ZnO nanorods and Mn/ZnO microflowers with nano-sized petals exhibit singly ionized oxygen vacancies, V+O. This is strongly supported by a green photoluminescence emission at 2.22 eV and an EPR g value of 1.953, both of which are suppressed greatly after annealing in an oxygen atmosphere. A strong red emission observed during exposure to X-rays reveals the presence of F+ centres as a consequence of the V+O. Mn/ZnO displayed enhanced H<inf>2</inf> generation with visible light exposure, when compared to pure ZnO and annealed Mn/ZnO in the visible region, which directly correlated with the oxygen vacancy concentration. There is an interesting correlation between the intensities of the EPR lines at the g-value of 1.953 due to the oxygen vacancies, the intensity of light emitted from the exposure to X-rays, the intensity of the photoluminescence due to oxygen vacancies and the quantity of H<inf>2</inf> produced by the photocatalytic effect when comparing the three different nanomaterials, viz. pure ZnO, Mn/ZnO before and after annealing, all having been made exactly by the same methodologies. © The Royal Society of Chemistry 2015.

Robin Jude Vimal Michael

Periyakaruppan Thangiah Manoharan

Annealing

Light

Manganese

nanorods

Oxygen

photoluminescence

Vacancies

Zinc oxide

GREEN PHOTOLUMINESCENCE

Intensity of light

Oxygen atmosphere

OXYGEN VACANCY CONCENTRATION

PHOTOCATALYTIC EFFECT

SINGLY IONIZED OXYGEN

STRONG RED EMISSIONS

Visible region

Oxygen vacancies

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Nanoscale

Four different nanocomposites of AuAgZnO with differing compositions of silver and gold were made by solution combustion method where the EDAX analysis gave the exact composition. Nanocomposites were formed as nanospheres. The composites contained bimetallic AuAg particles on the surface of ZnO semiconductor, the interface being silver. The deconvoluted UV-DRS spectra revealed the presence of two plasmons due to Au and Ag. The amount of gold dominates the AuAg indicating the presence of only a thin layer of silver below gold causing a blue-shifted gold plasmon band and red-shifted silver plasmon band in comparison to their pure entity. The intensity of the former gets increased due to interparticle interaction with silver. Presence of excess gold in one sample of the starting materials tends to form amorphous Au2O3 as proved by both EDAX and XPS. The number of oxygen vacancies in ZnO as seen in EPR depends on AuAg metal content effects the photocatalytic degradation of Rhodamine-B and the photocatalytic production of hydrogen. The interparticle interaction of Ag with Au and ZnO also plays a major role in photocatalytic process. An in vitro cytotoxicity study of AuAgZnO nanocomposites on MCF-7 cell lines is compared with the effect of gold alone in AuZnO. The current study revealed that the presence of silver in the bimetallic system suppresses the efficacy of Au and even ZnO. Gold by itself is a powerful cytotoxic nanoagent even with small amount of ZnO, the latter being known for its nontoxicity. It is interesting to note that Ag has a negative role in cytotoxicity but it contributes positively to photocatalysis. © 2017 American Chemical Society.

Journal of Physical Chemistry C

Effect of Silver on Plasmonic, Photocatalytic, and Cytotoxicity of Gold in AuAgZnO Nanocomposites

Sodium Lauryl Sulphate (SLS) surfactant and propylene diamine (PD), assisted wet chemical synthesis was used to make ZnS-Cu2S nanoflakes wherein the added copper(ii) transforms into copper(i) sulphide and is found to be deposited on the surface of ZnS. With a variation of copper concentration from 0 to 5% there is a morphological transformation from ZnS nanorods eventually to ZnS-Cu2S nanoflakes through a transition morphology of nanocactus leaves. During the addition of copper there is an incorporation of Cu2S into the ZnS phase (100) as is clearly evidenced by various characterization methods. Visible light photocatalytic hydrogen production activities using these nanoflakes of ZnS-Cu2S are reported with good results. The influence of Cu2S shifts the band gap of ZnS from the UV to the visible region, reducing the need for an expensive co-catalyst like platinum for photolysis of water. Though hydrogen production is not as high as that depicted by other earlier works the material that we have created is a relatively cheap, simple two component heterostructure with no expensive third component. It is also free from toxic materials such as CdS. However, our results are better than for most other copper loaded ZnS systems in the literature. Furthermore, the morphological evolution to nanoflakes from nanorods, the concentration and dispersion of Cu2S over ZnS and the interface between Cu2S and ZnS semiconductors play a vital role in hydrogen production. 5% Cu2S on ZnS seems to be the optimum concentration for maximum evolution of hydrogen. © 2015 The Royal Society of Chemistry.

