Publications by authors named "Rajiv Pandey"

11 Publications

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Unfolding Photophysical Properties of Poly(3-hexylthiophene)-MoS2 Organic-Inorganic Hybrid Materials: An Application to Self-Powered Photodetectors.

Nanotechnology 2021 Jun 3. Epub 2021 Jun 3.

Physics, Motilal Nehru National Institute of Technology, Allahabad, Allahabad, 211004, INDIA.

Self-powered photodetectors have grown as inevitable members of the optoelectronic device family. However, it is still challenging to achieve self-powered photodetection with good responsivity in the visible spectrum region. Herein, we report solution-processable poly(3-hexylthiophene) (P3HT)-molybdenum disulfide (MoS2) organic-inorganic hybrid material, which can be used as the active layer in self-powered photodetectors. The morphological and structural properties of the synthesized P3HT-MoS2 hybrid material has been discussed using atomic force microscopy and transmission electron microscopy, respectively. The hybrid material loaded with 1 wt% MoS2 has shown an enhancement in the self-assembly of polymer in the form of fibrillar formation and excellent structural features in terms of π-conjugation. The self-powered photodetectors have been fabricated in indium tin oxide (ITO) coated glass/P3HT-MoS2/Al configuration. The merit of P3HT-MoS2 hybrid photodetectors is measured under the illumination of 470, 530, and 627 nm light in ambient conditions. P3HT-MoS2 photodetectors show significantly higher responsivity and detectivity. The photo responsivity and detectivity in P3HT-MoS2 devices are found to be 271.2 mA/W and 4.4 × 1010 jones at zero bias, respectively, for 470 nm light with the optical power density of 74.1 µW/cm2. Furthermore, the photocurrent switching behaviour at periodic illuminations of 1 Hz has also been examined for P3HT-MoS2 self-powered photodetectors.
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http://dx.doi.org/10.1088/1361-6528/ac07d2DOI Listing
June 2021

Target 5000: a standardized all-Ireland pathway for the diagnosis and management of inherited retinal degenerations.

Orphanet J Rare Dis 2021 May 5;16(1):200. Epub 2021 May 5.

Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, Dublin, Ireland.

Introduction: Inherited retinal degenerations (IRD) are rare genetic disorders with > 300 known genetic loci, manifesting variably progressive visual dysfunction. IRDs were historically underserved due to lack of effective interventions. Many novel therapies will require accurate diagnosis (phenotype and genotype), thus an efficient and effective pathway for assessment and management is required.

Methods: Using surveys of existing practice patterns and advice from international experts, an all-Ireland IRD service (Target 5000) was designed. Detailed phenotyping was followed by next generation genetic sequencing in both a research and accredited laboratory. Unresolved pedigrees underwent further studies (whole gene/whole exome/whole genome sequencing). Novel variants were interrogated for pathogenicity (cascade screening, in silico analysis, functional studies). A multidisciplinary team (MDT; ophthalmologists, physicians, geneticists, genetic counsellors) reconciled phenotype with genotype. A bespoke care plan was created for each patient comprising supports, existing interventions, and novel therapies/clinical trials.

Results And Discussion: Prior to Target 5000, a significant cohort of patients were not engaged with healthcare/support services due to lack of effective interventions. Pathogenic or likely pathogenic variants in IRD-associated genes were detected in 62.3%, with 11.6% having variants of unknown significance. The genotyping arm of Target 5000 allowed a 42.73% cost saving over independent testing, plus the value of MDT expertise/processing. Partial funding has transferred from charitable sources to government resources.

Conclusion: Target 5000 demonstrates efficacious and efficient clinical/genetic diagnosis, while discovering novel IRD-implicated genes/variants and investigating mechanisms of disease and avenues of intervention. This model could be used to develop similar IRD programmes in small/medium-sized nations.
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http://dx.doi.org/10.1186/s13023-021-01841-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8097252PMC
May 2021

Effects of ambient climate and three warming treatments on fruit production in an alpine, subarctic meadow community.

Am J Bot 2021 03;108(3):411-422

Department of Plant and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-405 30, Gothenburg, Sweden.

