Publications by authors named "Arshad Saleem Bhatti"

8 Publications

  • Page 1 of 1

Tuning optical properties of CsPbBr3 by mixing Nd3+trivalent lanthanide halide cations for blue light emitting devices.

Nanotechnology 2022 Jan 13. Epub 2022 Jan 13.

Department of Physics, COMSATS Institute of Information Technology, Center for Micro and Nano Devices, Park Road, Islamabad, 44000, PAKISTAN.

In recent years, significant progress has been made in the red and green perovskite quantum dots (PQDs) based light-emitting devices. However, a scarcity of blue-emitting devices that are extremely efficient precludes their research and development for optoelectronic applications. Taking advantage of tunable bandgaps of PQDs over the entire visible spectrum, herein we tune optical properties of CSPbBr3 by mixing Nd3+ trivalent lanthanide halide cations for blue light-emitting devices. The CsPbBr3 PQDs doped with Nd3+ trivalent lanthanide halide cations emitted strong photoemission from green into the blue region. By adjusting their doping concentration, a tunable wavelength from (515 nm) to (450 nm) was achieved with FWHM from (37.83 nm) to (16.6 nm). We simultaneously observed PL linewidth broadening thermal quenching of PL and the blue shift of the optical bandgap from temperature-dependent PL studies. The Nd3+ cations into CsPbBr3 PQDs more efficiently reduced non-radiative recombination. As a result of the efficient removal of defects from PQDs, the photoluminescence quantum yield (PLQY) has been significantly increased to 91% in the blue-emitting region. Significantly, Nd3+ PQDs exhibit excellent long-term stability against the external environment, including water, temperature, and ultraviolet light irradiation. Moreover, we successfully transformed Nd3+ doped PQDs into highly fluorescent nanocomposites. Incorporating these findings, we fabricate and test a stable blue light-emitting LED with EL emission at (462 nm), (475 nm), and successfully produce white light emission from Nd3+ doped nanocomposites with a CIE at (0.32, 0.34), respectively. The findings imply that low-cost Nd3+ doped perovskites may be attractive as light converters in LCDs with a broad color gamut.
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http://dx.doi.org/10.1088/1361-6528/ac4b2eDOI Listing
January 2022

Trioctylphosphine-Assisted Pre-protection Low-Temperature Solvothermal Synthesis of Highly Stable CsPbBr/TiO Nanocomposites.

J Phys Chem Lett 2021 Apr 13;12(15):3786-3794. Epub 2021 Apr 13.

Centre for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44500, Pakistan.

Lead halide perovskite quantum dots (PQDs) are reported as a promising branch of perovskites, which have recently emerged as a field in luminescent materials research. However, before the practical applications of PQDs can be realized, the problem of poor stability has not yet been solved. Herein, we propose a trioctylphosphine (TOP)-assisted pre-protection low-temperature solvothermal synthesis of highly stable CsPbBr/TiO nanocomposites. Due to the protection of branched ligands and the lower temperature of shell formation, these TOP-modified CsPbBr PQDs are successfully incorporated into a TiO monolith without a loss of fluorescence intensity. Because the excellent nature of both parent materials is preserved in CsPbBr/TiO nanocomposites, it is found that the as-prepared CsPbBr/TiO nanocomposites not only display excellent photocatalytic activity but also yield improved PL stability, enabling us to build highly stable white light-emitting diodes and to photodegrade rhodamine B.
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http://dx.doi.org/10.1021/acs.jpclett.1c00693DOI Listing
April 2021

A versatile approach for shape-controlled synthesis of ultrathin perovskite nanostructures.

Dalton Trans 2021 Mar;50(9):3308-3314

Centre for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Islamabad, 44500, Pakistan.

Very recently, ultrathin perovskite nanostructures, with the advantages of perovskite and ultrathin properties, have received an enormous level of interest due to their many fascinating properties, such as a strong quantum confinement effect and a large specific surface area. In spite of this incredible success of perovskite nanocrystals (NCs), the development of perovskite NCs is still in its infancy, and the production of high-quality ultrathin perovskite nanostructures has been a hot topic in the fields of nanoscience and nanotechnology. Herein, we demonstrate that ultrathin CsPbBr3 perovskite nanosheets (NSs) can be obtained by a simple mixing of precursor-ligand complexes under ambient conditions. It was found that the formation of NSs is ascribed to the stepwise self-assembly of the initially formed different types of ultrathin nanostructures. Due to the disappearance of grain boundaries and protection of branched ligands, these NSs exhibit enhanced optical properties compared to other types of samples. This direct synthesis method opens up a promising road for the synthesis of ultrathin NSs and guides the fabrication of other ultrathin nanostructures.
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http://dx.doi.org/10.1039/d0dt04203jDOI Listing
March 2021

Pressure-Driven Transformation of CsPbBrI Nanoparticles into Stable Nanosheets in Solution through Self-Assembly.

J Phys Chem Lett 2020 Nov 10;11(22):9862-9868. Epub 2020 Nov 10.

Belarusian State University of Informatics and Radioelectronics, P. Browki St. 6, 220013 Minsk, Belarus.

