Noninvasive cardiac-specific biomarkers for the diagnosis and prevention of vascular stenosis in cardiovascular disorder.

Background: The most frequent lesion in the blood vessels feeding the myocardium is vascular stenosis, a condition that develops slowly but can prove to be deadly in a long run. Non-invasive biomarkers could play a significant role in timely diagnosis, detection and management for vascular stenosis events associated with cardiovascular disorders. Aims: The study aimed to investigate high sensitivity troponin I (hs-TnI), cardiac troponin I (c-TnI) and high sensitivity C-reactive protein (hs-CRP) that may be used solely or in combination in detecting the extent of vascular stenosis in CVD patients. Methodology: 274 patients with dyspnea/orthopnea complaints visiting the cardiologists were enrolled in this study. Angiographic study was conducted on the enrolled patients to examine the extent of stenosis in the five prominent vessels (LDA, LCX, PDA/PLV, RCA, and OM) connected to the myocardium. Samples from all the cases suspected to be having coronary artery stenosis were collected, and subjected to biochemical evaluation of certain cardiac inflammatory biomarkers (c-TnI, hsTn-I and hs-CRP) to check their sensitivity with the level of vascular stenosis. The extent of mild and culprit stenosis was detected during angiographic examination and the same was reported in the form significant (≥50% stenosis in the vessels) and non-significant (<50% stenosis in the vessels) Carotid Stenosis. Ethical Clearance for the study was provided by Dr. Ram Manohar Lohia Institute of Medical Sciences Institutional Ethical Committee. Informed consent was obtained from all the participants enrolled in the study. Results: We observed that 85% of the total population enrolled in this study was suffering from hypertension followed by 62.40% detected with sporadic episodes of chest pain. Most of the subjects (42% of the total population) had stenosis in their LAD followed by 38% who had stenosis in their RCA. Almost 23% patients were reported to have stenosis in their LCX followed by OM (18% patients), PDA/PLV (13%) and only 10% patients had blockage problem in their diagonal. 24% of the subjects were found to have stenosis in a single vessel and hence were categorized in the Single Vessel Disease (SVD) group while 76% were having stenosis in two or more than two arteries (Multiple Vessel Disease). hs-TnI level was found to be correlated with the levels of stenosis and was higher in the MVD group as compared to the SVD group. Conclusion: hs-TnI could be used as a novel marker as it shows prominence in detecting the level of stenosis quite earlier as compared to c-TnI which gets detected only after a long duration in the CVD patients admitted for angiography. hs- CRP gets readily detected as inflammation marker in these patients and hence could be used in combination with hs-TnI to detect the risk of developing coronary artery disease.

Evaluation of Spermatogenic Activity of Polyherbal Compound Musalyadi Churna and its Protective Effect Against Nicotine-Induced Testicular Degeneration in Sprague-Dawley Rats.

Background: The ancient science of life known as Ayurveda uses a variety of formulations or herbal compounds to treat a wide range of illnesses. Male infertility accounts for half of all infertility worldwide, and numerous etiological variables play a role. A pharmacologically active tobacco component called nicotine has a negative impact on male fertility and the reproductive system. Musalyadi Churna (MSC) is one of the polyherbal compound formulations mentioned in Ayurveda Classics for aphrodisiac therapy and recommended for the treatment of male infertility. Objective: The current study aims to evaluate the spermatogenic potential of MSC along with its protective effect against testicular degeneration induced by nicotine in rat models. Materials and Methods: Sixty adult Sprague-Dawley male rats were used in the experiment, which were divided into ten groups of six rats each. Nicotine was administered orally as disease control. The standard and vehicle control were also included along with study drug groups in which MSC was administered orally to the rats. The study was conducted for 70 days for each group with assessment of body weight and food consumption. After treatment, rats were weighed and sacrificed for evaluation of parameters like organ weight, epididymal sperm count, and sperm morphology along with histological assessment. The data were statistically evaluated using analysis of variance test and Bonferroni multiple-comparison range test to compare different treatment groups. Results and Conclusion: In the present study, MSC possesses substantial spermatogenic efficacy, and the result indicates that the study drug possesses a protective effect against nicotine-induced impaired testicular functions in rats, but further research to elucidate its exact mechanism of action is essential.

