Bifunctional Systems Research Articles

Nucleation, growth mechanism, and bifunctional electrochromic supercapacitive properties of NiO thin films

Bifunctional devices combining display and energy storage capabilities are crucial for next-generation optoelectronic technology. This study investigates the application of nickel oxide (NiO) thin films for bifunctional electrochromic energy storage systems. The amorphous Ni(OH)2 thin films were electrodeposited with a focus on their time-dependent properties. The Scharifker-Hills model revealed a mixed nucleation process during the electrodeposition. The deposited thin films were examined for their physicochemical properties using X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron Spectroscopy (XPS), and morphological studies. Rietveld refinement of the XRD pattern confirmed a cubic NiO polycrystalline phase, while XPS identified Ni3+ as the dominant oxidation state. Significant morphological changes were observed with the varying deposition time. The NiO electrode deposited for 120 minute exhibited optimal characteristics including the highest areal capacitance of 161.77 mF/cm2, along with excellent cyclic stability of 96.54 % even after 2000 cyclic voltammetry cycles. The electrochromic study demonstrated optical modulation ranging within 55–82 % at 532 nm, with a maximum coloration efficiency of 86.90 cm2/C. This research demonstrates the viability of NiO thin films as bifunctional electrochromic energy storage systems and the advancement of optoelectronic devices that integrate display and energy storage functionalities.

Transforming Waste into Valuable Chemicals: CO2 Conversion Enabled by Porphyrin-Based Catalysts

Carbon dioxide is the primary greenhouse gas responsible for global warming and the resulting climate change, which is provoking a significant increase in extreme weather events that impact our health, environment, and economy. Nowadays the scientific community is focusing many efforts on the use of CO2 as a C1 source in the synthesis of a wide range of useful products, in alignment with circular economy principles [1].Here we report the reaction of CO2 with epoxides and aziridines, forming cyclic carbonates and oxazolidin-2-ones, by a 100% atom-efficient procedure promoted by porphyrin-based catalytic systems [2]. Considering that the contemporary presence of electrophile and nucleophile promoters is usually required for these classes of transformations, several binary and bifunctional porphyrin-based systems will be discussed with the final goal to underline the advantages of employing these systems in terms of broad applicability and eco-tolerance. Porphyrins exhibit remarkable chemical versatility, allowing for precise tuning of catalytic performances and reaction chemo-selectivity. Furthermore, the heterogenization of single-site catalysts onto solid supports enhances practical applicability [3].In addition, synthetic protocols will also be discussed from a mechanistic point of view on the basis of spectroscopic and theoretical studies and taking into account the identification of active intermediates [4].

Porous starch embedded with anthocyanins-CMC coating as bifunctional packaging with seafood freshness monitoring properties

In line with the growing demand for more sustainable and efficient materials for food packaging, new bifunctional pH-responsive composites were developed with the dual purpose of packaging and indicating seafood spoilage. Within this study, a fully bio-based composite based on porous starch (PS) was prepared via microwave irradiation (∼1 g/cm3) followed by functionalization via dip-coating with an active solution of anthocyanins-carboxymethyl cellulose (CMC). Here, the edible anthocyanins (Ath) endowed excellent antioxidant and pH-sensing properties to the resulting bifunctional composite (PS-ACMC), covering a pH range of 6–11.5, making it compelling for developing smart food-packaging materials. Moreover, results indicated that the coating scarcely altered the excellent mechanical properties developed by the PS sample, which were comparable with the commercial expanded polystyrene foams. Concurrently, to enhance the competitive properties of the starch component, bifunctional PS-CMC systems were devised crosslinking starch with citric acid. The obtained citrate-starch specimens exhibited a superior porous structure with lower density (∼0.61 g/cm3), antioxidant properties, and about 40% less solubility in water compared to the neat starch sample. Remarkably, this functionalization hindered the colour-switching properties when the active coating was added, likely due to a strong fixation of the CMC with the natural dye. However, PS-ACMC composites exhibited a rapid and effective colour response, transitioning from violet to greenish-blue, facilitating visual and real-time assessment of the freshness when using shrimp as test specimens. The results reported underscored the high potential of such bifunctional biocomposites in obtaining sustainable and smart freshness-monitoring packaging for seafood.

The Hydrolytic Activity of Copper(II) Complexes with 1,4,7-Triazacyclononane Derivatives for the Hydrolysis of Phosphate Diesters.

