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In the context of the proposed work, two different amino acids (Glycine, Phenylalanine) have interacted with copper ions in a phosphate buffer (PBS) in place of enzymes. This interaction resulted in the nucleation of copper phosphate crystals and the formation of flower-shaped amino acid-copper hybrid nanostructures (AA-hNFs), which grew through self-assembly. While Cu (II) ions in the structure of AA-hNFs were used as Fenton's agent for the catalytic activity. SEM, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy measurements were used to define the AA-hNFs' characterisation. The peroxidase-like activities of AA-hNFs were investigated by UV/VIS spectrophotometer. Metal nanoparticles have peroxidase-like activity. A class of enzymes known as peroxidases is able to catalyze the conversion of hydrogen peroxide into hydroxyl radicals. These radicals also take part in electron transfers with substrates, which results in color during oxidation. When cupric oxide nanoparticles are added to the peroxidase substrate while H 2 O 2 is present, a blue color product with a maximum absorbance at=652 nm can result, demonstrating the catalytic activity of a peroxidase. The morphology and composition of AA-hNFs were carefully characterized and the synthesized parameters were optimized systematically. Results showed that the nanoparticles were dispersed with an average diameter of 7-9 μm and indicated a uniform flower shape. The results of the investigation are anticipated to significantly advance a number of technical and scientific sectors., (© 2023 Wiley-VHCA AG, Zurich, Switzerland.)

Immobilized enzymes are a significant technological approach to retain enzyme activity and reduce enzyme catalytic cost. In this work, trypsin-incorporated Zn 3 (PO 4 ) 2 hybrid nanoflowers were prepared via mild precipitation and coordination reactions. The controllable preparation of hybrid nanoflowers was achieved by systematically investigating the effects of the raw-material ratio, material concentration and reaction temperature on product morphology and physicochemical properties. The enzyme content of hybrid nanoflowers was about 6.5%, and the maximum specific surface area reached 68.35 m 2 /g. The hybrid nanoflowers exhibit excellent catalytic activity and environmental tolerance compared to free trypsin, which was attributed to the orderly accumulation of nanosheets and proper anchoring formation. Further, the enzyme activity retention rate was still higher than 80% after 12 repeated uses. Therefore, trypsin/Zn 3 (PO 4 ) 2 hybrid nanoflowers-which combine functionalities of excellent heat resistance, storage stability and reusability-exhibit potential industrial application prospects.

Organic-inorganic hybrid nanoflowers (HNFs) of laccase@Zn 3 (PO 4 ) 2 were fabricated through a facile, simple, and rapid one-step strategy. In this process, laccase was involved in nucleation and fast anisotropic growth reactions with Zn (II) and phosphate ions. The average pore size of the prepared HNFs was 54.5 nm, and its BET-specific surface area was 59.5 m 2  g -1 . In comparison with the free laccase, the entrapped enzyme activity in the constructed HNFs was 86.4%. In addition, the hybrid biocatalyst displayed a maximum rate of reaction (V max ) of 1640.2 ± 3.6 μmol min -1 with respect to the native enzyme. The constructed HNFs maintained 45.1% and 60% of the original laccase activity after 12 successive reusability cycles and 30 days of storage at 4 °C, respectively. The as-obtained HNFs demonstrated a high bioremoval percentage of Direct blue-71 (94.1%) within a 10-h-treatment at 40 °C and 15 mg l -1 of the dye concentration. The pseudo-first order and second order were the best-fitted kinetic models for the dye removal using Zn 3 (PO 4 ) 2 nanoflakes and the fabricated HNFs, respectively. Besides, liquid chromatography-mass spectrometry (LC-MS) revealed biotransformation of the dye into less toxic metabolites as verified by testing on some bacterial strains., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This paper reports synthesis, properties and gas sensing applications of ZnO nanoflowers and CdO-ZnO nanorices prepared by hydrothermal process. The morphological characterizations confirmed the formation of well-defined nanoflowers and nanorices structures for ZnO and CdO-ZnO nanomaterials, respectively. The structural properties revealed the wurtzite hexagonal phase of the synthesized materials. The sensor devices based on ZnO nanoflowers and CdO-ZnO nanorices were fabricated and tested towards various gases including ethanol, methanol, ammonia, carbon monoxide, methane and formaldehyde. The fabricated gas sensor based on CdO-ZnO nanorices exhibited a high response (34.5) towards 300 ppm formaldehyde gas at 350 °C compared to ZnO nanoflowers (14.5) under the same experimental conditions. The response and recovery times for ZnO nanoflowers-based sensor were~9.8 s and ~6 s while for CdO-ZnO based sensor, these were ~10s and ~6s, respectively. A rapid response (34.5) for CdO-ZnO nanorices based formaldehyde gas sensor was observed as compared to other gases such as ammonia (12.3), methanol (16.5), ethanol (20), carbon monoxide (16.3) and methane (12.4), which confirm the high-selectivity towards formaldehyde gas. Finally, a plausible formaldehyde gas sensing mechanism is proposed., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Enzyme-mimetic properties of nanomaterials can be efficiently tuned by controlling their size, composition, and structure. Here, ultrathin PdCu alloy nanosheet-assembled three-dimensional (3D) nanoflowers (Pd 1 Cu x NAFs) with tunable surface composition are obtained via a generalized strategy. In presence of H 2 O 2 , the as-synthesized Pd 1 Cu x NAFs can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to the oxidized form of TMB (oxTMB) with a characteristic absorption peak at 652 nm. Interestingly, Pd 1 Cu x NAFs show obviously composition-dependent peroxidase-like catalytic activities because of the synergistic interaction of nanoalloy. Additionally, different from 2D Pd nanosheets, the distinctive 3D superstructures are featured with rich approachable sites and proper layer spacing, which are in favor of fast mass transport and electron transfers during the catalytic process. Among the studied Pd 1 Cu x NAFs, the Pd 1 Cu 1.7 NAFs show the highest enzyme-like activities and can be successfully applied for the colorimetric detection of glucose with a low detection limit of 2.93 ± 0.53 μM. This work provides an efficient avenue to fabricate PdCu NAF nanozymes in biosensing toward glucose detection. Two-dimensional (2D) PdCu ultrathin nanosheet-assembled 3D nanoflowers (Pd 1 Cu x NAFs) with tunable surface composition exhibit substantially enhanced intrinsic peroxidase-like catalytic activities. The Pd 1 Cu 1.7 NAFs are successfully used as peroxidase mimic catalyst for the colorimetric detection of glucose with low detection limit of 2.93 μM.

