Decrease In Luminescence Intensity Research Articles

Towards a white-emitting phosphor Ca10V6O25 based material

To achieve a stable material capable of white-light emission, we fabricated Ca10V6O25 by both co-precipitation (CP) and microwave-assisted hydrothermal (MAH) methods at different temperatures. The effects of structural disorder at a short-range (Raman spectra), medium-range (UV–vis spectra), and long-range (X-ray diffraction) on the material structure and its effect on optical properties were investigated. Both CP and the MAH methods were efficient for obtaining pure Ca10V6O25 material with different morphologies. Significant changes in morphology and degree of structural order and disorder were found to affect the photoluminescence (PL) properties. All samples exhibited a broadband PL spectrum, characteristic associated to charge transfer processes of the [VO4]3- group, as well as transitions that occurred in the energy levels located within the band gap. The samples obtained by the MAH method at temperatures of 100 °C and 120 °C exhibited a lower structural disorder (at long- and short-ranges), the CIE chromaticity coordinates were located in the white region, MAH100 (x = 0.311 and y = 0.348) and MAH120 (x = 0.350 and y = 0.368). Furthermore, we conducted a detailed study of temperature dependence of PL spectra. All samples displayed decreased luminescence intensity as temperatures increased and low values of activation energy (approximately 2 meV). Finally, the as-synthetized Ca10V6O25 material has interesting properties for possible applications as a white-emitting phosphor under ultraviolet excitation.

Enhanced Photocurrent Generation in Proton‐Irradiated “Giant” CdSe/CdS Core/Shell Quantum Dots

AbstractGroup II–VI quantum dots (QDs) possess tunable electrical and optical properties that make them very attractive for high‐tech applications and power generation. The effects of proton irradiation on both the structural and physical properties of “giant” CdSe/CdS core–shell QDs (g‐CS QDs) are investigated. These experiments shed light on photoelectron delocalization in g‐CS QDs, where current linkages and strong variations in optical emission result from the spatial extension of the photoelectron wavefunctions over the conduction bands of CdSe and CdS. Monte Carlo simulations of ion–matter interactions show that the damaging rates can be set from the energy of impinging protons to promote the formation of structural defects in the core or shell. The formation of nanocavities is demonstrated after irradiation doses higher than ≈1017 H+ cm−2, while a continuous decrease in luminescence intensity is observed for increasing proton fluencies. This feature is accompanied by a concomitant lifetime decrease marking the rise of nonradiative phenomena and the occurrence of greater photocarrier transfers between CdS and CdSe. Current‐to‐voltage characterizations evidence that proton implantation can be implemented to enhance the photocurrent generation in g‐CS QDs. This increase is attributed to the delocalization of photoelectrons in the CdS shell, whose improvement is found to promote electron–hole pair separation.

Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application

M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.

Effect of temperature on up-conversion phenomena in Gd3(Al,Ga)5O12 crystals co-doped with Yb3+ and Tm3+

Single crystals of Gd3(Al,Ga)5O12 with intentional stoichiometry Gd3Ga2.5Al2.5O12 doped with 1%Tm3++x%Yb3+; (x = 1, 3, 5); were grown by the Czochralski method. Spectra and intensities of up-converted luminescence excited at 975 nm or 803 nm were measured as a function of temperature within 295 K–775 K region. It was found that for the two excitation wavelengths the growth of temperature brings about a decrease of an up-converted blue luminescence intensity. Thermally enhanced growth of nonradiative relaxation rates for excited states involved in the up-conversion process was determined based on an analysis of respective luminescence decay curves. Temperature-dependent change of fluorescence intensity ratio (FIR) for the 3F3,2 – 3H6/3H4 – 3H6 up-converted bands was observed and resulting absolute temperature sensitivity of 0.058 K-1 was found for GAGG:1%Tm,3%Yb at 725 K.

