopic bands (core, shell, and joint interface). Qualitatively, rather low ac values last in a wide plateau of frequencies well up to 10 kHz in the sample-1 (~1 kHz in the sample-3) in a multilayer capacitor. A Nyquist plot is stretched in an elliptical shape along its Z-axis in account of a core-shell of a series combination of two parallel joined resistance and capacitance.14,15 Small C-CaIn2O4 core-shells of a critically thin C-sp2 shell are thus promptly tuning a wide frequency plateau of small ac values with usefully enhanced r values in a hybrid dielectric phase. 12


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CONCLUSIONS A biogenic complex of Ca2+/In3+ species dispersed in a natural aloe-vera gel is explored to obtain a stable C-CaIn2O4 of tunable core-shells by hydrothermal reactions in its small tissues at moderate temperature  a facile biogenic synthesis. A mixed gel (dried in air) when finely pulverized in camphor, dispersed in a thin layer (1-2 mm thickness), and ignited, it burns in a self-propagating flame with the camphor in air, forming a sample C-CaIn2O4. Part of a hot carbon soot releasing as the sample burns in air, adsorbs and reacts on nascent CaIn2O4 in a C-sp2 surface layer. A finely tunable core-shell is grown in situ in this process in functional properties. It thins down in layers as a master C-CaIn2O4 sample-1 is heated at 400-600 °C in air. The results are characterized with XRD, HRTEM, SAED, and lattice images of the samples prepared of small C-CaIn2O4 core-shells. A group of D-bands of 1345, 1400 and 1480 cm-1, a single G-band of 1618 cm-1, and a C=O stretching at 1730 cm-1 (the Raman bands) account in a GO-like shell ( ~ 3 nm) in the sample-1. A thinner shell confines in a 2D-network of D-bands of lower energies (up to 1255 cm-1 as   1), while the G-band rises-up a maximum to 1625 cm-1 (  0.5 nm). A core-shell C-CaIn2O4 stores charges in layers in a fairly enhanced density  a ‘supercapacitor’ of promptly tailored ԑr and ac in multiple electronic bands-1  5 over 1 to 106 Hz. A thin critical shell (  0.5 nm) feeds a huge ԑr(s) ~ 6.9x106, as   0, on a moderate dc  0.8x10-4 S-cm-1. After decayed rapidly, a static ԑr()  7.6x103 extends over   102 Hz (bands-2  5) at outset of nearly two orders of enhanced ac values at   ∞. Adversely, a ԑr() value falls-down by three-to-two orders as surface charges delocalize in a thicker shell. A static r(∞) lasts to be two-to-three orders larger than the basic CaO/In2O3 values, or a spinel MgAl2O4 (ԑr  14 at   106 Hz).40 The results open scope of developing (i) a conductive C-sp2 network in oxides, (ii) dynamics of charge carriers in multiple bands, and (iii) correlated properties useful for applications.  ASSOCIATED CONTENT S

Supporting Information

The supporting information is available free of charge on the ACS publication website. XRD patterns, N2 absorption-desorption, elemental mapping, TG-DTG curves, HRTEM images, and dispersions of ε′ and ε″ values (in multiple bands of charge carriers over frequencies)

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for C-CaIn2O4 of small core-shells. The shell thickness is critically tuned from 3 nm to 0.5 nm by heating a master sample-1 at 400-600 C in air (PDF).  AUTHOR INFORMATION Corresponding Author *Email: [email protected]. Phone: (091) 8145693155. Fax: (091) 3222-282274/282700

ORCID S. Ram: 0000-0001-5801-2758. Author Contributions The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest.