A new composite, AgPW@PDA@Nisin, with shell-core structure was successfully synthesized by a polydopamine (PDA) surfaced conjugated nisin (an antibacterial 34 amino acid polycyclic peptide) as shell and polyoxometalates (Ag 3 PW 12 O 40  = AgPW) as core. The composite was characterized by the zeta potential, scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction analysis (XRD), fourier transform infrared (FT-IR). The AgPW@PDA@Nisin showed flower hierarchical structure and potential antibacterial activity against S. aureus ATCC29213. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of it were 4 and 32 μg/mL. AgPW@PDA@Nisin nanoflowers-induced bacterial death bears the characteristic of cell morphology, membrane integrity and permeability changing, nucleotide leakage. It indicated that the AgPW@PDA@Nisin interfere with the cell membrane, resulting in antibacterial activity against S. aureus. The cytotoxicity of the nanoflowers was low on HDF-a (human dermal fibroblasts) cells. A new class of hybrid inorganic-organic nanoflowers based on polyoxometalates and nisin with enhanced antibacterial properties can be developed for food preservation., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Ligand-induced chirality in asymmetric CdSe/CdS core-shell nanocrystals (NCs) has been extensively applied in chiral biosensors, regioselective syntheses and assemblies, circularly polarized luminescence (CPL), and chiroptic-based devices due to their excellent physiochemical properties, such as the tunable quantum confinement effects, surface functionality, and chemical stability. Herein, we present CdSe/CdS NCs with various morphologies such as nanoflowers, tadpoles, and dot/rods (DRs) with chirality induced by surface chiral ligands. The observed circular dichroism (CD) and CPL activities are closely associated with the geometrical characteristics of the nanostructures, such as the shell thickness and the aspect ratio of the CdSe/CdS NCs. Furthermore, in situ observations of the growth of tadpoles with a single tail indicate that the CD response is mainly attributed to the CdS shell, which has a maximum tail length of ∼45 nm (approximately λ/10 of the incident light wavelength). On the other hand, the CPL activity is only related to the CdSe core, and the activity benefits from a thin CdS shell with a relatively high photoluminescence quantum yield (QY). Further theoretical models demonstrated the aspect-ratio-dependent g -factor and QY variations in these asymmetric nanostructures. These findings provide insights into not only the asymmetric synthesis of CdSe/CdS NCs, but also the rational design of CdSe/CdS nanostructures with tunable CD and CPL activities.

The current industrial revolution signifies the high-value of biocatalysis engineering. Over the past decade, multiple micro- and nanostructured materials have been attempted for immobilization of enzymes to improve their catalytic properties. Conventional immobilization strategies result in improved stability, while insolubilized enzymes generally lost their activity compared to free counterparts. Recently, a new generation organic-inorganic hybrid nanoflowers with unique properties have received great attention as a novel and incentive immobilization approach owing to their simple fabrication, high biocatalytic efficiency, and enzyme stabilizing capability. The hybrid nanoflowers biocatalytic system implicates metal ions and biomolecules (enzymes). In contrast to free or conventionally immobilized enzymes, single enzyme or multi enzyme-incorporated flowers-like hybrid nanoconstructs demonstrated elevated catalytic activities and stabilities over a very broader range of experimental conditions, i.e., pHs, temperatures and salt concentration. This review discusses the recent developments in the fabrication strategies to diversifying nanoflowers, types, characteristics, and applications of organic-inorganic hybrid nanoflowers as a host platform to engineer different kinds of enzymes with requisite functionalities for biocatalysis applications in different sectors of the modern world. Based on experimental and theoretical literature data, the review is wrapped up with concluding remarks and an outlook in terms of upcoming challenges and prospects for their scale-up applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Nanoengineering the topology of titanium (Ti) implants has the potential to enhance cytocompability and biocompatibility properties as implant surfaces play a decisive role in determining clinical success. Despite developments in various surface engineering strategies, antibacterial properties of Ti still need to be enhanced. Here a facile, cost-effective hydrothermal route was used to develop nano-patterned structures on a Ti surface. Changing hydrothermal treatment parameters such as temperature, pressure, and time, resulted in various topographies, crystal phases, and hydrophobicity. Specifically, hydrothermal treatment performed at 225 °C for 5 h, presented a novel topography with nanoflower features, exhibited no mammalian cell cytotoxicity for a time period of 14 days, and increased calcium deposition from osteoblasts. Treated samples also demonstrated antibacterial properties (without resorting to the use of antibiotics) against Staphylococcus aureus and methicillin resistant Staphylococcus aureus. In conclusion, hydrothermal oxidation on an etched Ti surface can generate surface properties that have excellent prospects for the biomedical field., (Copyright © 2019 Elsevier Inc. All rights reserved.)

