Enhancing Photothermal Energy Transduction through Inter- and Intramolecular Interactions of Multiple Two-Photon Dyes Appended onto Calix[4]arene.

Organic dyes-based photothermal agents (OPTAs) have received increasing attention as alternative to inorganic materials due to their higher biocompatibility and extensive diversification. Maximizing nonradiative deexcitation channels is crucial to improve the photothermal conversion efficiency (PCE) of OPTAs. This is typically achieved through individual molecular design or collective enhancement using supramolecular strategies.

Engineering MOF/carbon nitride heterojunctions for effective dual photocatalytic CO conversion and oxygen evolution reactions.

Photocatalysis appears as one of the most promising avenues to shift towards sustainable sources of energy, owing to its ability to transform solar light into chemical energy, production of chemical fuels oxygen evolution (OER) and CO reduction (CORR) reactions. Ti metal-organic frameworks (MOFs) and graphitic carbon nitride derivatives, poly-heptazine imides (PHI) are appealing CORR and OER photo-catalysts respectively. Engineering of an innovative Z-scheme heterojunction by assembling a Ti-MOF and PHI offers an unparalleled opportunity to mimick an artificial photosynthesis device for dual CORR/OER catalysis.

Panchromatic light harvesting and record power conversion efficiency for carboxylic/cyanoacrylic Fe(ii) NHC co-sensitized FeSSCs.

Fe(ii) pyridyl-NHC sensitizers bearing thienylcyanoacrylic (ThCA) anchoring groups have been designed and characterized with the aim of enhancing the metal to surface charge separation and the light harvesting window in iron-sensitized DSSCs (FeSSCs). In these new Fe(ii) dyes, the introduction of the ThCA moiety remarkably extended the spectral response and the photocurrent, in comparison with their carboxylic analogues. The co-sensitization based on a mixture of a carboxylic and a ThCA-iron complex produced a panchromatic absorption, up to 800 nm and the best photocurrent and efficiency ( : 9 mA cm and PCE: 2%) ever reported for an FeSSC.

F-Center-Mediated Growth of Patterned Organic Semiconductor Films on Alkali Halides.

Organic semiconductors combine flexible tailoring of their optoelectronic properties by synthetic means with strong light-matter coupling, which is advantageous for organic electronic device applications. Although spatially selective deposition has been demonstrated, lateral patterning of organic films with simultaneous control of molecular and crystalline orientation is lacking as traditional lithography is not applicable. Here, a new patterning approach based on surface-localized F-centers (halide vacancies) generated by electron irradiation of alkali halides is presented, which allows structural control of molecular adlayers.

Revealing Weak Dimensional Confinement Effects in Excitonic Silver/Bismuth Double Perovskites.

Lead-free perovskites are attracting increasing interest as nontoxic materials for advanced optoelectronic applications. Here, we report on a family of silver/bismuth bromide double perovskites with lower dimensionality obtained by incorporating phenethylammonium (PEA) as an organic spacer, leading to the realization of two-dimensional double perovskites in the form of (PEA)AgBiBr ( = 1) and the first reported (PEA)CsAgBiBr ( = 2). In contrast to the situation prevailing in lead halide perovskites, we find a rather weak influence of electronic and dielectric confinement on the photophysics of the lead-free double perovskites, with both the 3D CsAgBiBr and the 2D = 1 and = 2 materials being dominated by strong excitonic effects.

Tuning the Interfacial Energetics in WO/WO and WO/TiO Heterojunctions by Nanostructure Morphological Engineering.

Nowadays, semiconducting heterojunction-based devices exhibit the best photocatalytic performance, with transition metal oxides such as tungsten (WO) and titanium (TiO) being the workhorse materials employed in these composites. Contrary to their bulk counterparts, WO and TiO nanostructures offer a huge versatility because their optoelectronic properties (i.e.

Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols.

A number of factors contribute to orbital energy alignment with respect to the Fermi level in molecular tunnel junctions. Here, we report a combined experimental and theoretical effort to quantify the effect of metal image potentials on the highest occupied molecular orbital to Fermi level offset, ε, for molecular junctions based on self-assembled monolayers (SAMs) of oligophenylene ethynylene dithiols (OPX) on Au. Our experimental approach involves the use of both transport and photoelectron spectroscopy to extract the offsets, ε and ε, respectively.