New insights into UV laser irradiation effect on luminescent behavior of vitrified films based on mesogenic lanthanide(III) β-diketonate complexes

We revealed the effect of the prolonged UV laser irradiation on luminescent behavior of photonic materials based on mesogenic lanthanide(III) β-diketonate complexes by using a novel 3 μm vitrified film of an europium(III) β-diketonate complex. We used the Eu3+ ions to monitor the UV laser-induced photophysical processes in the film. Despite the fact that usually prolonged UV irradiation leads to irreversible photofragmentation of ligands, we had observed no photodecomposition of the complexes after the irradiation of the film with the 337 nm laser for 5 h. The spectroscopic study revealed (i) a 16.5-fold luminescence intensity decrease due to laser-induced changes in inner coordination spheres of the Eu3+ ions and (ii) the main channel of non-radiative energy losses from the Eu3+ ions through the multiphonon relaxation. These features open up new possibilities for designing advanced photonics materials with excellent photostability and luminescent properties controlled during operation.

A Strategy for Prompt Phase Transfer of Upconverting Nanoparticles Through Surface Oleate-Mediated Supramolecular Assembly of Amino-β-Cyclodextrin.

Lanthanide-doped upconverting nanoparticles (UCNPs) are promising for applications as wide as biosensing, bioimaging, controlled drug release, and cancer therapy. These applications require surface engineering of as-prepared nanocrystals, commonly coated with hydrophobic ligand of oleic acid, to enable an aqueous dispersion. However, literature-reported approaches often require a long time and/or multiple step treatment, along with several fold upconversion luminescence (UCL) intensity decrease. Here, we describe a strategy allowing oleate-capped UCNPs to become water-soluble and open-modified, with almost undiminished UCL, through ultrasonication of minutes. The prompt phase transfer was enabled by oleate-mediated supramolecular self-assembly of amino modified β-cyclodextrin (amino-β-CD) onto UCNPs surface. We showed that this method is valid for a wide range of UCNPs with quite different sizes (6–400 nm), various dopant types (Er, Tm, and Ho), and hierarchical structures (core, core-shell). Importantly, the amino group of amino-β-CD on the surface of treated UCNPs provide possibilities to introduce entities for biotargeting or functionalization, as exemplified here, a carboxylic-containing near infrared dye (Cy 7.5) that sensitizes UCNPs to enhance their UCL by ~4,820 fold when excited at ~808 nm. The described method has implications for all types of oleate-capped inorganic nanocrystals, facilitating their myriad bioapplications.

Sub-nanosecond excitonic luminescence in ZnO:In nanocrystals

The effects of indium concentration influence on the morphology, luminescence spectra and luminescence decay kinetics of ZnO:In nanocrystals prepared by the solar physical vapour deposition method are investigated. While undoped ZnO nanocrystals exhibit tetrapod-like morphology, with increasing indium concentration the tetrapods are transformed into particles whose average size decreases with increasing indium concentration. The results of time-resolved luminescence studies of undoped and indium doped ZnO nanocrystals showed that by increasing indium concentration the decay time falls and luminescence intensity decreases.

Regulation of morphologies and luminescence of β-NaGdF4:Ybc+,Er3+ upconversion nanoparticles by hydrothermal method and their dual-mode thermometric properties

Exploring the thermometric properties of UCNPs is of great importance for non-contact fluoresce thermometers. Ln-doped β-NaGdF4:Yb3+,Er3+ upconversion nanoparticles (UCNPs) have been fabricated by varying the ratio of citric ions to molecules in precursor. Morphology of the as-prepared β-NaGdF4:Yb3+,Er3+ UCNPs turns from hexagonal prisms to agglomerations of smaller particles with decreased dimension. Luminescence intensity decreases and red-to-green ratio increases with increasing ratio of citric ions to molecules. A dual-mode thermometric property has been found in the as-prepared β-NaGdF4:Yb3+,Er3+ UCNPs. The first mode derives from the temperature dependent fluoresce-intensity-ratios of thermally coupled manifolds of Er3+ (2H11/2) and (4S3/2) manifolds, of which the maximum relative sensitivity value is 0.0036 K−1. The other mode derives from temperature dependent red-to-green ratios, which is a linear function of temperature and the maximum relative sensitivity value is 0.0238 K−1. The β-NaGdF4:Yb3+,Er3+ UCNPs with morphology of agglomerations of smaller particles with high surface-to-volume ratios show advanced sensitivities, which are suitable for noncontact optical thermometer.

