Arrays of nanorods composed of ZnO nanodots exhibiting enhanced UV emission and stability

Yin, Yunfei; Sun, Ye; Yu, Miao; Liu, X.; Yang, Bin; Liu, D.; Liu, Shiqiang; Cao, Wenwu; Ashfold, Michael N. R.

doi:10.1039/c4nr01558d

Cited by 9 publications

(9 citation statements)

References 51 publications

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“…We have recently proposed 22 that ZnO nanodot formation during TEOS treatment of thin ZnO nanorods ( prepared using similar growth conditions (0.002 M concentrations of HMT and Zn(NO 3 ) 2 ) to those used when growing Type B nanorods in the present work) is facilitated by nanopores in the silica coating formed by hydrolysis and water condensation of TEOS. 36,37 The presence of such nanopores allows reactive solution to reach the ZnO core and cause local dissolution.…”

Section: Resultsmentioning

confidence: 95%

Reagent concentration dependent variations in the stability and photoluminescence of silica-coated ZnO nanorods

Yin

Sun

Wang

et al. 2015

Inorg. Chem. Front.

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Silica (SiO 2 ) coating is finding increasing use as a means of improving the properties of ZnO nanomaterials. However, the current literature contains seemingly contradictory reports of the effect of such coatings on their photoluminescence (PL) properties. Two types of ZnO nanorod (henceforth termed Types A and B) were synthesized using the same hydrothermal method (differing only in the chosen precursor concentrations), then subjected to the exact same SiO 2 -coating procedure. SiO 2 coating is seen to have a strikingly different effect on the Type A and B nanorod morphologies and their PL. In the case of Type A nanorods, (i.e. nanorods grown using high precursor concentrations), SiO 2 coating has no discernible morphological effect but causes an obvious increase in the intensity of the visible component within the PL emission. Type B nanorods (grown from 20-times less concentrated reactive solution), in contrast, show a very different response to SiO 2 coating: morphologically, they appear as many ZnO nanodots in the silica shell that surrounds the etched ZnO core, and their ultraviolet PL is boosted. Systematic investigation of the effects of various other post-treatments on the PL from Type A and B nanorods leads to the conclusion that the different responses to SiO 2 coating can be traced to the different nanorod growth chemistries -i.e. by precipitation from Zn(OH) 2 intermediates (Type A nanorods) or by direct reaction of Zn 2+ and OH − ions (Type B material). The present study advances our understanding both of the controlled synthesis and of routes to optimising the properties of bare and silica-coated ZnO nanomaterials for nanodevice applications.

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Section: Resultsmentioning

confidence: 95%

Reagent concentration dependent variations in the stability and photoluminescence of silica-coated ZnO nanorods

Yin

Sun

Wang

et al. 2015

Inorg. Chem. Front.

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“…3−5 ZnO is one of the potential alternatives as it has a theoretical capacity of 978 mAh g −1 , 3 however it has been reported to suffer from severe capacity loss in the first few cycles, even at slow charging rates. 6−11 Attempts have been made to control the capacity fading by using nano-scale ZnO particles, 3,12−14 coating of ZnO with carbon, 15 nickel, 16 copper, 17 tin, 10,18 and even replacing oxygen with nitrogen 5 and phosphorous 19,20 resulting in modest improvements. In order to successfully stabilize cycling behavior of ZnO the overall lithation/delithiation mechanism must be understood at the atomic level to properly engineer better performing anodes.…”

mentioning

confidence: 99%

In Situ XAFS Study of the Capacity Fading Mechanisms in ZnO Anodes for Lithium-Ion Batteries