RSC Advances

Cu2S-incorporated ZnS nanocomposites for photocatalytic hydrogen evolution

Silver doped zinc oxide nanoparticles are synthesized by a solution combustion method. The samples characterized by a variety of spectroscopic and other techniques clearly reveal the presence of silver nanoparticles as well as silver clusters. The silver in the two forms was identified by careful deconvolution of X-ray photoelectron spectral results. Their formation was also confirmed by the presence of plasmons, the concentration and energy of which increase on increasing silver input, indicating the presence of perpendicular excitons since aggregates of clusters are known to shift the plasmon resonances depending on their topologies. Further confirmation of clusters came from EPR (electron paramagnetic resonance), HRSEM (high resolution scanning electron microscopy) and HRTEM (high resolution transmission electron microscopy); direct proof for clusters came from matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectral measurements. The antimicrobial activity of the silver doped zinc oxide polymer nanocomposites as biomedical devices are measured by zone of inhibition. Also, samples coated on paper disk with acacia binder are evaluated by a disk diffusion method. While pure zinc oxide does not show any antimicrobial property, the activity of silver-doped zinc oxide is comparable to that of commercial antibiotics and found to be related to nanoparticulate silver. Similarly, the microbial adherence to the surface of polymer nanocomposite which mimics a biomedical device also was influenced by nanoparticles of silver. The photocatalytic water treatment was carried out using silver carrying nanoparticles with Rhodamine-B and 4-chlorophenol as model pollutants. The increased photocatalytic activity of silver containing zinc oxide as compared to pure zinc oxide nanoparticles is attributed to the synergistic display of the properties of silver nanoparticles and clusters in zinc oxide. This activity depends upon the dispersion of silver nanoparticles over the zinc oxide lattice where charge separation plays a dominant role. The mechanisms for both photocatalysis and antimicrobial activity are discussed. © 2014 the Owner Societies.

Physical Chemistry Chemical Physics

Spectroscopic dimensions of silver nanoparticles and clusters in ZnO matrix and their role in bioinspired antifouling and photocatalysis

Nanocomposites of gold nanoparticles and semiconductor ZnO with wurtzite structure, made by solution combustion synthesis (SCS), as a function of the Zn/fuel ratio with polyethylene glycol (PEG) as fuel exhibit the presence of both nanoparticles and clusters. Atomic gold clusters present on the surface of ZnO nanorods which can be identified by XPS and SEM are easily monitored and characterized by positive ion MALDI experiments as mostly odd numbered clusters, Au3 to Au11 in decreasing amounts. Low concentrations of the fuel produce AuClO and nanoparticles (NPs), with no clusters. Au-ZnO nanocomposites at all [Au] exhibit single blue shifted plasmon absorption and corresponding photoluminescence (PL). Increasing particle size prefers surface plasmon resonance (SPR) scattering of metal that could lead to PL enhancement; however, available ZnO surface in the Au-ZnO composite becomes more important than the particle size of the composite with higher [Au]. The catalytic activity of these Au-ZnO nanocomposites tested on 4-nitrophenol clearly revealed the presence of an intermediate with both NPs and clusters playing different roles. An in vitro study of cytotoxicity on MCF-7 cell lines revealed that these gold nanostructures have turned out to be powerful nanoagents for destruction of cancer cells even with small amounts of gold particles/clusters. The nanorods of ZnO, known to be nontoxic to normal cells, play a lesser role in the anticancer activity of these Au-ZnO nanocomposites. © the Partner Organisations 2014.

Fulltext

Fuel mediated solution combustion synthesis of ZnO supported gold clusters and nanoparticles and their catalytic activity and in vitro cytotoxicity

Scientific Reports

Effect of aspect ratio and surface defects on the photocatalytic activity of ZnO nanorods

Oxygen deficient ZnO1−xnanosheets with high visible light photocatalytic activity

Oxygen vacancies and intense luminescence in manganese loaded Zno microflowers for visible light water splitting

Journal	Data powered by TypesetNanoscale
Publisher	Data powered by TypesetRoyal Society of Chemistry
ISSN	20403364
Open Access	No