Anion-controlled geometrically different Cu(II) ion-based coordination polymers and green synthetic route for copper nanoparticles: a combined experimental and computational insight

The Cu(II) ion-based polymeric complexes [Cu(2,2′-bpy).(N3)2]n (I), [Cu2(2,2′-bpy)2.(N3)4]n (II), and monomeric complex [Cu(2,2′-bpy).(NO3)2].5H2O (III) have been synthesized with rigid (–N3) and aromatic (2,2′-bpy = 2,2′-bipyridyl) ligand. The rigid azide group is responsible for the formation of 1-D extended structures in complexes I and II where as in the case of complex III, a monomeric complex is formed due to lack of a bridging group like –N3, resulting in limitation in dimensionality. The thermal stability of the 1-D complexes is comparatively higher than monomeric complex III. Hirshfeld surface analysis has also been applied to investigate other weak interactions and compared with the results from single-crystal X-ray data. Due to the presence of paramagnetic metal centers and long metal···metal distances in complexes I and II and presence of lattice water molecules in complex III, decrease in luminescence intensities have been observed. To attain further insights into the aforementioned interesting species, some chemical concepts such as highest occupied molecular orbital–lowest unoccupied molecular orbital gap, electronic chemical potential, chemical hardness, and electrophilicity index, identified as a derivative of electronic energy, have also been emphasized employing the quantum chemical calculations in the framework of the density functional theory method using the M06-2X/ 6-31G** level of study. Further, these complexes have been used to synthesize copper nanoparticles by applying a green synthetic route.

Composites of CaAl2O4: Eu2+, Nd3+/Ca0.25Sr0.75S: Eu2+ in Polyacrylonitrile Fibers with Tri-Stimuli-Responsive Persistent Luminescence

In this study, ultraviolet(UV) light-excited CaAl2O4: Eu2+, Nd3+ and visible light-excited Ca0.25Sr0.75S: Eu2+ were incorporated in the polyacrylonitrile (PAN) fibers by wet-spinning. Scanning electron microscopy, X-ray diffraction, photoluminescence, and decay analysis were used to characterize the morphology, inner structure, photoluminescence and afterglow behavior of the composite fibers, respectively. The results indicated random distribution of the two inorganic phosphors into the PAN fiber. To investigate the stimuli-responsive properties of the composite fiber, experiments were performed under UV light, visible light and D65 lamp. The results revealed that, the obtained composite fibers featured a blue emission of CaAl2O4: Eu2+, Nd3+ at 450 nm and a red emission of Ca0.25Sr0.75S: Eu2+ at 620 nm. Furthermore, decay curves indicated the decrease of luminescence intensity of the composite fiber when the two phosphors were simultaneously excited, which are attributed to the different irradiation source. It is expected that this multicolor fiber could be used in high-level information anti-counterfeiting label in clothes and smart clothing.

Porous CaCO3 carriers loaded with scintillation nanoparticles and photosensitizer molecules for photodynamic activation

We report the creation of a novel composition on the base of porous CaCO3 microspheres loaded with both scintillating gadolinium orthovanadate nanoparticles doped with europium ions GdVO4:Eu3+ (VNPs) and Methylene Blue (MB) photosensitizer molecules. It has been shown that upon both UV- and X-ray excitations of VNPs, an excitation energy transfer from VNPs to MB dye molecules takes place that is revealed in the donor VNPs luminescence intensity and lifetime decrease, as well as MB FRET-induced luminescence appearance. The rise time of the acceptor MB luminescence, which follows the donor decay time has been observed that allows distinguishing of nanosecond acceptor emission due to direct acceptor excitation from the much longer-lived sub-millisecond FRET-induced acceptor one. Using the rise time of acceptor luminescence, FRET efficiency (E = 59%) rate constant (kt=2.28·103s−1) and physical separation of the donor to acceptor within CaCO3 microparticles (rda=2.45nm) at the optimal acceptor concentration have been calculated. The efficiency of created CaCO3@VNPs@MB composition in free radical generation has been analyzed.

