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Polycrystalline nanoparticles of Al-doped and Ce-co-doped ZnO were processed through sol)gel co-precipitation. Crystallite sizes determined from XRD were in the range of 10.90 to 48.77 nm. FTIR spectra indicated a stretching mode of Zn-O bond. The insertion of Al and Ce at Zn-O site created Al-O and Ce-O bonds. UV-vis spectra favoured the formation of impurity levels by doping and co-doping. Their overlapping with the conduction band edge led to the reduction of band-gap. Blue-green emission which arises from radiative recombination of a photogenerated hole with an electron occupying oxygen vacancy was observed in photo)luminescence spectra. FESEM suggested granular growth in undoped ZnO which changed to diverse structures such as nano-bar and cluster of elongated grains. Significant improvement in room temperature ferromagnetism (RTFM) was noticed by co-doping of Ce in Al-doped ZnO. Formation of bound magnetic polarons (Ce3+-Vo-Ce3+) was the primary mechanism responsible for the improvement in RTFM. [ABSTRACT FROM AUTHOR]

This review is focused upon unique optical properties of rare earth (RE) doped ZnO nanostructures derived by a cost-effective sol-gel method. Doping of RE elements improves the properties of ZnO due to their special electronic structure, small crystal field splitting and partially filled 4f energy level, surrounded by full 5s and 5p orbitals. RE-element-induced defects regulate energy transfer dynamics, which can add superior features in ZnO. The biocompatibility of ZnO along with its special calibre of sustained tuneable features by RE doping makes it an excellent candidate for a highly demanding field, i.e. bio-imaging. Here, five RE elements, Tb, Ce, Gd, Y and Eu, are chosen to comprehensively review alterations in the optical parameters of ZnO by their doping. Band gap tuning and luminous properties of RE doped ZnO nanostructures, as well as their features and applications in diverse sectors, are majorly highlighted. [ABSTRACT FROM AUTHOR]

To the best of our knowledge, we present the first study on temperature-dependent photoluminescence (PL) of Al-doped and Ag co-doped ZnO nanoparticles (NPs) obtained by sol-gel co-precipitation. FTIR spectra revealed the presence of Zn-O, Al-O and Ag-O bonds in the respective samples. FESEM images showed spherical NPs in undoped ZnO, which were transformed into granular and rod-like structure by Al doping and subsequently Ag co-doping developed flower-like structure having pin pointed nanorods embedded in petals. Red-shift of the band-gap of ZnO was noticed which is attributed to the contribution of charge carriers by Al and Ag. The PL emission peaks got red-shifted on incorporating with Al and Ag because of the creation of extended energy level network. Reduction from room temperature to −10°C also led to a red-shift of PL emission peaks. This combined impact of doping, co-doping and temperature opens-up a new avenue of designing materials for luminescence thermometry. [ABSTRACT FROM AUTHOR]

Highly transparent thin films of aluminium doped ZnO along with specific silver co-doping are deposited by sol-gel spin coating, which show preferred single orientation along (100) plane. Presence of Al dopant reduces, whereas co-doping with Ag improves crystallinity. Films show sharp absorption in near UV region and band gap observes minor shifts. UV and blue emission peaks are seen in the photoluminescence spectra. UV and blue emission peaks, respectively, demonstrate a fairly large i.e. 43% and 77% rise in the normalised intensity. Presence of Ag causes rise in UV peak because of enhanced excitonic recombination probability. Rise of blue emission intensity is ascribed to creation of Ag-Al interstitials. Surface roughness increases to 210.0 nm with Al increment into ZnO and drops drastically to 81.1 nm by Ag co-doping. Boundaries of nanostructures club together with rise in Al amount and thereafter Ag co-doping is seen to reduce the particle size. [ABSTRACT FROM AUTHOR]

Undoped and Ca doped ZnO Wurtzite nanostructures were prepared via sol-gel co-precipitation. Heavy Ca doping causes structural deterioration due to larger ionic radius of Ca2+. Strain-induced deformation has been analysed by W-H method. Rietveld analysis has revealed changes in bond length due to doping. Optical transparency and band gap have been determined by UV-Vis and Tauc's plot, respectively. Band gap is seen to increase with doping. PL study with three different excitation wavelengths, before and after heat treatment of the samples, recommends that 300 nm is the most suitable for obtaining emission in the blue region. SEM has revealed that the low amount of doping causes clustering of particles, but heavy doping reduces it. [ABSTRACT FROM AUTHOR]