Premise: Climate change is having major impacts on alpine and arctic regions, and inter-annual variations in temperature are likely to increase. How increased climate variability will impact plant reproduction is unclear.

Methods: In a 4-year study on fruit production by an alpine plant community in northern Sweden, we applied three warming regimes: (1) a static level of warming with open-top chambers (OTC), (2) press warming, a yearly stepwise increase in warming, and (3) pulse warming, a single-year pulse event of higher warming. We analyzed the relationship between fruit production and monthly temperatures during the budding period, fruiting period, and whole fruit production period and the effect of winter and summer precipitation on fruit production.

Results: Year and treatment had a significant effect on total fruit production by evergreen shrubs, Cassiope tetragona, and Dryas octopetala, with large variations between treatments and years. Year, but not treatment, had a significant effect on deciduous shrubs and graminoids, both of which increased fruit production over the 4 years, while forbs were negatively affected by the press warming, but not by year. Fruit production was influenced by ambient temperature during the previous-year budding period, current-year fruiting period, and whole fruit production period. Minimum and average temperatures were more important than maximum temperature. In general, fruit production was negatively correlated with increased precipitation.

Conclusions: These results indicate that predicted increased climate variability and increased precipitation due to climate change may affect plant reproductive output and long-term community dynamics in alpine meadow communities.
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http://dx.doi.org/10.1002/ajb2.1631DOI Listing
March 2021

Factors associated with non-attendance in the Irish national diabetic retinopathy screening programme (INDEAR study report no. 2).

Acta Diabetol 2021 May 23;58(5):643-650. Epub 2021 Jan 23.

Mater Retina Research Group, Mater Misericordiae University Hospital, Dublin, Ireland.

Aims: We aimed to determine the patient and screening-level factors that are associated with non-attendance in the Irish National Diabetic Retinal screening programme (Diabetic RetinaScreen). To accomplish this, we modelled a selection of predictors derived from the historical screening records of patients with diabetes.

Methods: In this cohort study, appointment data from the national diabetic retinopathy screening programme (RetinaScreen) were extracted and augmented using publicly available meteorological and geospatial data. A total of 653,969 appointments from 158,655 patients were included for analysis. Mixed-effects models (univariable and multivariable) were used to estimate the influence of several variables on non-attendance to screening appointments.

Results: All variables considered for analysis were statistically significant. Variables of note, with meaningful effect, were age (OR: 1.23 per decade away from 70; 95% CI: [1.22-1.24]), type 2 diabetes (OR: 1.10; 95% CI: [1.06-1.14]) and socio-economic deprivation (OR: 1.12; 95% CI: [1.09-1.16]). A majority (52%) of missed appointments were from patients who had missed three or more appointments.

Conclusions: This study is the first to outline factors that are associated with non-attendance within the Irish national diabetic retinopathy screening service. In particular, when corrected for age and other factors, patients with type 2 diabetes had higher rates of non-attendance. Additionally, this is the first study of any diabetic screening programme to demonstrate that weather may influence attendance. This research provides unique insight to guide the implementation of an optimal and cost-effective intervention strategy to improve attendance.
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http://dx.doi.org/10.1007/s00592-021-01671-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8076137PMC
May 2021

Irish National Diabetic RetinaScreen Programme: report on five rounds of retinopathy screening and screen-positive referrals. (INDEAR study report no. 1).

Br J Ophthalmol 2020 Dec 17. Epub 2020 Dec 17.

Diabetic RetinaScreen, National Screening Service, Health Service Executive, Dublin, Ireland

Objective: To study the uptake of annual diabetic retinopathy screening and study the 5-year trends in the detection of screen-positive diabetic retinopathy and non-diabetes-related eye disease in a cohort of annually screened individuals.

Design: Retrospective retinopathy screening attendance and retinopathy grading analysis.

Setting: Community-based retinopathy screening centres for the Diabetic RetinaScreen Programme.

Participants: 171 557 were identified by the screening programme to be eligible for annual diabetic retinopathy screening. 120 048 individuals over the age of 12 consented to and attended at least one screening appointment between February 2013 to December 2018.

Main Outcome Measures: Detection rate per 100 000 of any retinopathy, screen-positive referrable retinopathy and nondiabetic eye disease.