In this study, various sonochemical conditions were applied to prepare the microsheets, nanosheets and nanoflowers of a metal-organic framework (MOF; [Zn 6 (IDC) 4 (OH) 2 (Hprz) 2 ] n ) that is composed of Zn(II) cations coordinated with the linear N-donor piperazine (prz) and rigid planar imidazole-4,5-dicarboxylate (H 3 IDC) ligands. The PXRD patterns approved purity of the samples and the FT-IR spectra related the detected bonds and functional groups to [Zn 6 (IDC) 4 (OH) 2 (Hprz) 2 ] n crystals. The morphological results indicated that any changes in the synthesis conditions can affect nucleation and morphology of the nanostructures. The prepared MOF nanosheets and nanoflowers (with particle size average of 95 and 116 nm, respectively) were employed to adsorb the ampicillin, amoxicillin and cloxacillin antibiotics. Then, the MOFs were calcined at 550 ℃ and atmospheric pressure to produce ZnO nanoparticles and the resultant nanoparticles were adopted to photodegrade the antibiotics. These nanoparticles can photodegrade 37% of the amoxicillin compounds within 180 min. Among the examined samples, the nanoflowers demonstrated the highest adsorption capacity by eliminating 92.5%, 88% and 89% of the antibiotic molecules from the 60-ppm amoxicillin, ampicillin and cloxacillin solutions, respectively. Also, these nanoflowers are thermally stable up to 365 ℃. The associated adsorption process was found to follow pseudo-first-order kinetics, in the case of amoxicillin., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The formation of growth-mediated structures from gold nanoparticle seeds was studied in the presence of amine-modified single-strand DNA sequences and reducing agents such as hydroxylamine and hydroquinone. In the case of hydroxylamine, spherical gold nanoparticle seeds (0.45 nM) were incubated with amine-modified single-strand DNA probes PMR (amine-5'-ACATCAGT-3') and PML (amine-5'-GATAAGCT-3'), which resulted in gold nanoflowers and nanospheres, respectively. When the concentration of the nanoparticle seeds was varied (0.15-0.45 nM), only the PMR sequence showed growth-mediated development of gold nanoflowers. The size of the gold nanoparticles obtained is independent of the seed concentration for both PMR and PML sequences. In contrast, in the presence of the reducing agent hydroquinone, the growth processes are identical in for both the sequences. At a lower seed concentrations (0.15 nM), gold nanoflowers of larger size were observed for both sequences, whereas at higher seed concentrations (0.45 nM), much smaller gold nanospheres resulted. The formation and stability of nanoflowers and nanospheres for PMR and PML with hydroxylamine-based reduction were further studied in detail with diverse controlled amine-modified (5'-, 3'- and both end-modified) and non-modified DNA sequences with other mutants of these two sequences., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanostructured materials have potential as platforms for analytical assays and catalytic reactions. Herein, we report the synthesis of electrocatalytically active cobalt phosphate nanostructures (CPNs) using a simple, low-cost, and scalable preparation method. The electrocatalytic properties of CPNs toward the electrooxidation of glucose (Glu) were studied by cyclic voltammetry and chronoamperometry in relevant biological electrolytes, such as phosphate-buffered saline (PBS), at physiological pH (7.4). Using CPNs, Glu detection could be achieved over a wide range of biologically relevant concentrations, from 1 to 30 mM Glu in PBS, with a sensitivity of 7.90 nA/mM cm 2 and a limit of detection of 0.3 mM, thus fulfilling the necessary requirements for human blood Glu detection. In addition, CPNs showed a high structural and functional stability over time at physiological pH. The CPN-coated electrodes could also be used for Glu detection in the presence of interfering agents (e.g., ascorbic acid and dopamine) and in human serum. Density functional theory calculations were performed to evaluate the interaction of Glu with different faceted cobalt phosphate surfaces; the results revealed that specific surface presentations of under-coordinated cobalt led to the strongest interaction with Glu, suggesting that enhanced detection of Glu by CPNs can be achieved by lowering the surface coordination of cobalt. Our results highlight the potential use of phosphate-based nanostructures as catalysts for electrochemical sensing of biochemical analytes.

An organic-inorganic hybrid glucoamylase nanoflower was prepared in single pot by simple, facile and highly efficient method. The stepwise formation of enzyme-embedded hybrid nanoflowers and influence of experimental parameters viz. pH of solution mixture, enzyme and copper ion concentration on the activity of prepared hybrid nanoflowers were systematically investigated. The self-assembled hybrid glucoamylase nanoflowers were synthesized by mixing aqueous solution of copper sulphate (200mM) with PBS (pH 7.5, 5mM) containing glucoamylase (1mg/mL) in 24h at room temperature. These prepared nanoflowers were further characterized by FT-IR, SEM and XRD. The hybrid nanoflowers exhibited 204% enhanced activity recovery and two folds improvement in thermal stability in terms of half-life (in the range of 50-70°C) with respect to the free form. The hybrid glucoamylase nanoflowers retained 70% residual activity after eight successive cycles indicating their excellent durability. Additionally, the nanoflowers retained up to 91% residual activity upto 25 days of storage. Moreover, the conformational changes occurred in glucoamylase structure after preparing hybrid nanoflowers were evaluated by FT-IR spectroscopy data tools., (Copyright © 2016 Elsevier B.V. All rights reserved.)

We herein report the spontaneous interfacial reaction between copper foil with 0.01 M phosphate buffered saline (PBS) to form free-standing cupric phosphate (Cu3(PO4)2) nanoflowers at ambient temperature. The underlying chemistry was thoroughly investigated and it is found that the formation of nanoflower is synergistically caused by dissolved oxygen, chlorine ions and phosphate ions. Enzyme-Cu3(PO4)2 hybrid nanoflower was further prepared successfully by using an enzyme-dissolving PBS solution and the enzymes in the hybrid exhibit enhanced biological activity. This work provides a facile route for large-scale synthesis of hierarchical inorganic and functional protein-inorganic hybrid architectures via a simple one-step solution-immersion reaction without using either template or surfactant, thus offering great potential for biosensing application among others., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Fundamental parameters influencing the ion-producing efficiency of palladium nanostructures (nanoparticles [Pd-NP], nanoflowers, nanofilms) during laser irradiation were studied in this paper. The nanostructures were immobilized on the surface of different solid inorganic carrier materials (porous and mono-crystalline silicon, anodic porous aluminum oxide, glass and polished steel) by using classical galvanic deposition, electroless local deposition and sputtering. It was the goal of this study to investigate the influence of both the nanoparticular layer as well as the carrier material on ion production for selected analyte molecules. Our experiments demonstrated that the dimensions of the synthesized nanostructures, the thickness of the active layers, surface disorders, thermal conductivity and physically or chemically adsorbed water influenced signal intensities of analyte ions during surface-assisted laser desorption/ionization (SALDI) while no effects such as plasmon resonance, photoelectric effect or catalytic activity were expected to occur. Excellent LDI abilities were seen for Pd-NPs immobilized on steel, while Pd nanoflowers on porous silicon exhibited several disadvantages; viz, strong memory effects, dependency of the analytical signal on amount of physically and chemically adsorbed water inside porous carrier, reduced SALDI activity from unstable connections between Pd and semiconductor material, decrease of the melting point of pure silicon after Pd immobilization and resulting strong laser ablation of metal/semiconductor complex, as well as significantly changed surface morphology after laser irradiation. The analytical performance of Pd-NP/steel was further improved by applying a hydrophobic coating to the steel surface before galvanic deposition. This procedure increased the distance between Pd-NPs, thus reducing thermal stress upon LDI; it simultaneously decreased spot sizes of deposited sample solutions., (Copyright © 2014 John Wiley & Sons, Ltd.)

