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Zafar F, Saif K, Andreescu D, Andreescu S, Hayat A. A Target Responsive Metal Organic Framework Derived Bimetallic Apta-Switch for Reagentless Molecular Recognition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2025. [PMID: 39743662 DOI: 10.1021/acs.langmuir.4c03752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2025]
Abstract
By integrating iron-cobalt squarate bimetallic metal-organic framework (Fe-Co-SqBMoF) based smart material (SM) with functional DNA (fDNA), we designed a target responsive fDNA@Fe-Co-SqBMoF bioelectrode that exhibits recognition induced switchable response to serve as a reagentless single step electrochemical apta-switch (REA). The construct takes advantage of fDNA ability to bind and concentrate target on the receptor interface, while Fe-Co-SqBMoF@SM multifeatures to serve as an immobilization matrix and a signal generating electrochemical switch. Fe-Co-SqBMoF was introduced to prepare a redox active pencil graphite electrode (PGE), while fDNA (aptamer) was decorated on the receptor PGE to impart specificity and selectivity. The Fe-Co-SqBMoF synthesis was characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy, dynamic light scattering (DLS), and UV-visible (UV-vis) analysis, while each step of fDNA decoration and bioelectrode fabrication was characterized via field emission scanning electron microscopy (FE-SEM), static water contact angle measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). To explore the potential application of the fDNA@Fe-Co-SqBMoF bioelectrode, we designed a REA for detection of aflatoxin B1 (AFB1) which permitted the detection of AFB1 in the linear range 0.7-1000 pg/mL with an LOD of 0.54 pg. The practical applicability of an fDNA@Fe-Co-SqBMoF based REA was demonstrated in milk and water samples.
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Rehman AU, Andreescu D, Tiwari S, Andreescu S. Rapid Single-Step Detection of Polyfluoroalkyl Substances (PFAS) Using Electropolymerized Phenoxazine Dyes. Anal Chem 2024; 96:17506-17516. [PMID: 39405503 DOI: 10.1021/acs.analchem.4c02480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2024]
Abstract
Per- and polyfluoroalkyl substances (PFAS) are highly stable ubiquitous contaminants that have been recently added to the list of regulated chemicals. While methods for PFAS detection exist, analysis is difficult, involving a tedious protocol and expensive instrumentation. Here, we demonstrate the first implementation of a phenoxazine dye as a sensing probe that facilitates rapid and inexpensive detection of representative PFAS, e.g., perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), at sensitivity levels covering the recently established Environmental Protection Agency (EPA) limits. The method comprises an electrode modified with a stable redox film of Meldola blue (MB) in its electropolymerized form (epMB), which provides amino sites for electrostatic interactions with PFAS. Long-chain PFAS bind specifically to the epMB, inducing a hydrophobic-type cluster formation through ion-pair and F-F interactions. This binding generates concentration-dependent changes in the epMB/epMB+ oxidation, enabling rapid and sensitive quantification in a single step with high sensitivity, reaching a limit of detection of 0.4 ppt for PFOS and 1.65 ppt for PFOA. The sensor demonstrates good selectivity toward common interfering compounds like humic acid, sodium chloride and fluoride, metallic ions (Cu, Hg, As), as well as pesticides. In addition to PFOS and PFOA, the sensors can measure other perfluoroalkyl compounds, demonstrating potential as a tool for rapid quantification of a total PFAS index, with affinity for long-chain PFAS. This work highlights the integration of redox receptors into an electrochemical sensor to solve the grand challenge of PFAS analysis using a rapid and inexpensive procedure, with potential for field deployment.
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Othman A, Gowda A, Andreescu D, Hassan MH, Babu SV, Seo J, Andreescu S. Two decades of ceria nanoparticle research: structure, properties and emerging applications. MATERIALS HORIZONS 2024; 11:3213-3266. [PMID: 38717455 DOI: 10.1039/d4mh00055b] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
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.