The association of histopathologic features after neoadjuvant chemo-immunotherapy with clinical outcome: Sub-analyses from the randomized double-blinded, placebo-controlled, Phase III IMagyn050/GOG3015/ENGOT-ov39 study.

OBJECTIVE: Histopathologic characteristics after neoadjuvant chemotherapy (NACT) may correlate with outcome. This study evaluates histopathologic features after immunotherapy and NACT/bevacizumab, and associated clinical outcomes. METHODS: Evaluable tissue from IMagyn050/GOG3015/ENGOT-ov39 patients from prespecified anatomic sites from interval cytoreductive surgery (ICS) after NACT/bevacizumab plus atezolizumab/placebo underwent central histopathologic scoring and analyzed with clinical outcomes. RESULTS: The predefined population had 243 evaluable NACT patients, with 48.1% tumors being PD-L1-positive. No statistically significant differences in PFS (16.9 months vs. 19.2 months, p = 0.21) or OS (41.5 months vs. 45.1 months, p = 0.67) between treatment arms were seen. Substantial residual tumor (RT) (3+) was identified in 26% atezolizumab vs. 24% placebo arms (p = 0.94). Most showed no (1+) necrosis (82% vs. 96%, respectively, p = 0.69), moderate (2+) to severe (3+) fibrosis (71% vs. 75%, respectively, p = 0.82), and extensive (2+) inflammation (53% vs. 47% respectively, p = 0.48). No significant histopathologic differences were identified by tissue site or by arm. Multivariate analyses showed increased risk for progression with moderate and substantial RT (13.6 mon vs. 21.1 mon, hazard ratio 2.0, p < 0.01; 13.6 mon vs. 21.1 mon, HR 1.9, p < 0.01, respectively); but decreased risk for death with extensive inflammation (46.9 mon vs. 36.3 mon, HR 0.65, p = 0.02). Inflammation also correlated with greater likelihood of response to NACT/bevacizumab plus immunotherapy (odds ratio 2.9, p < 0.01). Modeling showed inflammation as a consistent but modest predictor for OS. CONCLUSIONS: Detailed histologic assessment of ICS specimens appear to identify characteristics, such as inflammation and residual tumor, that may provide insight to certain clinical outcomes. Future work potentially leveraging emerging tools may provide further insight into outcomes.

Color tunable luminescence in ThO2:Er3+,Yb3+ nanocrystals: a promising new platform for upconversion.

Lanthanide-doped luminescent nanoparticles are an appealing system for many applications in the area of biomedical, solar cell, thermometry, anti-counterfeiting, etc. due to their sensitivity, reliability, high photochemical stability, and high optical transparency in the visible-NIR range. A color-tunable upconversion-luminescence (UCL) in a new low phonon energy ThO2 host based on modulating sensitizer concentration has been realized in this work and it may work as a potential candidate to replace corrosive and toxic fluoride based hosts in the future. Er3+-Yb3+ co-doped thoria nanoparticles were prepared using a gel combustion route and their structural and luminescence properties were determined as a function of the Yb3+ concentration. Phonon dispersion measurements have established the dynamic structural stability of the thoria nanoparticles. Density functional theory (DFT) was used to calculate the defect formation energy, highlighting the feasibility of dual ion (Er3+ and Yb3+) doping in thoria. The morphology and average size of the doped thoria was studied using high resolution transmission electron microscopy (HRTEM), and any defects evolving as a result of aliovalent doping were probed using positron annihilation lifetime spectroscopy (PALS). With 980 nm laser excitation, the nanothoria emits green and near-red light. A significant enhancement of the red-to-green intensity ratio of Er3+ ions in nanothoria was observed with an increase in Yb3+ concentration which resulted in beautiful color tunability from green to yellow light in going from lower (up to ∼5 mol%) to higher (10 and 15 mol%) Yb3+ concentration. The power dependence and the dynamics of the upconverted emission confirm the existence of two-photon upconversion processes for the green and red emissions.

Profile of Childhood Cancers From Hospital-Based Cancer Registries in India, 2012-19.