This study demonstrates the hydrothermal synthesis of 3D flower-like MoS2 nanostructures by varying the heating ramp rate ranging from 1.5 to 5 °C/min. These nanostructures were evaluated for the adsorption and photocatalytic degradation of Rhodamine B (RhB), Methylene Blue (MB), and Tetracycline (TC). Structural and optical properties were characterized using XRD, Raman spectroscopy, FESEM, UV–Vis–NIR spectrophotometry, and XPS. The BET technique assessed surface area, pore size, and volume. Notably, materials synthesized at the slowest heating rate (1.5 °C/min) exhibited superior performance, achieving 98 % degradation of RhB and MB, and 93 % for TC. High adsorption and photocatalytic efficiency were attributed to nanosheets' high density, large specific surface area, zeta potential, and suitable band gap. The study also analyzed the effects of dye concentration and catalyst dosage on RhB degradation, highlighting the synergistic effect of adsorption and photocatalysis in wastewater treatment.

The fabrication of hybrid protein-Cu3(PO4)2 nanoflowers (NFs) via an intermediate toroidal structure is dramatically accelerated under shear using a vortex fluidic device (VFD), which possesses a rapidly rotating angled tube. As-prepared laccase NFs (LNFs) exhibit ≈1.8-fold increase in catalytic activity compared to free laccase under diffusion control, which is further enhanced by ≈ 2.9-fold for the catalysis under shear in the VFD. A new LNF immobilization platform, LNF@silica incorporated in a VFD tube, was subsequently developed by mixing the LNFs for 15 min with silica hydrogel resulting in gelation along the VFD tube surface. The resulting LNFs@silica coating is highly stable and reusable, which allows a dramatic 16-fold enhancement in catalytic rates relative to LNF@silica inside glass vials. Ultraviolet-visible spectroscopy-based real-time monitoring within the LNFs@silica-coated tube reveals good stability of the coating in continuous flow processing. The results demonstrate the utility of the VFD microfluidic platform, further highlighting its ability to control chemical and enzymatic processes.

Zinc Oxide (ZnO) has a huge potential in absorbing light quanta and solar spectrum. Being an appealing semiconductor, ZnO has been synthesized widely to escalate its ability as a nanostructure. In this review, nanostructures of ZnO have been studied as a means to provide simple approaches using anodization. 1 D nanostructures of nanorods, nanotubes and nanowires, and 3 D nanostructures of nanoflowers are chosen due to these dimensional structures synthesized thrivingly via anodization. Observations were made on parameters of times, voltages, and electrolyte concentration. The enlightenment of these synthesis presents the simple approaches and understanding to be imposed on for future endeavor. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) is an odorless gas with a pungent smell that can affect health differently based on exposure and concentration. In this study, indium oxide was decorated with cobalt oxide (In 2 O 3 /Co 3 O 4) flower-like nanocomposites (NFs) as gas-sensitive materials, revealing p-type semiconducting characteristics. The detection of ammonia (NH 3) at low concentrations is a significant challenge for chemoresistive gas sensors. Porous Co 3 O 4 nanoflowers were combined with In 2 O 3 nanoparticles to form p-n heterojunctions for NH 3 detection. The p-n heterojunction effect and the capability of the sub-valent band to hold vacancies within In 2 O 3 nanoparticles effectively inhibit electron-hole recombination and extend the carrier lifetime. The In 2 O 3 /Co 3 O 4 = 0.04 ratio-based gas sensor exhibited excellent selectivity, achieving a low detection limit of 500 ppb for NH 3 at 250 °C. The rapid diffusion of gas within the porous Co 3 O 4 NSs and In 2 O 3 nanoparticles accounted for the high response (7.72) and fast response/recovery time (92 s/51 s) of the In 2 O 3 /Co 3 O 4 -based gas sensor to 10 ppm NH 3. This study presents a method for fabricating NH 3 gas sensors with trace-level detection capabilities by adjusting the band structure of nanoparticles and three-dimensional metal-oxide nanostructures. [ABSTRACT FROM AUTHOR]

Since the use of diverse synthesis approaches can induce the variation in the density of active sites, which impacts electrocatalytic performance, the strategy utilized to fabricate the electrode materials for energy devices is just as important as the materials themselves. Herein, porous NiFe-oxide nanoflowers (NiFe-NFs) and macroparticles (NiFe-MPs) and corresponding S-doped NiFe-oxide nanoflowers (NiFeS-NFs) and macroparticles (NiFeS-MPs) were fabricated using facile co-precipitation and hydrothermal-sulfurization strategies, respectively. The prepared NiFe-NFs, NiFeS-NFs, NiFe-MPs, and NiFeS-MPs materials were investigated for their electrocatalytic HER in 1 M KOH electrolyte. The results indicated that NiFe-NFs displayed an overpotential of 177 mV @ 10 mA/cm2 for HER, whereas the NiFe-MPs, having similar composition, exhibited a high HER overpotential of 187 mV @ 10 mA/cm2. The enhanced HER catalytic performance of NiFe-NFs was attributed to the extensive exposure of active sites at the edges and vertices of nanocubes in the NFs-architecture. Moreover, after sulfurization, NiFeS-NFs and NiFeS-MPs demonstrated a considerable enhancement in their HER activity (54 mV and 152 mV @ 10 mA/cm2, respectively) as compared to un-sulfurized materials, which can be attributed to the enhanced conductivity of materials after S-doping, as supported by theoretical studies. Further, the capacitance experiments showed a significant increment in specific capacitances of NFs and MPs after sulfurization, from 69 to 604 F/g and from 185 to 514 F/g, respectively. This work shows that morphological and compositional changes in metal oxide-based materials may considerably enhance their catalytic activity and capacitance. [Display omitted] • A facile strategy is developed to prepare bimetal oxides/sulfer doped bimetal oxides. • Prepared S-doped/undoped NiFe-oxides possessed nanoflowers/macroparticles morphologies. • Prepared NiFeS-oxide with nanoflowers morphology showed excellent OER and HER. • Prepared nanoflowers type NiFeS-oxide exhibited remarkable charge storage capacilty. [ABSTRACT FROM AUTHOR]

