Search

A set of eight heteroleptic bis-diimine copper dye complexes with two different ancillary ligands (functionalised 2,9-dimethyl-1,10-phenanthroline (dmp) and functionalised 6,6'-diphenyl-2,2'-bipyridine (dpbpy)) are investigated for their potential use as sensitizers in dye-sensitized solar cells (DSSCs), using first principles density functional theory (DFT) and time dependent DFT (TDDFT). A detailed analysis of the structural properties, projected density of electronic states and Kohn-Sham energy levels, and optical absorption spectra in the UV-visible region reveals that substituting the thiophene group in the ancillary ligand, and enhancing conjugation in the anchoring ligand, lead to increase in the light harvesting efficiency (LHE). However, a natural transition orbital (NTO) analysis, shows that the nature of charge transfer depends mainly on the nature of the parent ancillary group and is not significantly affected by the structural modifications. Importantly, the lower energy excitations lead to favourable mixed metal to ligand charge transfer (MLCT) and ligand to ligand charge transfer (LLCT), as well as good electron injection. The best charge transfer directionality is found in the dmp-based dyes, particularly thiophene substituted dyes, thus making these the more effective sensitizers in DSSCs.

Photovoltaic (PV) materials with high efficiencies are currently the lead-based perovskites. However, nontoxic, stable, lead-free perovskites are of immense interest as environment-friendly green m...

Purpose Chronic kidney disease (CKD) is an emerging health problem worldwide. In CKD corneal endothelial changes also occur probably due to accumulation of inflammatory cytokines and increased multiple toxic products. The aim of this study was to analyze the effect of CKD on corneal endothelium and correlate the findings with severity of disease with help of noninvasive technique. Methods The study comprised 75 eyes of 75 cases divided into three groups with group A comprising of CKD cases on dialysis, group B of nondialysis CKD cases, and group C of controls. Each group had 25 cases each of either sex and between 15-80 age groups. All patients were investigated for blood urea, serum creatinine, and blood sugar and underwent complete ophthalmic examination of both eyes along with wide-field specular microscopy examination. Results The majority of patients (33.3%) belonged to age range of 61-70 years with male predominance and the most common cause of CKD was found to be diabetes with 17 (34%) cases. We found normal corneal endothelial cell density (ECD) with the mean ECD of 2364.52 ± 397.72 mm2 in the dialysis group, 2467.8 ± 352.88 mm2 in nondialysis group, and 2521.68 ± 250.26 mm2 in the control group of patients. However, we found significant increase in coefficient of variation (CV) with 36 ± 5.8% in dialysis group, 37 ± 4.5% in nondialysis group and 32 ± 0.8% in controls (P = 0.001) and decreased hexagonality (Hx) with 47 ± 7.3% in dialysis group, 46 ± 4.7% in nondialysis group and 51 ± 6.7% in the controls (P = 0.031). This showed increased tendency of pleomorphism and polymegathism in corneal endothelial cells in CKD cases. No correlation was found between blood urea or serum creatinine levels with endothelial parameters in any group. Conclusion CKD causes morphological changes like polymegathism and pleomorphism in corneal endothelium and hence these cases are more vulnerable and special care should be taken before any intraocular surgical procedure.

In the present work, pure and Fullerene (C60)-doped methyl ammonium lead halide (CH3NH3PbI3) perovskite thin films were prepared on glass substrates by spin coating method at different concentrations of fullerene (C60).The structural, morphological, and optical characteristics of as-prepared thin films were analysed using experimental and computational methods. The X-ray diffraction studies and their Reitveld refinement analysis of the samples confirms that all deposited perovskite thin films have tetragonal structure and are highly oriented along the (110) plane. The morphology of the perovskite films was investigated by field emission scanning electron microscope (FE-SEM). The elemental composition of perovskite thin films was confirmed by Energy Dispersive X-rays Analysis (EDAX). The addition of fullerene (C60) resulted in the increase of grain size sand a more compact surface development of the perovskite thin films with fewer flaws as compared with perovskite thin films without (C60) was evaluated. Also, geometrical, electronic and optical properties were studied by using the first principles DFT computational method. Optical properties have been studied experimentally and verified computationally. All the perovskite thin film samples exhibit direct band-gap which is suitable for solar cells applications.