OBJECTIVE: To describe the clinical pattern of childhood and adolescent cancers across India using hospital-based data in the National Cancer Registry Program. METHODS: Records of 60720 cancer cases in the 0-19 year age group for the period 2012-2019 from 96 hospital-based cancer registries were reviewed. Childhood cancers were classified based on the International Classification of Childhood Cancer (ICCC). Descriptive analysis was used to examine the distribution of cancer by five-year age groups, sex and ICCC diagnostic groups and subgroups. Data were analysed using IBM SPSS software and visualised using R software. RESULTS: 3.2% and 4.6% of all cancer cases in India were among children in the 0-14 year and 0-19 year age groups respectively. The male-to-female ratio for all cancers was 1.72 for 0-14 years and 1.73 for 0-19 years. The four leading groups of cancers among 0-14 year olds were leukemia (40%), lymphoma (12%), central nervous system tumor (11%) and bone cancer (8%). The four leading cancers among the 0-19 year age group were leukemia (36%), lymphoma (12%), bone (11%) and central nervous system tumor (10%). CONCLUSION: Cancers in the 0-14 and 0-19 age groups accounted for a considerable proportion of all cancers with significant male preponderance. Such information helps to fine-tune research and planning strategies.

Positron re-emission, reflection, and diffraction from W(100) surface at very low energies.

The energy distributions of scattered and re-emitted low-energy positrons from a W(100) surface were measured as a function of incident positron energy from 0 to 25 eV. Given that tungsten has a negative work function of about -3 eV for positrons, one can envisage three scenarios of very low-energy positron scattering from such a surface. First, a positron approaching the sample surface with energy say 1 eV above the vacuum level will see a potential barrier of about 2 eV height and will be reflected back to the vacuum. Second, when the energy of incident positrons increases up to the top of the surface potential barrier (positron work function), they start entering the solid and, therefore, the reflectivity of positrons from the surface reduces. Positrons entering the solid are thermalised within few picoseconds and have a chance to escape back to the vacuum with kinetic energy about 3 eV above the vacuum level undergoing so-calledre-emission. Third, coherent scattering of low-energy positrons may occur on the crystal surface, i.e. positron diffraction. All the three scenarios of low-energy positrons scattering are studied here experimentally. Measured spectra are very sensitive to the surface conditions of the sample: they change dramatically after surface oxidation or thin film deposition.

Epidemiology of cancers among older adults in India: findings from the National Cancer Registry Programme.

OBJECTIVE: This study describes the epidemiology, clinical extent of disease at diagnosis and treatment modalities of cancer among older adults (aged 60 years and older) in India. STUDY DESIGN: Secondary data analysis of the National Cancer Registry Programme, which includes 28 Population-Based Cancer Registries (PBCRs) and 96 Hospital-Based Cancer Registries (HBCRs). METHODS: PBCR data were used to estimate the incidence in terms of crude rate (CR), age-adjusted incidence rate (AAR), age-specific rate (ASpR) and cumulative risk. Trends in the AAR were calculated with the Annual Percentage Change (APC) using join-point regression. HBCR data were used to describe the clinical extent of the disease at diagnosis and the treatment modalities. RESULTS: There is a wide heterogeneity across the country for the incidence of cancer and for the leading cancer sites among older adults. Males had a higher incidence rate compared to females in the majority of the registries. Aizawl had the highest AARs among both genders (males: 1388.8; females: 1033.0). Females had the highest ASpR at 65-69 years (482.8), whereas for males it was above 75 years (710.4). Cervical, stomach and oesophageal cancers were on the decline. The incidence of cancer among older adults was estimated to increase by 13.5% in 2025 as compared to 2020. CONCLUSION: The increasing cancer incidence among older adults in India poses a huge burden on the health system. There is a need to increase their participation in clinical trials, advocating comprehensive geriatric assessment and strengthening geriatric oncology within programs addressing older adult's care to deal with the rising cancer burden on the health system borne by them.

An assessment of childhood cancer care services in India - gaps, challenges and the way forward.

