A comparison of manganese activated CdS nanorods with the nonactivated ones prepared by simple chemical methods in micellar medium reveals quantum confinement and blue shift in optical spectroscopy as a function of Mn 2+. Powder XRD of all samples reveals orientation along the 002 plane, confirmed by HRTEM. Nonactivated CdS gives a blue band edge emission at 455 nm in the PL spectrum getting quenched on Mn2+ addition. The PL spectra of Mn2+ added CdS exhibit first an emission at 367.7 nm, which later gets subjected to Davydov splitting with a separation of ̃0.045 eV, the singlet intensity decreasing and the doublet intensity increasing with Mn2+ input. This PL property is manifested in EPR as due to two different Mn2+ environments: (i) individual tetrahedrally coordinated uncoupled Mn2+ ions; (ii) Mn2+-Mn2+ physical dimer moieties. These are interpreted to arise from (i) the formation of a first layer of MnS on a CdS surface and (ii) the latter due to a second layer of MnS on top of the first to form MnS-MnS dimers. Mn2+ is present as metastable β-MnS. The vydov splitting is accompanied by a small energy shift. The double layer formation is confirmed by a bleaching experiment. Also noted is a low intensity band edge emission of CdS perturbed by Mn2+ blue-shifted from the quenched 455 nm emission. ICP and EDS confirm the purity of samples. © 2009 American Chemical Society.

Periyakaruppan Thangiah Manoharan

Band-edge emissions

Blue shift

Blue-shifted

CDS NANOROD

Chemical method

Davydov splitting

DOUBLE LAYER FORMATION

LOW-INTENSITY

MICELLAR MEDIUM

Optical spectroscopy

PL emission

PL PROPERTY

PL spectra

Powder XRD

SECOND LAYER

Small energy

Cadmium compounds

Data storage equipment

Electron resonance

Electron spin resonance spectroscopy

Emission spectroscopy

Inductively coupled plasma

LASER RADIATION

Manganese compounds

nanorods

Oligomers

Paramagnetic resonance

quantum theory

Semiconducting cadmium compounds

Manganese

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

Journal of Physical Chemistry C

Nanocrystals of CdS/Mn2+ synthesized using sodium lauryl sulphate (SLS) surfactant and two ligands, i.e. butylenediamine (BD) and propylenediamine (PD), of differing lengths show a dominant presence of the hexagonal phase. The increasing [Mn2+] in the CdS/Mn2+ crystals from BD medium leads to a red shift in the band gap absorption with increasing intensity while the optical properties are reversed in CdS/PD crystals. Such changes can be explained by the switching of the randomly blinking nanocrystals into coherently emitting nanocrystals. The photoluminescence of CdS/Mn2+ materials with similarities and differences between SLS/BD and SLS/PD media exhibits two emissions: at 2.25 eV due to cadmium ion vacancies exhibiting Davydov-type splitting from neighbouring Cd2+-Cd2+ vacancies, and at 2.18 eV from manganese d-d emission. Thus, addition of Mn2+ leads to a decrease in the intensity of vacancy emission and increase in d-d emission due to occupation of cadmium vacant sites by manganese. Interestingly, SLS/PD medium creates more defects in CdS nanocrystals than SLS/BD medium. Note that the CdS/Mn2+ nanocrystals made from SLS/BD medium exhibit weak ferromagnetism in pre-annealed samples, becoming stronger after annealing, while the preannealed samples from SLS/PD origin have the simultaneous presence of both superparamagnetism and ferromagnetism, which turns to complete ferromagnetism on annealing. An attempt has also been made to compare the various properties of nanomaterials made as a function of two surfactants and three diamines of differing lengths. These nanoparticles are in the size range of 10 to 15 nm. A simple photo-resistance experiment on CdS and carbon nanoparticles-based heterostructure reveals its photosensitivity. This journal is © the Partner Organisations 2014.

