INORGANIC NANOCRYSTALS AND THEIR USE IN FUNCTIONAL COMPOSITE MATERIALS
This research aims to develop and improve chemical methods for the synthesis of inorganic nanocrystals of a variety of materials. Illustrative examples comprise the chemical synthesis of quantum dots, plasmonic metal nanoparticles and superparamagnetic iron oxides. These nanomaterials can be prepared as pure phases or as multi-phase materials which in turn are used as fillers in polymer matrices in order to fabricate nanocomposites. Thus chemical aspects have been particularly relevant in our research on nanoengineering composite particles, in particular, the surface chemistry of these materials has been investigated aiming their use as fillers in natural and synthetic polymer matrices. The nanocomposites have been evaluated for diverse applications such as in the fabrication of antimicrobial surfaces, drug delivery and new platforms for SERS (Surface Enhanced Raman Scattering) analytical detection.

see for example:
R. J. B. Pinto, M. C. Neves, C. P. Neto, T. Trindade “Growth and chemical stability of copper nanostructures on cellulosic fibers”, Eur. J. Inorg. Chem., 2013, 31, 5043-5049.
A. C. Estrada, A. L. Daniel-da-Silva, T. Trindade, “Photothermally enhanced drug release by κ-carrageenan hydrogels reinforced with multi-walled carbon nanotubes“, RSC Adv. 2013, 3, 10828-10836.
S. Fateixa, A. V. Girão, H. I. S. Nogueira, T. Trindade, “Polymer based silver nanocomposites as versatile solid film and aqueous emulsion SERS substrates”, J. Mater. Chem. 2011, 21, 15629-15636.
R. J. B. Pinto, P. A. A. P. Marques, C. P. Neto, T. Trindade, S. Daina, P. Sadocco, “Antibacterial activity of nanocomposites of silver and bacterial or vegetable cellulosic fibers“, Acta Biomaterialia 2009, 5, 2279-2289.
P. A. A. P. Marques, H. I. S. Nogueira, R. J. B. Pinto, C. P. Neto, T. Trindade, “Silver-bacterial cellulosic sponges as active SERS substrates”, J. Raman Spect., 2008, 39, 439-443.
A. S. Pereira, P. Rauwel, M. S. Reis, N. J. O. Silva, A. Barros-Timmons, T. Trindade, “Polymer encapsulation effects on the magnetism of EuS nanocrystals”, J. Mater. Chem., 2008, 18, 4572–4578.
O. C. Monteiro, H. I. S. Nogueira, M. Motevalli, T. Trindade “Use of alkyldithiocarbamato complexes of bismuth (III) for the preparation of nano- and micro-sized Bi2S3particles and the X-ray crystal structures of [Bi{S2CN(CH3)(C6H13)}3and [Bi{S2CN(CH3)C6H13)}3(C12H8N2)]”, Chem. Mater.,2001, 13, 2103-2111.

"Nanocomposite particles for bio-applications: materials and biointerfaces", T. Trindade, A. L. Daniel-da-Silva (editors), Pan Stanford Publishing, Singapore, 2011.
NANOPARTICLES FOR BIOAPPLICATIONS
Nanoparticles are now well established as potential new vectors for a number of applications in medicine (Nanomedicine). We have been interested in the synthesis, chemical functionalization and characterization of fluorescent and/or magnetic inorganic nanoparticles for in vitro bioapplications, such as optical biolabelling and magnetic bioseparation. In this context, we have carried out research that merges important concepts and procedures from colloidal science and coordination chemistry. An illustrative example is the chemical strategy developed in our laboratories based on a sol-gel method that result into fluorescent silica nanoparticles containing lanthanide complexes. Lanthanide complexes, namely those of Tb(III) and Eu(III), are characterized by well defined and narrow emission bands, relatively long emission lifetimes and large Stoke shifts. These properties make these compounds very interesting as functional units in nanoparticles that have potential as tags for time-gated luminescence bio-detection. More recently, we have extended this research to the fabrication of hybrid nanosilicas containing other functional units (e.g. corrole complexes) aiming their potential application in photodynamic therapy (PDT). Methods of surface functionalization have been important aspects in developing this research, not only due to their challenging nature but also because of the relevance of interfaces in nanoparticles applications, namely when contacting with biological systems. In this context, diverse surface modification routes have been investigated that include the growth of amorphous silica shells by using conventional sol-gel method and, microemulsions and multiple emulsions as nanoreactors. Two main routes for the chemical functionalization of the silica nanoparticles have been employed: i) the covalent grafting of organic molecules with specific functional groups and ii) the electrostatic assembly of polyelectrolytes that can be also chemically functionalized. For example, 1D ferromagnetic nanostructures such as nickel nanowires have been surface modified with polyelectrolytes carrying organic fluorophore molecules, thus leading to multimodal (fluorescent/magnetic) bioprobes that can be of interest for the separation and manipulation (e.g. magnetic tweezers) of cells using in vitro protocols.