Controlling n-type conductivity of β-Ga2O3 by Nb doping

It has been confirmed that Si, Sn, and Ge are effective n-type dopants for β-Ga2O3. This letter shows that Nb doping is also a viable method for controlling the electrical resistivity and carrier density of β-Ga2O3, corresponding to the theoretical calculations about the doping of Ga2O3 with Nb [H. Peelaers and C. G. Van de Walle, Phys. Rev. B 94(19), 4 (2016)]. β-Ga2O3 single crystals with different Nb concentrations were grown by the optical floating zone method. The electrical resistivity can be varied from 3.6 × 102 Ω cm to 5.5 × 10−3 Ω cm by increasing the Nb doping concentration, and the related free carrier concentration increases from 9.55 × 1016 cm−3 to 1.8 × 1019 cm−3. The transmittance spectra and photoluminescence spectra were measured to systematically study the optical properties of Nb-doped β-Ga2O3 single crystals. The strong absorption near the IR region in the crystals is related to the increase in conductive electrons, and the decrease in blue luminescence intensity indicates a decrease in the VO concentration induced by increasing the carrier concentration.

Effect of Al/Ga substitution on the structural and luminescence properties of Y3(Al1-xGax)5O12: Ce3+ phosphors

As candidates for display and lighting materials, a series of gallium-substituted cerium-doped yttrium aluminum garnet (Y3(GaxAl1-x)5O12: Ce3+) phosphors were synthesized by high temperature solid-state reaction. The phases, morphology, luminescence spectra and thermal stability of the phosphors were investigated. The volatilization of Ga2O3 induces the constituents out of stoichiometric ratio and different impurities in the system. The excitation and emission spectra occur red shift (339 nm - 351 nm) and blue shift (465 nm - 437 nm), and blue shift (541 nm - 517 nm), respectively. The spectra have no further blue shift and the luminescence intensity decrease with x over 0.4. Combining crystal structure with PL spectrum, the distortion of dodecahedron and crystal field splitting of 5d level of Ce3+ are influenced by Ga3+ in octahedral coordination polyhedron rather than tetrahedron. The crystalline perfection and Ga3+ occupying the tetrahedron induce less garnet phase formation, more impurities and the 5d level located in the conductive bands, thus accounting for the x = 0.4 turning points of the PL and PLE intensity. Based on the thermal quenching and CIE, the Y3(GaxAl1-x)5O12: Ce3+0.06 phosphors have great potential for use on the w-LED.

Highly sensitive fluorescence sensing of zearalenone using a novel aptasensor based on upconverting nanoparticles.

A facile strategy was successfully developed for the detection of zearalenone (ZEN). In this assay, highly fluorescent upconversion nanoparticles were synthesized and conjugated with the complementary oligonucleotide of ZEN aptamer for use as signal probes. Magnetic nanoparticles immobilized with the ZEN aptamer were assigned as capture probes. The results exhibited that the linear correlation between the decreased luminescence intensity of the signal and the concentration of ZEN was very strong (R2=0.9957) in the range of 0.05-100μg/L. In addition, the limit of detection of the proposed method (0.126μg/kg for corn and 0.007μg/L for beer) was significantly lower than the existing methods. Furthermore, the reliability of the competitive immunoassay format was validated by comparing the results determined in real food samples to those obtained from a commercially available method. Overall, the novel aptasensor have showed great potential for rapid and accurate ZEN determination.

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

We develop a two-color thermometry (TCT) phosphor based on [Y$_{1-x}$Dy$_x$(acetylacetonate)$_3$(1,10-phenanthroline)] ([Y$_{1-x}$Dy$_x$(acac)$_3$(phen)]) molecular crystals for use in heterogeneous materials. We characterize the optical properties of [Y$_{1-x}$Dy$_x$(acac)$_3$(phen)] crystals at different temperatures and Dy concentrations and find that the emission is strongly quenched by increasing temperature and concentration. We also observe a broad background emission (due to the ligands) and find that [Y$_{1-x}$Dy$_x$(acac)$_3$(phen)] photodegrades under 355 nm illumination with the photodegradation resulting in decreased luminescence intensity. However, while decreasing the overall emission intensity, photodegradation is not found to influence the integrated intensity ratio of the ${}^4I_{15/2} \rightarrow {}^6H_{15/2}$ and ${}^4F_{9/2} \rightarrow {}^6H_{15/2}$ transitions. This ratio allows us to compute the temperature of the complex Based on the temperature dependence of these ratios we calculate that [Y$_{1-x}$Dy$_x$(acac)$_3$(phen)] has a maximum sensitivity of 1.5 \% K$^{-1}$ and our TCT system has a minimum temperature resolution of 1.8 K. Finally, we demonstrate the use of [Y$_{1-x}$Dy$_x$(acac)$_3$(phen)] as a TCT phosphor by determining a dynamic temperature profile using the emission from [Y$_{1-x}$Dy$_x$(acac)$_3$(phen)].

