Anna A. Semenova

Planar SERS nanostructures with stochastic silver ring morphology for biosensor chips

Surface-enhanced Raman spectroscopy (SERS) of living cells has rapidly become a powerful trend in biomedical diagnostics. It is a common belief that highly ordered, artificially engineered substrates are the best future decision in this field. This paper, however, describes an alternative successful solution, a new effortless chemical approach to the design of nanostructured silver and heterometallic continuous coatings with a stochastic “coffee ring” morphology. The coatings are formed from an ultrasonic mist of aqueous diamminesilver hydroxide, free of reducing agents and nonvolatile pollutants, under mild conditions, at about 200–270 °C in air. They consist of 30–100 micrometer wide and 100–400 nm high silver rings composed, in turn, of a porous silver matrix with 10–50 nm silver grains decorating the sponge. This hierarchic structure originates from ultrasonic droplet evaporation, contact-line motion, silver(I) oxide decomposition and evolution of a growing ensemble of silver rings. The fabricated substrates are a remarkable example of a new scalable and low cost material suitable for SERS analyses of living cells. They evoke no hemolysis and reduce erythrocyte lateral mobility due to suitable “coffee ring” sizes and a tight contact with the silver nanostructure. A high SERS enhancement, characteristic of pure silver rings, made it possible to record Raman scattering spectra from submembrane hemoglobin in its natural cellular environment inside single living erythrocytes, thus making the substrates promising for various biosensor chips.

Probing cytochrome c in living mitochondria with surface-enhanced Raman spectroscopy

Selective study of the electron transport chain components in living mitochondria is essential for fundamental biophysical research and for the development of new medical diagnostic methods. However, many important details of inter- and intramembrane mitochondrial processes have remained in shadow due to the lack of non-invasive techniques. Here we suggest a novel label-free approach based on the surface-enhanced Raman spectroscopy (SERS) to monitor the redox state and conformation of cytochrome c in the electron transport chain in living mitochondria. We demonstrate that SERS spectra of living mitochondria placed on hierarchically structured silver-ring substrates provide exclusive information about cytochrome c behavior under modulation of inner mitochondrial membrane potential, proton gradient and the activity of ATP-synthetase. Mathematical simulation explains the observed enhancement of Raman scattering due to high concentration of electric near-field and large contact area between mitochondria and nanostructured surfaces.

Unusual silver nanostructures prepared by aerosol spray pyrolysis

We report a new simple synthetic approach to chemically pure silver nanoparticles with a complex morphology using ultrasonic aerosol spray pyrolysis of aqueous diaminsilver hydroxide. The resulting morphology of the nanostructured materials is dependent on the hot and condensation zone temperatures and includes porous spheroids, cuboids and more complex overgrowth structures. The growth features seem to be connected with the fast decomposition of diaminsilver hydroxide in mist droplets via Ag2O and its further thermal decomposition assisted by reduction with ammonia to pure silver. The aqueous diaminsilver hydroxide, compared to other salts and complexes, gives a large benefit owing to the simplicity, promptness and low temperature conditions of the production process, which are typically lower than 250 °C. The latter allows, in particular, the production of new types of nanoparticle morphologies which are suitable for SERS measurements.

Hierarchic nanostructuring by self–reduction of silver (I) oxide complexes

Silver nanoparticles superficially decorated with hierarchically smaller nanoparticles are obtained for the first time in the course of aging of silver globules in aerated aqueous ammonia. The process is caused at the beginning by gentle etching of metallic silver across extended defects and smoothing of their edges with oxygen dissolved in aqueous ammonia due to silver (I) stabilization within a soluble ammonia complex for a 1–2 day incubation period, then the complex accumulates as an intermediate product and gradually decays into nanosilver because of the ligand loss for the remaining 4–5 days. The as-formed metallic silver deposits onto larger silver particles heterogeneously decorating their surface; this broadens the initial plasmonic peak and causes a weak red shift because of nanostructuring. The latter makes a substantial contribution to the overall optical properties of the nanoparticles of a complex morphology and has to be considered as an important factor affecting optical characteristics of nanoparticle ensembles and their possible plasmonic applications.