 ACKNOWLEDGMENTS The authors gratefully thank the Ministry of the Human Resource and Development, Government of India, for in part of the financial support.  REFERENCES 1. Liu, X.; Li, C.; Quan, Z.; Cheng, Z.; Lin, J. Tunable luminescence properties of CaIn2O4:Eu3+ phoshors. J. Phys. Chem. C 2007, 111(44), 16601-16607, DOI 10.1021/jp074868o. 2. Xu, X. S.; Groot, J. de.; Sun, Q.-C.; Sales, B. C.; Mandrus, D.; Angst, M.; Litvinchuk, A. P.; Musfeldt, J. L. Lattice dynamical probe of charge order and antipolar bilayer stacking in LuFe2O4. Phys. Rev. B 2010, 82, 014304-1-8, DOI 10.1103/PhysRevB.82.014304. 3. Groot, J. de.; Mueller, T.; Rosenberg, R. A.; Keavney, D. J.; Islam, Z.; Kim, J.-W.; Angst, M. Charge order in LuFe2O4: an unlikely route to ferroelectricity. Phys. Rev. Lett. 2012, 108(18), 187601-1-5, DOI 10.1103/PhysRevLett.108.187601. 4. Lafuerza, S.; García, J.; Subías, G.; Blasco, J.; Martín, J. H.; Pascarelli, S. Electronic states of RFe2O4 (R = Lu, Yb, Tm, Y) mixed-valence compounds determined by soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism. Phys. Rev. B 2014, 90, 245137-1-13, DOI 10.1103/PhysRevB.90.245137. 5. Misra, S.; Karan, T.; Ram, S. Dynamics of surface spins in small core-shell magnets of Li0.35Zn0.35Fe2.35O4 bonds over a carbon surface and tailored magnetic properties. J. Phys. Chem. C 2015, 119 (40), 23184-23195 DOI 10.1021/acs.jpcc.5b04635.

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(e)

(b)

(a)

(c)

(d)

As-burnt Burning

Annealed

(f)

(g)

Calcium acetate

Indium acetate

5 m

Poly(saccharides) (C6H12O6)n, n = 3

H2O

H C O Ca In

(i) Template

(h)

Carbon

AO4 unit BO6 unit

A B B

B

B A

B

B A

(j)

(k)

Figure 1. (a) An aloe-vera plant, (b) a nectar from its leaves, (c) a nectar uploading Ca2+ and In3+ species, (d) a dried gel after (c), and (e) as-burnt and annealed C-CaIn2O4 in air. (f) An optical micrograph (b), (g) basic reactants, (h) polysaccharides capping Ca2+ and In3+ in (i) a cell, and (j) a spinel AB2O4 bonding over (k) carbon via its AO4 and BO6 polygons.


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(200)

(c) CaIn2O4 network

20

30

(423) (008)

(404)

(420) (421)

(314) (400) (410) (402) (330)

(224) (215)

(312)

(310) (311) (005)

(213)

(131)*

40

50

60

(413) (422) (404) (325) (316) (501)

(004)

(202)

(220) (213) (301) (204) (105) (312) (303) (321) (224) (215) (400) (314) (411) (206) (305)

(b)

(112) (200)

(103)

(211)

(220)* (102)

(410)*

(a)

(211)* (004)

Ca In O O (vacancy)

(103)

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


70

Diffraction angle 2 (degree)

80

Figure 2. XRD patterns of (a) refined C-CaIn2O4 core-shells and (b) bulk CaIn2O4 (after JCPDS file 01-071-3853 in Ref. 30) of a tetragonal crystal structure, with (c) a structural unit of a CaIn2O4 network.



(200)

I200/I103

[200]

[200] a

61

(100)

(103)

(d)

c

(e)

 Diffraction (103) (200) (013)

X-ray

(f)

b

(200)

Preferential growth

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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 (013)

(200)



(103)

(103)

(c) (b)

(a)

29.0

29.5

30.0

30.5

31.0

Diffraction angle 2 (degree)

31.5

Figure 3. XRD in (200) peak growing over (103) peak in intensity and shifting over lower 2 values in a preferential growth in annealing (a) an as-burnt C-CaIn2O4 at (b) 400 °C and (c) 600 °C in air. (d) Relative peak intensities, (e) projections of the two planes, and (f) a diagram showing XRD from a (200) plate.