Pelliccione

Ding

Timofeeva

et al. 2015

J. Electrochem. Soc.

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Correlation of electrochemical performance and in situ X-ray absorption fine structure (XAFS) spectroscopy measurements on ZnO anodes for lithium-ion batteries has enabled a detailed examination of the capacity fading mechanisms in this material. ZnO electrodes were galvanostatically charged/discharged in situ for several cycles while XAFS spectra at the Zn K-edge were taken. X-ray absorption near edge structure (XANES) spectroscopy provided information on the oxidation state of Zn atoms in each charged and discharged state. Modeling of extended X-ray absorption fine structure (EXAFS) provided detailed information on the Zn-O, Zn-Zn and even Zn-Li coordination numbers and atomic distances for each charged and discharged electrode states. Based on the changes in atomic arrangement deduced from EXAFS fitting results, it is suggested that metallic Zn nanoparticles larger than 10 nm in diameter and bulk-like properties are created during the first few cycles. In the first discharged state, a small fraction of metallic Zn is oxidized back to ZnO, but such re-oxidation is only observed in the first discharged state. On subsequent cycling, the local Zn environment is unchanged, indicating that majority of zinc is no longer participating in any electrochemical reaction. The observed rapid capacity fade is correlated to the irreversible conversion of ZnO to metallic Zn and segregation of Zn atoms into the large metallic zinc nanoparticles during the first charge, which is essentially conversion of the high capacity ZnO electrode to a poorly performing metallic Zn anode.Lithium-ion batteries (LIBs) are the primary power source for portable electronic applications. Graphite is the most common anode material in commercially available products due to its excellent cycle life and specific capacity (theoretical capacity of 372 mAh g −1 ). 1,2 However, for LIBs to be viable options for large scale applications such as electric vehicles, significant improvements in energy and power densities, along with cycle life of next generation LIBs are needed. Metal oxides are often discussed as reasonable alternatives to traditional carbon anode materials as they exhibit theoretical capacities upwards of three times higher than graphitic anodes. 3−5 ZnO is one of the potential alternatives as it has a theoretical capacity of 978 mAh g −1 , 3 however it has been reported to suffer from severe capacity loss in the first few cycles, even at slow charging rates. 6−11 Attempts have been made to control the capacity fading by using nano-scale ZnO particles, 3,12−14 coating of ZnO with carbon, 15 nickel, 16 copper, 17 tin, 10,18 and even replacing oxygen with nitrogen 5 and phosphorous 19,20 resulting in modest improvements. In order to successfully stabilize cycling behavior of ZnO the overall lithation/delithiation mechanism must be understood at the atomic level to properly engineer better performing anodes. The proposed reduction-oxidation reactions are 4,5,9where ZnO is converted to Zn and Li 2 O on initial charging and, upon further chargin...

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“…The RT PL spectrum of the ZNF sample consists of a sharp near-band-edge UV emission centered at 382 nm and a broad, defect-related, visible-band emission. The latter can be further partitioned into an oxygen-deficiency-related green emission centered at 520 nm [47] and an oxygen-rich-related orange emission centered at 600 nm [48]. With increasing temperature, both the UV and visible-band emissions from the ZNF sample shift to longer wavelengths and decline in intensityobservations that match previous findings [18] and are not considered further.…”

Section: Resultsmentioning

confidence: 80%

High-performance photoluminescence-based oxygen sensing with Pr-modified ZnO nanofibers

Jiang

Zhang

et al. 2019

Applied Surface Science

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Praseodymium (Pr)-modified zinc oxide (ZnO) nanofibers have been fabricated using an electrospinning-calcination method. These Pr-modified ZnO nanofibers present porous morphologies containing numerous ZnO nanocrystallites with average sizes that are much smaller than those found in pure ZnO nanofibers formed by the same procedures. Most Pr is identified at the surface of / interface between the nanocrystallites. In addition to the morphological modifications, addition of Pr is also shown to enhance the crystalline quality of the ZnO.Consequently, the Pr-modified ZnO nanofibers have a higher UV emission efficiency and exhibit a much-enhanced UV emission-based O 2 sensing performance than the pure ZnO nanofibers. By way of illustration, the Pr-modified nanofibers show O 2 sensing responses of R = 39% at room temperature and R = 71% at 115 °C (cf. R = 19% and 52% with the pure ZnO nanofibers at these same operating temperatures). These results suggest that electrospun Pr-modified ZnO nanofibers hold real promise for high-performance optical gas sensing applications.

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Arrays of nanorods composed of ZnO nanodots exhibiting enhanced UV emission and stability

Abstract: A novel one-step coating and assembly approach was employed to fabricate well-defined ZnO nanodot/SiO2 nanorod arrays, which exhibit much enhanced UV emission efficiencies and excellent stability.

Cited by 9 publications

References 51 publications

Reagent concentration dependent variations in the stability and photoluminescence of silica-coated ZnO nanorods

Reagent concentration dependent variations in the stability and photoluminescence of silica-coated ZnO nanorods

In Situ XAFS Study of the Capacity Fading Mechanisms in ZnO Anodes for Lithium-Ion Batteries

High-performance photoluminescence-based oxygen sensing with Pr-modified ZnO nanofibers

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