Effect of calcination temperature on Cu doped NiO nanoparticles prepared via wet-chemical method: Structural, optical and morphological studies

Varunkumar, K.; Hussain, Rafikul; Hegde, Gurumurthy; Ethiraj, Anita Sagadevan

doi:10.1016/j.mssp.2017.04.009

Cited by 95 publications

(37 citation statements)

References 56 publications

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“…To further investigate the inner filter effect, the optical band gaps (E g ) of carbon dots and Ni 2+ were estimated from Tauc plot (Figure 5e and f) [57] . The Tauc plot showed that the optical band gaps of carbon dots and Ni 2+ are 5.3 and 3.8 eV, respectively, which are close the literature values [58–59] . The larger optical band gap of carbon dots confirmed that the emission energy after energy absorption was sufficient to be absorbed by Ni 2+ (Figure 5g), which is in consistency with the overlapped carbon dot emission and Ni 2+ absorption in Figure 5d.…”

Section: Resultssupporting

confidence: 75%

“…[57] The Tauc plot showed that the optical band gaps of carbon dots and Ni 2 + are 5.3 and 3.8 eV, respectively, which are close the literature values. [58][59] The larger optical band gap of carbon dots confirmed that the emission energy after energy absorption was sufficient to be absorbed by Ni 2 + (Figure 5g), which is in consistency with the overlapped carbon dot emission and Ni 2 + absorption in Figure 5d. Moreover, we believed that the functional groups of carbon dots, such as carbonyl, hydroxyl, and carboxylate groups, induced Ni 2 + via electrostatic attraction leading to effective inner filter effect.…”

Section: Ni 2 + Ion Detectionsupporting

confidence: 79%

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Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

et al. 2021

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In this work, the novel, simple Ni 2 + sensors with high sensitivity, selectivity, accuracy, practicality, and adsorption capacity were developed from the label-free carbon dots. The carbon dots were prepared from polyurethane through a onestep pyrolysis method. They exhibited excitation-independent photoluminescence and offered a fluorescence quantum yield of 24 %. They were then tested for metal ion sensing, showing selectivity towards Ni 2 + against a range of metal ions with a detection limit of 3.14 μM, the best for the carbon dots reported to date. A carbon dot-loaded paper-based sensor was also fabricated for Ni 2 + detection, showing a limit of detection of 43.3 μM. The detection of Ni 2 + in real water samples showed excellent recovery of 95.6 to 99.2 %. The selective detection of Ni 2 + by the carbon dots arose from the inner filter effect and complex formation, leading to fluorescence quenching of the carbon dots. X-ray absorption analysis further confirmed the unique interaction and electron transfer from the carbon dots to Ni 2 + . In addition to high-performance sensing, the carbon dots demonstrated high adsorbent capacity towards Ni 2 + , in which one nanoparticle could accommodate up to 182 Ni 2 + ions, equivalent to 234.8 mg g À 1 . This work demonstrates the unique sensing and adsorbent properties of polyurethanederived carbon dots towards Ni 2 + , which can be applied for simultaneous monitoring and cleaning.

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Section: Resultssupporting

confidence: 75%

Section: Ni 2 + Ion Detectionsupporting

confidence: 79%

Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

et al. 2021

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“…No SiO 2 diffraction peak was observed in the catalysts other than these. NiO and Fe 2 O 3 diffraction peaks can be supported by studies in the literature (Lu et al 2016;Lin et al 2019;Varunkumar et al 2017).…”