Background: Childhood cancers are emerging as an essential concern in India where there is lack of a specific programme component or policy to address childhood cancer control. There is limited information on the status and quality of childhood cancer care services in India. This paper describes the childhood cancer care services available at secondary and tertiary-level hospitals in India through a cross sectional study design. Methods: The survey was conducted in 137 tertiary-level and 92 secondary-level hospitals in 26 states and 4 Union Territories (UTs), ensuring a uniform representation of public and private care hospitals. The study tool collected data on the organisational infrastructure, type of oncology services, health workforce, equipment, treatment and referral protocols, and treatment guidelines. Descriptive statistics was used to primarily present the health service status and data on childhood cancer care services in proportions and mean. Findings: A dedicated pediatric oncology department was available in 41.6% of the public, 48.6% of private, and 64% Non Government Organization (NGO) managed tertiary-level hospitals. In 36 (39%) of the 92 hospitals providing secondary care, childhood cancer care was provided. The availability of bone (41.5%) and positron emission tomography (PET) scans (25.9%) was lower in public tertiary hospitals, whereas histopathology, computerised tomography (CT scan), and magnetic resonance imaging (MRI) were lower in public secondary hospitals than private and NGO managed hospitals for the corresponding level of care. Most tertiary hospitals had the required supportive care facilities except for play therapy and hospice care. Less than 50% of the public tertiary hospitals had stocks of the four categories of cancer-treating drugs and essential infrastructure for radiotherapy and chemotherapy. Most secondary-level hospitals not treating childhood cancer had referral linkages with tertiary hospitals. Interpretation: The situational analysis of childhood cancer care services in India showed the concentration of availability of childhood cancer care services at the tertiary level of health care. There were gaps in the availability of specialised pediatric oncology care in all the tertiary hospitals. The availability of childhood cancer care services was higher in private and NGO-managed hospitals than in public hospitals. Integration of childhood cancer as a part of the national cancer control response should be taken up as a matter of priority. The need of the hour is to formulate a childhood cancer policy that will enable timely access to care universally. Funding: World Health Organization, India provided funding and technical support.

TAScope-guided rapid sequence intubation of a case of retrognathia with a history of failed intubation.

A 72-year-old female with symptomatic cholelithiasis was posted for laparoscopic cholecystectomy. She had been previously posted for the same surgery at a different center, but the surgery was not performed due to failed intubation. On airway examination, reduced thyromental distance, prominent incisors, and retrognathia were observed. We planned and executed rapid sequence intubation under videolaryngoscope guidance using The Anaesthetist Society Scope, and the surgery proceeded uneventfully. At the end of the surgery, she was extubated over a bougie, observed, and shifted out without complications.

Radiation response of Y3Al5O12 and Nd3+-Y3Al5O12 to Swift heavy ions: insight into structural damage and defect dynamics.

Understanding the behavior of a material under irradiation is paramount to its application in the nuclear industry. The present work explores the radiation response of garnet Y3Al5O12 (YAG) and Nd3+-substituted Y3Al5O12 (Nd-YAG) under a 100 MeV Iodine beam at varying fluences to mimic the effect of fission fragments. This is relevant to the potential application of garnet as a host for minor actinide (MA) transmutation (Nd3+: surrogate for long-lived MA (Am3+, Np3+, Cm3+)). The un-irradiated and irradiated YAG and Nd-YAG samples were investigated by X-ray diffraction and Raman spectroscopy. Positron annihilation spectroscopy, thermal spike modelling and theoretical studies have been employed to understand the role of substitution and defect energetics in influencing this radiation response. Although both materials were not completely amorphized under the present irradiation conditions, a tremendous loss in crystallinity could be observed with increase in fluence, the damage being much more in Nd-YAG. Ion track radii of 2.17 nm and 2.91 nm were estimated for YAG and Nd-YAG respectively. Thermal-spike calculations show an increase in radiation-induced transient temperatures upon Nd-substitution that causes greater radiation damage in Nd-YAG. The enhancement in radiation-induced damage with increasing ion-fluence manifests in broadening and weakening of the Raman modes and XRD peaks. An increase in the average positron annihilation lifetime indicated the creation of oxygen vacancies. The defect formation energies of Y3Al5O12 have been theoretically estimated via density functional theory (DFT) and unfavorable energies required for creating cation pair anti-sites have been proposed as one of the possible reasons for the relatively poorer radiation response of YAG. The irradiation behavior of Y3Al5O12 has been compared with disordered fluorite (YSZ) and zirconate pyrochlores, which are well-researched ceramics for MA transmutation.