Background: Radiotherapy plays a critical role in the management of many patients with head-and-neck (H&N) cancer. To study the incidence of dry eye associated with radiotherapy and correlate them with dose of radiation.Methods: This Hospital based prospective study comprises of 100 patients of head and neck tumors who received radiotherapy by linear accelerator from 2015 to 2017. Ocular examination was done prior to the start of therapy, 1st follow up at 15th day of therapy, 2nd at last day of therapy (23-35 fraction), 3rd at 3 months after completion of therapy for side effects, 4th at 6 months, 5th at 12 month and 6th at 18 months after completion of therapy for assessing dry eye.Results: 59% patients developed dry eye. 44 patients received dose 45-55 Gy and out from these 13 (29.50%) patients developed dry eye, 40 patients received dose 56-65 Gy and out from these 33 (78.00%) patients developed dry eye and 16 patients received dose 66-70 Gy and out from these 13 (95.00%) patients developed dry eye.Conclusions: We concluded that the incidence of dry eye increased with increased total radiation dose. The current study suggests the importance of total dose as well as dose per fraction despite advancement of radiotherapy techniques and using protective mechanisms for eye complications developed.

Background: In India, cataract is the foremost cause of blindness, leading to the mild-to-severe morbidity. Objective: The objective of the study was to find out the epidemiologic profile and risk factors of posterior polar cataract/posterior subcapsular cataract. Materials and Methods: A prospective non-comparative observational study involving 50 patients having posterior polar cataracts attending our outpatient department was selected and was questioned about their locality, systemic diseases, ocular disease, and use of steroid in any form which were included in the study. Results: Of the 50 patients, 30 were male and 20 females, most patients were in the age group of 61–70 years. About 66% of the patient belongs to the rural locality. Most of the females were homemaker, 24% were farmer, 8% were shopkeeper, and 6% retired persons while 2% each of electrician, computer programmer, and bus driver. About 48% had bilateral cataracts, 42% (21) were pseudophakic in one eye, and 1% (5) unilateral cataract. About 24% of patients had hypertension, 18% of patients had of asthma/chronic obstructive pulmonary disease, 16% of patients had diabetes mellitus, 2% of patients had h/o arthritis, 8% had skin disease, 6% had h/o injudicious use of over-the-counter topical drops while 4% of patients of thyroid disease were noted and 34% of patients had h/o steroid use. The most common type of cataract seen Grade I (52%, 26 patients), followed by Grade II (36%, 18 patients), Grade III (8%, 4 patients), and Grade IV (4%, 2 patients). Conclusion: With increasing injudicious use of steroid can result in formation of posterior polar/posterior subcapsular cataract in young age and professional office class workers who are seeking medical help at early stage. An ultrasound should be done to rule out posterior capsular defect if suspected and the patient should be counseled well about the complication prior taking into surgery.

We report a density functional theory (DFT)/time dependent DFT (TDDFT) computational investigation on some factors affecting the nature of charge transfer in CdS quantum dots (QDs) of two different sizes attached to one or two units of dyes among three species viz., coumarine (C343), fluorescein (FLU) and NKX-2388 (NKX). The direction and nature of charge transfers have been ascertained from natural transition orbital analysis. Factors affecting the charge transfer mechanism include the interaction of dyes with QDs, the interaction of a dye with another dye and the effect of solvation. The strength of interaction of the dye and QD depends on the orientation of the dye unit(s) and the type of anchoring group of the dyes and even the direction of charge transfer reverses for different orientation of the dye with respect to the QD in some systems. In addition, hybridized energy levels of the dye–QD composites are formed which leads to direct charge transfer. We observe both direct and indirect charge transfers for different excited states, which is indeed an interesting feature. Interestingly, when two dye molecules are attached to a QD, the direct charge transfer exists between dyes of the same species only. The energy levels, as well as corresponding absorption peaks, exhibit pronounced energy shifts in implicit solvation models.