Results: Uptake of screening had reached 67.2% in the fifth round of screening. Detection rate of screen-positive retinopathy reduced from 13 229 to 4237 per 100 000 screened over five rounds. Detection of proliferative disease had reduced from 2898 to 713 per 100 000 screened. Non-diabetic eye disease detection and referral to treatment centres increased almost eightfold from 393 in round 1 to 3225 per 100 000 screened. The majority of individuals referred to treatment centres for ophthalmologist assessment are over the age of 50 years.

Conclusions: Screening programme has seen a reduced detection rate both screen-positive retinopathy referral in Ireland over five rounds of screening. Management of nondiabetic eye diseases poses a significant challenge in improving visual outcomes of people living with diabetes in Ireland.
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http://dx.doi.org/10.1136/bjophthalmol-2020-317508DOI Listing
December 2020

Nature rejuvenation: Long-term (1989-2016) vs short-term memory approach based appraisal of water quality of the upper part of Ganga River, India.

Environ Technol Innov 2020 Nov 16;20:101164. Epub 2020 Sep 16.

Nanjing University of Information Science and Technology, School of Hydrology and Water Resources, Nanjing, Jiangsu Province, 210044, China.

The deteriorating water quality (WQ) of the sacred north-flowing perennial Indian River, Ganga was a serious concern in recent decades for population adjoining to the river and policy planners. The present evaluation attempts to assess the long-term (1989-2016) physiochemical characteristics of WQ of river Ganga at five upstream locations (Uttarkashi, Tehri, Rudraprayag, Devprayag, and Rishikesh) of Uttarakhand, India using comprehensive pollution index (CPI) and environmetrics (PCA and CA). These methods were used to categorize, summarize expensive datasets, and grouping the similar polluted areas along the river stretches. The WQ of river at all the locations were within the good category and most of the physiochemical parameters were well within their acceptable limit for drinking WQ. Considerably, CPI demonstrated the river WQ was in slight pollution range (CPI: 0.40-1.00) in the year 2007 and 2015 at all the five locations. The positive correlation coefficient (R > 0.50) among NO NO, Ca, Na, B, and K indicates the significant contribution of organic and inorganic salts through runoffs from catchments due to weathering of rocks. PCA confirmed the input source of nutrients in the river from both natural and anthropogenic sources. Moreover, the upstream WQ assessed was found to be good as compared to the severely polluted downstream region. Due to COVID-19 and shutdown in the country, reduction of pollution load in the river was observed due to the rejuvenation capability of river Ganga. This information can assist the environmentalist, policymaker, and water resources planners & managers to prepare strategic planning in advance to maintain the aesthetic and cultural value of Ganga river in future.
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http://dx.doi.org/10.1016/j.eti.2020.101164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493808PMC
November 2020

Polymer/Graphene oxide nanocomposite thin film for NO sensor: An in situ investigation of electronic, morphological, structural, and spectroscopic properties.

Sci Rep 2020 Feb 19;10(1):2981. Epub 2020 Feb 19.

School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, 221005, India.

The higher operating temperature of metal oxide and air instability of organic based NO sensor causes extremely urgent for development of a reliable low cost sensor to detect NO at room temperature. Therefore, we present a fabrication of large area Polymer/GO nano hybrid thin film for polymer thin film transistors (PTFTs) based NO sensors assisted via facile method named 'spreading-solidifying (SS) method', grown over air/liquid interface and successive investigation of effect of NO on film via several characterizations. The PTFTs sensor has demonstrated swift and high response towards low concentration of NO gas with air stability and provided real time non-invasive type NO sensor. Herein, we are reporting the nanohybrid PBTTT/GO composite based PTFT sensor with good repeatability and sensor response for low concentration NO. The thin film grown via SS technique has reported very good adsorption/desorption of target analyte having response/recovery time of 75 s/523 s for 10 ppm concentration of NO gas. It has been observed that % change in drain current (sensor response) saturated with increasing concentration of NO. The transient analysis demonstrates the fast sensor response and recovery time. Furthermore, in order to understand the insight of high performance of sensor, effect of NO on nanohybrid film and sensing mechanism, an in situ investigations was conducted via multiple technique viz. spectral, electronic, structural, and morphological characterization. Finally, the performance of sensor and the site of adsorption of NO at polymer chains were argued using schematic diagram. This work shows the simple fabrication process for mass production, low cost and room temperature operated gas sensors for monitoring the real-time environment conditions and gives an insight about the sensing mechanism adsorption site of NO.
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http://dx.doi.org/10.1038/s41598-020-59726-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031537PMC
February 2020

Corrosion prevention of commercial alloys by air-water interface grown, edge on oriented, ultrathin squaraine film.