A pilot randomized clinical trial comparing muscle transplant versus hang back recession in extra-large angle exotropia.

PURPOSE: For extra-large angle exotropia (>60 prism diopters, PD), single-setting surgical alternatives are scarce; frequently, more than two muscle or two eye procedures are indicated. To evaluate the viability of single eye surgery, a current randomized comparative trial is undertaken. METHODS: Twenty adult patients with extra-large angle exotropia underwent a thorough orthoptic evaluation before being divided into two groups at random. Ten patients in group 1 underwent medial rectus resection (5.5-7.5 mm), followed by transplant-aided lateral rectus recession (effective length: 4-5.5 mm) (9 mm). In group two, ten different patients underwent medial rectus resection (5.5-7 mm), but this time, the lateral rectus recession (9 mm) was aided with a hang-back suture (5-7 mm). The two procedures were compared at baseline and six months post-operatively. RESULTS: There was no significant difference in the groups' median ages (P = .95). In groups one and two, the median corrections achieved were 81.00 (79.50-85.50) PD and 81.00 (79.75-86.50) PD, respectively. The differences in corrections were statistically insignificant (p = .99). In all patients, abduction limitation was frequently noted in the immediate post-operative period, which improved over time. In each group, there were two patients (>90 prisms) with residual deviation of at least 30 PD, for which the contralateral eyes were operated. CONCLUSIONS: The hang-back recession was as successful as muscle transplant procedure in correcting 80-90 PD of exotropia with notable clinical benefits and ease.

A case report of pulmonary alveolar microlithiasis with pulmonary tuberculosis.

Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive disease characterised by the deposition of calcium phosphate microliths in the alveoli. PAM has been reported in all continents and there is often a familial history. There is clinical-radiological dissociation as there is often a paucity of symptoms in contrast to the imaging findings. Patients often remain asymptomatic until the third or fourth decade of life, and dyspnea is the most common symptom. PAM is caused by a mutation within the solute carrier family 34 member 2 gene (the SLC34A2 gene) located on chromosome 4p15.2, which encodes a sodium/phosphate co-transporter. The imaging appearance of the disease is quite pathognomic with the high-resolution computed tomography (HRCT) demonstrating a diffuse micronodular appearance. Transbronchial lung biopsy also confirms the diagnosis. There is no effective therapy at present except lung transplantation. We herein, present a case of PAM along with clinical history, imaging study, histopathological study and genetic study of a 43-year-old female adult patient along with genetic analysis.

Intra-operative aberrometry versus conventional biometry for intraocular lens power calculation: A prospective observational study from a tertiary referral center.

Purpose: To evaluate the per operative intra-ocular lens (IOL) power calculation using intra-operative aberrometry (ORA) and its comparison with conventional methods. Methods: Patients with cataract planned for phacoemulsification by a single surgeon under topical anesthesia were enrolled in this prospective observational study in this prospective observational study. All patients underwent pre-operative biometry (Manual SRK-II and IOLMaster® 500) to determine the intra-ocular lens (IOL) power. Intra-operative aberrometry using ORA was also performed; however, IOL was inserted according to IOLMaster® (SRK/T). Spherical equivalent (SE) was recorded on post-operative days 1, 7, and 30. Patients were divided into three groups based on axial lengths for analysis. Comparative analysis was performed for the calculated IOL powers and prediction errors of ORA with conventional methods. Adjusted IOL power to calculate the emmetropic IOL using the LiHue formula was also determined and was compared with existing methods. A P-value less than 0.05 was considered statistically significant. Results: A total of 115 eyes from 113 patients were included, with a median age of 54.90 ± 14.3 years. The mean axial length was found to be 23.94 ± 2.3 mm. There was good agreement (87%) between ORA and IOLMaster® for calculated IOL powers with a mean difference of 0.047 ± 0.5D between the two (P = 0.33). A positive correlation was found between IOL power calculated using ORA, IOLMaster®, SRK-II, and adjusted IOL. Conclusion: The use of intra-operative aberrometry (ORA) to calculate IOL power in patients undergoing uncomplicated phacoemulsification is non-inferior relative to standard pre-operative measurement and planning.