see for example
P. C. Pinheiro, C. T. Sousa, J. P. Araújo, A. J. Guiomar, Tito Trindade, “Functionalization of nickel nanowires with a fluorophore aiming at new probes for multimodal bioanalysis”, J. Colloid Interface Sci., 2013, DOI: http://dx.doi.org/10.1016/j.jcis.2013.07.065.
J. F. B. Barata, A. L. Daniel-da-Silva, M. G. P. M. S. Neves, J. A. S. Cavaleiro, T. Trindade, “Corrole-silica hybrid particles: synthesis and effects on singlet oxygen generation”, RSC Adv., 2013, 3, 274-280.
C. M. Granadeiro, R. A. S. Ferreira, P. C. R. Soares-Santos, L. D. Carlos, T. Trindade, H. I. S. Nogueira, “Lanthanopolyoxotungstates in silica nanoparticles: multi-wavelength photoluminescent core/shell materials “, J. Mater. Chem. 2010, 20, 3313-3318.
K. O. Iwu, P. C. R. Soares-Santos, H. I. S. Nogueira, L. D. Carlos, T. Trindade,“Nanoencapsulation of Luminescent 3-Hydroxypicolinate Lanthanide Complexes“, J. Phys. Chem. C, 2009, 113, 7567-7573.
A. S. Pereira, M. Peres, M. J. Soares, E. Alves, A. Neves, T. Monteiro, T. Trindade, “Synthesis, surface modification and optical properties of Tb(III)-doped ZnO nanocrystals”, Nanotechnology,2006, 17, 834-839.
P. C. R. Soares-Santos, H. I. S. Nogueira, R. A. Sá-Ferreira, V. M. S. Félix, M. Drew, L. D. Carlos, T. Trindade, “Novel lanthanide luminescent materials based on complexes of 3-hydroxypicolinic acid and silica nanoparticles”, Chem. Mater, 2003, 15, 100-108.
ECO-NANOMAGNETS FOR WATER PURIFICATION AND MONITORING
Water is the most treasured chemical compound for humankind. The scarcity of drinking water or the contamination of water sources in some regions of the world are perceived as serious threats, not only to the affected populations but also to global peace. In general, water pollution has been regarded as a priority problem for which the scientific community has been called for innovative solutions. This requires an integrated set of approaches from diverse scientific fields besides global policies. This research aims to contribute for this environmental issue by carrying out interdisciplinary research aiming the development of new water monitoring and purification technologies. As such, we have developed new sorbents for the magnetic uptake of water pollutants such as metal species, organic dyes and pharmaceuticals. These materials comprise a magnetic core (e.g. Fe3O4) that can be regarded as a new class of sorbents with wide applicability and selectivity by judicious tailoring of the particles’ surface chemistry. Thus core/shell particles made of magnetite coated with siliceous shells functionalized with thiolate moieties have shown high efficiency for the magnetic removal of aqueous mercury ions. On the other hand, nanocomposite particles of superparamagnetic magnetite coated with a biopolymer have shown potential for the magnetic removal of organic dyes such as methylene blue. The ultimate goal of this research is to create conditions for the application of this nanotechnology in the magnetic removal of diverse pollutants from water in real contexts.