This work reports on the synthesis of different morphologies of gold nanoparticles using a microwave assisted route that is rapid, in situ and seedless. Unlike many currently employed fabricating methods, this method takes place in a single step in microwave. Gold nanospheres with an average particle size of 26 nm were synthesized with only using fructose as a novel reducing agent without any other addition of stabilizers. Branched Gold nanostars were fabricated using fructose, trisodium citrate and NaOH. Varying the concentrations of the Au and NaOH also resulted in the formation of stable gold nanospheres with particle sizes of 4.8 nm and 13 nm respectively. Using fructose along with triethanol amine led to the formation of homogeneously distributed gold nanoflowers. The mechanism for the formation of various morphologies is also presented. Such morphologies are of potential interest in applications such as sensing and catalysis due to the well understood size dependent behaviour of Gold. [ABSTRACT FROM AUTHOR]

ZnO-flaky-like nanoflowers with enhanced photocatalytic activity were synthesized by a new hydrothermal technique. The material was characterized and the photocatalytic studies were conducted under solar light irradiation for a model azo dye, Orange G. The material was compared with ZnO nanosphere and nanorod. The results showed the particle size of the nanostructures as a nanorod is 62–81 nm, as a nanosphere is 40–70 nm and as flaky nanoflowers is 20–30 nm (thickness of the flake). The photocatalytic activity showed an enhanced 2-fold increase in the activity for nanoflowers when compared to nanorods and spheres. The Brauner–Emmett–Teller results showed that the nanoflowers (14.197 m2 g−1) had a higher surface area nearly 3.5 times when compared to the nanospheres (4.06 m2 g−1) and seven times with nanorods (2.1 m2 g−1) which is the possibility of such high photocatalytic activity. The smaller particle size and the arrangement of nanoflowers play an important role in enhanced photocatalytic activity. ZnO flaky-nanoflowers as enhanced photocatalyst for the degradation of organics under solar light irradiation. It showed a two-fold increase in activity than ZnO nanospheres and nanorods. [ABSTRACT FROM AUTHOR]

The sustainable development of pollution‐free technologies for environmental remediation has concerned significant attraction due to rapid growth of industrialization. Herein, synthesis of nanoflower‐like NiO porous nanostructures prepared from different nickel precursors by solvothermal method in combination with calcination treatment is reported. The obtained porous NiO‐Ac (prepared from nickel acetate) and NiO‐S (prepared from nickel sulfate) nanostructures are analyzed by a powder X‐ray diffractometer (XRD), transmission electron microscope (TEM), and BET to determine their structure, morphology, and surface area. Photocatalytic measurement of NiO‐Ac and NiO‐S demonstrates that, these nanostructures show excellent photo degradation behavior toward methylene blue (MB) under ultraviolet radiation. About 85% of MB in 100 min is removed using NiO‐S nanostructured catalyst. Compared with NiO‐Ac, the porous NiO‐S nanoflowers exhibit higher photocatalytic activity due to their large surface area (100.79 m2 g−1) and smaller band gap (3.0 eV). [ABSTRACT FROM AUTHOR]

Pistacia Atlantica biomass was utilized as an activated carbon precursor for the preparation of copper oxide/activated carbon (CuO/AC) nanocomposites and the electrochemical hydrogen storage (EHS) capacities of copper oxide with different morphologies and provided nanocomposites were studied. Further, the influence of copper oxide pores size upon the EHS capacity was studied through chronopotentiometry system. Under 1 mA current, the discharge capacities of CuO nanoflowers (CuO nf), CuO nanoparticles (CuO np), Pistacia Atlantica activated carbon (AC), copper oxide nanoflower/activated carbon (CuO nf /AC), and copper oxide nanoparticle/activated carbon (CuO np /AC) were reached to 650, 850, 1200, 2000, and 3000 mAh/g after 25 cycles, respectively. Outcomes reveal that the coating of copper oxide upon the AC with different pores size leads to get better discharge capacity. Therefore, produced nanostructures with inexpensive and simple manner can be utilized for EHS and can be applied as Renew. Energy to reduce the use of fossil fuels. Image 1 • Preparation of CuO/ Pistacia Atlantica based-AC nanocomposites. • Investigation of CuO pores size influence on the electrochemical hydrogen storage. • The coating via CuO with different pores size leads to different discharge capacity. • The discharge capacity of CuO np /AC is greater than CuO nf /AC after 25 cycles. [ABSTRACT FROM AUTHOR]

• We have synthesized flower and rods-like ZnO nanostructures by a hydrothermal method. • Gas sensing properties of synthesized ZnO nanostructures strongly depend on their morphology and size. • The hierarchical leaf-like nanoflowers show excellent gas sensing properties. • The ZnO sensors shows highest response towards NO 2 at ppb level. Here, we report the hydrothermal synthesis of flower-shaped ZnO nanostructures and investigated their morphology-dependent gas sensing properties. Scanning electron microscope (SEM) study confirmed the formation of two kinds of floral structures. At short reaction time, flower-like structures (2–3 μm in size) composed of nanoparticles are formed, whereas floral assemblies (˜ 5 μm) of nanorods are formed at long reaction time. X-ray diffraction (XRD) confirmed the formation of the hexagonal wurtzite structure of ZnO. The average crystallite size of prepared nanoflowers and nanorods were found to be 21 nm and 43 nm, respectively. These results are supported by transmission electron microscopy (TEM). The band gap of ZnO nanostructures was calculated from the UV–vis absorption spectrum and found to be 3.0 eV and 3.19 eV for ZnO nanoflowers and nanorods, respectively. Broad absorption peak in the visible region of photoluminescence (PL) spectra confirmed the presence of oxygen vacancies in both specimens. Furthermore, morphology dependent gas sensing property was investigated for ethanol, benzene, carbon monoxide, and nitrogen dioxide at different operating temperatures and concentrations. Although both morphologies have shown good sensitivity and selectivity towards NO 2 at ppb, the response of nanoflower was higher than that of nanorods, which was attributed to its relatively higher surface area and amount of surface defects. [ABSTRACT FROM AUTHOR]