Complex neurocysticercosis lesions on imaging: Explained through correlative histomorphology.

OBJECTIVES: Neurocysticercosis, the commonest neuro-parasite, sometimes presents as complex ring enhancing lesion causing diagnostic dilemma. We aim to establish radio-histo-morphological equivalents of early events in degeneration of the parasite to explain such imaging phenotypes. METHODS: We compared patterns of degeneration in 23 randomly selected complex NCC on MRI with histo-morphology in 30 cysts obtained from an unrelated post mortem brain. RESULTS: The anatomy of the parasite and the degenerative patterns of the scolex (hydropic changes, calcification, evagination, and fragmentation) and the cyst wall (undulation, accessory loculi, and frank disruption) were well demonstrated on both. The intact scolex remarkably resembled head of intestinal Taenia. The complex lesions were conglomeration of multiple communicating cysts with a single parent cyst and multiple daughter cysts. The parent cysts contained a solitary variably degenerated scolex, had thicker walls and associated chronic inflammation. The remaining cysts of the lesion complex contained no scolex, had poorly organized walls, turbid contents, and florid perilesional enhancement with leakage of contrast. Three lesions assumed a multi-cystic pseudo-tumorous pattern, of which two resolved into solitary calcific remnants on follow up. CONCLUSION: Complex lesion in NCC result from degeneration of solitary parasite with perilesional gliosis, surrounded by multiple non-larval daughter cysts inciting acute intra and perilesional inflammation due to enhanced antigenic challenge. Possibly, attempted abortive asexual reproduction by the cellulose cyst as a preterminal event results in a "limited Racemose like transition." Correct interpretation has diagnostic and therapeutic implications as active lesions and their fibrocalcific residue may have greater epileptogenic potential.

Stabilization of Eu2+ in Li2B4O7 with the BO3 network through U6+ co-doping and defect engineering.

Owing to the unique 4f-5d transitions and the involvement of 5d electrons, the divalent europium (Eu2+) ion is extensively used as a dopant ion in luminescent materials for phosphor-converted light emitting diodes (pc-LEDs) and other technological applications. Earlier reports in most of the cases have shown that the reduction of Eu3+ to Eu2+ requires very high temperatures and large hydrogen flux. In this study, a co-doping strategy with higher valent U6+ ions was utilized to successfully stabilize Eu2+ ions in the Li2B4O7 (LTB) host with both the BO3 and BO4 network in low H2 flux of only 8%. It is postulated that charge transfer occurs from U to Eu, resulting in the reduction of the charged state of Eu and the reaction probably proceeds via the formation of paramagnetic transient [U5+-Eu3+] species in the co-doped LTB. The same is also believed to be facilitated by the enhanced formation of Li-O type vacancy clusters in co-doped samples and enhanced oxygen vacancies in a reducing atmosphere. We believe this work will pave a new pathway for stabilizing the unusual oxidation state of lanthanides and transition metal ions through co-doping with hexavalent uranium ions.

Oxygen vacancy and valence engineering in CeO2 through distinct sized ion doping and their impact on oxygen reduction reaction catalysis.

Defect tuning in ceria to enhance its catalytic properties is a subject of great interest for the scientific community owing to the growing demand for catalytic materials in drug, automobile and chemical industries. Doping induced defect engineering was found to be one of the most sought out strategies particularly in oxides for achieving multifunctionality. Here, in this study, we have doped ceria with distinct sized trivalent rare-earth ions, namely, Y3+, Eu3+ and La3+, using combustion techniques. Positron annihilation lifetime spectroscopy (PALS) suggested enhanced defect density with doping in general and higher concentration of oxygen vacancies in La3+ doped ceria compared to Y3+ and Eu3+ counterparts. X-ray photoelectron spectroscopy (XPS) suggested the existence of both Ce3+ and Ce4+, with the former having higher fraction in CeO2:La3+ compared to CeO2:Y3+. The electron transfer resistance (Rct) reduced in all the doped samples when compared to undoped ceria and they demonstrated improved catalytic activity towards the oxygen reduction reaction (ORR). The highest reduction in Rct was seen in the 5% La doped sample owing to the very high concentration of oxygen vacancies and Ce3+/Ce4+ ratio and CeO2:5.0% La3+ showed the best performance towards ORR electrocatalysis. The studies are expected to help in further tuning the catalysts in terms of dopant concentrations, and in future work, the strategy will be to control the Ce3+/Ce4+ ratio and see its implication in both catalytic and magnetic applications.