A Series of Iron(II)-NHC Sensitizers with Remarkable Power Conversion Efficiency in Photoelectrochemical Cells*.

A series of six new Fe(II)NHC-carboxylic sensitizers with their ancillary ligand decorated with functions of varied electronic properties have been designed with the aim to increase the metal-to- surface charge separation and light harvesting in iron-based dye-sensitized solar cells (DSSCs). ARM130 scored the highest efficiency ever reported for an iron-sensitized solar cell (1.83 %) using Mg and NBu I-based electrolyte and a thick 20 μm TiO anode.

Competition between the Photothermal Effect and Emission in Potential Phototherapy Agents.

Planar donor-acceptor-donor (D-A-D) organic molecules have been highlighted as promising photothermal agents due to their good light-to-heat conversion ratio, easy degradation, and chemical tunability. Very recently, it has been demonstrated that their photothermal conversion can be boosted by appending rather long alkyl chains. Despite this behavior being tentatively associated with the population of a nonradiative twisted intramolecular charge transfer (TICT) state driven by an intramolecular motion, the precise mechanisms and the role played by the environment, and most notably aggregation, still remain elusive.

Challenges for Incorporating Optical Switchability in Organic-Based Electronic Devices.

Transistors operate by controlling the current flowing from a source to a drain electrode via a third electrode (gate), thus giving access to a binary treatment (ON/OFF or 0/1) of the signal currently exploited in microelectronics. Introducing a second independent lever to modulate the current would allow for more complex logic functions amenable to a single electronic component and hence to new opportunities for advanced electrical signal processing. One avenue is to add this second dimension with light by incorporating photochromic molecules in current organic-based electronic devices.

Measurement of the conformational switching of azobenzenes from the macro- to attomolar scale in self-assembled 2D and 3D nanostructures.

It is important, but challenging, to measure the (photo)induced switching of molecules in different chemical environments, from solution through thin layers to solid bulk crystals. We compare the cis-trans conformational switching of commercial azobenzene molecules in different liquid and solid environments: polar solutions, liquid polymers, 2D nanostructures and 3D crystals. We achieve this goal by using complementary techniques: optical absorption spectroscopy, femtosecond transient absorption spectroscopy, Kelvin probe force microscopy and reflectance spectroscopy, supported by density functional theory calculations.

Understanding the Structural and Electronic Properties of Photoactive Tungsten Oxide Nanoparticles from Density Functional Theory and Approaches.

Tungsten trioxide (WO)-derived nanostructures have emerged recently as feasible semiconductors for photocatalytic purposes due to their visible-light harvesting that overcomes the drawbacks presented by TiO-derived nanoparticles (NPs). However, applications are still limited by the lack of fundamental knowledge at the nanoscale due to poor understanding of the physical processes that affect their photoactivity. To fill this gap, we report here a detailed computational study using a combined density functional theory (DFT)- scheme to investigate the electronic structure of realistic WO NPs containing up to 1680 atoms.

Reversal of the Direction of Rectification Induced by Fermi Level Pinning at Molecule-Electrode Interfaces in Redox-Active Tunneling Junctions.

Control over the energy level alignment in molecular junctions is notoriously difficult, making it challenging to control basic electronic functions such as the direction of rectification. Therefore, alternative approaches to control electronic functions in molecular junctions are needed. This paper describes switching of the direction of rectification by changing the bottom electrode material M = Ag, Au, or Pt in M-S(CH)S-BTTF//EGaIn junctions based on self-assembled monolayers incorporating benzotetrathiafulvalene (BTTF) with EGaIn (eutectic alloy of Ga and In) as the top electrode.

On the reliability of acquiring molecular junction parameters by Lorentzian fitting of / curves.

Fitting the I/V curves of molecular junctions by simple analytical models is often done to extract relevant molecular parameters such as energy level alignment or interfacial electronic coupling to build up useful property-relationships. However, such models can suffer from severe limitations and hence provide unreliable molecular parameters. This is illustrated here by extracting key molecular parameters by fitting computed voltage-dependent transmission spectra and by comparing them to the values obtained by fitting the calculated I/V curves with a typical Lorentzian model used in the literature.

Iron's Wake: The Performance of Quantum Mechanical-Derived Versus General-Purpose Force Fields Tested on a Luminescent Iron Complex.