Abstract Three dimensional (3D) flower-like BiOCl nanostructures were synthesized by a facile and mild solution chemistry method at room temperature without any post-treatment. It is found that the volume ratios of ethylene glycol to water (EG-W) play an important role in the nucleation and growth of BiOCl, which consequently determine the self-assembly and thus the morphology of BiOCl nanostructures. In the solution of high EG-W ratio, the thin nanosheets self-assemble into 3D flower-like nanostructures, resulting in large surface area and abundant oxygen vacancies. The oxygen vacancies facilitate the trapping and transfer of photogenerated electrons to adsorbed oxygen molecules, producing active O 2 ·− species. As a result, the BiOCl nanoflowers exhibit much higher photocatalytic activity for RhB degradation under visible light irradiation than their nanosheets counterparts synthesized in the solution of low EG-W ratios. Graphical abstract Unlabelled Image Highlights • 3D flower-like BiOCl were synthesized via a facile solution chemistry method. • The ratios of EG-W in synthesis affect the morphology and activity of BiOCl. • Flower-like BiOCl exhibits superior visible-light-driven photocatalytic activity. [ABSTRACT FROM AUTHOR]

Flower-shaped Pt-Pd nanostructures supported on carbon (Pt-Pd/C) were successfully synthesized by simple wet-chemical processing by controlling the rate of reduction of a dissolved metal precursor. L-ascorbic acid (AA) was employed as a green and clean reductive agent for the coreduction of [PtCl 6 ] 2− and [PdCl 4 ] 2− in an aqueous solution. The electrocatalytic activity of nanoporous Pt-Pd/C on the oxygen reduction reaction (ORR) was investigated by rotating disk electrode voltammetry in a 0.1 M HClO 4 solution. In particular, the Pt 77 -Pd 23 /C catalyst showed surpassing ORR activity and acceptable stability under acidic conditions compared to the commercial Pt electrocatalyst. The outstanding electrocatalytic activity was achieved by a combination of the high surface area of flower-like nanostructures and the bimetallic synergetic effect. The morphology, composition and structure of the Pt-Pd/C nanoflowers were confirmed by scanning transmission electron microscopy (STEM), TEM, X-ray photoelectron spectroscopy and X-ray diffraction. Overall, the Pt-Pd/C bimetallic nanostructures are expected to become promising cathode material in fuel cells to replace monometallic Pt ones. [ABSTRACT FROM AUTHOR]

Hierarchical nanostructures of bismuth sulfide (Bi2S3) have been synthesized in orthorhombic phase by hydrothermal method. Conducting polymer polyaniline (PANI) has been synthesized by the chemical oxidative polymerization method and further coupled with Bi2S3 in various weight percentages (1, 2, 5, and 10 wt%) of PANI/Bi2S3 nanocomposite by chemisorption method. The potentiality of these prepared nanostructures has been investigated for the photodegradation of methylene blue (MB) aqueous solutions. Among all, PANI/Bi2S3 (5 wt%) nanocomposite displayed the highest photodegradation efficiency. An ~ 9-fold augment in the photocatalytic activity of bismuth sulfide has been found after its incorporation in PANI matrix. This enhancement is ascribed to the formation of staggered heterojunction and interfacial sites between PANI and Bi2S3 that suppressed recombination of photogenerated charge carriers leading to quicker deterioration of MB. The mechanism for the photocatalytic degradation of methylene blue has been proposed. Based on our results, it is suggested that the coupling of conducting polymer with metal chalcogenides is an important approach for solving the environmental remediation challenge.Hierarchical nanostructures of Bi2S3 have been synthesized by facile hydrothermal method and coupled with conducting polymer polyaniline (PANI) via simple chemisorption method. A remarkable improvement in the photocatalytic efficiency of Bi2S3 has been observed after coupling with PANI. The enhancement in the photocatalytic efficiency of Bi2S3 after incorporating in PANI is attributed to the faster transfer of photogenerated charge carriers at the interface due to the formation of type II heterojunction between matched band edges of PANI and Bi2S3. The present study focuses on designing new nanocomposite photocatalyts for achieving enhanced visible-light-driven photocatalytic performance and improved photoresponse of narrow band gap materials. [ABSTRACT FROM AUTHOR]

In this study, different morphologies of polyaniline (PAni) nanostructures were obtained via interfacial polymerization. The influence of the time and temperature of polymerization on morphology was investigated. At room temperature the growth of nanosheets and nanoflowers with long polymerization time (1–5 days) was observed. In the syntheses carried out at 50 °C the same nanostructures were obtained with only a few hours of polymerization, which illustrates that the increase in temperature considerably reduced the synthesis time and also provided the growth of nanofibers, morphology not found in the syntheses performed at room temperature. The characterization by XRD indicated the presence of diffraction peaks characteristic of PAni nanostructures with high crystallinity. As the conductivity of PAni is directly related to its crystallinity, it is expected that the nanostructures obtained have high conductivity, which may represent a greater potential for diverse applications. It can be concluded that the proposed synthesis presents a simple alternative for obtaining PAni nanostructures with different morphologies and high crystallinity. [ABSTRACT FROM AUTHOR]

The edge sites of NiMoS are highly catalytically active and are preferred over the surfaces. However, the stacking of the NiMoS layers is thermodynamically favored and limits the exposure of the active surface. Herein, we engineer the nanoflower structure to expose surface active sites through the synthesis of NiMoS nanoflowers assembled from ultrathin nanosheets. The well‐controlled fabrication of small NiMoS nanoflowers under the assistance of small silica nanospheres exposes abundant active sites. The exposed active sites and high surface area lead to superior hydrodesulfurization performance. [ABSTRACT FROM AUTHOR]

Two types of ZnO nanostructures were electro-hydrothermally deposited on mesh 100 and 200 copper grids. To investigate the nanostructures, multiple material analyses were used to analyze the material properties. FESEM images indicate that nanoflowers/ nanorods could be grown on the mesh 100 copper grids while a single layer of ZnO nanorods could be grown on the mesh 200 copper grids. Since the size of the grid holes might influence the chemical reactions during the growth of the nanostructures, all the other material analyzes also reveale1 distinct material characteristics of these two types of nanostructures on the copper grid. Based on the experimental results, modulating the ZnO nanostructure will be helpful for future applications of ZnO nanostructures on copper substrates. [ABSTRACT FROM AUTHOR]