Cyclometalated Ir(iii) complexes incorporating a photoactive anthracene-based ligand: syntheses, crystal structures and luminescence switching by light irradiation.

Two cyclometalated complexes [Ir(dfppy)2(aip)](PF6) (1) and [Ir(ppy)2(aip)](PF6) (2) have been synthesized based on a photoactive anthracene-based ligand aip and cyclometalating ligands dfppyH and ppyH [dfppyH = (2-(2,4-difluorophenyl)-pyridine), ppyH = 2-phenyl-pyridine]. Their crystal structures indicate that an aip ligand uses its phenanthroline moiety to chelate an {Ir(dfppy)2}+ unit in 1, while an {Ir(ppy)2}+ unit in 2. In CH2Cl2, the anthracene units in aip, 1 and 2 underwent photo-oxidation upon irradiation with 365 nm light, forming species aip-O, 1-O and 2-O, respectively. This photo-oxidation resulted in luminescence switching, from a luminescent state (emission at 493 nm) to a non-luminescent state for aip, while from a non-luminescent state to a luminescent state with an emission at 519 nm for 1 and 578 nm for 2. Additionally, the luminescence of aip, 1-O and 2-O in CH2Cl2 can be modulated by using TFA to protonate the imidazole units and/or non-coordinated phenanthroline moiety in these compounds. Upon adding TFA, aip showed luminescence quenching, while species 1-O and 2-O revealed both luminescence-intensity decrease and emission-wavelength increase (Δλ = 9 nm for 1-O, and Δλ = 4 nm for 2-O). In this paper, we discuss the luminescence switching/modulation of aip, 1 and 2 by light-irradiation-induced photo-oxidation of their anthracene units and by TFA treatment.

DEPENDENCE OF PHOTOLUMINESCENCE OF NANOPARTICLE ENSEMBLES OF STANNUM (IV) COMPLEXES IN SILICA POROUS MATRIX ON CONCENTRATION OF SATURATING SOLUTION

Dependence of photoluminescence of high-molecular nanoformations of dyes on the basis of stannum (IV) complexes in porous glass on concentration of saturating solution has been researched. The results have been compared with photoluminescence of corresponding solutions, in which the effect of concentration quenching, was due to the Franck-Condon principle, was observed. It was found that intensity of luminescence for nanoparticle ensembles was always higher than in solution. At that, decrease of luminescence intensity alongside with concentration growth of saturating solution was observed as well. However, the observed dependence was more complicated than in solution. It can be explained by the fact that the pores with maximal sizes are filled at large concentrations of saturating solution of dye. The dye particles act almost the same as in solution, where photoluminescence is fainter, in such pores.

Disintegration of Hexagonal NaYF4:Yb3+,Er3+ Upconverting Nanoparticles in Aqueous Media: The Role of Fluoride in Solubility Equilibrium

The disintegration of hexagonal NaYF4:Yb3+,Er3+ upconverting nanoparticles (UCNP) was studied by incubating various nanoparticle concentrations in aqueous suspensions over time while monitoring the upconversion emission intensity and measuring the dissolved particle-constituting ion concentrations. The results revealed that the ions dissolved into water resulting apparently in anisotropic structural disintegration of the UCNPs as observed with transmission electron microscopy. The UCNP disintegration caused partial loss of active ions Yb3+ and Er3+ from the host matrix and therefore decrease in the upconversion luminescence intensity. The decrease, however, was strongly dependent on the UCNP concentration, and dramatic drop in the intensity was observed especially at diluted nanoparticle suspensions, where the nanoparticles disintegrated almost completely until the solubility equilibrium was achieved. At the concentrated suspensions the equilibrium was achieved already with minimal disintegration, and the...

