1,721,053 research outputs found
Laser-Assisted Synthesis of Non-Equilibrium Nanoalloys
No full textVincenzo Amendola is Professor of Physical Chemistry at Padova University, where he established and directs the Laser-Assisted Synthesis and Plasmonics (LASP) lab. He obtained a PhD in Materials Science and Engineering in 2008 and the Italian qualification as Full Professor in 2017, after research experience at Massachusetts Institute of Technology and Cambridge University. He is part of the Program Committee of the ANGEL conference series and he is a current member of the ChemPhysChem Editorial Advisory Board
Plasmonic Absorption in Antigen-Induced Aggregated Gold Nanoparticles: Toward a Figure of Merit for Optical Nanosensors
Full text linkGold nanoparticles (Au NPs) have been extensively used for colorimetric and optical detection of various analytes, exploiting the difference in optical properties when the NPs are dispersed or aggregated. The properties of Au NPs-based optical sensors depend strongly on the particle size, spacing, number, and disposition in the aggregate, which explains the different performances reported so far for this class of sensors. Here, we investigated the optical response of a model Au NP immunosensor and the correlation of its plasmonic absorption with the analyte-dependent aggregation state, supported by transmission electron microscopy and numerical calculations. The antigen–antibody system used for this study is the C-reactive protein (CRP)/anti-CRP couple, well-established and of great applicative interest. The results provide several insights into the evaluation of the extent and type of antigen-induced aggregation for receptor-conjugated Au NPs and point toward the identification of a figure of merit of great utility in the development of particle aggregates with the optimal structure for desirable nanosensor response
Wide range detection of C-Reactive protein with a homogeneous immunofluorimetric assay based on cooperative fluorescence quenching assisted by gold nanoparticles
No full textHomogeneous sandwich immunofluorimetric assays are valued for the rapid, low-cost and accurate detection of analytes in liquid phase. However, their exploitation with analytes covering a wide range of concentrations is limited by low sensitivity and the hook effect. Here, we describe a homogeneous immunofluorimetric system based on the quenching of fluorescence in a Förster resonance energy transfer (FRET) donor/acceptor couple of antibody functionalized with two different dyes, respectively fluorescein (donor) and eosin (acceptor), which form a sandwich multi-component assembly with antibody-functionalized gold nanoparticles (GNPs) in the presence of the analyte. The resulting cooperative fluorescence quenching is assisted by the GNPs scaffold through the nanomaterial-surface energy transfer (NSET) effect, which gives an extended linear response versus the antigen concentration that is not possible with the bi-component assays. This immunofluorimetric method allows accurate, reproducible and immediate detection of C-reactive protein (CRP) in the wide concentration range of clinical interest (over two orders of magnitude from 3.5 to 455 nM, 0.4–52 mg/L), without the hook effect. Moreover, the method does not require sample treatment or washing steps. The concept of this multi-component FRET/NSET fluorescence quenching system can be extended to any analyte amenable to the detection with homogeneous sandwich assays
Numerical modelling of the optical properties of plasmonic and latex nanoparticles to improve the detection limit of immuno-turbidimetric assays
Full text linkTurbidimetric assays with latex nanoparticles are widely applied for the detection of biological analytes, because of their rapidity, low cost, reproducibility, and automatization. However, the detection limit can be lowered only at the price of a reduced dynamic range, due to the rapid saturation of the light scattering signal at high analyte concentration. Here, we use numerical calculations to investigate the possibility of increasing the performance of immuno-turbidimetric assays without compromising the measurement dynamic range, by combining plasmonic (gold, silver) and latex nanoparticles. Our modelling results show that plasmonic nanoparticles are compatible with a large signal change even when small aggregates are formed, i.e., at low analyte concentration. The working principle relies on the remarkable modification of the surface plasmon band when noble metal nanoparticles form oligomers, and also when latex particles are included in the aggregate. At high analyte concentration, when larger aggregates form, the latex particles can provide the required linear response of standard immuno-turbidimetric assays. Thus, the combination of the two components can be a successful strategy to improve the detection limit and the dynamic range, while maintaining all the advantages of the homogeneous immuno-turbidimetric assays
Photophysics of transition metal complexes (2017-2018)
No full textThis Chapter aims at summarizing the major advances achieved, over 2017 and 2018, in the scope of the photophysics of d-block metals complexes. In the last years, one of the central research themes has been the development of luminescent complexes based on earth-abundant metal ions, which could effectively replace second and third-row transition-metal compounds in e.g. light-emitting diodes, dye-sensitized solar cells, photocatalysis and sensing. However, although inconvenient in some ways, second and third-row transition-metal chromophores have continued to be important building blocks in the development of biomedical drugs and optical sensors, as well as in artificial photosynthesis and photocatalysis
Recent applications of organic cages in sensing and separation processes in solution