Recently synthetized iron complexes have achieved long-lived excited states and stabilities which are comparable, or even superior, to their ruthenium analogues, thus representing an eco-friendly and cheaper alternative to those materials based on rare metals. Most of computational tools which could help unravel the origin of this large efficiency rely on ab-initio methods which are not able, however, to capture the nanosecond time scale underlying these photophysical processes and the influence of their realistic environment. Therefore, it exists an urgent need of developing new low-cost, but still accurate enough, computational methodologies capable to deal with the steady-state and transient spectroscopy of transition metal complexes in solution.

A New Class of Rigid Multi(azobenzene) Switches Featuring Electronic Decoupling: Unravelling the Isomerization in Individual Photochromes.

We report a novel class of star-shaped multiazobenzene photoswitches comprising individual photochromes connected to a central trisubstituted 1,3,5-benzene core. The unique design of such C-symmetric molecules, consisting of conformationally rigid and pseudoplanar scaffolds, made it possible to explore the role of electronic decoupling in the isomerization of the individual azobenzene units. The design of our tris-, bis-, and mono(azobenzene) compounds limits the π-conjugation between the switches belonging to the same molecule, thus enabling the efficient and independent isomerization of each photochrome.

A tool box to ascertain the nature of doping and photoresponse in single-walled carbon nanotubes.

The effect of doping on the electronic properties in bulk single-walled carbon nanotube (SWCNT) samples is studied for the first time using a new in situ Raman spectroelectrochemical method, and further verified by DFT calculations and photoresponse. We use p-/n-doped SWCNTs prepared by diazonium reactions as a versatile chemical strategy to control the SWCNT behavior. The measured and calculated data testify an acceptor effect of 4-aminobenzenesulfonic acid (p-doping), and a donor effect (n-doping) in the case of benzyl alcohol.

Electronic Decoupling in C-Symmetrical Light-Responsive Tris(Azobenzene) Scaffolds: Self-Assembly and Multiphotochromism.

We report the synthesis of a novel C-symmetrical multiphotochromic molecule bearing three azobenzene units at positions 1, 3, 5 of the central phenyl ring. The unique geometrical design of such a rigid scaffold enables the electronic decoupling of the azobenzene moieties to guarantee their simultaneous isomerization. Photoswitching of all azobenzenes in solution was demonstrated by means of UV-vis absorption spectroscopy and high performance liquid chromatography (HPLC) analysis.

Influence of the donor unit on the rectification ratio in tunnel junctions based on donor-acceptor SAMs using PTM units as acceptors.

Dyads formed by an electron donor unit (D) covalently linked to an electron acceptor (A) by an organic bridge are promising materials as molecular rectifiers. Very recently, we have reported the charge transport measurements across self-assembled monolayers (SAMs) of two D-A systems consisting of the ferrocene (Fc) electron-donor linked to a polychlorotriphenylmethane (PTM) electron-acceptor in its non-radical (SAM 1) and radical (SAM 2) forms. Interestingly, we observed that the non-radical SAM 1 showed rectification behavior of 2 orders of magnitude higher than its radical analogue dyad 2.

Design of Perchlorotriphenylmethyl (PTM) Radical-Based Compounds for Optoelectronic Applications: The Role of Orbital Delocalization.

Perchlorotriphenylmethyl (PTM) radical-based compounds are widely exploited as molecular switching units. However, their application in optoelectronics is limited by the fact that they exhibit intense absorption bands only in a narrow range of the UV region around 385 nm. Recent experimental works have reported new PTM based compounds which present a broad absorption in the visible region although the origin of this behavior is not fully explained.

Edge Functionalization of Structurally Defined Graphene Nanoribbons for Modulating the Self-Assembled Structures.

Edge functionalization of bottom-up synthesized graphene nanoribbons (GNRs) with anthraquinone and naphthalene/perylene monoimide units has been achieved through a Suzuki coupling of polyphenylene precursors bearing bromo groups, prior to the intramolecular oxidative cyclo-dehydrogenation. High efficiency of the substitution has been validated by MALDI-TOF MS analysis of the functionalized precursors and FT-IR, Raman, and XPS analyses of the resulting GNRs. Moreover, AFM measurements demonstrated the modulation of the self-assembling behavior of the edge-functionalized GNRs, revealing that GNR-PMI formed an intriguing rectangular network.