Influence of thiol capping on the photoluminescence properties of L‐cysteine‐, mercaptoethanol‐ and mercaptopropionic acid‐capped ZnS nanoparticles

Mercaptoethanol (ME), mercaptopropionic acid (MPA) and L‐cysteine (L‐Cys) having ‐SH functional groups were used as surface passivating agents for the wet chemical synthesis of ZnS nanoparticles. The effect of the thiol group on the optical and photoluminescence (PL) properties of ZnS nanoparticles was studied. L‐Cysteine‐capped ZnS nanoparticles showed the highest PL intensity among the studied capping agents, with a PL emission peak at 455 nm. The PL intensity was found to be dependent on the concentration of Zn²⁺ and S^2– precursors. The effect of buffer on the PL intensity of L‐Cys‐capped ZnS nanoparticles was also studied. UV/Vis spectra showed blue shifting of the absorption edge. Copyright © 2015 John Wiley & Sons, Ltd.     

Optical and structural characterization of CdS/ZnS and CdS:Cu2+/ZnS core–shell nanoparticles

Core‐shell CdS/ZnS (Zn 0.025?0.125 M) and CdS:Cu²⁺(1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu²⁺/ZnS core–shell nanoparticles. All absorption peaks of the synthesized samples were highly blue‐shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core–shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of capping agent concentration on thermoluminescence and photoluminescence of copper‐doped zinc sulfide nanoparticles

Copper‐doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent were prepared using a chemical route technique. These particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy and X‐ray diffraction (XRD). Optical absorption studies showed that the absorption edge shifted towards the blue region as the concentration of the capping agent increased. Using effective mass approximation, calculation of the nanoparticle size indicated that effective band gap energy increases with decreasing particle size. The thermoluminescence (TL) properties of sodium hexameta phosphate (SHMP)‐passivated ZnS:Cu nanoparticles were investigated after UV irradiation at room temperature. The TL glow curve of capped ZnS:Cu showed variations in TL peak position and intensity with the change in capping agent concentration. The photoluminescence (PL) spectra of ZnS:Cu nanoparticles excited at 254 nm exhibited a broad green emission band peaking around 510 nm, which confirmed the characteristic feature of Zn²⁺ as well as Cu²⁺ ions as the luminescent centres in the lattice. The PL spectra of ZnS:Cu nanoparticles with increasing capping agent concentrations revealed that the emission becomes more intense and shifted towards shorter wavelengths as the sizes of the samples were reduced. Copyright © 2014 John Wiley & Sons, Ltd.     

Luminescence study of monodispersed ZnS nanoparticles

Monodispersed ZnS nanoparticles have been successfully synthesized by a chemical precipitation method in an air atmosphere using polyvinylpyrrolidone (PVP) and sodium hexametaphosphate (SHMP) as surfactants. The synthesized nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT‐IR), UV–Vis optical absorption and photoluminescence (PL) spectra. Prepared surfactants capped ZnS nanoparticles are highly homogeneous and well dispersed. Optical absorption spectra showed a strong blue shift from the uncapped particles due to the quantum confinement effect. The capped ZnS emission intensity is enhanced than more the uncapped particles. The size of the synthesized particles is around 4–6.5 nm range. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,effect of capping agents and optical properties of manganese‐doped zinc sulphide nanoparticles

Mn²⁺‐doped ZnS nanoparticles have been successfully synthesized by a chemical precipitation method, using non‐ionic surfactants such as PMMA and PEG. The particles were prepared in an air atmosphere at 80°C. X‐ray diffraction (XRD), transmission electron microscopy (TEM), UV‐visible and photoluminescence (PL) studies were used to investigate the effect of the capping agent on the size, morphology and optical properties of the ZnS–Mn²⁺ nanoparticles. Enhanced PL was observed from the surfactant‐capped ZnS–Mn²⁺ nanoparticles. The PL spectra showed a broad blue emission band in the range 460–445 nm and a Mn²⁺‐related yellow‐orange emission band in the range 581–583 nm. Copyright © 2012 John Wiley & Sons, Ltd.     

Luminescence study on Mn,Ni co‐doped zinc sulfide nanocrystals

Zinc sulfide (ZnS) doped with transition metal has been used as phosphor for various optoelectronic applications. In the present report, ZnS:Mn doped and ZnS:Mn,Ni co‐doped were prepared using chemical co‐precipitation method using polyvinyl pyrolidone as a surfactant. The structural studies were carried out using an X‐ray diffraction technique; optical studies have been performed using ultraviolet–visible light absorption and photoluminescence (PL) spectroscopy. The presences of functional groups were confirmed using Fourier transform infrared spectroscopy. The X‐ray diffraction study and Reitveld analysis confirms the formation of cubic phase with crystalline size 2–3 nm for undoped and doped ZnS nanoparticles. A novel and enhanced luminescence characteristic have been observed in PL spectra. The luminescence intensity of Mn,Ni co‐doped ZnS in the blue region is much higher of that of ZnS. The PL results indicate that the doping of Ni creates shallow trap states or luminescence centres in the forbidden energy gap, which quenches the Mn states emission. Concentration quenching has been observed in Mn‐doped ZnS nanoparticles. From CIE coordinates, it is seen that the yellow and blue light emission of ZnS:Mn,Ni co‐doped nanophosphor may be a promising candidate for display devices and phosphor converted light‐emitting diode applications.     