see for example
D. S. Tavares, A. L. Daniel-da-Silva, C. B. Lopes, N. J. O. Silva, V. S. Amaral, J. Rocha, E. Pereira, T. Trindade, “Efficient sorbents based on magnetite coated with siliceous hybrid shells for removal of mercury ions”, J. Mater. Chem. A. 2013, 1, 8134-8143.
A. M. Salgueiro, A. L. Daniel-da-Silva, A. V. Girão, P. C. Pinheiro, T. Trindade, “Unusual dye absorption behavior of k-carrageenan coated superparamagnetic nanoparticles”, Chem. Eng. J., 2013, DOI:10.1016/j.cej.2013.06.015
P. Figueira, C. B. Lopes, A. L. Daniel-da-Silva, E. Pereira, A. C. Duarte, T. Trindade, T. Water Res., 2011, 45, 5773.
P. I. Girginova, A. L. Daniel-da-Silva, C. B. Lopes, P. Figueira, M. Otero, V. S. Amaral, E. Pereira, T. Trindade, “Silica coated magnetite particles for magnetic removal of Hg2+from water” J. Colloid Interface Sci. 2010, 345, 234-240.
CHEMICAL MODIFICATION OF SURFACES USING SINGLE-MOLECULE PRECURSORS
A single molecule precursor allows the production of a semiconductor in a one step route by providing both elements in the same precursor compound. Earlier work has shown the potential of this strategy for the CVD of thin films of a range of semiconductors and metals. The use of coordination compounds as single molecule precursors to produce colloidal inorganic nanocrystals has emerged in the nineties as an alternative route to produce such nanomaterials. A paradigmatic example is the use of metal alkyldithiocarbamates or alkyldiselenocarbamates to produce colloidal nanocrystals of metal sulfides or metal selenides, respectively. We have extended the use of this type of precursors for the surface modification of materials of variable dimensionality and chemical composition. In particular, we have been interested in growing metal chalcogenide nanophases at the materials’ surfaces by promoting the solution phase thermolysis of the precursor in situ. Thus highly photoluminescent CdSe quantum dots can be capped with ZnS shells by using a zinc(II) dithiocarbamate as single-molecule precursor. This one-step route can lead to other materials whose surfaces are modified with nanophases that confer specific functionalities of interest in energy and biological applications. An illustrative example is the growth of metal sulfides onto SiO2 or TiO2 suspensions aiming their use in photocatalytic processes or as antimicrobial materials. Research is in progress for the application of this strategy to carbon nanostructures.

see for example
S. Fateixa, M. C. Neves, A. Almeida, J. Oliveira, T. Trindade, “Anti-fungal activity of SiO2/Ag2S nanocomposites against Aspergillus niger”, Colloids Surfaces B 2009, 74, 304-308.
M. C. Neves, O. C. Monteiro, R. Hempelmann, A M. S. Silva, T. Trindade, “From Single-Molecule Precursors to Coupled Ag2S/TiO2Nanocomposites”, Eur. J. Inorg. Chem. 2008, 4380-4386.
M. C. Neves, M. A. Martins, P. C. R. Soares-Santos, P. Rauwel, R. A. Sá Ferreira, T. Monteiro, L. D. Carlos, T. Trindade, “Photoluminescent, transparent and flexible di-ureasil hybrids containing CdSe/ZnS quantum dots”, Nanotechnology, 2008, 19, 155601.
O. C. Monteiro, A. C. C. Esteves, T. Trindade, “The synthesis of SiO2@CdS nanocomposites using single-molecule precursors”, Chem. Mater., 2002, 14, 2900-2904.
DEVELOPMENT OF NEW FORMS OF PIGMENTATION
With this research topic we aim to exploit chemical routes that involve known inorganic pigments and their modifications, enabling innovative and competitive forms for their use. These approaches somehow mimic procedures that have been used by Nature in producing functional pigments using common materials such as the interference pigments found in the wings of butterflies. Hence, a special focus has been the development of chemical methods that enable control of the optical and morphological properties of particulates that can be arranged in a variety of substrates. An illustrative example is the chemical bath deposition method that we have developed in order to coat a variety of substrates (e.g. glasses, natural fibers, polymer beads) with BiVO4 pigments. The color palette of this pigment can be further extended by doping the host monoclinic structure with foreign ions such as Ce(III). Also, the development of inorganic–organic hybrids (e.g. Fe2O3/cellulose) has been exploited leading to pigments that besides the coloristic properties might confer other properties such as improved mechanical and thermal behavior.

