Two decades of ceria nanoparticle research: structure, properties and emerging applications.

Cerium oxide nanoparticles (CeNPs) are versatile materials with unique and unusual properties that vary depending on their surface chemistry, size, shape, coating, oxidation states, crystallinity, dopant, and structural and surface defects. This review encompasses advances made over the past twenty years in the development of CeNPs and ceria-based nanostructures, the structural determinants affecting their activity, and translation of these distinct features into applications. The two oxidation states of nanosized CeNPs (Ce3+/Ce4+) coexisting at the nanoscale level facilitate the formation of oxygen vacancies and defect states, which confer extremely high reactivity and oxygen buffering capacity and the ability to act as catalysts for oxidation and reduction reactions. However, the method of synthesis, surface functionalization, surface coating and defects are important factors in determining their properties. This review highlights key properties of CeNPs, their synthesis, interactions, and reaction pathways and provides examples of emerging applications. Due to their unique properties, CeNPs have become quintessential candidates for catalysis, chemical mechanical planarization (CMP), sensing, biomedical applications, and environmental remediation, with tremendous potential to create novel products and translational innovations in a wide range of industries. This review highlights the timely relevance and the transformative potential of these materials in addressing societal challenges and driving technological advancements across these fields.

Interaction, transformation and toxicity assessment of particles and additives used in the semiconducting industry.

Chemical mechanical planarization (CMP) is a widely used technique for the manufacturing of integrated circuit chips in the semiconductor industry. The process generates large amounts of waste containing engineered particles, chemical additives, and chemo-mechanically removed compounds. The environmental and health effects associated with the release of CMP materials are largely unknown and have recently become of significant concern. Using a zebrafish embryo assay, we established toxicity profiles of individual CMP particle abrasives (SiO2 and CeO2), chemical additives (hydrogen peroxide, proline, glycine, nicotinic acid, and benzotriazole), as well as three model representative slurries and their resulting waste. These materials were characterized before and after use in a typical CMP process in order to assess changes that may affect their toxicological profile and alter their surface chemistry due to polishing. Toxicity outcome in zebrafish is discussed in relation with the physicochemical characteristics of the abrasive particles and with the type and concentration profile of the slurry components pre and post-polishing, as well as the interactions between particle abrasives and additives. This work provides toxicological information of realistic CMP slurries and their polishing waste, and can be used as a guideline to predict the impact of these materials in the environment.

Functional Paper-Based Platform for Rapid Capture and Detection of CeO2 Nanoparticles.

Development of systems for capture, sequestration, and tracking of nanoparticles (NPs) is becoming a significant focus in many aspects of nanotechnology and environmental research. These systems enable a broad range of applications for evaluating concentration, distribution, and effects of NPs for environmental, clinical, epidemiological, and occupational exposure studies. Herein, we describe the first example of a ligand-graft multifunctional platform for capture and detection of cerium oxide (CeO2 or ceria) NPs. The approach involves the use of redox-active ligands containing o-dihydroxy functionality, enabling multivalent binding, surface retention, and formation of charge transfer complexes between the grafted ligand and the NPs. Using this strategy, paper-based and microarray-printed platforms with NP-capture ability involving either catechol or ascorbic acid as ligands were successfully fabricated. Surface modification was determined by infrared spectroscopy, electron microscopy, X-ray spectroscopy, and thermogravimetric analysis. Functionality was demonstrated for the rapid assessment of NPs in chemical mechanical planarization (CMP) slurries and CMP wastewaters. This novel approach can enable further development of devices and separation technologies including platforms for retention and separation of NPs and measurement tools for detection of NPs in various environments.

Observation of the formation of anisotropic silver microstructures by evanescent wave and electron microscopy.

Using a well-known galvanic displacement reaction, ∼25-40 µm long silver ribbons grown after mixing ∼50 nm copper particles with AgNO3 solution were observed as a function of Ag(+) concentration and their growth was characterized in real-time and in situ by evanescent wave (EW) microscopy. At low Ag(+) concentration, chain-like structures consisting of both Ag and Cu were observed. When the sequence of mixing these two reactants was reversed, different Ag microstructures (platelets and dendrites) were formed and were also characterized by EW microscopy. Dependence of the morphology of all these microstructures on silver ion concentration was determined by EW microscopy in conjunction with scanning and transmission electron microscopy.