Section: Characterization Resultssupporting

confidence: 66%

Development of NiFeSi mixed oxide catalysts for CO methanation

2021

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NiFeSi mixed oxide catalysts were prepared using the surfactant-assisted co-precipitation method to remove the CO which may be present in the fuel before entering the fuel cell, and the catalysts were calcined at two different temperatures in order to determine the effect of the calcination temperature on the characteristic properties. Catalysts were prepared in four different NiO, Fe 2 O 3 and SiO 2 weight ratios. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N 2 physisorption, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) analysis were used to characterize the catalysts. CO methanation was done using 1% CO, 50% H 2 and the remainder He feed condition. The reaction temperature varied between the 125 °C and 375 °C. X-ray diffraction analysis showed that catalysts composed of NiO, Fe 2 O 3 and SiO 2 crystal phases. Catalysts calcined at 500 °C gave highest surface areas and their structures are composed of spherical particles on the surface. Low surface areas were obtained in catalysts calcined at 700 °C due to structural deterioration, such as small pores breaking down and combining to form large pores. Due to the increase in calcination temperature from 500 °C to 700 °C, the rod-like particles were formed from spherical particles. Activity studies were done over the catalysts calcined at 500 °C since they have highest surface area values. Between the catalysts, 0.8/0.2/1 NiFeSi mixed oxide catalyst gave the highest activity which gave 50% CO conversion at 188 °C and 100% CO conversion at T > 275 °C.

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“…Optical properties such as band gaps are smaller for nanoparticles as compared to those of bulk materials, and in general, the smaller the particle size, the smaller the gap [20], going down to a lower limit, where the trend is reversed due to confinement effects [21]. However, more parameters, such as the structural defects, impurities [22][23][24][25], and porosity [20], of nanoparticles play a role in determining band gaps, since they induce the delocalization of molecular orbitals in the conduction band edge, creating shallow/deep traps in the electronic energy and the boundaries of internal holes, which are also the sources of traps. Since morphology and size can be synthesis-controlled, a correlation has been proposed between the NiO solvothermal synthetic process and optical properties [26] as well as the calcination temperature [27].…”

Section: Introductionmentioning

confidence: 99%

NiO Pseudocapacitance and Optical Properties: Does The Shape Win?

et al. 2020

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In the present paper, we investigate the effects of alkali and operational temperature on NiO capacitive and optical properties. The NiO samples were prepared by a straightforward, surfactant-free hydrothermal synthesis, employing Ni(NO3)2 and either urea or moderately sterically hindered triethylamine (TEA). The syntheses were followed by calcinations at either 400 or 600 °C. NiO samples were characterized by XRD, scanning electron microscopy, and nitrogen adsorption isotherms. The optical properties were investigated by reflectance spectroscopy, and the pseudocapacitance was studied by cyclic voltammetry and galvanostatic charge charge-discharge measurements. We found that the synthesis with TEA yielded nanoflowers whereas the morphology of the synthesis with urea varied with the calcination temperature and resulted in nanoparticles or nanoslices at calcination temperatures of 400 and 600 °C, respectively. The NiO samples prepared at a lower temperature displayed a favorable combination of surface area and porosity that allowed for high performance with capacitances of 502 and 520 F g−1 at a current density of 1 A g−1 for nanoflowers and nanoparticles, respectively. The band gaps of all the samples were compatible with the estimated nanoparticle sizes. Finally, we used the synthesized NiO samples for the preparation of screen-printed electrodes (SPEs) modified by drop-casting and probed them against a [Fe(CN)6]3−/4− probe.

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Effect of calcination temperature on Cu doped NiO nanoparticles prepared via wet-chemical method: Structural, optical and morphological studies

Cited by 95 publications

References 56 publications

Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

Development of NiFeSi mixed oxide catalysts for CO methanation

NiO Pseudocapacitance and Optical Properties: Does The Shape Win?

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Effect of calcination temperature on Cu doped NiO nanoparticles prepared via wet-chemical method: Structural, optical and morphological studies

Cited by 95 publications

References 56 publications

Highly sensitive Ni2+ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

Highly sensitive Ni2+ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

Development of NiFeSi mixed oxide catalysts for CO methanation

NiO Pseudocapacitance and Optical Properties: Does The Shape Win?

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Product

Resources

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Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

Highly sensitive Ni²⁺ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity