The application of colloidal quantum dots (CQDs) for the production of low cost photodetectors offers a promising alternative to the expensive epitaxially-grown structures. Technologies based on near-/mid-IR CQDs are not so developed as a full-grown application of visible spectral range CQDs like CdSe. Lead chalcogenide colloidal quantum dots are promising nanomaterials exhibiting an excellent photosensitivity in the near-IR and mid-IR ranges. Bulk materials PbS and PbSe CQDs have band gaps 0.41 and 0.27 eV respectively.

In the past decades a lot of effort was put into the development of the efficient and scalable synthetic methods for the preparation of lead chalcogenide CQDs. It is rather complicated to get broad range of nanocrystals sizes and the narrow size distribution by a single method even for the most developed material namely lead sulfide CQDs.

The procedure for the preparation of smaller PbS nanocrystals by resizing of larger one was developed in our lab by application of oleylamine/oleic acid mixture. Solvents effect and reagent ratio was investigated more in detail. It was found that this transformation is much more general and both lead selenide and telluride nanocrystalls could be resized applying the same reagent. The combination of resizing approach with earlier developed synthetic methods allows to produce the PbS colloidal quantum dots for near IR-applications.

For the further applications of lead chalcogenides CQDs a preparation of photoconductive thin films is necessary. Ligand exchange process in thin films of PbS CQDs was studied by FTIR spectroscopy applying HATR accessory. This innovative approach allows to study the both efficiency and the rate of ligand exchange. Exchange processes were studied for the several ligands (iodide, thiocyanate). Impact of the solvent on the exchange result was analyzed.

Water is necessary to all human activities and to life in general. Because of this, it was made central to all components of the EU Green Deal and to several United Nation Sustainable Development Goals, starting with SDG6 on «clean water and sanitation». Industrialization, population grow, and their needs have contributed to the degradation and scarcity of safe water. Inorganic elements are one example among many of water contaminants. Arsenic and mercury are two elements that cause great concern. Chronic As exposure could cause cancer, neuropathies, bronchopulmonary and cardiovascular diseases, and chromosome aberrations. The World Health Organization guideline of As in drinking water is set to 10 μg/L, but in different parts of the world, As concentrations significantly higher than 50 μg/L have been detected (Smedley and Kinniburgh, 2002). Mercury is neurotoxic, volatile, persistent, and bioaccumulates in the organisms. For these reasons efforts have been made to develop effective pollution control technologies towards the efficient and enhanced As and Hg removal from contaminated sites. In this communication it will be reported the synthesis, characterization, and application of hybrid nanostructures to remove As and Hg from water, and their concentration in a solid phase, promoting the recycling of these elements. The nanocomposites combine the interesting properties of graphite nanoplatelets, with the magnetic properties of cobalt and manganese spinel ferrites, and exhibit good sorption properties towards As and Hg. For some systems (nanocomposite/element) the sorption process was sensitive to solution pH, evidencing that electrostatic interactions could be the main binding mechanism involved. Removal efficiencies up to 80% were achieved using only a few milligrams per liter of nanocomposite. In binary solutions, occurred a preferential removal of Hg, however the initial As concentrations was higher. The kinetic behavior was well described by pseudo-second order or Elovich equations, suggestion chemisorption process.

Plasmonic nanostructures represent a suitable platform for the detection of biomolecules interaction. Their surface functionalization can be performed through different strategies such as polymer coating or solgel-based coverages. Optimal thickness, homogeneity and hydrophilicity of the functional layer can play a crucial role in defining the sensing capabilities that are required to perform bioassays.

In this framework, we combined two complementary approaches that improve the aforementioned features. First, the nanostructure surface was covered with a thin layer of Tetraethyl orthosilicate (TEOS) which improve the chemical homogeneity of the surface. Then a commercial polymer bearing biomolecule-active moieties (Lucidant MCP polymers) is coated on the TEOS layer. The polymer layer decreases the contact angle of the surface preventing the aggregation of biomolecules during immobilization.

The total thickness of the functionalized nanostructure was below 10 nm, ensuring the biomolecules to be placed in proximity of the sensing surface. In this way the functionalized nanostructure is compatible, at the same time, with both Surface Plasmon Resonance (SPR) and Plasmonic Enhanced Fluorescence (PEF) modality of detection.

In our more recent studies, we focused on PEF and surfaces optimized with the combined layer of TEOS and MCP polymer were evaluated in a commercial microarray scanner for protein assay. The fluorescence signal was collected and analyzed giving an effective improvement of the fluorescence intensity compared to a plasmonic nanostructure coated only with MCP polymer or a flat gold surface with the same combined TEOS and MCP coating.