A new route for SERS analysis of intact erythrocytes using polydisperse silver nanoplatelets on biocompatible scaffolds

Superior spectral sensitivity and functional abilities of anisotropic, instead of the usually used spherical, noble metal nanoparticles, allow development of new surface-enhanced Raman spectroscopy (SERS) approaches to analyse biological objects. We found and resolved for the first time the particular risks of survival of silver nanoparticles in different salines to succeed in recording the SERS spectra of intact erythrocytes as an important family of living cells. The ensemble of nanoplatelets with varied shapes and sizes grants multispectral absorption of laser irradiation since a fraction of the nanoparticles with a given position of a plasmonic band always exists in such a mixture, thereby providing an effective SERS amplification. At the same time, fast recrystallization of anisotropic silver nanoplatelets occurs in a standard chloride-based saline, being important to keep the erythrocytes alive but neglecting the benefits of the silver platelets as the most versatile and prospective components of SERS sensors. Substitution of chlorides with nitrates keeps both the intact cells and anisotropic nanoparticles safe on biocompatible cellulose SERS scaffolds containing the mixture of silver nanoplatelets thus promoting the development of new SERS devices for biomedical diagnostics.

Revisiting preparation routes of SERS materials

A. A. Semenova, I. A. Semenova, A. P. Semenov, E. A. Gudilina, E. A. Goodilin1,4,∗ Lomonosov Moscow State University, Faculty of Materials Science, Lenin Hills, Moscow, 119991, Russia Institute of Physical Materials Sciences of Siberian Branch of the Russian Academy of Sciences, Buryatia Republic, Ulan-Ude, 670047, Russia FSBI “N. N. Blokhin National Medical Research Center of Oncology” of the Ministry of Health of the Russian Federation, Moscow, 115478, Russia Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow, 119992, Russia

Surface enhanced Raman spectroscopy substrates with advanced spectral sensitivity prepared from five years old silver nanoplatelets

A new simple approach is suggested to prepare surface enhanced Raman spectroscopy (SERS) substrates with high effectiveness for various laser excitation wavelengths and analytes with different light absorption features by impregnation of porous cellulose materials by a mixture of silver nanoplatelets with a wide range of sizes and anisotropy. The suggested route provides a much better spectral sensitivity and flexible applications since SERS as a phenomenon is essential on the nanometer scale only. The mixing provides always a proper fraction of silver nanoparticles deposited onto the substrate thus guaranteeing the enhancement of Raman signals under given excitation conditions for a wider set of given analytes. The substrates were successfully prepared for the first time from silver nanoplatelets aged for five years. This confirms high chemical and morphological stability of stabilized silver nanoparticles and the ability to use them as precursors for application - ready materials.

Fullerene films deposited by evaporation in vacuum using spot-focused annular electron beam

A rapidly focused annular electron beam can provide for the effective evaporation of a fullerene mixture in a vacuum of ∼10−2 Pa. A 1-kW beam focused into a spot within 0.1–1 s produces explosive evaporation of a fullerene target at an extremely high efficiency of heating. A comparison of the Raman and electronic absorption spectra of the initial fullerene powder and a film deposited upon its evaporation shows that C60 and C70 fullerenes are evaporated without rupture of C-C covalent bonds. The electron beam evaporation in vacuum has been successfully used to obtain fullerene films on substrates with an area of ∼0.1 m2.

Interfacial self-assembly of nanostructured silver octahedra for surface-enhanced Raman spectroscopy

A novel robust and effective approach is suggested to form thin film substrates for surface-enhanced Raman spectroscopy (SERS) using interfacial self-assembly in demixing water/toluene Pickering em...

Vapor phase sers sensor based on mesoporous silica decorated with silver nanoparticles

A. S. Sarycheva, A. A. Semenova, E. A. Goodilin2,3,∗ Department of Materials Science and Engineering and A. J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA 19104, USA Lomonosov Moscow State University, Faculty of Materials Science, Lenin Hills, Moscow, 119991, Russia Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences Sciences, Moscow, 119991, Russia *goodilin@yandex.ru