RSC Advances

Davydov splitting in cadmium vacancy emission, ferromagnetism and photosensitivity in manganese incorporated CdS nanocrystals

Manganous ion doped CdS nanocrystals with different concentrations of Mn2+ have been synthesized by a chemical synthesis route. The as-synthesized Mn2+/CdS nanocrystals evince interesting optical emission properties; the intensity of cadmium vacancy emissions VCd decreases on the addition of the dopant ion, proving the displacement of cadmium by manganese which is accompanied by the appearance and enhancement of the Mn2+ d-d emission, 4T1 → 6A1. However, the intensity of the latter emission decreases on further increase in [Mn2+] due to strong cluster formation, such as Mn2+-Mn2+. The low temperature electron paramagnetic resonance measurements suggest strong antiferromagnetism due to strong exchange coupling between the spins of nearby Mn2+ centres both in pre- and post-annealed 5% Mn2+/CdS samples. These magnetic properties for pre- and post-annealed 5% Mn2+/CdS samples are explained by a core/shell (antiferromagnetism/ferromagnetism) model. The pre-annealed sample, on one hand, shows antiferromagnetic behavior with weak ferromagnetism below the Néel temperature, the latter due to uncompensated surface spins. On the other hand, annealing leads to the formation of more Mn2+-Mn2+ dimers or clusters due to ionic migration. This will result in increased antiferromagnetic character as compared to the pre-annealed sample. Both are confirmed by magnetization hysteresis curves at various temperatures. The electron microscopy images confirm the morphology prediction by XRD. © 2013 The Royal Society of Chemistry.

Coexistence of antiferromagnetism and ferromagnetism in Mn2+/CdS nanocrystals and their photophysical properties

We report a simple chemical route for converting the dimorphic CdS nanocrystals into pure hexagonal structure by loading ̃5 %Mn 2+ into CdS in presence of a surfactant rather than under harsh conditions reported earlier. Differential scanning calorimetric measurement was used to quantify the percentages of cubic and hexagonal components at lower manganese ion loading, which correlated well with the Short and Steward procedure using X-ray diffraction analysis. Annealing of all lower (&lt; 5 %) manganese ion-loaded samples transforms the cubic component into its hexagonal form. Systematic variation of manganese ion concentration in the range of 0-5 % helps tune in a new combination of photoluminescence bands, composed of a band edge, surface and manganese d-d emissions. The manganese ions located inside the CdS matrix studied by electron paramagnetic resonance (EPR) reveal progressively changing presence of (i) distorted tetrahedral nature of isolated Mn2? and (ii) cluster formation through dipolar and/or exchange coupling arising from Mn 2+-Mn 2+ interaction. There is a neat correlation between PL and EPR properties on the one hand and between EPR and magnetism on the other. Most important part of this investigation lies in manganese coupled ferromagnetism (FM) as compared to our earlier reported anti-FM-coupled superparamagnetism, the difference originating from the use of different ligands. Pre-annealed (as synthesized) and post-annealed CdS/Mn 2+ nanocrystals exhibit FM of manganese origin, the latter exhibiting increased FM due to annealing promoted migration of manganese ions to form more clusters, as confirmed by magnetization experiments. Electron microscopy reveals the formation of nanorods and nanoparticles. © Springer Science+Business Media B.V. 2012.

Journal of Nanoparticle Research

Manganous ion dictated morphology change and ferromagnetism in CdS nanocrystals

Nanorods of II-VI semiconductor CdS are prepared from simple precursors by wet chemical method. The CdS nanorods are characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD studies showed that the crystal structure of the nanorods is in the hexagonal phase of CdS. The preferred orientation of (0 0 2) direction suggests that the nanorods of CdS is grown along (0 0 2) direction. The growth direction is further confirmed by microstructural analysis using HRTEM. Growth mechanism of the nanorods is explained on the basis of the population balance equation (PBE) model. The PBE model explains that the initially formed nanodots undergo oriented attachment (under ageing) along a particular direction having effective dipole moment (in the case of CdS it is (0 0 2) followed by coalescence leading to the smooth nanorods). This process takes place by ageing of the reaction solutions. The quasi-spherical nature of the particles results in a non-integral aspect ratio for the nanorods. Optical studies by UV-vis spectroscopy show a blue-shifted absorption at 493 nm because of the quantum confined excitonic absorption. © 2008 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Growth and mechanism of CdS nanorods by microstructure analysis

Nanotechnology

Thermochemical growth of Mn-doped CdS nanoparticles and study of luminescence evolution

Phase and shape controlling of MnS nanocrystals in the solvothermal process

Optical Materials

The temperature dependence of photoluminescence and absorption spectra of vacuum-sublimed magnesium phthalocyanine thin films

The Journal of Physical Chemistry C

(Mn, Zn) Co-Doped CdS Nanowires

Davydov split PL emission and EPR correlation in β-mns layered cds nanorods

Journal	Journal of Physical Chemistry C
ISSN	19327447
Open Access	No