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Khan R, Uygun ZO, Andreescu D, Andreescu S. Sensitive Detection of Perfluoroalkyl Substances Using MXene-AgNP-Based Electrochemical Sensors. ACS Sens 2024; 9:3403-3412. [PMID: 38830812 DOI: 10.1021/acssensors.4c00776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Per- and polyfluoroalkyl substances (PFAS) pose a significant threat to the environment due to their persistence, ability to bioaccumulate, and harmful effects. Methods to quantify PFAS rapidly and effectively are essential to analyze and track contamination, but measuring PFAS down to the ultralow regulatory levels is extremely challenging. Here, we describe the development of a low-cost sensor that can measure a representative PFAS, perfluorooctanesulfonic acid (PFOS), at the parts per quadrillion (ppq) level within 5 min. The method combines the ability of PFOS to bind to silver nanoparticles (AgNPs) embedded within a fluorine-rich Ti3C2-based multilayered MXene, which provides a large surface area and accessible binding sites for direct impedimetric detection. Fundamentally, we show that MXene-AgNPs are capable of binding PFOS and other long-chain PFAS compounds, though the synergistic action of AgNPs and MXenes via electrostatic and F-F interactions. This binding induced concentration-dependent changes in the charge-transfer resistance, enabling rapid and direct quantification with extremely high sensitivity and no response to interferences. The sensor displayed a linear range from 50 ppq to 1.6 ppt (parts per trillion) with an impressively low limit of detection of 33 ppq and a limit of quantification of 99 ppq, making this sensor a promising candidate for low-cost screening of the PFAS content in water samples, using a simple and inexpensive procedure.
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Khan R, Andreescu D, Hassan MH, Ye J, Andreescu S. Nanoelectrochemistry Reveals Selective Interactions of Perfluoroalkyl Substances (PFASs) with Silver Nanoparticles. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202212561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Khan R, Andreescu D, Hassan MH, Ye J, Andreescu S. Nanoelectrochemistry Reveals Selective Interactions of Perfluoroalkyl Substances (PFASs) with Silver Nanoparticles. Angew Chem Int Ed Engl 2022; 61:e202209164. [DOI: 10.1002/anie.202209164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Indexed: 11/10/2022]
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Khan R, Andreescu D, Hassan MH, Ye J, Andreescu S. Nanoelectrochemistry Reveals Selective Interactions of Perfluoroalkyl Substances (PFASs) with Silver Nanoparticles. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202209164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kirk KA, Vasilescu A, Andreescu D, Senarathna D, Mondal S, Andreescu S. Collision-Based Electrochemical Detection of Lysozyme Aggregation. Anal Chem 2021; 93:2026-2037. [PMID: 33416307 DOI: 10.1021/acs.analchem.0c03578] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Proteins are utilized across many biomedical and pharmaceutical industries; therefore, methods for rapid and accurate monitoring of protein aggregation are needed to ensure proper product quality. Although these processes have been previously studied, it is difficult to comprehensively evaluate protein folding and aggregation by traditional characterization techniques such as atomic force microscopy (AFM), electron microscopy, or X-ray diffraction, which require sample pre-treatment and do not represent native state proteins in solution. Herein, we report early tracking of lysozyme (Lyz) aggregation states by using single-particle collision electrochemistry (SPCE) of silver nanoparticle (AgNP) redox probes. The method relies on monitoring the rapid interaction of Lyz with AgNPs, which decreases the number of single AgNPs available for collisions and ultimately the frequency of oxidative impacts in the chronoamperometric profile. When Lyz is in a non-aggregated monomeric form, the protein forms a homogeneous coverage onto the surface of AgNPs, stabilizing the particles. When Lyz is aggregated, part of the AgNP surface remains uncoated, promoting the agglomeration of Lyz-AgNP conjugates. The frequency of AgNP impacts decreases with increasing aggregation time, providing a metric to track protein aggregation. Visualizations of integrated oxidation charge-transfer data displayed significant differences between the charge transfer per impact for AgNP samples alone and in the presence of non-aggregated and aggregated Lyz with 99% confidence using parametric ANOVA tests. Electrochemical results revealed meaningful associations with UV-vis, circular dichroism, and AFM, demonstrating that SPCE can be used as an alternative method for studying protein aggregation. This electrochemical technique could serve as a powerful tool to indirectly evaluate protein stability and screen protein samples for formation of aggregates.