Dye-sensitized quantum dots (QDs) are promising candidates for dye-sensitized solar cells (DSSCs). Here, we report steady state (absorption and photoluminescence) optical measurements on several sizes of CdS QDs ligated with Coumarin 343 dye (C-343) and two different solvents, viz., chloroform and toluene. We further report detailed first principles density functional theory and time-dependent density functional theory studies of the geometric, electronic and optical (absorption and emission) properties of three different sized capped QDs, ligated with C-343 dye. The absorption spectrum shows a QD-size-independent peak, and another peak which shifts to blue with decrease in QD size. The first peak is found to arise from the dye molecule and the second one from the QD. Charge transfer using natural transition orbitals (NTOs) is found to occur from dye-to-QDs and is solvent-dependent. In the emission spectra, the luminescence intensity of the dye is quenched by the addition of the QD indicating a strong interaction between the QD and the dye.

Background: The aim was to study the demographic profile and analyze risk factor associated with dry eye disease in North West Rajasthan, India.Methods: This was a hospital-based study conducted in Department of Ophthalmology, Sardar Patel Medical College, Bikaner, Rajasthan. Sample size of this study was 100 patients. All participants underwent a general ophthalmic assessment including history of any previous ocular and systemic illness along with ocular examination on slit lamp and specific tests for dry eye (Schirmer's test and Tear film break up time) were performed.Results: Dry eye were seen maximum in age group 46 to 60 years (41%), followed by 61-75 years (23%). Female’s preponderance was seen compared with male. Dry eye patients belong from rural areas were (57%) while remaining (43%) from urban areas and among these highest were farmer/labourers (32%). Several known risk factors were found in this study which include post-menopause. Climatic condition like excessive wind, high temperature and computers users had strong association with dry eye. In Systemic disease rheumatoid arthritis was commonly associated with dry eye were. Smoking contact lens use were also associated with increased risk of developing dry eye.Conclusions: Dry eye disease are more common in older age group patients. Female’s preponderance were found in the study especially postmeopausal women. Dry eye disease are more common in patients belongs to rural areas. Risk factor associated with dry eye were Climatic condition like excessive wind, high temperature and computers users, systemic disease like rheumatoid arthritis Smoking, contact lens users.

Quantum dots a few nanometer in size exhibit unique properties in comparison to bulk due to quantum confinement. Their properties can be tuned according to their sizes. Dye sensitized quantum dot (DSQD) solar cells are based on the same principle with surface dangling bonds as a challenge. Researches have shown the existence and stability of nano-cages which are assembled such as to minimize the surface dangling bonds and hence maximize stability. Here, we report a first principles DFT study of optical and electronic properties of CdS-cage (Cd34S34) sensitized with nkx-2388 dye in three different geometric configurations of dye attachment. A significant distortion is found to occur in the geometric structure of the cage when it interacts strongly with the dye. The relative positioning of dye and cage energy levels is found to be different in different configurations. The absorption spectrum has been analyzed with the help of natural transition orbitals (NTO).

Low band gap (below 2 eV) semiconducting π-conjugated polymers made up of alternate donor and acceptor moieties having push-pull feature are promising materials for organic solar cells due to strong absorption of the solar spectrum. In this work, the band gap of a polysilole based push-pull polymer has been estimated by the application of periodic boundary condition (PBC) using density functional theory (DFT) with B3LYP functional and the 6-311G(d,p) basis set. The estimated band gap is found to be below 2 eV. The absorption spectra of the polymer obtained using time-dependent DFT (TDDFT) covers a wide range of wavelength.

Background: Conjunctival autografting after Pterygium excision can be done by fibrin glue or sutures but use of foreign material can cause discomfort and infection. Fibrin glue may cause hypersensitivity reaction and also have risk of viral transmission. To avoid these conjuctival autograft can be applied without suture or glue. Patient’s own blood act as a bioadhesive.Methods: We done a prospective randomized control study of 70 patients, 35 patients allocated in each group. Group A had conjunctival autograft with fibrin glue while group B had conjunctival autografting without glue or sutures.Results: In group A 31 and group B 26 patients had well placed conjunctival autograft while 4 in group A and 9 patients in group B had either displaced or dislodged graft. The results were statistically insignificant with P value of 0.219 and No complication was reported in any patient except recurrence. The 5 patients in group A and 6 in group B had recurrence which is not statistically significant.Conclusions: Graft stability is more with fibrin glue as compare to glueless and sutureless conjunctival autografting but using patients own blood as bioadhesive is safer and cost effective. The rate of recurrence is similar in both the groups.

Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6−311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.