Structural and optical properties of Cu‐doped ZnS nanoparticles formed in chitosan/sodium alginate multilayer films

Chitosan/alginate multilayers were fabricated using a spin‐coating method, and ZnS:Cu nanoparticles were generated within the network of two natural polysaccharides, chitosan and sodium alginate. The synthesized nanoparticles were characterized using an X‐ray diffractometer (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The results showed that cubic zinc blende‐structured ZnS:Cu nanoparticles with an average crystal size of ~ 3 nm were uniformly distributed. UV–vis spectra indicate a large quantum size effect and the absorption edge for the ZnS:Cu nanoparticles slightly shifted to longer wavelengths with increasing Cu ion concentrations. The photoluminescence of the Cu‐doped ZnS nanoparticles reached a maximum at a 1% doping level. The ZnS:Cu nanoparticles form and are distributed uniformly in the composite multilayer films with a surface average height of 25 nm. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications

Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo‐hydrothermal (S‐H) method using water–acetonitrile–ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), Fourier transform (FT)‐Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380–580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm^–1. Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of capping agent on the particle size of CdSe nanoparticles

CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route method the samples were capped by starch and in the chemical route method the samples were capped by mercaptoacetic acid (MAA). The samples were characterized by powder X‐ ray diffraction (XRD) and transmission electron microscopy (TEM). Both the samples showed zinc blend structure. The optical absorption spectra and Fourier transform infrared (FTIR) spectra were also studied. A blue shift was seen in the absorption spectra as compared with the bulk as well as the sample capped by starch. TEM images showed agglomeration for the starch‐capped sample as compared with the MAA‐capped sample. The particle size for the sample capped by MAA was found to be less as compared with the starch‐capped sample. A blue shift in the photoluminescence (PL) spectra was also recorded for the samples prepared by the chemical route as compared with the sample prepared by the green route as well as the bulk. The PL peak shifted towards the red side and increase in the peak intensity occurred with the change in the excitation wavelength. Change in PL intensity was observed with different pH at 685 nm. Copyright © 2016 John Wiley & Sons, Ltd.     

Blue emitting ZnO nanostructures grown through cellulose bio‐templates

This paper presents a green and cost‐effective recipe for the synthesis of blue‐emitting ZnO nanoparticles (NPs) using cellulose bio‐templates. Azadirachta indica (neem) leaf extract prepared in different solvents were used as biological templates to produce nanostructures of wurtzite ZnO with a particle size ~12–36 nm. A cellulose‐driven capping mechanism is used to describe the morphology of ZnO NPs. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), Fourier transform infra‐red (FTIR) and photoluminescence (PL) studies showed that solvents affect the growth process and the capping mechanism of bio‐template severely. Structural changes in ZnO NPs were evident with variation in pH, dielectric constants (DC) and boiling points (BP) of solvents. Furthermore, an energy band model is proposed to explain the origin of the blue emission in the as‐obtained ZnO NPs. PL excitation studies and the theoretical enthalpy values of individual defects were used to establish the association between the interstitial‐zinc‐related defect levels and the blue emission. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation on the pH‐independent photoluminescence emission from carbon dots impregnated on polymer matrix

Highly luminescent, polymer nanocomposite films based on poly(vinyl alcohol) (PVA), and monodispersed carbon dots (C‐dots) derived from multiwalled carbon nanotubes (MWCNTs), as coatings on substrates as well as free standing ones are obtained via solution‐based techniques. The synthesized films exhibit pH‐independent photoluminescence (PL) emission, which is an advantageous property compared with the pH‐dependent photoluminescence intensity variations, generally observed for the C‐dots dispersed in aqueous solution. The synthesized C‐dots and the nanocomposite films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infra‐red spectroscopy ( FTIR), ultraviolet (UV) ? visible spectroscopy and photoluminescence spectroscopy (PL) techniques. The TEM image provides clear evidence for the formation of C‐dots of almost uniform shape and average size of about 8 nm, homogeneously dispersed in aqueous medium. The strong anchoring of C‐dots within the polymer matrix can be confirmed from the XRD results. The FTIR spectral studies conclusively establish the presence of oxygen functional groups on the surfaces of the C‐dots. The photoluminescence (PL) emission spectra of the nanocomposite films are broad, covering most part of the visible region. The PL spectra do not show any luminescence intensity variations, when the pH of the medium is changed from 1 to 11. The pH‐independent luminescence, shown by these films offers ample scope for using them as coatings for designing diagnostic and imaging tools in bio medical applications. The non‐toxic nature of these nanocomposite films has been established on the basis of cytotoxicity studies.     