Charge density and pH effects on polycation adsorption on poly-Si, SiO2, and Si3N4 films and impact on removal during chemical mechanical polishing.

The pH-dependent interactions of five aqueous abrasive-free polycationic solutions, all at a concentration of 250 ppm, with poly-Si, SiO(2), and Si(3)N(4) films and IC1000 polishing pads used in chemical mechanical polishing have been investigated and compared with the interaction of poly(diallyldimethyl ammonium chloride) (PDADMAC) that was investigated recently. Three of the polycationic solutions, poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine), poly(allylamine), and poly(ethylene imine) (PEI) enhance poly-Si removal rates (RRs) to the range of about 500 to 600 nm/min at pH 10. In contrast, poly(acrylamide) (PAA) suppressed poly-Si RRs to about 50 nm/min, whereas with a copolymer of PAA and PDADMAC, the RRs were lower than those obtained with PDADMAC but higher than those obtained with PAA. For all the polycationic solutions, the RRs of both SiO(2), and Si(3)N(4) films were ~0 nm/min. These solutions offer a low-defect option for the processing of emerging FinFET devices. The variation in the RR magnitude and dependence on pH among the different polycations is related to the relative charge density of the polycations as well as the films being polished, consistent with ζ potential data. Based on the ζ potential data and earlier published reports, it is suggested that the strong polycation-mediated bridging interactions between the polarized and weakened Si-Si bonds of the poly-Si surface and the polyurethane IC 1000 pad are responsible for the high poly-Si RRs.

Role of poly(diallyldimethylammonium chloride) in selective polishing of polysilicon over silicon dioxide and silicon nitride films.

A cationic polymer, poly(diallyldimethylammonium chloride), or PDADMAC (MW ≈ 200,000), at a concentration of 250 ppm was used to enhance polysilicon removal rates (RRs) to ∼600 nm/min while simultaneously suppressing both silicon dioxide and silicon nitride RRs to <1 nm/min, both in the absence or in the presence of ceria or silica abrasives during chemical mechanical polishing (CMP). These results suggest that aqueous abrasive-free solutions of PDADMAC are very attractive candidates for several front-end-of-line (FEOL) CMP processes. Possible mechanisms for the enhancement of poly-Si RR and the suppression of oxide and nitride RRs are proposed on the basis of the RRs, contact angle data on poly-Si films, zeta potentials of polishing pads, polysilicon films, silicon nitride particles, and silica and ceria abrasives, thermogravimetric analysis, and UV-vis spectroscopy data.

Novel phosphate-functionalized silica-based dispersions for selectively polishing silicon nitride over silicon dioxide and polysilicon films.

We prepared and characterized novel phosphate-functionalized silica particles, and showed that, by using them during chemical mechanical polishing, both silicon dioxide and polysilicon removal rates can be suppressed while simultaneously enhancing silicon nitride removal rates. We achieved a silicon nitride:silicon dioxide:polysilicon removal rate selectivity of (>20):1:1. The measured removal rates of silicon dioxide, silicon nitride, and polysilicon are related to the electrostatic interactions and chemical reactivity between these films and the modified-silica abrasives.

Reverse selectivity--high silicon nitride and low silicon dioxide removal rates using ceria abrasive-based dispersions.

We show that by adding poly(acrylicacid-co-diallyldimethylammonium chloride), a cationic polymer with a weight average molecular weight of about 4200 g/mole, to ceria-based dispersions, it is possible to achieve a silicon nitride removal rate (RR) of >100 nm/min and a silicon dioxide RR of <2 nm/min at pH 4 and 4 psi down pressure during chemical mechanical polishing. Furthermore, the RRs of the silicon dioxide films can be tuned by varying the polymer to abrasive weight ratio in the dispersion while the nitride RR is unaffected. We also characterized the role of adsorption of this polymer additive on ceria, silica and silicon nitride powders using zeta potential, adsorption isotherms, UV-Vis spectroscopy, contact angle, thermo-gravimetric analysis and friction coefficient measurements. Our results show that the polymer film formed on the ceria particle surface is strongly bound to it, survives use in polishing and appears to control its reactivity with the silicon dioxide surface in conjunction with electrostatic interactions.