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Khan R, Rehman AU, Deshpande AS, Andreescu S, Andreescu D. Novel Materials Design for Capture and Electrochemical Detection of Perfluoroalkyl Species. ECS MEETING ABSTRACTS 2020; MA2020-01:2127-2127. [DOI: 10.1149/ma2020-01282127mtgabs] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Per and poly-fluoroalkyl substances (PFAS) are persistent organic pollutants, adversely affecting the environment. The strong carbon-fluorine bonds of PFASs make them resistant to physical and metabolic degradation leading to bioaccumulation, which can have serious effects on human’s health, wildlife and ecosystem. The conventional analytical techniques for the quantitative determination of PFASs in environmental matrices are HPLC, GC-MS, etc. Despite their high reliability and accuracy, these laboratory-based techniques are expensive and can analyze only a limited number of samples, which impedes their broad applicability. To advance analysis and fast screening of samples, there is a critical need to develop cost effective, sensitive, easy to handle and portable methods for field detection of PFASs. This presentation will describe rational design of materials with specific and characteristic binding abilities for PFAS that can be incorporated into passive samplers and sensors for on site detection. The interaction of several materials with selected PFAS species and their incorporation into passive samples and an electrochemical sensing design will be discussed. This approach provides a new method for achieving qualitative and quantitative analysis of PFASs in the field. The developed method has potential for the onsite, selective, and sensitive detection of PFASs.
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Karimi A, Andreescu S, Andreescu D. Single-Particle Investigation of Environmental Redox Processes of Arsenic on Cerium Oxide Nanoparticles by Collision Electrochemistry. ACS APPLIED MATERIALS & INTERFACES 2019; 11:24725-24734. [PMID: 31190542 DOI: 10.1021/acsami.9b05234] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Quantification of chemical reactions of nanoparticles (NPs) and their interaction with contaminants is a fundamental need to the understanding of chemical reactivity and surface chemistry of NPs released into the environment. Herein, we propose a novel strategy employing single-particle electrochemistry showing that it is possible to measure reactivity, speciation, and loading of As3+ on individual NPs, using cerium oxide (CeO2) as a model system. We demonstrate that redox reactions and adsorption processes can be electrochemically quantified with high sensitivity via the oxidation of As3+ to As5+ at 0.8 V versus Ag/AgCl or the reduction of As3+ to As0 at -0.3 V (vs Ag/AgCl) generated by collisions of single particles at an ultramicroelectrode. Using collision electrochemistry, As3+ concentrations were determined in basic conditions showing a maximum adsorption capacity at pH 8. In acidic environments (pH < 4), a small fraction of As3+ was oxidized to As5+ by surface Ce4+ and further adsorbed onto the CeO2 surface as a As5+ bidentate complex. The frequency of current spikes (oxidative or reductive) was proportional to the concentration of As3+ accumulated onto the NPs and was found to be representative of the As3+ concentration in solution. Given its sensitivity and speciation capability, the method can find many applications in the analytical, materials, and environmental chemistry fields where there is a need to quantify the reactivity and surface interactions of NPs. This is the first study demonstrating the capability of single-particle collision electrochemistry to monitor the interaction of heavy metal ions with metal oxide NPs. This knowledge is critical to the fundamental understanding of the risks associated with the release of NPs into the environment for their safe implementation and practical use.
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Andreescu D, Kirk KA, Narouei FH, Andreescu S. Electroanalytic Aspects of Single‐Entity Collision Methods for Bioanalytical and Environmental Applications. ChemElectroChem 2018. [DOI: 10.1002/celc.201800722] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Othman A, Andreescu D, Karunaratne DP, Babu SV, Andreescu S. Functional Paper-Based Platform for Rapid Capture and Detection of CeO 2 Nanoparticles. ACS APPLIED MATERIALS & INTERFACES 2017; 9:12893-12905. [PMID: 28340293 DOI: 10.1021/acsami.7b02823] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
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.