Tuneable luminescence properties of EDTA‐assisted ZnS:Mn nanocrystals from a yellow‐orange to a red emission band

Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn²⁺ ions by a wet chemical route stabilized by ethylenediamine tetra‐acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X‐ray diffraction (XRD), High‐resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)–visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow‐orange bands were red shifted towards the red region under the same excitation wavelength. The orange‐red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn²⁺ ions [⁴T₁(⁴G)‐⁶A₁(⁶S)]; the ZnS matrix varied with Mn²⁺ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn²⁺‐doped ZnS nanocrystal emission bands can be tuned from the yellow‐orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications.     

Synthesis and characterization of high quantum yield and oscillator strength 6‐chloro‐2‐(4‐cynophenyl)‐4‐phenyl quinoline (cl‐CN‐DPQ) organic phosphor for solid‐state lighting

A novel blue luminescent 6‐chloro‐2‐(4‐cynophenyl) substituted diphenyl quinoline (Cl‐CN DPQ) organic phosphor has been synthesized by the acid‐catalyzed Friedlander reaction and then characterized to confirm structural, optical and thermal properties. Structural properties of Cl‐CN‐DPQ were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X‐ray diffraction technique (XRD) and scanning electron microscopy (SEM) and energy dispersive analysis of X‐ray (EDAX) spectroscopy. FTIR spectra confirmed the presence of different functional groups and bond stretching. ¹H–NMR and ¹³C–NMR confirmed the formation of an organic Cl‐CN‐DPQ compound. X‐ray diffraction study provided its crystalline nature. The surface morphology of Cl‐CN‐DPQ was analyzed by SEM, while EDAX spectroscopy revealed the elemental analysis. Differential thermal analysis (TGA/DTA) disclosed its thermal stability up to 250°C. The optical properties of Cl‐CN‐DPQ were investigated by UV–vis absorption and photoluminescence (PL) measurements. Cl‐CN‐DPQ exhibits intense blue emission at 434 nm in a solid‐state crystalline powder with CIE co‐ordinates (0.157, 0.027), when excited at 373 nm. Cl‐CN‐DPQ shows remarkable Stokes shift in the range 14800–5100 cm^?1, which is the characteristic feature of intense light emission. A narrow full width at half‐maximum (FWHM) value of PL spectra in the range 42–48 nm was observed. Oscillator strength, energy band gap, quantum yield, and fluorescence energy yield were also examined using UV–vis absorption and photoluminescence spectra. These results prove its applications towards developing organic luminescence devices and displays, organic phosphor‐based solar cells and displays, organic lasers, chemical sensors and many more.     

Effect of synthesis method and chemical reagents on the structural parameters,particle size,and optical and photoluminescence properties of ZnS nanostructures

In this experimental study, ZnS nanostructures were synthesized using two hydrothermal and co‐precipitation methods with different precursors. Different reagents and precursors were changed to obtain the best product size and morphology. The structure and crystal phase of the products were studied using X‐ray diffraction (XRD) patterns. Some structural parameters were calculated using the XRD results and a product composition was obtained by energy dispersive X‐ray (EDX) analysis and Fourier transform infrared (FT‐IR) spectra to study the chemical composition. The size and morphology of ZnS nanostructures were obtained by scanning electron microscopy (SEM). The optical properties of the synthesized ZnS nanostructures were examined using ultraviolet–visible (UV–Vis) spectra to estimate the optical band gap. Band gap energies were higher than those in the ZnS bulk sample, mainly due to quantum size effects. The photoluminescence (PL) properties of the products were investigated using PL spectra. The results showed the effect of two factors, namely synthesis method and chemical reagents, on the structure parameters, crystallite size, product size and morphology, and optical and PL properties.     

In situ synthesis of CdS nanoparticles on bacterial cellulose nanofibers

CdS nanoparticles have been synthesized and stabilized on unique bacterial cellulose (BC) nanofibers in situ. The obtained nanocomposite material have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transformed infrared (FTIR), thermogravimetric analysis (TGA), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The results indicated that CdS nanoparticles of about 30 nm diameter deposited on BC nanofibres are well-dispersed in the BC nanofibre-network and the uniform spherical CdS nanoparticles are comprised of nano-sized CdS crystal. Moreover, the crystallite sizes of CdS crystals are about 8 nm. The nanocomposites would have potential application as photocatalyst, novel luminescence and photoelectron transfer devices.     

