A comparative study on recent progress in efficient ZnO based nanocomposite and heterojunction photocatalysts: A review

Goktas, Serkan; Göktaş, A.

doi:10.1016/j.jallcom.2021.158734

Cited by 384 publications

(154 citation statements)

References 173 publications

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“…1,2 Indeed, these materials are currently widely used in fluorescent displays, solar cells, sensors, photocatalysts, solid-state lasers, biosensors and biocompatible composite preparations with antiseptic properties. [3][4][5][6][7][8][9][10][11] In addition, ZnO and ZnS are increasingly being used to obtain unique nanoscale structures for solar energy, water decomposition, etc. [12][13][14][15] In recent years, the Cu decorated ZnO films or nanorod arrays have emerged as one of the most economical multifunctional semiconducting materials for the chemical conversion of greenhouse gas CO 2 into value-added methanol, [16][17][18][19] compositions with enhanced photocatalytic and antibacterial performances, 9,20,21 magnetic alloys, 22 sensitive layers for hazardous gases, 23 high performance transparent electrodes, [24][25][26] unassisted solar water splitting, 27 enhancement of visible luminescence and photocatalytic activity.…”

Section: Introductionmentioning

confidence: 99%

“…This, in particular, means that in the case of Zn complexes, the reorientation of the ligands does not lead to a decomposition of the complex, and pyrolysis in the gas phase is unlikely. The higher stability of the zinc complexes with dithiocarbamates may be due to its outer electron shell d 10 , which forms a coordination polyhedron with a high potential barrier to rotation around the S 2 CQNR 2 bond. Since overcoming this barrier is necessary for breaking part of the M-S coordination bonds through the rotation of the ligands (as in the case of copper), Zn stabilizes a more energetically favorable conformation, the destruction of which is possible only due to a collision.…”

Section: Introductionmentioning

confidence: 99%

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The effect of small addition of copper on the growth process, structure, surface charge and adsorption properties of ZnO films in the pyrolysis of dithiocarbamates

et al. 2021

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of small addition of copper on the growth process, structure, surface charge and adsorption properties of ZnO films in the pyrolysis of dithiocarbamates

et al. 2021

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“…Among all the transition metal oxide semiconductors tested for the photocatalytic purification of wastewaters, ZnO has certainly received great attention (second only to TiO 2 ) [29][30][31][32][33][34][35][36][37][38][39][40]. Moreover, some insulating materials, such as ZrO 2 , have also been considered for photocatalytic applications [41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Cerium-, Europium- and Erbium-Modified ZnO and ZrO2 for Photocatalytic Water Treatment Applications: A Review

et al. 2021

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In the last decades photocatalysis has become one of the most employed technologies for the implementation of the so-called Advanced Oxidation Processes (AOPs) for the removal of harmful pollutants from wastewaters. The materials identified as the best photocatalysts are transition metal oxides, in which the band structure allows charge carrier separation upon solar irradiation. The photoinduced charge carrier can thus cause oxidative and reductive redox reactions at the surface, inducing the formation of the radical species able to initiate the AOPs. Despite the great advantages of this process (non-toxic, cheap and environmentally clean), the main drawback lies in the fact that the most efficient semiconductors are only able to absorb UV irradiation, which accounts for only 5% of the total solar irradiation at the Earth’s surface and not enough to generate the required amount of electron-hole pairs. On the other hand, many efforts have been devoted to the sensitization of wide band gap transition metal oxides to visible light, which represents a higher percentage (almost 45%) in the solar electromagnetic spectrum. Among all the strategies to sensitize transition metal oxides to visible irradiation, doping with lanthanides has been less explored. In this regard, lanthanides offer a unique electronic configuration, consisting in 4f orbitals shielded by a 5s5p external shell. This occurrence, coupled with the different occupation of the localized 4f orbitals would provide an astounding opportunity to tune these materials’ properties. In this review we will focus in depth on the modification of two promising photocatalytic transition metal oxides, namely ZnO and ZrO2, with cerium, europium and erbium atoms. The aim of the work is to provide a comprehensive overview of the influence of lanthanides on the structural, optical and electronic properties of the modified materials, emphasizing the effect of the different 4f orbital occupation in the three considered doping atoms. Moreover, a large portion of the discussion will be devoted to the structural-properties relationships evidencing the improved light absorption working mechanism of each system and the resulting enhanced photocatalytic performance in the abatement of contaminants in aqueous environments.

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“…Due to their large surface volume ratio [19] and easy processability [19] nanomaterials offer an exciting set of properties for a variety of purposes examples of which include various types of sensors [99][18] , optoelectronics [107][18] , printed photovoltaic materials [18] and catalysts [110] .…”

Section: Nanoscale Zinc Oxide Synthesis Methodsmentioning

confidence: 99%

“…The results were then compared to classical nucleation theory [169][170] [171] , Crundwells' reaction kinetics theory of the surface growth of crystals in the presence of surface charge [172] and oriented attachment [397][141][179] [137] . To approximate the difference in energy barriers between growth in the [110] and [11 ̅ 0] directions, regression analysis was performed using the inbuilt regression analyser in Microsoft Excel based on a simplified Arrhenius effective reaction rate model [155] . The analysis was performed on the entire data set for aspect ratio with [OH -]/[Zn 2+ ] ratios of 0.8 and 1.2 with coefficient, relevant p-values and adjusted R 2 reported.…”

Section: Morphology Characterisation Via Scanning Electron Microscopymentioning

confidence: 99%

Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing

Lewis¹

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Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 °C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 °C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 °C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. Due to the high crystalline quality and amenity to printing, the IPL ZnO QDs have numerous potential uses ranging from sensing to opto-electronic devices.

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A comparative study on recent progress in efficient ZnO based nanocomposite and heterojunction photocatalysts: A review

Cited by 384 publications

References 173 publications

The effect of small addition of copper on the growth process, structure, surface charge and adsorption properties of ZnO films in the pyrolysis of dithiocarbamates

The effect of small addition of copper on the growth process, structure, surface charge and adsorption properties of ZnO films in the pyrolysis of dithiocarbamates

Cerium-, Europium- and Erbium-Modified ZnO and ZrO2 for Photocatalytic Water Treatment Applications: A Review

Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing

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