Lauric acid and myristic acid prevent testosterone induced prostatic hyperplasia in rats.

Numerous plants have proven to improve uncontrolled growth of the prostate gland and improve urinary tract symptoms associated with benign prostatic hyperplasia. Major components of those plants were lauric acid and myristic acid. Our study investigated whether lauric acid or myristic acid prevent testosterone induced prostatic hyperplasia in rats. Rats were divided into negative control and testosterone induced prostatic hyperplasia rats (positive control, low dose lauric acid treated, high dose lauric acid treated, low dose of myristic acid treated, high dose of myristic acid treated, finasteride treated). Testosterone and drug treatment were carried out for 14 days. Body weights were recorded before and after treatment. On 15th day, rats were sacrificed, prostates were weighed and histopathological studies were carried out. Lauric acid/myristic acid treatment showed significant inhibition of prostate enlargement and protection of histoarchitecture of prostate when compared with positive control group. In conclusion, the study showed that lauric acid/myristic acid reduced the increase of both prostate weight and prostate weight:body weight ratio, markers of testosterone induced prostatic hyperplasia in rats.

Oxidative stress and neopterin abnormalities in schizophrenia: a longitudinal study.

Oxidative stress abnormalities have been proposed to explain the pathogenesis of schizophrenia. The present study examined neopterin and oxidative stress abnormalities in schizophrenia patients before and after treatment. Serum neopterin, total anti-oxidants, nitrites and thiols in antipsychotic-naïve schizophrenia patients (n=45) were assessed at baseline before treatment in comparison with healthy controls (n=43). The schizophrenia patients on treatment were followed up for 3months and these parameters were reassessed (n=32). In comparison to healthy controls, schizophrenia patients had significantly higher levels of neopterin and nitrites and significantly lower levels of anti-oxidants before treatment. During follow-up assessments in schizophrenia patients after treatment with antipsychotics, there was a significant decrease in the neopterin levels and significant increase in anti-oxidant levels. Our study observations support increased oxidative stress in schizophrenia that improves with antipsychotic treatment.

Peptide bound hypohydroxyprolinuria in Handigodu Disease: a familial syndrome of spondylo epi(meta)physeal dysplasia.

Handigodu Disease (HD) is disorder of the osteoarticular system prevalent in few villages of two districts of the state Karnataka in southern India. 24 hrs urinary excretions of proline (Pro) and 4-hydroxyproline (Hyp) were analyzed by HPLC. Decreased peptide bound Hyp excretions (mumole/24 hrs) were found in patient group when compared with controls (Nonaffected; 113.02 +/- 67.96, Type-I; 36.22 +/- 20.76, Type-II; 45.74 +/- 14.95, Type-III; 40.46 +/- 22.68) and without significant difference in Pro excretions. Significant increased peptide bound Pro to Hyp ratio were found in patient group compared to control (Nonaffected n=63: 2.02 +/- 1.65, Type-I n=18: 3.144 +/- 1.42, Type-II n=28: 4.21 +/- 1.95, Type-III n=8: 8.60 +/- 6.55). 24 hrs urinary excretions of deoxypyridinoline (DPD) crosslinks were found without significant difference among affected and control, hence HD ruled out from general bone reduction. These results suggest hypohydroxyprolinuria may be because of reduced bone turnover or defective hydroxylation of prolyl residues during post translational modification of collagen biosynthesis.

Involvement of nitric oxide in 5-HT(3) receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.