Several works in the last years demonstrated the strategic role of piezoelectricity in wide range of applications, ranging from flexible pressure sensors [https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.201504755] to energy harvesting [https://doi.org/10.1016/j.energy.2019.01.043]. Piezoelectricity is an intrinsic property of materials that are able to convert an electrical potential that they are subjected into a mechanical deformation. Poly-vinylidene-fluoride (PVDF) is one of the most attractive piezo-polymer due to its flexibility, transparency, lightweight, high chemical resistance due to the presence of C-F bonds, good resistance to mechanical deformation, biocompatibility, high thermal stability, low cost, and durability in the human body. Moreover, several studies investigated the enhancement of its piezoelectric features due to nanoconfinement [https://doi.org/10.1080/00150193.2018.1456304]. We investigate the role of electrospinning parameters on thefproperties of PVDF-piezoelectric nanofibers-NFs. 19wt% PVDF was dissolved in solvents (50:50wt% of Dimethylformamide:Acetone). In this works, the electrospinning parameters were selected to enhance solvents’ evaporation, nanofibers’ stretching, their alignment. A main focus was dedicated to: applied-electric field, (i.e. the ratio between applied voltage and working distance), and the collector used during nanofibers depositions, (planar versus drum-rotating collector). Fourier-Transformed-Infrared-Spectroscopy (FTIR) was implemented to investigate the presence of the piezoelectric β-phase and γ-phase . All samples show peaks at 532 cm⁻¹ and 761 cm⁻¹ belonging to the α-phase And larger peaks belonging to the β-phase at 510 cm⁻¹ and 840 cm⁻¹ . Peaks belonging to the β-phase at 445 cm⁻¹, 1274 cm⁻¹ and 1430 cm⁻¹ are present only in NFs, processed at low electric-field, confirming that higher electric-field can negatively affect the instauration of the β-phase. FTIR-results confirmed no correlation among the piezoelectricity and nanofibers’distribution. Ferroelectric hysteresis loop, and displacement loop demonstrated that the presence of β-phase peaks was related to piezoelectric properties.

Obtaining such characteristics of dispersions of synthesized nanoparticles as concentration and particle size is an important task in nanotechnology, biomedicine, industry and many other fields. A rapidly developing method for such needs is nanoparticle tracking analysis. This method is very convenient when working with polydisperse samples, since it provides a more accurate particle size and intensity distribution than dynamic light scattering. This technique enables visualization and recording of nanoparticles sized from dozens of nanometers to couple of micrometers moving under Brownian motion. The key point of getting precise information about a nanodispersion is video processing, which allows to analyze the sample quickly without damaging it. Samples of polystyrene and gold nanoparticles with different characteristics were dispersed in water and studied using nanoparticle tracking analysis device. As the reference methods of nanoparticles characterization dynamic light scattering and transmission electron microscopy were used. One of the main problems, that occurs on the stage of video processing is a high noise rate, which may lead to recognition errors. Adjusting such parameters as shutter and gain may be needed to increase signals from weakly scattering particles like polystyrene latex nanoparticles. This study also represents the main advantages and drawbacks of using nanoparticle tracking analysis method in the study of nanoparticle samples of various concentration levels.

The more recent progress and technological improvement in nanostructured plasmonic surfaces has gathered huge interest in applications related to actual sensing challenges. In particular, fluorescence has been one of the most exploited measurement techniques within such a context. Specifically, resorting to custom structures supporting suitable plasmonic resonances, we studied their influence on the emission efficiency of the commercial ATTO700 fluorophore. An extended optical analysis in combination with a complementary investigation through finite-difference time-domain (FDTD) simulations have been performed to understand the coupling mechanism between the excitation of the plasmonic modes and the fluorescence absorption and emission processes. In addition, within this framework, we focused on the use of a buffer solution, flowing across the grating active surface, to mimic a real measurement. The refractive index of the surrounding medium is therefore altered, with a consequent modification of the resonance conditions. The result is a shift of the emission spectral features characterized by a reshaping of the fluorescence curve in terms of spectral weight and direction.

Therefore, the strongest signature of the plasmonic modes determines the spectral region characterized by the largest relative enhancement, as shown by both the optical measurements and the FDTD findings.

Besides, the electric field corresponding to the localized modes at the interface with the substrate carries and favors the fluorophore emission toward its side.

The creation of lightweight materials with precisely selected combinations of the required topological, mechanical, thermal and other physical and chemical properties is the "Holy Grail" of materials science. The extreme lattice metamaterials with unique topological and physicochemical properties represent a new type of matter that not normally does not exist in nature and can be considered as promising nanoscale building blocks. Multi-functional lattice structures utilizing metamaterials have the potential to radically change the future of products that we use in our daily lives and the way in which industries like aerospace and the medical field operate. Important vibrational, mechanical, thermal, electronic and transport characteristics of nanomaterials are controlled by phonons: by the propagating atomic vibrational waves. We propose a game-changing approach for additively manufactured extreme lattice metamaterials predictive performance improvement and unlocking the new functionalities through fine-tuning atomic vibrational inter-layer interactions within the transition domains of multilayer nanocomponents. The proposed approach is based on the recently discovered fundamental phenomenon of collective atomic vibrations, manifested within transition domains of multilayer nanostructures. For predictive excitation and adjustment of this phenomenon, we propose incorporation the multilayer low-dimensional carbon-based nano-enhanced interfaces into the transition domains of nanocomponents through the multistage technological chain, including conversion of all components into the nanoscale, the plasma-driven functionalization and assembling with multilayer nano-enhanced interfaces, the resonant acoustic mixing of all nanocomponents and growing the high-end elements by selective high-precision additive manufacturing.