Page 21 of 31

1625 1370

1285

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1465

1365

1620

1255

1470 1735 1618

(b) 1400

(c) 1200

1480

1345

(a)

1730

1300

1400

1500

-1

1600

1700

Raman shift (cm )

(d) InO3 tripod

(e) In2O3 chain InO3 –C unit (f) In2O3-C network O In

(g) In2O3-C network

In3O6-C unit

Figure 4. Raman bands in a C-sp2 surface layer reordered on heating (a) a C-CaIn2O4 sample1 at (b) 400 C and (c) 600 C in air for 2 h. The models illustrating how (d) a tripod InO3 breeds a network of (e) In2O3 and (f, g) a hybrid In2O3-C on InO3-C and derived In3O6-C (hexagonal ring) units in a surface layer.



(a)

Page 22 of 31

(c)

(b)

Layer

35 nm

50 nm

500 nm

100 nm

(e)

(d)

A

200 nm

50 nm

(g)

(f)

(h)

r2 r1

Carbon layer

A 25 nm

25 nm

150 nm

Figure 5. FESEM images in (a) a C-CaIn2O4 sample-1 heated at (b, c) 400 C and (d) 600 C in air for 2 h. HRTEM images showing (e, f) C-CaIn2O4 prisms (sample-3), (g) a carbon film embedding CaIn2O4, and (h) an exfoliated carbon film with SAED (sample-2).


Page 23 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b) 0.8 nm Layer

0.8 nm 0.8 nm

T

0.3010 nm

(200) Arrays (200)

Layer

Layer

A 5.0 nm

(c)

A Arrays

T T

T

(004)

3.1 nm

(d)

A

Boundary

0.3010 nm

(200) Arrays

1.0 nm

Figure 6. (a, b) HRTEM images of thin C-CaIn2O4 plates (sample-3) grown of core-shells along (200) planes in a network via interfaces, with (c) SAED (T : twins) and (d) magnified images from part of (a) plate A containing an interface layer.



6 x 10

7 A

x 103

(c)

6

2.0

5

A

1.5

4

1

r - value

1

r - value

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 31

1.0

(a)

3 0.5 2

2

2

B

C

3-5

D

0.0

1

0

A

0

1

10

10

B

(b)

2

10

3

4

10

5

10

10

Frequency (Hz)

2

D

3-5

C

6

10

1 0

10

1

10

2

10

3

10

Frequency (Hz)

4

10

5

10

Figure 7. Dispersion of εrvalues in multiple bands-1  5 over frequencies in small CCaIn2O4 core-shells on tailored -values (a) 2-3 nm, (b) 1-2 nm, and (c)  0.5 nm.


6

10

Page 25 of 31

-3 x 10

2

25

ac (S-cm-1)

-1

ac (S-cm )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

x 10-3

20

Band-5

15

4, 5

(b)

10

3 2

5

1 0

0

1

10

10

3

10

10

4

5

10

Band-5

6

10

Frequency (Hz)

10

Band-4

Band-2

(c) Band-1

0

2

Band-3

(a) 0

10

1

10

2

10

3

10

Frequency (Hz)

4

10

5

10

Figure 8. Dispersion of σacvalues (continuous curves fit the points in the Jonscher’s power law) in multiple bands-1  5 over frequencies in small C-CaIn2O4 core-shells on tailored values (a) 2-3 nm, (b) 1-2 nm, and (c)  0.5 nm.


6

10


tan

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 31

40 Bands-1, 2

30

20 Bands-3  5

(a) A

10

Bands-1, 2

(b)

Bands-3  5 B

0

(c)

Band-1

0

10

10

1

D

C

10

2

10

3

Frequency (Hz)

10

4

10

5

Figure 9. Dispersion of tan in multiple bands-1  5 over frequencies in small C-CaIn2O4 core-shells on tailored -values (a) 2-3 nm, (b) 1-2 nm, and (c)  0.5 nm.