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Hayat A, Andreescu D, Bulbul G, Andreescu S. Redox reactivity of cerium oxide nanoparticles against dopamine. J Colloid Interface Sci 2014; 418:240-5. [DOI: 10.1016/j.jcis.2013.12.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/26/2013] [Accepted: 12/03/2013] [Indexed: 11/29/2022]
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Sardesai NP, Andreescu D, Andreescu S. Electroanalytical Evaluation of Antioxidant Activity of Cerium Oxide Nanoparticles by Nanoparticle Collisions at Microelectrodes. J Am Chem Soc 2013; 135:16770-3. [DOI: 10.1021/ja408087s] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Sharpe E, Frasco T, Andreescu D, Andreescu S. Portable ceria nanoparticle-based assay for rapid detection of food antioxidants (NanoCerac). Analyst 2013; 138:249-62. [PMID: 23139929 PMCID: PMC3518284 DOI: 10.1039/c2an36205h] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
With increased awareness of nutrition and the advocacy for healthier food choices, there exists a great demand for a simple, easy-to-use test that can reliably measure the antioxidant capacity of dietary products. We report development and characterization of a portable nanoparticle based-assay, similar to a small sensor patch, for rapid and sensitive detection of food antioxidants. The assay is based on the use of immobilized ceria nanoparticles, which change color after interaction with antioxidants by means of redox and surface chemistry reactions. Monitoring corresponding optical changes enables sensitive detection of antioxidants in which the nanoceria provides an optical 'signature' of antioxidant power, while the antioxidants act as reducing agents. The sensor has been tested for the detection of common antioxidant compounds including ascorbic acid, gallic acid, vanillic acid, quercetin, caffeic acid, and epigallocatechin gallate and its function has been successfully applied for the assessment of antioxidant activity in real samples (teas and medicinal mushrooms). The colorimetric response was concentration dependent, with detection limits ranging from 20 to 400 μM depending on the antioxidant involved. Steady-state color intensity was achieved within seconds upon addition of antioxidants. The results are presented in terms of Gallic Acid Equivalents (GAE). The sensor performed favorably when compared with commonly used antioxidant detection methods. This assay is particularly appealing for remote sensing applications, where specialized equipment is not available, and also for high throughput analysis of a large number of samples. Potential applications for antioxidant detection in remote locations are envisioned.
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Ornatska M, Sharpe E, Andreescu D, Andreescu S. Paper Bioassay Based on Ceria Nanoparticles as Colorimetric Probes. Anal Chem 2011; 83:4273-80. [DOI: 10.1021/ac200697y] [Citation(s) in RCA: 285] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Sharpe E, Andreescu D, Andreescu S. Artificial Nanoparticle Antioxidants. ACS SYMPOSIUM SERIES 2011. [DOI: 10.1021/bk-2011-1083.ch008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Ispas C, Andreescu D, Patel A, Goia DV, Andreescu S, Wallace KN. Toxicity and developmental defects of different sizes and shape nickel nanoparticles in zebrafish. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:6349-56. [PMID: 19746736 PMCID: PMC2744893 DOI: 10.1021/es9010543] [Citation(s) in RCA: 165] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Metallic nanoparticles such as nickel are used in catalytic sensing, and electronic applications, but health and environmental affects have not been fully investigated. While some metal nanoparticles result in toxicity, it is also important to determine whether nanoparticles of the same metal but of different size and shape changes toxicity. Three different size nickel nanoparticle (Ni NPs) of 30, 60, and 100 nm and larger particle clusters of aggregated 60 nm entities with a dendritic structure were synthesized and exposed to zebrafish embryos assessing mortality and developmental defects. Ni NPs exposure was compared to soluble nickel salts. All three 30, 60, and 100 nm Ni NPs are equal to or less toxic than soluble nickel while dendritic clusters were more toxic. With each Ni NP exposure, thinning of the intestinal epithelium first occurs around the LD10 continuing into the LD50. LD50 exposure also results in skeletal muscle fiber separation. Exposure to soluble nickel does not cause intestinal defects while skeletal muscle separation occurs at concentrations well over LD50. These results suggest that configuration of nanoparticles may affect toxicity more than size and defects from Ni NPs exposure occur by different biological mechanisms than soluble nickel.
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Jitianu A, Kim MS, Andreescu D, Goia DV. A simple preparative route to highly stable dispersions of uniform silver nanoparticles. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2009; 9:1891-1896. [PMID: 19435055 DOI: 10.1166/jnn.2009.429] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Stable dispersions of uniform silver nanoparticles were prepared by heating silver salts in polyols in the presence of a naphthalene sulfonate/formaldehyde copolymer as dispersant. In the temperature range explored (150-190 degrees C) the modal size and the size distribution of the particles depended on the nature and concentration of the silver salt and the polyol used. Highly dispersed uniform nanoparticles with a diameter of approximately 12 nm were obtained by reducing silver salicylate in diethylene glycol at a metal concentration of 2.5 x 10(-2) mol x cm(-3). Larger silver nanoparticles (approximately 30 nm) and more concentrated dispersions (1.0 mol x cm(-3)) were prepared in ethylene glycol. In all cases the selected dispersant yielded remarkably stable silver sols and facilitated the transfer of the nanoparticles into water, while preserving the stability of the dispersions.