see for example
M. C. Neves, C. S. R. Freire, B. F. O. Costa, C. P. Neto, R. A. S. Ferreira, T. Trindade, “Cellulose/iron oxide hybrids as multifunctional pigments in thermoplastic starch based materials”, Cellulose, 2013, 20, 861-871.
M. A. B. Barata, M. C. Neves, C. P. Neto, T. Trindade, “Growth of BiVO4particles in cellulosic fibres by in situ reaction”, Dyes and Pigments, 2005, 65, 125-127.
M. C. Neves, T. Trindade, “Chemical Bath Deposition of BiVO4”, Thin Solid Films, 2002, 406, 93-97.
METAL COMPLEXES AND INORGANIC-ORGANIC HYBRIDS
Studies on the coordination chemistry of d- and f-metals has been of great interest due to their relevance for some of the topics already mentioned above. Besides fundamental knowledge that emerges from these studies, this research also aims: i) the synthesis of metal complexes that can be regarded as functional units for nanomaterials (e.g. fluorescent silicas); ii) the functionalization of nanomaterials’ surfaces with coordinating groups with chemical affinity for specific metal species (e.g. surface modification of eco-nanomagnets). Additionally, there are collaborations with other CICECO researchers in the synthesis and structural characterization of a variety of metal-organic frameworks.

see for example
F. Shi, L. Cunha-Silva, R. A. Sá Ferreira, L. Mafra, T. Trindade, L. D. Carlos, F. A. Almeida Paz, J. Rocha, “Interconvertable Modular Microporous Framework and Layered Lanthanide(III)-Etidronic Acid Coordination Polymers”, J. Am. Chem. Soc., 2008, 130, 150-167.
P. I. Girginova, F. A. Almeida Paz, P. C. R. Soares-Santos, R. A. Sá Ferreira, L. D. Carlos, V. S. Amaral, J. Klinowski, H. I. S. Nogueira, T. Trindade, “Synthesis, Characterisation and Luminescent Properties of Lanthanide-Organic Polymers with Picolinic and Glutaric Acids”, Eur. J. Inorg. Chem, 2007, 4238–4246.
F. Shi, L. Cunha-Silva, M. J. Hardie, T. Trindade, F. A. Almeida Paz, J. Rocha, “Heterodimetallic Germanium(IV) Complex Structures with Transition Metals”, Inorg. Chem., 2007, 46, 6502-6515.
F. Shi, F. A. A. Paz; P. Girginova; H. I. S. Nogueira, J. Rocha; V. Amaral; J. Klinowski; T. Trindade,“A novel cobalt(II)-molybdenum(V) phosphate organic-inorganic hybrid polymer”, J. Solid State Chem., 2006, 179, 1497-1505.
P. I. Girginova, F. A. Almeida-Paz, H. I. S. Nogueira, N. J. O. Silva, V. S. Amaral, J. Klinowski, T. Trindade, “Synthesis, Characterisation and Magnetic Properties of Cobalt(II) Complexes with 3- Hydroxypicolinic Acid (HpicOH): [Co(picOH)2(H2O)2] and mer-[N(CH3)4][Co(picOH)3]·H2O”, Polyhedron, 2005, 24, 563.