OBJECTIVES: The aim of the present study was to investigate the involvement of nitric oxide in 5-HT(3) receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats. MATERIALS AND METHODS: Fluid movement in jejunum and colon were determined simultaneously in the same rat, by modifying the Beubler method. Nomega-nitro-L-arginine (L-NNA, 20 mg/kg, s.c) alone and in combination with L-arginine (L-Arg, 150 mg/kg s.c) or D-arginine (D-Arg, 150 mg/kg, s.c) were administered 30 min before administration of 1-PBG (18.5 mug/kg, i.v). RESULTS: Intravenous administration of 1-phenylbiguanide (1-PBG) induced a net secretion of fluid in both jejunum and colon. 1-PBG had a more prominent secretory effect in the colon, causing a three-fold increase in volume of fluid secreted/g of colon than in the jejunum. Pretreatment with (L-NNA) prevented the 1-PBG-induced fluid accumulation in both jejunum and colon. The inhibitory effect of L-NNA on 1-PBG-induced fluid accumulation was reversed by L-Arg but not by D-Arg. CONCLUSION: These results provide evidence that nitric oxide plays an important role in 5-HT(3) receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.

A sensitive assay for ornithine amino transferase in rat brain mitochondria by ninhydrin method.

To establish/develop an assay method for measuring Ornithine Aminotransferase (EC.2.6.1.13) activity using rat brain mitochondria as a source of enzyme in presence and absence of Pyridoxal Phosphate (PLP). The modified method, with the improved sensitivity, is adopted for the assay of ornithine amino transferase activity in rat brain mitochondria. The enzyme activity was measured at 620 nm, the study showed that reaction was optimum at 37°C for 30 minutes. The assay is sensitive enough to detect activity at the order of nanomoles pyrroline-5-carboxylate/mg protein/minute and can be compared as an alternative to the radio isotopic method which is more cumbersome and aminobenzaldehyde method which is less sensitive. The K(m) & V(max) shows maximum activity in the presence of Pyridoxal Phosphate (Coenzyme) concentration at 0.05mM when compared with absence of Pyridoxal Phosphate as higher the concentration of Pyridoxal Phosphate affects the affinity of the enzyme to substrate. The OAT activity in different tissues of the rat was also studied and highest activity was found in liver and kidney.

Colloid aspects of chemical-mechanical planarization.

The essential parts of interconnects for silicon based logic and memory devices consist of metal wiring (e.g. copper), a barrier metal (Ta, TaN), and of insulation (SiO2, low-k polymer). The deposition of the conducting metal cannot be confined to trenches, resulting in additional coverage of Cu and Ta/TaN on the surface of the dielectrics, yielding an electrically conducting continuous but an uneven surface. The surplus metal must be removed until a perfectly flat surface consisting of electrically isolated metal lines is achieved with no imperfections. This task is accomplished by the chemical-mechanical planarization (CMP) process, in which the wafer is polished with a slurry containing abrasives of finely dispersed particles in submicrometer to nanometer size. The slurries also contain dissolved chemicals to modify the surfaces to be planarized. Eventually the final product must be cleared of any adhered particles and debris left after polishing is completed. Obviously the entire process deals with materials and interactions which are the focal subjects of colloid and surface science, such as the natures of abrasive particles and their stability in the slurry, the properties of various surfaces and their modifications, adhesion and detachment of the particles and different methods for the characterization of constituents, as well as elucidation of the relevant interfacial phenomena. This review endeavors to describe the colloid approach to optimize the materials and processes in order to achieve desirable polish rates and final surfaces with no imperfections. Specifically, the effects of the composition, size, shape, and charge of abrasive particles on the polish process and the quality of planarized wafers is described in detail. Furthermore, the interactions of metal surfaces with oxidizing, chelating, and other species which affect the dissolution and surface modification of metal (copper) surfaces are illustrated and related to the planarization process. Finally, using the packed column technique the adhesion phenomena of abrasives on metals and oxides is evaluated on suitable model systems, that contain the same additives in the slurries as in the actual planarization process. A close correlation is established in all cases between the attachment and detachment results with experimentally determined polish rates.