Very recently, two-dimensional (2D) perovskite nanosheets (PNSs), taking the advantages of perovskite as well as the 2D structure properties, have received an enormous level of interest throughout the scientific community. In spite of this incredible success in perovskite nanocrystals (NCs), self-assembly of many nanostructures in metal halide perovskites has not yet been realized, and producing highly efficient red-emitting PNSs remains challenging. In this Letter, we show that by using CsPbBrI perovskite nanoparticles (NPs) as a building block, PNSs can emerge spontaneously under high ambient pressure via template-free self-assembly without additional complicated operation. It is found that the formation of PNSs is ascribed to the high pressure that provides the driving force for the alignment of NPs in solution. Because of the disappearance of the grain boundaries between the adjacent NPs and increased crystallinity, these PNSs self-assembled from NPs exhibit enhanced properties compared to the initial NPs, including higher PL intensity and remarkable chemical stability toward light and water.
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http://dx.doi.org/10.1021/acs.jpclett.0c02747DOI Listing
November 2020

The adverse role of excess negative ions in reducing the photoluminescence from water soluble MAA-CdSe/ZnS quantum dots in various phosphate buffers.

Phys Chem Chem Phys 2018 Nov;20(46):29446-29451

Department of Biosciences, COMSATS University Islamabad (CUI), Park Road, Islamabad 45600, Pakistan.

The use of CdSe/ZnS quantum dots in making biosensors or biomarkers requires them to be water soluble, which can be achieved by conjugating with MAA. We report observation of modulation in the photoluminescence intensities of MAA conjugated CdSe/ZnS QDs (MAA-QDs) that depended strongly on the types and quantity of negative ions present in various kinds of phosphate buffers. The deterioration of PL was attributed to the presence of excess ions in the media that altered the energy and occupation of HOMO and LUMO levels of MAA. Instantaneously, strong reduction in the PL intensity with pH was observed. MAA-QDs incubated for more than 24 hours in the phosphate buffer at pH ∼ 7.0-8.0 showed recovery and enhanced PL intensity, which was attributed to the presence of excess positive ions and a small amount of OH-. Saline buffers showed no significant recovery due to the presence of additional Cl- ions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were successfully employed to determine the band edges of the MAA-QD system in the presence of excess positive or negative ions (Na+, H+, Cl-, and OH-) in the media. Thus, it is very important to have complete knowledge of the ions present in the buffer when using MAA-QDs for biomarking or biosensing applications.
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http://dx.doi.org/10.1039/c8cp06213gDOI Listing
November 2018

Efficient seed-mediated method for the large-scale synthesis of Au nanorods.

J Nanopart Res 2017 17;19(3):115. Epub 2017 Mar 17.

Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands.

Seed-mediated methods are widely followed for the synthesis of Au nanorods (NRs). However, mostly dilute concentrations of the Au precursor (HAuCl) are used in the growth solution, which leads to a low final concentration of NRs. Attempts of increasing the concentration of NRs by simply increasing the concentration of HAuCl, other reagents in the growth solution and seeds lead to a faster growth kinetics which is not favourable for NR growth. Herein, we demonstrate that the increase in growth kinetics for high concentrations of reagents in growth solution can be neutralised by decreasing the pH of the solution. The synthesis of the NRs can be scaled up by using higher concentrations of reagents and adding an optimum concentration of HCl in the growth solution. The concentration of HAuCl in the growth solution can be increased up to 5 mM, and 10-20 times more NRs can be synthesised for the same reaction volume compared to that of the conventional seed-mediated method. We have also noticed that a cetyltrimethylammonium bromide (CTAB)-to-HAuCl molar ratio of 50 is sufficient for obtaining high yield of NRs.
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http://dx.doi.org/10.1007/s11051-017-3815-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5357265PMC
March 2017

Synthesis of ZnO nanostructures for low temperature CO and UV sensing.

Sensors (Basel) 2012 Oct 16;12(10):13842-51. Epub 2012 Oct 16.

Thin Films Technology Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan.

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature using a vapor transport method. Needle-like ZnO nanobelts are unique as, according to our knowledge, there is no evidence of such morphology in previous literature. The structural, morphological and optical characterization was carried out using X-ray diffraction, scanning electron microscopy and diffused reflectance spectroscopy techniques. It was observed that the sensing response of comb-like structures for UV light was greater as compared to the other grown structures. Comb-like structure based gas sensors successfully detect CO at 75 °C while other structures did not show any response.
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http://dx.doi.org/10.3390/s121013842DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3545595PMC
October 2012

Measurement of soil radioactivity levels and radiation hazard assessment in southern Rechna interfluvial region, Pakistan.

Environ Monit Assess 2010 Oct 29;169(1-4):429-38. Epub 2009 Oct 29.

Department of Physics, COMSATS Institute of Information Technology, Islamabad, Pakistan.

Rechna interfluvial region is one of the main regions of Punjab, Pakistan. It is the area which is lying between River Ravi and River Chenab, alluvial-filled. Radioactivity levels in soil samples, collected from southern Rechna interfluvial region, Pakistan, have been estimated by using gamma-ray spectrometric technique. (226)Ra, (232)Th, the primordial radionuclide (40)K, and the artificial radionuclide (137)Cs have been measured in the soil of the study area. The mean radioactivity levels of (226)Ra, (232)Th, (40)K, and (137)Cs were found to be 50.6 +/- 1.7, 62.3 +/- 3.2, 662.2 +/- 32.1, and 3.1 +/- 0.3 Bq kg(-1), respectively. The mean radium equivalent activity (Ra(eq)), outdoor radiation hazard index (H(out)), indoor radiation hazard index (H(in)), and terrestrial absorbed dose rate for the area under study were determined as 190.8 +/- 8.7 Bq kg(-1), 0.52, 0.65, and 69.8 nGy h(-1), respectively. The annual effective dose to the general public was found to be 0.43 mSv. This value lies well below the limit of 1 mSv for general public as recommended by the International Commission on Radiological Protection. The measured values are comparable with other global radioactivity measurements and are found to be safe for the public and the environment.
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http://dx.doi.org/10.1007/s10661-009-1185-1DOI Listing
October 2010
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