Modulating the effective ionic radii of trivalent dopants in ceria using a combination of dopants to improve catalytic efficiency for the oxygen evolution reaction.

Aliovalent doping in ceria and defect engineering are important aspects in tuning the properties of ceria for advanced technological applications, especially in the emerging field of electrocatalytic water-splitting for harvesting renewable energy. However, the ambiguity regarding the choice of dopants/co-dopants and ways to deal with the size difference between dopants and lattice hosts remains a long-standing problem. In this study, ceria was aliovalently codoped with Sc3+ and La3+ while keeping the total concentration of dopants constant; the ionic radius of the former is smaller and that of the latter is larger than Ce4+. Variations in the relative amounts of these dopants helped to modulate the effective ionic radii and match that of the host. A systematic study on the role of these aliovalent dopants in defect evolution in ceria and in modulating the Ce3+ fraction using powder XRD, Rietveld refinement, positron annihilation lifetime spectroscopy, X-ray photoelectron spectroscopy, Eu3+ photoluminescence, and Raman spectroscopy is presented here. The evolved defects and their dependence on subtle factors other than charge compensation are further correlated with their electrocatalytic activity towards oxygen evolution reaction (OER) in alkaline medium. The catalyst with an optimum defect density, maximum Ce3+ fraction at the surface and the least effective ionic radius difference between the dopants and the host demonstrated the best performance towards the OER. This study demonstrates how effective ionic radius modulation in defect-engineered ceria through a judicious choice of codopants can enhance the catalytic property of ceria and provides immensely helpful information for designing ceria-based heterogeneous catalysts with desired functionalities.

Development of an external PIGE method using nitrogen from atmospheric air as external beam current normalizer and its application to nondestructive quantification of total boron mass fraction in boron containing neutron absorbers.

Beam current monitoring and normalization is a very important task in ion beam analysis experiments. Compared to current monitoring by conventional method, in situ or external beam current normalization is attractive in Particle Induced Gamma-ray Emission (PIGE), which involves simultaneous measurement of prompt gamma rays of analyte of interest and current normalizing element. In the present work, an external (in air) PIGE method has been standardized for quantification of low Z elements using nitrogen from atmospheric air as external current normalizer, in which 2313 keV of 14N(p,p'γ)14N is measured. It provides truly nondestructive and greener quantification method for low Z elements by external PIGE. The method was standardized by quantifying total boron mass fractions in ceramic/refractory boron-based samples using low energy proton beam from tandem accelerator. The samples were irradiated with 3.75 MeV proton beam and prompt gamma rays of analyte at 429, 718 and 2125 keV of 10B(p,αγ)7Be, 10B(p,p'γ)10B and 11B(p,p'γ)11B, respectively, and external current normalizers at 136 and 2313 keV were measured simultaneously using high resolution HPGe detector system. The obtained results were compared with external PIGE method using tantalum as external current normalizer, where 136 keV of 181Ta(p,p'γ)181Ta from beam exit window material (Ta) was used for current normalization. The developed method is found to be simple, rapid, convenient, reproducible, truly nondestructive and more economical as no additional beam monitoring instruments are required and it is especially advantageous for direct quantitative analysis of 'as received' samples.

Chemical characterization of automobile windshield glass samples for major, minor, and trace elemental concentration determination by INAA and its comparison with ED-XRF and DC Arc AES in terms of analytical capabilities and possible applications for glass forensics.

Automobile (car) windshield glass fragments serve as important forensic evidentiary materials and their chemical characterization mainly at minor and trace concentration levels is a key step in forensic investigations. For such glass analysis as well as for forensics, direct solid sample analysis by suitable analytical technique(s) is very important. In view of this, instrumental neutron activation analysis (INAA) using high flux neutrons from research reactor was utilized for chemical characterization of car windshield glass samples. Energy dispersive X-ray fluorescence (ED-XRF) and direct current arc carrier distillation atomic emission spectroscopy (DC Arc AES) methods were also utilized for the analysis of all glass samples for evaluating their analytical capabilities with respect to INAA. A comparative evaluation was carried out with respect to accuracy, precision, and detection limits under quality assurance/quality control (QA/QC). The methods were validated by analyzing certified reference materials (CRMs) G-2 and RGM-1 from USGS and NIST standard reference material (SRM) of sodalime glass (SRM 610). Concentrations of seventeen elements (Na, Ca, Sc, Cr, Fe, Co, Zn, Rb, Zr, Ba, La, Hf, Ce, Eu, Yb, Sm, and Th) were determined in all analyzed glass samples by INAA at major, minor, and trace concentration levels, indicating its capability for potential applications to forensic studies. Grouping study of these automobile glasses was carried out utilizing concentrations of transition elements and rare earth elements (REEs) in conjunction with statistical cluster analysis. In addition, it has been highlighted that some of the transition elements as well as REEs are important markers/discriminating elements for same brand automobile glasses obtained from two different sources/origins.