Dinitrophenyl derivatization of imino acids, spectral characteristics and HPLC analysis: application in urinary peptide-derived hydroxyproline and proline assay.

BACKGROUND: Assay of urinary imino acids, in particular peptide derived, is of immense utility in diagnosis of collagen-related disorders. The often-used methods for hydrolysis of urinary peptides need a long time and are cumbersome, hence the need for relatively simpler, but effective methods. METHODS: The method described, based on alkaline hydrolysis by autoclaving for 60 min followed by pre-column dinitrophenyl (DNP) derivatization and high-performance liquid chromatography (HPLC) analysis, demonstrates the complete hydrolysis and stability of urinary peptide derived imino acids. RESULTS: DNP derivatives of both imino acids had identical lambda max (380 nm) with molar epsilon of 28.224 x 10(3) and 17.036 x 10(3), respectively, for hydroxyproline (Hyp) and proline (Pro). HPLC run, extending up to 18 min, resolved major components of collagen products, namely Hyp, Hyl, Gly, Pro and Lys, with retention times of 6.5, 9.8, 10.5, 11.2 and 12.55 min, respectively. The assay method conformed to linear response for individual amino acid concentrations of 0.5-4.0 nmol per injection, with goodness of fit (r(2) value) 0.99 for both Hyp and Pro, and detection limit of 0.05-4.0 nmol of DNP derivatives. The recovery of Pro and Hyp, when spiked with urine prior to hydrolysis, were found to be 95% and 92%, respectively. CONCLUSION: Alkaline hydrolysis by autoclaving and DNP derivatization of imino acids followed by HPLC provides a method for the analysis of peptide-derived Hyp and Pro in urine. Hence, it is of utility to study collagen disorders.

Particle adhesion studies relevant to chemical mechanical polishing.

This study describes particle adhesion experiments carried out to elucidate interactions between particles in slurries used for polishing of wafers and disks. For this purpose the packed column technique was employed, which simulated chemical mechanical polishing of copper with silica and alumina, as well as of silicic oxide with ceria. The model systems consisted of uniform copper and glass beads as collectors, representing the wafers, and colloidal dispersions of silica, alumia, and silica coated with nanosize ceria, all of well-defined properties that are used as abrasives. It was shown that a strong correlation exists between deposition and detachment results of the adhesion studies and the polish rates measured using actual substrates with the same or similar slurries.

The use of monodispersed colloids in the polishing of copper and tantalum.

The properties of abrasive particles play a significant role in chemical mechanical polishing (CMP) of metal and dielectric films in semiconductor device manufacturing. This study investigates the effects of the particle size, shape, and hardness of abrasives on the polishing of copper and tantalum films in the presence of different slurry chemistries. Well-defined dispersions of uniform particles, including spherical silica of varying diameters, hematite of different shapes, and hematite cores coated with silica of different thicknesses, were prepared and used to polish blanket films of Cu and Ta. It was shown that the total surface area of the solids in the slurry controlled the rate of material removal by pure silica for both Cu and Ta, while the surface quality of the polished films was better when higher silica content was used. The shape or the aspect ratio of hematite particles had a minor effect on the removal rate. In contrast, when hematite particles coated with silica were employed in the polishing of Cu and Ta, the polish rate decreased with increasing thickness of the shell.

HPLC method for amino acids profile in biological fluids and inborn metabolic disorders of aminoacidopathies.

Quantification of total and individual amino acids in biological fluids such as plasma, urine and cerebrospinal fluid has an important diagnostic implication in laboratory medicine. The present paper describes protocols for the assay of total amino acids by modified method based on dinitrophenyl and HPLC profile involving pre-column derivatization with o-pthalaldehyde (OPA) derivatization, respectively. The method, based on the alkylation of-SH groups prior to OPA derivatization of amino acids followed by reverse phase high performance liquid chromatography, provide a comprehensive profile of more than twenty amino acids (including-SH group containing) in a single run lasting about 45 minutes. The present study, apart from establishing the normal profile of amino acids in plasma of Indian sub population, also presents HPLC profile for some of the rare amino acidopathies.