Sci Rep 2019 Sep 17;9(1):13488. Epub 2019 Sep 17.

School of Materials science and Technology, Indian Institute of Technology (BHU), Varanasi, Uttar Pradesh, 221005, India.

Copper is one of the most demanded commercial metal/alloys in world market. The demand for copper in industries such as electrical, electronics, automobile, telecommunications, defence, etc. as well as in daily life has escalated in the recent years due to its versatile physical and chemical properties. However destruction of copper surface by any means, preferably corrosion, can limit its vast application. For protection from corrosion, various techniques are used to coat metal substrates with passivating materials. These techniques are either complex as well as expensive, or provide incomplete protection in acid media. To address these issues, floating film transfer method (FFTM) is utilized in this work for obtaining ultrathin film of squaraine (passivating molecule) as well as their easy and fast transfer over copper substrate. The squaraine film is deposited on copper substrate in layers, viz., 1 to 4 layers. The corrosion behavior is examined in 0.1 M HCl using electrochemical techniques as well as surface characterization techniques, which portray that copper corrosion is hampered in harmony with the layers deposited. Nearly 40% corrosion protection is reached for copper coated with 1 layer of squaraine. However, the protection is amplified up to 98% with 4 layers of squaraine, which clearly substantiates the supremacy of this coating method over reported methods of protection. This technique and the material (squaraine) are both for the first time being used in the field of corrosion protection. The easy growth of ultrathin film at air-water interface as well as its rapid transfer over substrate promotes use of FFTM for efficient corrosion protection on industrial scale.
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http://dx.doi.org/10.1038/s41598-019-50092-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6748964PMC
September 2019

Homogenous Dispersion of MoS Nanosheets in Polyindole Matrix at Air-Water Interface Assisted by Langmuir Technique.

Langmuir 2017 11 13;33(47):13572-13580. Epub 2017 Nov 13.

School of Materials Science and Technology, Indian Institute of Technology, Banaras Hindu University , Varanasi-221005, India.

Two-dimensional (2D) inorganic layered materials when embedded in organic polymer matrix exhibit exotic properties that are grabbing contemporary attention for various applications. Here, nanosheet morphology of molybdenum disufide (MoS) synthesized via one-pot facile hydrothermal reaction are exfoliated in benign aqueous medium in the presence of indole to obtain a stable dispersion. These exfoliated nanosheets then act as host to template the controlled polymerization of indole. The preassembled MoS-polyindole (MoS-PIn) nanostructures are reorganized at the air-water interface using the Langmuir method to facilitate maximum interfacial interaction between nanosheet and polymer. This report emphasizes large area, homogeneous dispersion of uniform-sized MoS nanosheets (40-60 nm diameter) in the PIn matrix and the formation of stable and uniform film via the Langmuir-Schaefer (LS) method. These self-assembled, MoS decorated PIn LS films are characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The fabricated LS films in sandwiched structure Al/MoS-PIn/ITO as the Schottky diode portrayed remarkable enhancements in charge transport properties. Our study illustrates the potential of the MoS-PIn LS film in electronic applications and opens a new dimension for uniform dispersion of 2D materials in other polymers via the Langmuir method for device fabrication and enhancement of electrical properties.
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http://dx.doi.org/10.1021/acs.langmuir.7b03019DOI Listing
November 2017

Surface plasmon coupled metal enhanced spectral and charge transport properties of poly(3,3'''-dialkylquarterthiophene) Langmuir Schaefer films.

Nanoscale 2015 Apr;7(14):6083-92

School of Materials Science and Technology, Indian Institute of Technology (BHU), Varanasi-221005, India.