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Andreescu D, Matijević E, Goia DV. Formation of uniform colloidal ceria in polyol. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2006.05.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Andreescu D, Sau TK, Goia DV. Stabilizer-free nanosized gold sols. J Colloid Interface Sci 2006; 298:742-51. [PMID: 16473363 DOI: 10.1016/j.jcis.2006.01.011] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 01/06/2006] [Accepted: 01/06/2006] [Indexed: 11/27/2022]
Abstract
The paper describes a convenient, rapid, and reproducible method for the synthesis of stable dispersions of uniform gold nanoparticles at ambient temperatures by mixing aqueous solutions of tetrachloroauric acid and iso-ascorbic acid. The influence of the experimental conditions on the size of the gold particles and the stability of the final sols was monitored by dynamic light scattering and UV-vis spectrophotometry. It was found that the size of the resulting nanoparticles is affected by the concentration and the pH of gold solution, while the stability of the electrostatically stabilized final sols is strongly dependent on the excess of reductant in the system, the ionic strength, and the temperature of the precipitation. Since the preparation process does not require the addition of a dispersing agent, the surface of the resulting gold nanoparticles can be easily functionalized to make them suitable for applications in medicine, biology, and catalysis.
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Andreescu D, Wanekaya AK, Sadik OA, Wang J. Nanostructured polyamic acid membranes as novel electrode materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:6891-9. [PMID: 16008401 DOI: 10.1021/la050141k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
This paper describes a new approach for the preparation of polyamic acid (PAA) composites containing Ag and Au nanoparticles. The composite film of PAA and metal particles were obtained upon electrodeposition of a PAA solution containing gold or silver salts with subsequent thermal treatment, while imidization to polyimide is prevented. The structural characterization of the films is provided by 1H NMR and Fourier transform infrared spectroscopy (FTIR), while the presence of metallic nanoparticles within the polymeric matrix was confirmed by scanning electron microscopy (SEM), cyclic voltammetry (CV), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This approach utilizes the unique reactivity of PAA by preventing the cyclization of the reactive soluble intermediate into polyimides at low temperature to design polymer-assisted nanostructured materials. The ability to prevent the cyclization process should enable the design of a new class of electrode materials by use of thermal reduction and/or electrodeposition.
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Andreescu D, Andreescu S, Sadik OA. Chapter 7 New materials for biosensors, biochips and molecular bioelectronics. BIOSENSORS AND MODERN BIOSPECIFIC ANALYTICAL TECHNIQUES 2005. [DOI: 10.1016/s0166-526x(05)44007-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Andreescu S, Andreescu D, Sadik OA. A new electrocatalytic mechanism for the oxidation of phenols at platinum electrodes. Electrochem commun 2003. [DOI: 10.1016/s1388-2481(03)00166-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Avramescu A, Andreescu S, Noguer T, Bala C, Andreescu D, Marty JL. Biosensors designed for environmental and food quality control based on screen-printed graphite electrodes with different configurations. Anal Bioanal Chem 2002; 374:25-32. [PMID: 12207236 DOI: 10.1007/s00216-002-1312-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2001] [Revised: 03/04/2002] [Accepted: 04/11/2002] [Indexed: 10/27/2022]
Abstract
Graphite electrodes fabricated by screen-printing have been used as amperometric detectors in biosensors based on NAD(+)-dependent dehydrogenases, tyrosinase, or genetically modified acetylcholinesterases. The mono-enzyme sensors have been optimized as disposable or reusable devices for detection of a variety of substrates important in the food industry ( D-lactic acid, L-lactic acid, acetaldehyde) or in environmental pollution control (phenols and dithiocarbamate, carbamate and organophosphorus pesticides). The sensors were prepared in four configurations differing in enzyme confinement, enzyme immobilization and location of the immobilization agent in the biosensor assembly. Tests on real samples have been performed with the biosensors; D-lactic acid and acetaldehyde have been detected in wine and phenols in air.
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