Surface enhanced Raman spectroscopy (SERS) is a popular method of organic molecules detection in low concentrations. Being close to each other, noble metal nanoparticles, such as gold and silver, form hot spots, which can enhance signal of Raman spectroscopy. To obtain substrates with high value of enhancement coefficient and good signal reproducibility, metal nanoparticles should be uniformly distributed on the substrate surface. That could be achieved using titania nanosheets as a sublayer. Titania nanosheets represent 2D photocatalytic material, which demonstrates strong bond with metal nanoparticles, and, therefore, is perspective in production of reusable substrates for SERS with reproducible signal on the surface.

In present research, titania nanosheets were obtained during cesium titanate exfoliation using solutions of hydrochloric acid and tetrabutylammonium hydroxide. The nanosheets show lateral sizes up to 1 µm and thickness of 0.5 nm, which proves the formation of single-layered titania nanosheets. Silver nanoparticles were deposited on the surface of nanosheets via AgNO3 solution reduction using sodium borohydride. The optimized synthesis of the substrates allows achieving enhancement coefficient up to 5·10⁶ and ability to detects molecules of rhodamine 6G with concentration of 10^-8 M. Moreover, investigation of SERS signal distribution throughout the surface shows high reproducibility of it. Due to photocatalytic properties of titania, surface of the substrates can be cleaned after measurement by UV irradiation, and the substrates can be used repeatedly.

Pollution and scarcity of water resources are considered one of the biggest concerns nowadays. Thus, the development of new technologies or materials that allow the improvement of water quality and its reuse is still in progress. Heterogeneous semiconductor photocatalysis has attracted great interest among available Advanced Oxidation Processes (AOP) applied to wastewater decontamination [1]. These methods have been regarded as particularly effective options for eliminating certain organic pollutants, potentially harmful to living organisms even if present in small amounts. Bismuth vanadate (BiVO₄) has been investigated as a photocatalyst of interest due to its ability to harvest photons efficiently in the visible spectral region [2]. In addition, powdered BiVO4 shows high photochemical stability, good dispersibility, and resistance to corrosion in oxidative conditions. Photocatalysts can be designed with other functionalities such as magnetic properties by coupling nanoparticles of cobalt ferrites, in order to provide their easy and fast separation from waters by application of an external magnetic field.

In this communication, we will present the synthesis and characterization of magnetic heterostructures of BiVO₄/CoFe₂O₄ and their photocatalytic activity on the photodegradation of sulfamethoxazole (SMX) dissolved in water, and their reuse in further catalytic cycles.

A.C. Estrada acknowledges the research position funded by national funds (OE), through FCT-Fundação para a Ciência e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC).

[1] Ganiyu S.O.; Sable S.; El-Din M. G., Chemical Engineering Journal, 2022, 429, 132492; [2] Malathi A.; Madhavan J.; Ashokkumar M.; Arunachalam P., Appl. Catal., A, 2018, 555, 47-74.

Flexible and stretchable strain-pressure sensors received great interest due to growing demand in several applications of wide variety of fields, like industrial, automotive, robotics, sports and biomedical. They attracted significant interest to design body-integrated electronic-systems, allowing real-time detection and analysis of human-body movements. Sensors’ performance was strictly correlated with materials’ selection, that must satisfy requirements: high stretchability, excellent biocompatibility, great conformability, and low cost. To satisfy all features, we propose electrospun-nanofibers as sensitive elements, since they, thanks to their intrinsic properties, offered important strategies to design flexible sensors with superior electrical and mechanical performances. We proposed composite-PEO-MWCNTs nanofibers as sensitive materials. To realize new-piezoresistive structures able to be integrated in flexible sensors, optimizing their performance, we investigated two different rotating-collectors. The first collector is a non-conductive-wire and the second one is a non-conductive-hollow-wire of heat-shrinkable material. We demonstrated how these different collectors induced ordered nanofibers distribution respect to nanofibers’ randomly distribution into planar configurations, while their percolation behaviour was no affected by different distributions. For what concerned piezoresistive-performance, we demonstrated good electrical behaviour of nanofibers before and after applied-deformations, confirming their complete reliability and reuse as sensitive nanomaterials. Piezoresistive-responses confirmed an increase of nanofibers’ resistance with the increasing of applied pressure. A dimensionless parameter|∆R/R0|was calculated and plotted as a function of applied pressure to define sensitivity and resolution of sensors. All results highlighted good sensors’ resolution and sensitivity achieved when ordered nanofibers were collected onto both wire substrate, thus being able to extend the deformation range to which the sensitive nanomaterial can be subjected. New flexible-pressure sensor is proposed as device direct integrable into textile.