Hybrid devices and 2D materials

An important activity of the group is the development of innovative methodologies to fabricate molecular hybrid micron-sized devices (microchips) that could improve the performance in a reliable and cost effective manner of those currently used. It is hoped that in a not-too-distant future such molecular microchips can be used as the ultimate boundary for molecular memories, refrigerators and/or quantum computing. To achieve this objective, we actively develop novel protocols for the efficient nanostructuration, organization and integration of functional molecular materials on substrates and solid supports, in general.  Nowadays, the main research of the group are 2D materials though integration of nanostructured spin crossover and magnetic molecules into devices has also been a centre of interest over the past years. All of them are explained next:

I. 2D Materials

Coordination polymers (CPs) have been wished over the last years as a complementary approach to graphene and related 2D materials thanks to their rich synthetic chemistry, chemical flexibility and the presence of metal ions that add novel optical, magnetic and/or electrical properties. All these premises have already crystallized in different examples of 2D coordination polymers (CPs) relevant for different applications. Though, despite these pioneering examples, control over the synthesis and applications of 2D materials based on coordination polymers still remains a significant research challenge.

With this aim, we have focalized on the understanding of the mechanisms involved in the exfoliation of 2D-CPs and/or the obtaining of novel 2D flakes with novel and unusual properties. As an example, in the figure below we report the delamination of crystals of the 2D spin crossover (SCO) {[Fe(L1)2](ClO4)2}∝ (1) CP by liquid–phase exfo-liation (LPE) in water. The application of this top–down technique results in the formation of flakes with controlled thicknesses, down to 1–2 nm thick (mostly mono– and bi–layer) that retain the chemical composition and SCO inter-conversion of the bulk material. Moreover, these flakes can be handled as stable colloidal dispersions for many days al-lowing for its transfer in a controlled manner to solid substrates and the formation of thermochromic polymeric films as a proof–of–concept of device. These maiden results will definitely open new venues and opportunities for the investigation and future integration of these original switchable 2D materials in devices

Selected publications:
ACS App. Nano Mater. 2018, submited

II. Spin Crossover Switches

Successful nanostructuration approaches developed along the last few years have allowed the preparation of robust valence tautomeric (VT) switchable (micro-/nano-) structures of a variety of dimensions and morphologies. These results are expected to definitely foster the implementation of these materials on hybrid molecular electronic devices but also to endorse new applications in other different fields such as sensors, drug delivery or water remediation, among others.

Selected publications:
 ACS nano 2016, 10 (3), 3206-3213
Chemical Communications 2016, 52 (78), 11617-11626
Journal of Materials Chemistry C 2016,  4 (25), 5879-5889
Chemistry-A European Journal 2015, 21 (28), 10094-10099
Inorganic Chemistry 2014, 53 (16), 8742-8748

III. Magnetic Sensors

In the search for smaller, faster, more selective and efficient products and processes, the engineering of spatial nano-and microarrangements of pure and composite materials is of vital importance for the creation of new devices. A very representative example of versatility and potentiality arises from the field of molecular magnetism, since it provides a privileged way to synthesize magnetic nanomaterials with a variety of physical properties, in macroscopic amounts and of homogenous size.[

With this aim, surface‐confined molecular coolers for cryogenics or the direct measurements of the linear ac susceptibility and magnetic relaxation of a few molecular monolayers deposited on a μ-SQUID sensor have been reported. In order to integrate the molecules into the device, Dip Pen Nanolithography (DPN) has been the technique of choice. It enabled the structuration of the molecules on the most sensitive areas of the sensor without the need for any previous functionalization of the molecule or the substrate, while controlling the number of molecular units deposited on each array. As a proof-of-concept, this strategy has successfully allowed for the controlled deposition of few nanoparticles on a 1 μm2 cross-like graphene surface with high accuracy (see image below).

This work has been mostly developed in collaboration with the group MolChip from Zaragoza http://www.icma.unizar-csic.es/ICMAportal/grupos.do?id=43

Selected publications:
Advanced Materials 2013, 25 (21), 2984-2988
Nanoscale 2013, 5 (24), 12565-12573
Small 2012, 8 (10), 1465-1491
Chemical Society Reviews 2012, 41 (1), 258-302
Chemical Communications 2011, 47 (18), 5175-5177
Advanced Materials 2010, 22 (3), 352-355