No full textOrganic cages are three-dimensional polycyclic compounds of great interest in the scientific community due to their unique features, which generally include simple synthesis based on the dynamic covalent chemistry strategies, structural tunability and high selectivity. In this feature article, we present the advances over the last ten years in the application of organic cages as chemosensors or components in chemosensing devices for the determination of analytes (pollutants, analytes of biological interest) in complex aqueous media including wine, fruit juice, urine. Details on the recent applications of organic cages as selective (back-)extractants or masking agents for potential applications in relevant separation processes, such as the plutonium and uranium recovery by extraction, are also provided. Over the last ten years, organic cages with permanent porosity in the liquid and solid states have been highly appreciated as porous materials able to discriminate molecules of different sizes. These features, combined with good solvent processability and film-forming tendency, have proved useful in the fabrication of membranes for gas separation, solvent nanofiltration and water remediation processes. An overview of the recent applications of organic cages in membrane separation technologies is given.Cages at work: structural tunability results in tailored properties, which makes these systems suitable for countless applications in sensing and separation processes, both in solution and the solid state
Optical Properties of Anisotropic Gold Nanoparticles for Solar Light Harvesting and Photo-Thermoelectric Conversion
Full text linkGold nanoparticles (Au NPs) are renowned for their optical properties, nonetheless, challenges persist for applications in broadband quantitative light harvesting from ultraviolet to the near infrared, for instance matching the emission spectrum of sunlight. The challenges are related to limited spectral coverage, low photothermal conversion efficiency, low photostability, low environmental, and economic sustainability of the NPs synthesis. Here, the optical properties of spherical Au NPs are compared with two anisotropic Au nanostructures, aggregated Au nanospheres and Au nanocorals, purposely designed to exhibit broadband absorption. The anisotropic Au NPs are obtained by a convenient, green, and scalable laser ablation in liquid procedure, with the nanocorals exhibiting flat plasmon absorption extending beyond 2500 nm. The optical and photothermal capabilities of these nanostructures are compared with experimental and numerical calculations. Besides, the Au NPs are tested against the direct transduction of light into electricity by photo-thermoelectric generators (photo-TEGs). In fact, the conversion efficiency of TEGs depends on the presence of a steep temperature gradient, achievable under broadband illumination of the anisotropic NPs. This investigation guides to the optimal anisotropic gold NPs for panchromatic light harvesting, which finds relevance across diverse sectors from sunlight energy conversion to photothermal effects in optoelectronics and biomedical applications
Artificial Neural Networks Applied to Colorimetric Nanosensors: AnUndergraduate Experience Tailorable from Gold NanoparticlesSynthesis to Optical Spectroscopy and Machine Learning
Full text linkNowadays, technologies involving nanoparticles, colloids,sensors, and artificial intelligence are widespread in society, media, andindustry. It is thus mandatory to integrate them into the curricula ofstudents enrolled in chemistry and materials science. To this purpose, wedesigned a simple assay for the detection of glutathione (GSH) usingsurface-clean gold nanoparticles (Au NPs). The alteration of the electricdouble layer of the Au NPs with increasing GSH concentration causes theparticles to aggregate, producing a measurable change in color. Thisbehavior, which is widely exploited for optical sensing, has been introducedin an undergraduate course to familiarize the students with the concepts ofnanoparticles, colloids, colloidal stability, and sensor features (selectivity,sensitivity, detection range). Nonetheless, there are no analytical models toquantitatively relate the absorption of Au NP colorimetric sensors toanalyte concentration, which is the ideal condition for resorting to machinelearning (ML). Hence, an artificial neural network was instructed in a students'collective data-sharing experiment about machinelearning. Overall, the laboratory experience is safe and highly tailorable to students'background, course duration, availableinstruments, and teacher's didactic objectives. For instance, it can be lifted to the Master's or Ph.D. level by improving thespectroscopic and ML contents or shifted toward the industrial ground by focusing on the nanoparticle synthesis. We propose theintegration of this laboratory experience in the undergraduate and Master's academic programs to stimulate the students with acollection of hot topics that at the same time can consolidate their preparation on arguments of great relevance for their professionallif
Laser Ablation Synthesis of Silver Nanoparticles Embedded in Graphitic Carbon Matrix
No full textWe obtained a nanocomposite of silver nanoparticles embedded in a graphitic carbon matrix by laser ablation of an Ag plate in toluene solution. The AgNP nanocomposite has been characterized by UV–vis spectroscopy, micro–Raman spectroscopy and HRTEM analysis. AgNP surface plasmon resonance (SPR) is quenched by the carbon matrix, but it can be easily restored by thermal oxidation in air of the matrix. The synthesis procedure is very fast and easy and the matrix prevents AgNP aggregation and growth. The solid nanocomposite can be obtained either as a film or as a bulk sample simply by evaporating the solvent. This technique can be easily adopted for several types of metals
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