The coupling of organic molecule excitons with metal nano-structure surface plasmons can improve the performance of optoelectronic devices. This paper presents the effect of localized silver metal surface plasmons on spectral as well as charge transport properties of ordered molecular Langmuir Schaefer (LS) films of a fluorescent conducting multifunctional organic polymer: poly (3,3'''-dialkylquarterthiophene) [PQT-12]. The stability and thickness of the PQT-12 LS film were studied by the pressure vs. area isotherm curve. Atomic force microscopy images indicate the formation of a smooth ordered polymer thin LS film of PQT-12 over silver nanostructure island films [SNIF] (∼40 to 50 nm in size). Raman, electronic absorption and fluorescence spectral measurements of the PQT-12 LS film, near SNIF i.e. the near field, show a plasmon coupled enhancement of ∼13 fold in the intensity of Raman bands along with a two-fold enhancement in the absorption band (531 nm) and a six-fold enhancement in the fluorescence band (665 nm) coupled with a decrease in fluorescence decay time with improved photostability as compared to an identical control sample containing no SNIF i.e. the far field condition. These results indicate the formation of a plasmon coupled unified fluorophore system due to adsorption of the PQT-12 LS film over SNIF. The effect of plasmonic coupling is also studied by applying an electric field in sandwiched structures of Al/PQT-12 LS/SNIF/ITO with respect to Al/PQT-12 LS/ITO. Nearly three orders of magnitude enhancement in the current density (J-V plot) of the PQT-12 LS film is observed in the presence of SNIF, which further increases, on illuminating the film by green laser light [532 nm], while the fluorescence intensity and decay time decrease. X-ray photoelectron spectroscopic measurements of SNIF also show a red shift in 3d3/2 and 3d5/2 transitions of silver in the PQT-12 coated LS film, which indicates partial charge transfer from the PQT-12 polymer backbone to SNIF and causes an enhancement in conductivity. This again supports the formation of a field controlled radiating plasmon coupled fluorophore unified system. These findings show greater potential in developing a voltage controlled high photon flux electroluminescent material for multifarious applications.
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http://dx.doi.org/10.1039/c5nr00682aDOI Listing
April 2015

Enhanced osteoblast proliferation and corrosion resistance of commercially pure titanium through surface nanostructuring by ultrasonic shot peening and stress relieving.

J Oral Implantol 2014 Jul;40 Spec No:347-55

1  Faculty of Dental Sciences, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.

This investigation was carried out to study the effect of a novel process of surface modification, surface nanostructuring by ultrasonic shot peening, on osteoblast proliferation and corrosion behavior of commercially pure titanium (c p-Ti) in simulated body fluid. A mechanically polished disc of c p-Ti was subjected to ultrasonic shot peening with stainless steel balls to create nanostructure at the surface. A nanostructure (<20 nm) with inhomogeneous distribution was revealed by atomic force and scanning electron microscopy. There was an increase of approximately 10% in cell proliferation, but there was drastic fall in corrosion resistance. Corrosion rate was increased by 327% in the shot peened condition. In order to examine the role of residual stresses associated with the shot peened surface on these aspects, a part of the shot peened specimen was annealed at 400°C for 1 hour. A marked influence of annealing treatment was observed on surface structure, cell proliferation, and corrosion resistance. Surface nanostructure was much more prominent, with increased number density and sharper grain boundaries; cell proliferation was enhanced to approximately 50% and corrosion rate was reduced by 86.2% and 41% as compared with that of the shot peened and the as received conditions, respectively. The highly significant improvement in cell proliferation, resulting from annealing of the shot peened specimen, was attributed to increased volume fraction of stabilized nanostructure, stress recovery, and crystallization of the oxide film. Increase in corrosion resistance from annealing of shot peened material was related to more effective passivation. Thus, the surface of c p-Ti, modified by this novel process, possessed a unique quality of enhancing cell proliferation as well as the corrosion resistance and could be highly effective in reducing treatment time of patients adopting dental and orthopedic implants of titanium and its alloys.
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http://dx.doi.org/10.1563/AAID-JOI-D-12-00006DOI Listing
July 2014