Self-assembly of arsenic nanoparticles into magnetic nanotubules and their SERS activity
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Self‑assembly of arsenic nanoparticles into magnetic nanotubules and their SERS activity Laden Sherpa1 · Ajay Tripathi1 · Manish Singh2 · Rajiv Mandal3 · Archana Tiwari1 Received: 4 May 2020 / Accepted: 19 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Nano-arsenic are synthesized using Bergenia ciliata root extracts in water from arsenic trioxide. The synthesized As nanoparticles, with an average diameter of 13(1) nm, self-assemble into nanotubules with average Feret diameter of 530(20) nm. These As nanotubules/nanoparticles have direct bandgap of 2.737 eV and incorporate multiple defect-related states within the gap. The presence of weak ferromagnetism in these nanotubules/nanoparticles are attributed to the dipolar interactions amongst the charges on the defect sites. Owing to van der Waals interactions between nanotubules and smaller nanoparticles, nanotubules present surface roughness and are utilized as surface-enhanced Raman spectroscopy substrate for probing methylene blue dye with an enhancement factor > 103. Keywords Arsenic · Green synthesis · Magnetic nanoparticles · Self-assembly · SERS
1 Introduction Arsenic compounds, in bulk as well as nanoscale, have been refined chemically and physically over the years to treat various diseases including cancer and tumors [1, 2]. Thanks to its strong reducing and galvanic replacement capabilities, nano-arsenic have been used to fabricate gold nanocrystals for sensing applications [3]. Nano-arsenic such as single layer of grey arsenic, arsenene, and its quantum dots have also been examined as novel class of materials with interesting optical and electronic properties [4]. These properties can be readily tuned either by oxidation or by application of strain [5]. In comparison to other metals, only limited works have been done on nano-arsenic and its derivatives. Till date, arsenic, arsenic trioxide (As2O3 ) and arsenic sulphide Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00339-020-03741-w) contains supplementary material, which is available to authorized users. * Archana Tiwari [email protected] 1
Department of Physics, School of Physical Sciences, Sikkim University, Gangtok, Sikkim 737102, India
2
Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269, USA
3
Department of Metallurgy, IIT BHU, Varanasi 221005, India
nanosystems have been synthesised using chemical and physical techniques [6, 7]. The use of green reagents such as plant extracts for the synthesis of metal nanoparticles (NP) not only helps in reducing the metal salts and capping them, but also provoke their surface functionalization which may transform the NP into suitable drug carriers [8]. The functional groups can also initiate site-specific or directed selfassembly in nanoscale materials [9, 10]. Self-assemblies of NP appear due to minimization of free energy and offer thermal equilibrium [11, 12]. During such a process, particles interact amongs
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