Víctor Vega-Mayoral

• Doktor Znanosti (Doctor in Science)
• PostDoc Position at Madrid Institute for Advanced Studies

The optoelectronic properties of Ag₂S nanocrystals with different surface passivation treatments have been investigated using femtosecond transient absorption spectroscopy. Plain Ag₂S nanocrystals and improved surface-passivated nanostructures were studied under different...

CuInS2 quantum dots have been studied in a broad range of applications, but despite this, the fine details of their charge carrier dynamics remain a subject of intense debate. Two of the most relevant points of discussion are the hole dynamics and the influence of Cu:In synthesis stoichiometry on them. It has been proposed that Cu-deficiency leads...

The burgeoning field of 2D heterostructures targets the combination of 2D materials with 3D, 1D, or 0D nanomaterials. Among the most popular 2D materials, the 2H polytype of molybdenum disulfide (MoS2) features a well‐defined bandgap that becomes direct at the monolayer level, which can be exploited for photodetection. A notable limitation of 2H‐Mo...

Highly emissive core/shell Ag2S nanocrystals (NCs) passivated with a Ag2(S, Se) and a graded ZnS shell were synthesized, and the temperature dependence of their photoluminescence quantum yield (PLQY) was quantified...

The creation of complex hollow nanostructures with precise control over size and shape represents a great challenge in supramolecular soft materials. Here, we have further developed a bioinspired methodology for the formation of aqueous nanotubes of well‐defined dimensions and pore coating through the self‐assembly of amphiphiles that are chemicall...

Donor-acceptor systems have garnered significant attention in the fields of semiconducting materials and light harvesting. ¹ Particularly intriguing are porphyrin diads, wherein porphyrins are covalently bonded to nanographenes, forming a dyad with an expected electron transfer from the porphyrin to the nanographene. In our study, we leverage the e...

Porphyrins, a type of heterocyclic aromatic compounds consisting of tetrapyrroles connected by four substituted methine groups, are appealing building blocks for solar energy applications. However, their photosensitization capability is limited by their large optical energy gap, which results in a mismatch in absorption toward efficient harvesting...

The development of sodium ion batteries will require high‐performance electrodes with very large areal capacity and reasonable rate performance. Although red phosphorus is a very promising electrode material, it has not yet fulfilled these requirements. Here, liquid phase exfoliation is used to convert solid red phosphorus into amorphous, quasi‐2D...

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted increasing interests for (opto)-electronics and spintronics. They generally consist of van der Waals stacked layers and exhibit layer-depended electronic properties. While considerable efforts have been made to regulate the charge transport within a layer, precise contro...

The bottom‐up synthesis of an unprecedentedly large cove‐edged nanographene, hexa‐peri‐hexabenzo‐bis‐peri‐octacene (HBPO), is reported in this work. Chiral high‐performance liquid chromatography and density functional theory (DFT) calculations revealed multiple conformations in solution. Two different molecular conformations, “waggling” and “butter...

The bottom‐up synthesis of an unprecedentedly large cove‐edged nanographene, hexa‐peri‐hexabenzo‐bis‐peri‐octacene (HBPO), is reported in this work. Chiral high‐performance liquid chromatography and density functional theory (DFT) calculations revealed multiple conformations in solution. Two different molecular conformations, “waggling” and “butter...

Photo-excited state’s dynamics, and optical gain properties of a novel and promising coved-edge nanographene are presented. Observation of ASE with ~1 mJ/cm ² threshold, and 80% of Quantum Yield, open the door towards future photonic applications.

Gold nanoclusters (AuNCs) are nanomaterials with interesting photoluminescent properties that can be endowed with biomolecular recognition and biocompatibility when stabilized with proteins. The interplay between the optical features of AuNCs and the function added by the protein makes them perfect candidates for generating hybrid protein‐inorganic...

The building of van der Waals heterostructures and the decoration of 2D materials with organic molecules share a common goal: to obtain ultrathin materials with tailored properties. Performing controlled chemistry on van der Waals heterostructures would add an extra level of complexity, providing a pathway towards 2D-2D-0D mixed-dimensional heteros...

Frankeite is a naturally occuring 2D material, which stands out due to its p-type behaviour and low bandgap (<0.7 eV). In this project we investigate the photophysics of Frankeite functionalized with porphyrin-decorated maleimide, a hybrid interface of great potential for optoelectronics.

Due to their high porosity, aerogels can be efficiently used as host matrices for functional materials. The solid matrix is advantageous over liquid suspensions because it maintains the nanoparticles static and inhibits agglomeration and precipitation. The current paper reports on the controlled addition of less than 0.1 wt% of WS2 nanotubes (WS2 N...

The propensity of many 2D materials to oxidize in ambient conditions can complicate production and limit applications potential. Here we describe ambient liquid phase exfoliation of GeS, a layered material known for its chemical instability. Ambient exfoliation in organic solvents such as N-methyl-pyrrolidone yields good quality multi-layer GeS nan...

Strong coupling of electric transition dipoles with optical or plasmonic resonators modifies their light-matter interaction and, therefore, their optical spectra. Semiconducting WS2 nanotubes intrinsically provide the dipoles through their excitonic resonances, and the optical cavity via their cylindrical shape. We investigate the nonequilibrium li...

Recent advances in the liquid-phase exfoliation (LPE) of layered materials have facilitated significant progress in the creation of functional inks. While ethanol/water blends have been shown to yield reasonable nanosheet dispersions with the potential for refinement into printable inks, the exfoliated mass is typically too low for practical use. H...