Defect engineering in trivalent ion doped ceria through vanadium assisted charge compensation: insight using photoluminescence, positron annihilation and electron spin resonance spectroscopy.

Pair matching charge compensation with trivalent and pentavalent dopants in ceria was found to be an attractive strategy in engineering defects with minimal distortions in the lattice and obtaining enhanced catalytic properties. In the present study, charge compensation with a vanadium codopant in trivalent ion doped ceria is studied. Defect evolution in the trivalent ion doped ceria with vanadium codoping has been studied in CeO2:Eu3+, CeO2:La3+,Eu3+ and CeO2:Y3+,Eu3+ systems and the choices of the dopant and co-dopant are triggered by their ionic radius. Eu3+ photoluminescence (PL) is used as a spectroscopic probe to monitor local structural changes around the dopants. Positron lifetime studies showed that oxygen vacancies formed due to trivalent ion doping are weakly associated when larger ions are doped and result in the formation of vacancy aggregates. Positron lifetime studies along with XRD studies show that vanadium codoping effectively removes the vacancies but the distortions are significant when the size mismatch between the pair match used for charge compensation is higher. Photoluminescence demonstrated that the oxygen vacancies associated with Eu are more effectively removed in the case of Y codoped samples. Electron Spin Resonance (ESR) studies suggested that vanadium in excess over the stoichiometric concentration of the trivalent ion can lead to additional defects. These studies are expected to help in tuning the vacancy concentrations as well as controlling the lattice distortions for technological applications such as catalysis, ionic conductivity, etc.

Multiphoton light emission in barium stannate perovskites driven by oxygen vacancies, Eu3+ and La3+: accessing the role of defects and local structures.

Defect engineering in perovskites has been found to be the most efficient approach to manipulate their performance in ultraviolet-to-visible photon conversion. Under UV irradiation, BaSnO3 exhibited multicolor photoluminescence (MCPL) in the bluish white region. Its origin has not been well studied in the literature and has been probed in this work using synchrotron radiation, positron annihilation and density functional theory. To achieve desirable performance of doped BaSnO3 in optoelectronics, it is imperative to have correct information on the dopant local site, doping induced defect evolution and efficacy of host to dopant energy transfer (HDET). Extended X-ray absorption fine structure (EXAFS) showed that Eu3+ ions stabilize at both Ba2+ and Sn4+ sites consistent with the highly negative formation energy of around -6.26 eV. Eu3+ doping leads to an intense 5D0→7F1 orange emission and a feeble 5D0→7F2 red emission and an internal quantum yield (IQY) of ∼21% mediated by ET from the defect level of EuBa and EuSn sites to the valence band maximum (VBM). X-ray absorption near edge structure (XANES) ruled out any role of Sn2+ in the PL of BaSnO3 or Eu2+ in the PL of BaSnO3:Eu3+. Interestingly, when co-doped, Eu3+ stabilizes at Sn4+ sites whereas La3+ stabilizes at Ba2+ sites with a formation energy value of -6.44 eV. Based on the asymmetry ratio in emission spectra, it was found that La3+ ions lead to lowering of symmetry around Eu3+ due to increased vacancies and structural distortions, and also suppress the luminescence IQY. We have performed experimental positron annihilation lifetime spectroscopy (PALS) to probe the defects in BaSnO3 in pristine samples and on doping/co-doping. The positron lifetimes for saturation trapping of positrons in various kinds of defects envisaged in BaSnO3 and in the defect free system were calculated using the MIKA Doppler program. Such deep insight into the effect of local structures, dopant sites, defect evolution, ET, etc. on the optical properties of BaSnO3 is expected to provide very deep insight for material scientists into the fabrication of perovskite-based optoelectronic and light-emitting devices.