Toward Developing Techniques─Agnostic Machine Learning Classification Models for Forensically Relevant Glass Fragments.

Glass fragments found in crime scenes may constitute important forensic evidence when properly analyzed, for example, to determine their origin. This analysis could be greatly helped by having a large and diverse database of glass fragments and by using it for constructing reliable machine learning (ML)-based glass classification models. Ideally, the samples that make up this database should be analyzed by a single accurate and standardized analytical technique. However, due to differences in equipment across laboratories, this is not feasible. With this in mind, in this work, we investigated if and how measurement performed at different laboratories on the same set of glass fragments could be combined in the context of ML. First, we demonstrated that elemental analysis methods such as particle-induced X-ray emission (PIXE), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS), particle-induced Gamma-ray emission (PIGE), instrumental neutron activation analysis (INAA), and prompt Gamma-ray neutron activation analysis (PGAA) could each produce lab-specific ML-based classification models. Next, we determined rules for the successful combinations of data from different laboratories and techniques and demonstrated that when followed, they give rise to improved models, and conversely, poor combinations will lead to poor-performing models. Thus, the combination of PIXE and LA-ICP-MS improves the performances by ∼10-15%, while combining PGAA with other techniques provides poorer performances in comparison with the lab-specific models. Finally, we demonstrated that the poor performances of the SEM-EDS technique, still in use by law enforcement agencies, could be greatly improved by replacing SEM-EDS measurements for Fe and Ca by PIXE measurements for these elements. These findings suggest a process whereby forensic laboratories using different elemental analysis techniques could upload their data into a unified database and get reliable classification based on lab-agnostic models. This in turn brings us closer to a more exhaustive extraction of information from glass fragment evidence and furthermore may form the basis for international-wide collaboration between law enforcement agencies.

A polydiacetylene (PDA) impregnated poly(vinylidene fluoride) (PVDF) membrane for sensitive detection of fluoride ions.

Fluoride is present in groundwater and drinking water across the world and plays crucial roles in regulating oral health. Although a 0.7-1.2 ppm concentration of fluoride in water supplies is deemed optimal for enamel development and dental health, its higher concentration causes endemic fluorosis, acute gastric, urolithiasis, and kidney infection, making the detection of fluoride highly important. However, the standard methods of fluoride detection, such as potentiometric or ion-selective detection, require specific instruments and often pre-treatment before analysis and do not offer the scope for on-site detection. Herein, we report the development of a polydiacetylene (PDA) grafted poly(vinylidene fluoride) (PVDF) membrane for sensitive solid-phase detection of fluoride. The sensors were prepared by functionalizing PDA with the boronic acid functionality as the F- recognition unit and impregnating it on PVDF strips. Upon exposure to fluoride, the strips displayed a visible color change from blue to red. The solid-phase sensor showed selectivity against common anions and can detect F- ions as low as 0.11 ppm. The real sample analysis in water and toothpaste and validation by ion chromatography demonstrate its potential application as an efficient lab-on-membrane for fluoride ions.

Development of an innovative external (in air) Particle Induced Gamma-ray Emission method for rapid non-destructive determination of isotopic composition of boron in "As received" boron based ceramic neutron absorbers.

Boron is an important element in nuclear reactor technology due to its high neutron absorption cross section of 10B isotope. Isotopic composition of B (IC, 10B/11B atom ratio) determination in finished neutron absorbers is a necessity under chemical quality control (CQC). We report an innovative greener method for rapid and non-destructive approach of isotopic composition determination of B in "as received" boron based ceramic neutron absorbers including boron carbides and hexa-borides by external (in air) Particle Induced Gamma-ray Emission (PIGE) using 3.5 MeV proton beam. It involves irradiation of "as received" powder samples wrapped in a thin Mylar film and measurement of prompt gamma rays at 429, 718 and 2125 keV from 10B(p,αγ)7Be, 10B(p,p'γ)10B and 11B(p,p'γ)11B, respectively, using a HPGe detector system. The method was standardized with natural and enriched B4C powders. For validation, the results of isotopic composition obtained from "as received" samples were compared with that obtained from pellet samples using both external and vacuum chamber PIGE methods. IC values obtained for natural to 10B enriched samples (19.8-67 atom % of 10B) are very encouraging with 1-2% and 0.3-0.7% uncertainties from single and replicate sample experiments. The method is truly non-destructive as the samples can be returned back as such after the experiment as they are not radioactive. Compared to existing PIGE method for isotopic composition of B, the developed method keeps promise for wide applications as it is simple, sensitive and rapid and it does not require vacuum, pellet preparation with a binder, exact mass of the sample and beam current measurement.