10

6

Page 27 of 31

30

2.5

2.0

(c)

1.5

1.5

3, 2

5, 4

1.0

(b) 3

1.0

22

0.0

5

0.0

0.5

1.0

15 10

(a)

5 (b)

0.0

1 1.5

2.0

Z' (M  )

2.5

2

4

0.5

0.5

20

0

-Z'' (M)

25

-Z'' (M)

2.0

-Z'' (M)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.0

4

0.5

3.0

1.0

8 1.5

3

5, 4

2

2.0

Z' (M  )

1

2

2.5

B

(c) A

11

1

C

0

5

10

15

Z' (M)

20

25

Figure 10. The Nyquist plots dispersing in multiple bands-1  5 over frequencies in small CCaIn2O4 core-shells on tailored -values (a) 2-3 nm, (b) 1-2 nm, and (c)  0.5 nm, with (b, c) magnified plots in the insets.


30


Page 28 of 31

Table 1. Interplanar spacings (dhkl) and relative intensities (Ip) in XRD peaks in preferentially grown C-CaIn2O4 of small core-shells (plates) in (200) facets (annealed at 600C in air)

dhkl (nm) Observed

Calculated

0.4125* 0.3825 0.3015 0.2906 0.2828* 0.2518* 0.2480 0.2272* 0.2086 0.1983 0.1904 0.1869 0.1784 0.1618 0.1598 0.1517 0.1505 0.1465 0.1437 0.1419 0.1351 0.1334 0.1291 0.1247 0.1238

0.4131* 0.3831 0.3011 0.2901 0.2823* 0.2518* 0.2483 0.2272* 0.2089 0.1986 0.1904 0.1870 0.1778 0.1616 0.1599 0.1511 0.1505 0.1460 0.1441 0.1419 0.1346 0.1334 0.1287 0.1247 0.1242

Ip

h

k

l

1 8 100 23 9 15 22 24 24 3 27 35 11 5 14 18 5 1 10 3 1 2 7 2 3

2 1 2 1 4 2 0 1 2 0 3 3 3 2 2 3 4 4 4 3 4 4 4 4 0

2 0 0 0 1 1 0 3 1 0 1 1 1 2 1 1 0 1 0 3 2 2 0 2 0

0* 2 0 3 0* 1* 4 1* 3 5 0 1 2 4 5 4 0 0 2 0 0 1 4 3 8

The dhkl are calculated in a tetragonal lattice, a = 0.6021 nm and c = 0.9932 nm. *An orthorhombic phase (a = 1.1632 nm, b = 1.1735 nm and c = 0.2875 nm). The Ip values are normalized over a maximum value 100 in (200) peak.


Page 29 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. A high pressure effect of an inbuilt C-sp2 surface layer on structural parameters in preferentially grown C-CaIn2O4 of small core-shells (plates) in (200) facets C-CaIn2O4 Sample-1 Sample-2 Sample-3 Bulk*

Lattice parameters (nm) a c c/a 0.5994 0.6004 0.6021 0.6214

0.9860 0.9891 0.9932 0.9842

1.6450 1.6474 1.6496 1.5838

D (nm)

Vt (nm3)

δ (nm)

ρ (g-cm-3)

 (%)

15 16 20 ---

0.3543 0.3566 0.3601 0.3800

2-3 1-2 ≤ 0.5 ---

6.256 6.215 6.155 5.833

0.85 0.65 0.43 -----

*The values are reported from JCPDS file 01-071-3853 in ref. 30.



Page 30 of 31

Table 3. Dielectric and electrical properties in preferentially grown C-CaIn2O4 of small coreshells (plates) in (200) facets C-CaIn2O4

Ԑr(s)

Ԑr()

σac() (S-cm-1)

σac(0) (S-cm-1)

Sample-1

2.1x103

0.6x102

0.7x10-3

0.9x10-5

Sample-2

0.6x106

7.5x103

2.2x10-2

1.9x10-3

Sample-3

6.9x106

7.6x103

2.1x10-3

7.9x10-5

The values σac() and Ԑr() are reported at 106 Hz frequency.


Page 31 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC

[200]

61

(100)

H2O

(103) (200)

[200]

I200/I103 b

c

Growth

A model microscopic structure of a biogenic complex capping Ca2+/In3+ in polysaccharides and a preferential (200) growth of C-CaInO4 core-shells.


Biogenic Synthesis of Tunable CoreâShell C-CaIn2O4, Interface

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