We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent. Moreover, the oxidation process can be stopped at will by two different passivation procedures, namely the non-covalent functionalization w...

Titanium disulfide is a promising material for a range of applications, including lithium-ion battery (LIBs) anodes. However, its applications-potential has been severely hindered the tendency of exfoliated TiS2 to rapidly oxidize in ambient conditions. Here we confirm that, although layered TiS2 powder can be exfoliated by sonication in aqueous su...

Molybdenum dioxide (MoO2) is a layered material which shows promise for a number of applications in the electrochemical energy storage arena. Mostly studied as a bulk layered material, MoO2 has not previously been exfoliated in large quantities. Here we demonstrate liquid phase exfoliation of MoO2 in the solvent isopropanol, yielding reasonable amo...

Mixed networks of conducting and non-conducting nanoparticles show promise in a range of applications where fast charge transport is important. While the dependence of network conductivity on the conductive mass fraction (Mf) is well understood, little is known about the Mf-dependence of mobility and carrier density. This is particularly important...

We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent. Moreover, the oxidation process can be stopped at will by two different passivation procedures, namely the non-covalent functionalization w...

Mixtures of carbon nanotubes and 2D nanosheets are important in electrochemical applications where the nanosheets are the active material, while the nanotubes provide electrical conductivity and mechanical reinforcement. While the conductivity of such nano:nano composites has been studied, the mechanical properties have not. Here we report a detail...

To realise real-time, wearable personal health monitors, sensitive, low stiffness, inexpensive smart materials must be identified. Previously, room-temperature, low-viscosity nanocomposites based on graphene-doped Silly Putty (G-putty) were demonstrated. Displaying unprecedented electromechanical sensitivity and physical properties, G-putty is an i...

Electroconductive substrates are emerging as promising functional materials for biomedical applications. Here, the development of biohybrids of collagen and pristine graphene that effectively harness both the biofunctionality of the protein component and the increased stiffness and enhanced electrical conductivity (matching native cardiac tissue) o...

Identifying cheap, yet effective, oxygen evolution catalysts is critical to the advancement of water splitting. Using liquid exfoliated Co(OH)2 nanosheets as a model system, a simple procedure is developed to maximize the activity of any oxygen evolution reaction nanocatalyst. First the nanosheet edges are confirmed as the active areas by analyzing...

Transition metal dichalcogenides hold promise for applications in novel optoelectronic devices. There is therefore a need for materials that can be obtained in large quantities and with well understood optical properties. In this report, we present a thorough photoluminescence (PL) investigations of monolayer tungsten disulphide obtained via liquid...

Many promising supercapacitor electrode materials have high resistivity and require conductive additives to function effectively. However, the detailed role of the additive is not understood. Here, this question is resolved by applying a quantitative model for resistance-limited supercapacitor electrodes to Co(OH)2-nanosheet/carbon nanotube composi...

The optoelectronic properties of a material are determined by the processes following light-matter interaction. Here we use femtosecond optical spectroscopy to systematically study photoexcited carrier relaxation in few-layer MoS2 flakes as a function of excitation density and sample thickness. We find bimolecular coalescence of charges into indire...

With the aim of increasing carrier mobility in nanosheet-network devices, we have investigated MoS2–graphene composites as active regions in printed photodetectors. Combining liquid exfoliation and inkjet-printing, we fabricated all-printed photodetectors with graphene electrodes and MoS2–graphene composite channels with various graphene mass fract...

The absorption spectra of 2D semiconductors are dominated by excitons with binding energy of several hundreds of meV. Nevertheless, even single layers show an appreciable photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating some degree of free charge carrier photogeneration. Here, we perform ultraf...

Signal modulation in optoelectronics is obtained by modulation of either the refractive index or the absorbance by an electric field. However, electromodulators have not kept up with the miniaturization of other electronic and optical components. Here we show a strong transverse electroabsorption signal in a monolayer of the 2D semiconductor MoS2....

Transition metal dichalcogenides (TMD) hold promise for applications in novel optoelectronic devices. There is therefore a need for materials that can be obtained in large quantities and with well understood optical properties. In this report, we present thorough photoluminescence (PL) investigations of monolayer tungsten disulphide obtained via li...

To translate electrical into optical signals one uses the modulation of either the refractive index or the absorbance of a material by an electric field. Contemporary electroabsorption modulators (EAMs) employ the quantum confined Stark effect (QCSE), the field-induced red-shift and broadening of the strong excitonic absorption resonances character...

Semiconducting transition metal dichalcogenides (TMDs) have been applied as the active layer in photodetectors and solar cells, displaying substantial charge photogeneration yields. However, their large exciton binding energy, which increases with decreasing thickness (number of layers), as well as the strong resonance peaks in the absorption spect...

While liquid exfoliation is a powerful technique to produce defect-free nanosheets in large quantities, its usefulness is limited by broad nanosheet thickness distributions and low monolayer contents. Here we demonstrate liquid processing techniques, based on iterative centrifugation cascades, which can be designed to achieve either highly efficien...

While liquid phase exfoliation can be used to produce nanosheets stabilized in polymer solutions, very little is known about the resultant nanosheet size, thickness, or monolayer content. The present study uses semiquantitative spectroscopic metrics based on extinction, Raman, and photoluminescence (PL) spectroscopy to investigate these parameters...

Ionic surfactants, which are widely used to stabilize nanomaterials in dispersions, can drastically alter the nanomaterial’s photophysical properties. Here, we use femtosecond optical spectroscopy to study the dynamics of excitons and charges in few-layer flakes of the two-dimensional semiconductor MoS 2 . We compare samples obtained via exfoliatio...