Hydrolytically stable citrate capped Fe3O4@UiO-66-NH2 MOF: A hetero-structure composite with enhanced activity towards Cr (VI) adsorption and photocatalytic H2 evolution.

Design and facile fabrication of a magnetically separable hetero-structure photocatalyst as well as an adsorbent having dual green benefits towards energy conversion and pollutant remediation are quite indispensable in the current scenario. In this regard, a composite of citrate capped Fe3O4 and UiO-66-NH2 has been designed to remediate Cr (VI) by adsorption and harvest photons from visible light for clean energy (H2) conversion. The material was prepared by the union of citrate capped Fe3O4 (CCM) and versatile aqueous stable Zr-based MOF (UiO-66-NH2) through in-situ solvothermal method. The composite of CCM with MOF (MU-2) was studied through sophisticated analysis techniques; PXRD, FT-IR, BET, UV-Visible DRS, PL, TG, HRTEM and XPS etc. to reveal the inherent characteristics of the material. BET surface analysis revealed high specific surface area (572.13 m2 g-1) of MU-2 in comparison to its pristine MOF. Furthermore, the dual function composite MU-2's VSM studies showed that its magnetic saturation is 3.07 emu g-1 that is suitable for magnetic separation after desired reaction from aqueous media. The Cr (VI) sorption studies revealed that the composite adsorbent (MU-2) showed maximum monolayer adsorption capacity (Qm) of 743 mg g-1 which followed pseudo second order kinetics. Moreover, the sorption thermodynamics revealed that the process was spontaneous and endothermic in nature. In addition to it, the synthesized composite material displayed enhanced activity towards photocatalytic H2 evolution with a maximum evolution rate of 417 µmole h-1 with an apparent conversion efficiency (ACE) of 3.12 %. Typically, MU-2 displays high adsorptions of Cr (VI) as well as some extent of Cr (VI) reduction owning to its populous active sites and free carboxylate groups respectively. Moreover, the synergistic effect of CCM and UNH in the composite resulted in Z scheme mediated charge transfer mechanism that showed enhanced H2 photo-evolution rates. Hence, MU-2 can be readily utilized as magnetically retrievable dual function composite for Cr (VI) adsorption and photocatalytic H2 evolution.

Brilliant Nonlinear Optical Response of Ho3+ and Yb3+ Activated YVO4 Nanophosphor and Its Conjugation with Fe3O4 for Smart Anticounterfeit and Hyperthermia Applications.

YVO4:Ho3+/Yb3+ nanophosphors prepared by an effective polyol-mediated route show dual-mode behavior in photoluminescence. Upon 980 nm excitation, the upconversion red emission spectrum exhibits a bright red peak at ∼650 nm, characteristic of the electronic transition of the Ho3+ ion via involvement of two-photon absorption, which has been confirmed by the power-dependent luminescence study. Moreover, at 300 nm excitation, downconversion emission peaks are observed at 550, 650, and ∼755 nm. The nonradiative resonant energy transfer occurs from the V-O charge transfer band to Ho3+ ions, resulting in an improved emission of Ho3+ ions. Moreover, polyethylene glycol-coated nanoparticles make it suitable for water dispersibility; and these particles are conjugated with Fe3O4 nanoparticles to form magnetic-luminescent hybrid nanoparticles. Highly water-dispersible magnetic-luminescent hybrid material attained the hyperthermia temperature (∼42 °C) under an applied AC magnetic field. The specific absorption rate value is found to be high (138 W/g), which is more than that of pure superparamagnetic Fe3O4 nanoparticles. At 300 nm excitation, the high quantum yield value of ∼27% is obtained from YVO4:Ho3+/Yb3+, which suggests that it is a good phosphor material. By employing the neutron activation analysis technique, it is shown that nanophosphor particles can absorb Au3+ up to the ppm level. Interestingly, such nanophosphor also shows the potentiality for anticounterfeiting applications.

Enrichment of Crystal Field Modification via Incorporation of Alkali K+ Ions in YVO4:Ho3+/Yb3+ Nanophosphor and Its Hybrid with Superparamagnetic Iron Oxide Nanoparticles for Optical, Advanced Anticounterfeiting, Uranyl Detection, and Hyperthermia Applications.