Transition metal doped ZnO: (Co/Ni/Cu) nanostructures grown using hydrothermal technique at an optimized growth temperature of 200 °C and a growth time of 3 hours exhibit violet photoluminescence emission. The scanning electron micrographs recorded from the as synthesized samples (ZnO:Co, ZnO:Ni and ZnO:Cu) display nanorods, nanosheet and nanoflower morphology depending upon the dopant/doping percentage. The X-ray diffraction and Raman analysis confirm that hexagonal wurtzite structure of ZnO is retained even after nominal doping of Co, Ni and Cu ions. Optical properties of hydrothermally grown ZnO crystals were analysed with respect to doping concentration (3, 4 and 5 wt%) of Co, Ni and Cu. The optical band gap of ZnO:Co decreases with increasing doping concentration, where as in the case of ZnO:Ni and ZnO:Cu, the band gap increases with increasing the doping concetration. Intense violet deep level emission was observed from ZnO:Co, ZnO:Ni and ZnO:Cu samples at room temperature and the intensity of violet luminescence decreased with increasing the doping concentration of Co2+, Ni2+ and Cu2+ ions into ZnO. • Hydrothermal growth of ZnO doped with Co, Ni and Cu. • Morphological variation of ZnO doped with Co, Ni and Cu. • Lattice volume contraction of ZnO. • Bandgap tuning of ZnO nanostructures with respect to dopants Co, Ni and Cu. • Photoluminescence emission of ZnO from UV to Visible region. [ABSTRACT FROM AUTHOR]

ZnO nanostructures hold substantial promise for gas-sensing applications owing to their outstanding ethanol sensing performance, yet their sensing performance toward NH 3 has rarely been reported. Here, we report on a successful preparation of sunflower-like ZnO nanostructures and ZnO nanoparticle via a facile hydrothermal method, and demonstrate that the ZnO nanoflowers have high gas-sensing performances toward NH 3 under a low concentration of 10–50 ppm. Further structural characterization reveals that the sunflower-like nanostructure comprises six triangles-like and one sphere-like nanostructures, and the triangle-like nanostructure is single crystalline with {0 0 1} crystal face. As a consequence of their unique morphology, the nanoflowers show much improved NH 3 sensing performances than the nanoparticles with a high sensitivity of 49.5. [ABSTRACT FROM AUTHOR]

A green strategy for the synthesis of bimetallic core-shell Au@Pd nanoflowers (NFs) employing banana pseudo-stem-derived TEMPO-oxidized cellulose nanocrystals (TCNC) as both capping and shape-directing agent via seed-mediated method is presented. Flower-like nanostructures of Au@Pd bound to TEMPO-oxidized cellulose nanocrystals (TCNC-Au@Pd) were decorated on amino-functionalized graphene (NH 2 -RGO) without losing their unique structure, allowing them to be deployed as an efficient, reusable and a green alternative heterogeneous catalyst. The decisive role of TCNC in the structural metamorphosis of nanoparticle morphology were inferred from the structural and morphology analyses. According to our study, the presence of –OH rich TCNC appears to play a pivotal role in the structured evolution of intricate nanostructure morphology. The feasibility of the bio-supported catalyst has been investigated in two concurrently prevalent model catalytic reactions, namely the oxygen reduction reaction (ORR) and the reduction of 4-nitrophenol, the best model reactions in fuel cell and industrial catalytic applications, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition. Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Facile template-free electrochemical routes were then developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, rod, sheet, and cabbage onto the aligned MWCNTs at room temperature. Especially, among all the synthesis methods for Au nanocrystals, this is the first report using electrochemical technique to synthesize wide variety shapes of gold nanostructures (GNs) onto the aligned MWCNTs. The morphology of electrodeposited Au nanostructures was controlled by adjustment of the deposition time and potential, the number of potential cycles, the kind of deposition bath, and electrodeposition method. Transmission electron microscopy and field-emission scanning electron microscopy were used to characterize the products. Cyclic voltammograms showed that the MWCNT/Ta electrodes modified with GNs have higher sensitivity compared to the unmodified electrodes in the presence of Fe/Fe redox couple. These kinds of aligned-CNT/Au nanostructure hybrid materials introduced by these efficient and simple electrochemical methods could lead to the development of a new generation device for ultrasensitive catalytic and biological application. [ABSTRACT FROM AUTHOR]

The nanocomposites of graphene loaded- nanoflowers (GR-) had been successfully prepared. Materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) spectra. A possible formation mechanism of this architecture was proposed. The experimental results revealed that these nanoflowers exhibited excellent UV-light photocatalytic activities for pollutant methyl orange (MO) dye degradation. These new nanostructures were expected to show considerable potential applications in the water treatment. The nanocomposites of graphene-loaded-ZnS nanoflowers had been prepared. The possible formation mechanism of this architecture was proposed. The experimental results revealed that these nanoflowers exhibited excellent UV-light photocatalytic activities for pollutant methyl orange dye degradation. [ABSTRACT FROM AUTHOR]

The flower-like nanostructures of an Au core and Pd petals with the average size of 47.8 nm were fabricated through the successive reduction of HAuCl4 and NaPdCl4 at room temperature. During the synthesis, Cacumen Platycladi leaf extract served as weak reductant and capping agent. Characterization techniques such as Energy-dispersive X-ray spectroscopy, UV-Vis spectroscopy, and X-ray diffraction characterizations were employed to confirm that the as-synthesized nanoparticles have the structure of core-shell. The obtained core-shell nanoflowers exhibited good surface enhanced Raman spectroscopic activity with Rhodamine 6G. [ABSTRACT FROM AUTHOR]