(Invited) New Phosphor Exploration By the Single Particle Diagnosis Approach

The luminescence property of Eu2+ or Ce3+doped phosphor is so affected by the coordination environment of luminescent center. The usage of different host material leads to new phosphor. The search for new phosphor is roughly classified to two methods. One is to employ a known crystal structure that is suitable for luminescent center doping and is not studied for host crystal. However, the promising candidates are already studied in most cases. The other is to find new host material by analyzing single crystals or powder product. In the single crystal analysis, a large size crystal is necessary to determine the crystal structure. In the powder process, at least it is necessary to synthesize the new material as single phase to solve the crystal structure from powder XRD data. Both normally require much time and effort. We have developed a new efficient method to find new phosphors from a powder mixture synthesized by a standard process. We have named the new method “Single Particle Diagnosis Approach”. Even if the powder product is not a single phase, by considering each (isolated) particle, it can be treated as a single phase and a single crystal. The crystal structure and luminescence properties of candidate single particles are analyzed and new phosphors are efficiently discovered. Here we show some examples. 1) In Ba3N2-Si3N4-AlN quasi-ternary system, seven luminescent particles with different colors and morphologies were selected from the twenty powder samples. Among them, two particles were found to be new phosphors (yellow Ba5Si11Al7N25:Eu2+ and blue BaSi4Al3N9:Eu2+)1. 2) In addition to above example, Li3N was employed as the fourth component. As the number of components increases, the number of experiments dramatically increases in the combinatorial synthesis. In the single particle diagnosis approach, the increment of experiments number is suppressed. From Ba3N2-Si3N4-AlN-Li3N quasi-quaternary system, we found new green phosphor Ba2LiSi7AlN12:Eu2+. It shows a narrow-band emission and a small decrease of luminescence intensity even at 300 °C 2. 3) An interesting example is a new orange phosphor using Sr3N2-Si3N4-AlN quasi-ternary system. XRD and EDS analyses showed the composition of new phosphor particle to be Sr2Si2+3xAl2-xB2-2xN8+x:Eu2+. Boron component is not included in the staring materials. It is contamination from BN crucible. By using BN powder and Mo crucible instead, Sr2Si2+3xAl2-xB2-2xN8+x Eu2+ was obtained as a main phase3. One of the merits of this approach is that the small amount of a new phosphor (including unintended new phosphors) in a powder sample is not overlooked. 1. N. Hirosaki, T. Takeda, S. Funahashi, R.-J. Xie. Chem. Mat. 26 (2014) 4280. 2. T. Takeda, N. Hirosaki, S. Funahashi, R.-J. Xie. Chem. Mat. 27 (2015) 5892. 3. S. Funahashi, Y. Michiue, T. Takeda, R.-J. Xie, N. Hirosaki, Acta Cryst. C70 (2014) 452.

Argon annealing induced morphological transformation from nanowire to nanoflake and high photocurrent gain of ZnO:Al films

Pristine ZnO nanowire grown via thermal oxidation technique has been one of the facile synthetic routes. However, nucleation of Zn thin film over ultra thin metal layer and subsequent heat treatment would open up the possibilities of metal incorporation into ZnO matrix. The present work demonstrates the formation of ZnO:Al nanowires by oxidizing bi-layered Zn/Al film and subsequent investigation of photoresponse phenomenon of as grown and argon annealed samples in comparison to pristine ZnO nanowire. For as grown ZnO:Al, surface localized native defects effectively form complex with aluminium related defects (AlZn), (generated in small numbers); thereby restricting the donor capacity of aluminium. However, argon annealing provides additional defect centres (both native and AlZn) and at the same time help dissociating the complexes. These phenomena account additional surface charge density and surface reconstruction, causing morphological transformations from nanowire to nanoflake. SIMS depth profile studies reflect that post synthesis argon annealing triggers aluminium surface doping, In this study we have demonstrated high photocurrent gain of ZnO:Al nanowires after argon annealing, attributed to oxygen chemisorption-desorption phenomenon. Photoluminescence spectra revealed that argon annealing has resulted in improvement of near band edge emission and decrease of green luminescence intensity of ZnO:Al sample. In this study violet-blue emission was observed at 3.11eV after argon annealing of both ZnO and ZnO:Al samples, attributed to emission from the localized defect related complexes of oxygen vacancy and characteristic peak at 3.0eV may be attributed to interstitial zinc (Zni) related complex.