In this work, we report a polyol route for easy synthesis of upconversion (UC) phosphor nanoparticles, YVO4:Ho3+-Yb3+-K+, which enables large-scale production and enhancement of luminescence. Upon 980 nm laser excitation, the UC emission spectrum shows a sharp bright peak at ∼650 nm of Ho3+ ion; and the luminescence intensity increases twofold upon K+ codoping. Upon 300 nm excitation, the downconversion emission spectrum shows a broad peak in the 400-500 nm range (related to the charge transfer band of V-O) along with Ho3+ peaks. In addition, the polyethylene glycol-coated UC nanoparticles are highly water-dispersible and their hybrid with Fe3O4 nanoparticles shows magnetic-luminescence properties. A hyperthermia temperature is achieved from this hybrid. Both UC and hybrid nanoparticles show interesting security ink properties upon excitation by a 980 nm laser. The particles are invisible in normal light but visible upon 980 nm excitation and are useful in display devices, advanced anticounterfeiting purposes, and therapy of cancer via hyperthermia and bioimaging (since it shows red emission at ∼650 nm). Using UC nanoparticles, detection of uranyl down to 20 ppm has been achieved.

Phthalimide conjugation turns the AIE-active tetraphenylethylene unit non-emissive: its use in turn-on sensing of hydrazine in solution and the solid- and vapour-phase.

Hydrazine is a vital precursor used in several pharmaceuticals and pesticide industries and upon exposure can cause severe health hazards. Herein, a new AIEgen, tetraphenylethylene phthalimide (TPE-PMI), is synthesized in a one-step solvent-free mechanochemical approach exploiting the simple condensation between TPE-NH2 and phthalic anhydride and used for the selective and sensitive detection of hydrazine. TPE-PMI with an AIE-active TPE-moiety is non-emissive in the solid phase by design. Hydrazine performs the cleavage of TPE-PMI in a typical "Gabriel synthesis" pathway to release AIE-active TPE-NH2 in an aqueous solution to emit blue fluorescence. A gradual rise in fluorescence intensity at 462 nm was due to the increasing hydrazine concentration and TPE-PMI showed a linear relationship with hydrazine in the concentration range from 0.2 to 3 µM. The selectivity study confirmed that the probe is inert to amines, amino acids, metal anions, anions and even common oxidants and reductants. The detection limit is 6.4 ppb which is lower than the US Environmental Protection Agency standard (10 ppb). The practical utilities of TPE-PMI were successfully demonstrated through quantitative detection of hydrazine vapour on solid platforms like paper strips and TLC plates. Furthermore, on-site detection of hydrazine in the solid phase was demonstrated by spiking the soil samples with measured quantities of hydrazine and quantitation through image analysis. This cost-effective sensing tool was successfully utilized in in vitro detection of hydrazine in live HeLa cells.

Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

Removal of selenium from Se enriched natural soils by a consortium of Bacillus isolates.

Four bacterial strains designated as SNTP-1, NS-2 to NS-4 were isolated from selenium contaminated soils of Nawanshahr-Hoshiarpur region of Punjab, India, by enrichment technique and a consortium was developed using these isolates. The isolates were observed to be belonging to Bacillus sp. In soil microcosm, complete removal was observed by the consortium in selenite augmented soils while the rate of removal with consortia in selenate treatment was 72% after 120 days. Population survival of isolates showed stability at lower treatments and decline at higher levels of Se enrichment. The consortium can, thus, be used for removal of Se contaminated sites.

Changes in selenium speciation associated with increasing tissue concentrations of selenium in wheat grain.

Wheat (Triticum aestivum) collected in the Nawanshahr-Hoshiarpur Region (Punjab, India) showed the highest selenium concentrations ever recorded in cereal grains (29-185 microg g(-1)). There was a strong positive relationship between the selenium content in shoots and that in kernels, showing that grain selenium concentration can be predicted from that in the vegetative tissues of the plant. The identity and content of the selenocompounds in the grain samples and in wheat-based reference materials were investigated by HPLC-ICP-dynamic reaction cell-MS. Reversed-phase, cation exchange, and anion exchange HPLC were used to separate the selenium species after ultrasound-assisted enzymatic extraction with an ultrasonic probe. Selenomethionine and selenate accounted for 72-85% and 2-6% of the sum of the selenium species, respectively. The proportion of organic Se species varied with increasing Se content; namely, SeMet showed a relative reduction whereas the other organoselenium compounds increased up to 18-22% of the total chromatographed selenium. Se-methyl-selenocysteine was detected as a minor compound (0.2-0.5%) in high-Se wheat by both reversed-phase and cation exchange HPLC using retention time matching with the standard substance spiked to the sample extracts. Regular consumption of locally produced wheat-based food items may lead the population of the study area to an excessive intake of selenium. On the other hand, the large predominance of selenomethionine shows that local wheat can be a promising raw material for naturally enriched products to be used to supplement human and animal diets in low selenium areas.