Abstract: Zinc cadmium sulfide (Zn x Cd1− x S) nanoflower structure was grown for the first time on glass substrates by microwave-assisted chemical bath deposition with two preparation stages. The first stage was at 80°C for 20min, and the second was at 95°C. Scanning electron microscopy images showed that the nanoflower structure grown on the thin films covered the substrates. The zinc ratio (x) was 0.72 in the Zn x Cd1− x S nanoflowers and 0.30 in the thin film. X-ray diffraction analysis revealed that Zn x Cd1− x S nanocrystalline structure had a hexagonal wurtzite phase. The optical bandgap of the prepared Zn x Cd1− x S nanocrystalline structure calculated from the optical absorption was 2.66eV. Photoluminescence spectra showed two main emission peaks located at 383 and 478nm. An aluminum grid was deposited onto the prepared Zn x Cd1− x S nanocrystalline structure by thermal evaporation to fabricate a photodetector device. The photoelectric properties of the Al/Zn x Cd1− x S device were investigated by the current–voltage characteristic and photoresponse analyses. Under illumination by 365 and 405nm light and 5V bias, the device had faster rise and decay times, but the device was more sensitive to 405nm than 365nm. [Copyright &y& Elsevier]

Abstract: Cobalt hexacyanoferrate (CoHCF) nanostructure was synthesized by anodic oxidation of metallic cobalt nanoflowers in a solution of K3Fe(CN)6. The synthesized CoHCF sample was then employed to prepare a modified carbon paste electrode. The modified electrode was characterized electrochemically in a phosphate buffer solution at physiological pH. Two redox transitions were appeared in the voltammograms which were related to the redox processes of CoII/CoIII and FeII/FeIII in the solid state of CoHCF. The modified electrode was successfully applied to the electrooxidation of nitrite and sulfite and these substrates were oxidized electrocatalytically on the modified electrode surface via the active FeIII species. The catalytic rate constants, the electron transfer coefficients and diffusion coefficients involved in the electrocatalytic oxidation of the compounds were reported. The modified electrode was applied to the amperometric determination of nitrite and sulfite. [Copyright &y& Elsevier]

Abstract: Biosensors have shown great potential for health care and environmental monitoring. The performance of biosensors depends on their components, among which the matrix material, i.e., the layer between the recognition layer of biomolecule and transducer, plays a crucial role in defining the stability, sensitivity and shelf-life of a biosensor. Recently, zinc oxide (ZnO) nanostructures and thin films have attracted much interest as materials for biosensors due to their biocompatibility, chemical stability, high isoelectric point, electrochemical activity, high electron mobility, ease of synthesis by diverse methods and high surface-to-volume ratio. ZnO nanostructures have shown the binding of biomolecules in desired orientations with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes ZnO nanostructures suitable candidate for future small integrated biosensor devices. This review highlights recent advances in various approaches towards synthesis of ZnO nanostructures and thin films and their applications in biosensor technology. [Copyright &y& Elsevier]

CuO three-dimensional (3D) flower-like nanostructures were successfully synthesized by a simple method at 100°C with Cu(NO3)2·3H2O and NH3·H2O for 6 h in the absence of any additives. We found that NH3·H2O amount was critical for CuO morphology evolution. The phase analysis was carried out using X-ray diffraction (XRD) and the result confirmed that the CuO nanoflowers were single-phase. The morphological investigations by field emission scanning electron microscope (FESEM) revealed that the CuO nanoflowers were mono-dispersed in a large quantity and consisted of nanosheets. And then, CuO nanoflowers were successfully used to modify a gold electrode to detect H2O2 with cyclic voltammetry (CV) and amperometric (AC). It was found that CuO nanoflowers may be of great potential for H2O2 electrochemical sensing. [ABSTRACT FROM AUTHOR]

Abstract: Well-defined flower-like CdS nanostructures have been synthesized by applying ultrasound and microwave simultaneously, which consist of hexagonal nanopyramids and/or nanoplates depending on different sulfur sources. It is shown that the synergistic effect of microwave and sonochemistry is the main mechanism for the formation of the nanoflowers. Optical characterization of the nanoflowers shows a large blue-shift up to 100nm in comparing with simple low-dimensional CdS nanostructures. This structure induced shift in optical properties may have potential applications in optoelectronics devices, catalysis, and solar cells. [Copyright &y& Elsevier]

The superior photocatalytic performance of the optimally deigned ZnO nanoflower can be ascribed to the improved surface area and effective separation of photoinduced charge carriers. The optimal ZnO nanoflower consist of c-axis oriented nanorods which accumulated uniformly to form sea urchin like unique hierarchy. [Display omitted] • Variety of ZnO nanoflowers were synthesized without using structure directing reagents. • ZnO with optimal flower like structure exhibit superior photocatalytic performance. • The superior performance can be correlated with the synergy of improved surface area and charge transfer properties. • A probable mechanism explicable for optimal flower formation is also discussed. Zinc oxides (ZnO) nanoflowers have gained enormous attention in photocatalytic applications, despite of the fact that optimization of explicitly designed nanoflower for effective application is still underexplored. In this work, a variety of ZnO nanoflowers were successfully synthesized without using structure directing reagents. ZnO nanoflowers with different morphologies (viz., sea urchin, southern cone marigold and rose flowers) were synthesized through controlling the growth direction by concentrating on synthesis process alone. The photocatalytic performance of ZnO nanoflowers follow order of sea urchin > rose > southern cone marigold flower. These results suggest that optimal ZnO nanoflower (sea urchin) with improved physicochemical parameters such as specific surface area; reduced charge carrier recombination; high aspect ratio and uniform growth along c-axis etc. holds the significant advantage over other morphology. The effective separation and transportation of photogenerated charge carriers were boosted by the existence of high aspect ratio flower like structure, which is confirmed through the detailed photoelectrochemical study. The photocatalysis results substantiated that ZnO nanoflowers display the performance in a morphology-dependent manner and confirms that difference in the intrinsic morphology and the physical accessibility act as a deciding factor in optimizing the best performing ZnO nanoflower. Subsequently, a probable mechanism of optimal flower formation is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Flower-like ZnO nanostructures have been successfully synthesized by the simple chemical precipitation method at room temperature in distilled water medium and without using any capping agent. The nanostructure of the sample has been analyzed by using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The XRD pattern confirmed that the sample is of hexagonal phase of ZnO. The UV–visible optical absorption measurement shows the presence of UV absorption at ~260nm in the sample dispersed in water. The room-temperature photoluminescence (PL) spectrum of the sample consists of near-band edge emission at ~360nm as well as a violet emission band due to the presence of defect states in the sample. Also a reasonable growth mechanism is proposed for formation of flower-like ZnO nano-structures. [Copyright &y& Elsevier]