Optical studies of CdS:Mn nanoparticles

Cadmium sulphide nanoparticles were grown using a wet chemical method, by dissolving the reactants, cadmium chloride and sodium sulphide in water, in the presence of mercaptoethanol (ME), which was used as a capping agent. Manganese chloride was used to dope the nanoparticles. It was found that the particle size varied with different concentrations of ME. At higher concentrations of ME, smaller sized nanoparticles were synthesized. This method also reveals the high stability of nanoparticles in water. Nanoparticle properties were investigated using UV–vis absorption, photoluminescence spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The particle sizes were measured by the XRD technique, SEM and optical absorption spectra and were in the range 2–6 nm. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,characterization and optical studies of highly luminescent ZnS nanoparticles associated with hypromellose matrix as a green and novel stabilizer

ZnS nanoparticles stabilized by a carbohydrate‐based matrix, hypromellose (hydroxypropyl methylcellulose) were prepared via a wet chemical method. The nanocomposite was characterized by X‐ray diffraction, transmission electon microscopy and Fourier transform infrared spectroscopy. X‐Ray diffraction patterns revealed a zinc blende structure. Thermogravimetric analysis suggested that polymer attached to the surface decomposes at 700 °C. Absorption measurements were carried out and calculation of the diameter polydispersity index (DPI) suggests the formation of monodisperse nanoparticles. The optical properties of the as‐prepared samples were studied by UV/vis spectroscopy and steady‐state photoluminescence (PL) spectroscopy. The PL studies indicate the applicability of these nanoparticles as biocompatible sensors or luminescence markers in future. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescence investigation of a cerium‐doped yttrium vanadate phosphor

Cerium (Ce³⁺)‐doped (1, 3, and 7 mol%) yttrium vanadate phosphors were prepared using a co‐precipitation technique. The structural and optical properties of the synthesized samples were studied using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HR‐TEM), optical absorption, and photoluminescence (PL) spectroscopy techniques. The tetragonal structure and the formation of the nanosized crystallites in the YVO₄:Ce phosphor were confirmed using XRD analysis. HR‐TEM morphology showed rod‐like nanoparticles of different sizes. Optical absorption spectra demonstrated strong absorption bands at 268 and 276 nm. PL spectra showed strong peaks at 546, 574, and 691 nm following excitation at 300 nm. The calculated CIE chromaticity coordinates demonstrated that YVO₄:Ce could be used as a novel phosphor for the development of light‐emitting diode lamps.     

Enhanced photoluminescence properties of electrospun Dy3+‐doped ZnO nanofibres for white lighting devices

Dy³⁺‐doped ZnO nanofibres with diameters from 200 to 500 nm were made using an electrospinning technique. The as‐fabricated amorphous nanofibres resulted in good crystalline continuous nanofibres through calcination. Dy³⁺‐doped ZnO nanofibres were characterized using scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) light spectroscopy, Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). XRD showed the well defined peaks of ZnO. UV–vis spectra showed a good absorption band at 360 nm. FTIR spectra showed a Zn–O stretching vibration confirming the presence of ZnO. Photoluminescence spectra of Dy³⁺‐doped ZnO nanofibres showed an emission peak in the visible region that was free from any ZnO defect emission. Emissions at 480 nm and 575 nm in the Dy³⁺‐doped ZnO nanofibres were the characteristic peaks of dopant Dy³⁺ and implied efficient energy transfer from host to dopant. Luminescence intensity was found to be increased with increasing doping concentration and reduction in nanofibre diameter. Colour coordinates were calculated from photometric characterizations, which resembled the properties for warm white lighting devices.     

Cell culture and characterization of cross-linked poly(vinyl alcohol)-g-starch 3D scaffold for tissue engineering

The research goal of this experiment is chemically to cross-link poly(vinyl alcohol) (PVA) and starch to form a 3D scaffold that is effective water absorbent, has a stable structure, and supports cell growth. PVA and starch can be chemically cross-linked to form a PVA-g-starch 3D scaffold polymer, as observed by Fourier transform infrared spectroscopy (FTIR), with an absorbency of up to 800%. Tensile testing reveals that, as the amount of starch increases, the strength of the 3D scaffold strength reaches 4 × 10⁻² MPa. Scanning electron microscope (SEM) observations of the material reveal that the 3D scaffold is highly porous formed using a homogenizer at 500 rpm. In an enzymatic degradation, the 3D scaffold was degraded by various enzymes at a rate of up to approximately 30–60% in 28 days. In vitro tests revealed that cells proliferate and grow in the 3D scaffold material. Energy dispersive spectrometer (EDS) analysis further verified that the bio-compatibility of this scaffold.