A set of substituted 1,4,7-triazacyclononane ligands was synthesised, including a wide series of novel derivatives bearing a thiazole or thiophene side group, with the potential to incorporate these derivatives into a polymeric material; some previously known/studied ligands were also synthesised for comparative purposes. The corresponding copper(II) complexes were prepared, and their ability to mediate the hydrolysis of phosphate ester bonds was studied via UV-Vis spectrophotometry, using bis(p-nitrophenyl)phosphate as a model substrate. Some of the prepared complexes showed a considerable enhancement of the phosphate ester hydrolysis in comparison with previously studied systems, which makes them some of the most effective complexes ever tested for this purpose. Therefore, these novel, potentially bifunctional systems could provide the possibility of creating new coating materials for medicinal devices that could prevent biofilm formation.

The interplay between particle size and hierarchy of zeolite ZSM-5 during the CO2-to-aromatics process.

The CO2-to-aromatics process is a chemical reaction that converts carbon dioxide (CO2) into valuable petrochemical, i.e., aromatics (especially, benzene, toluene, and xylene) over the metal/zeolite bifunctional catalytic systems. These aromatics are used in producing plastics, fibers, and other industrial products, which are currently exclusively sourced from fossil-derived feedstocks. The significance of this process lies in its potential to mitigate climate change by reducing greenhouse gas emissions while simultaneously producing valuable chemicals. Consequently, these CO2-derived aromatics can reduce the reliance on fossil fuels as a source of feedstocks, which can help to promote a more sustainable and circular economy. Owing to the existence of a wider straight channel favoring the aromatization process, the zeolite ZSM-5 is extensively used to yield aromatics during CO2 hydrogenation over bifunctional (metal/zeolite) catalytic systems. To provide a better understanding of this unique property of zeolite ZSM-5, this work investigates the impact of particle size and hierarchy of the zeolite and how these to govern reaction performance and overall selectivity. As a result, an improved understanding of the zeolite-catalyzed hydrocarbon conversion process has been obtained.

Simultaneous multifunctional transcriptome engineering by CRISPR RNA scaffold.

RNA processing and metabolism are subjected to precise regulation in the cell to ensure integrity and functions of RNA. Though targeted RNA engineering has become feasible with the discovery and engineering of the CRISPR-Cas13 system, simultaneous modulation of different RNA processing steps remains unavailable. In addition, off-target events resulting from effectors fused with dCas13 limit its application. Here we developed a novel platform, Combinatorial RNA Engineering via Scaffold Tagged gRNA (CREST), which can simultaneously execute multiple RNA modulation functions on different RNA targets. In CREST, RNA scaffolds are appended to the 3' end of Cas13 gRNA and their cognate RNA binding proteins are fused with enzymatic domains for manipulation. Taking RNA alternative splicing, A-to-G and C-to-U base editing as examples, we developed bifunctional and tri-functional CREST systems for simultaneously RNA manipulation. Furthermore, by fusing two split fragments of the deaminase domain of ADAR2 to dCas13 and/or PUFc respectively, we reconstituted its enzyme activity at target sites. This split design can reduce nearly 99% of off-target events otherwise induced by a full-length effector. The flexibility of the CREST framework will enrich the transcriptome engineering toolbox for the study of RNA biology.

Water-Soluble Gd(III)-Porphyrin Complexes Capable of Both Photosensitization and Relaxation Enhancement.

With the aim of developing more stable Gd(III)-porphyrin complexes, two types of ligands 1 and 2 with carboxylic acid anchors were synthesized. Due to the N-substituted pyridyl cation attached to the porphyrin core, these porphyrin ligands were highly water-soluble and formed the corresponding Gd(III) chelates, Gd-1 and Gd-2. Gd-1 was sufficiently stable in neutral buffer, presumably due to the preferred conformation of the carboxylate-terminated anchors connected to nitrogen in the meta position of the pyridyl group helping to stabilize Gd(III) complexation by the porphyrin center. 1H NMRD (nuclear magnetic relaxation dispersion) measurements on Gd-1 revealed high longitudinal water proton relaxivity (r1 = 21.2 mM-1 s-1 at 60 MHz and 25 °C), which originates from slow rotational motion resulting from aggregation in aqueous solution. Under visible light irradiation, Gd-1 showed extensive photoinduced DNA cleavage in line with efficient photoinduced singlet oxygen generation. Cell-based assays revealed no significant dark cytotoxicity of Gd-1, while it showed sufficient photocytotoxicity on cancer cell lines under visible light irradiation. These results indicate the potential of this Gd(III)-porphyrin complex (Gd-1) as a core for the development of bifunctional systems acting as an efficient photodynamic therapy photosensitizer (PDT-PS) with magnetic resonance imaging (MRI) detection capabilities.

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO 2 /Epoxide Copolymer

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO ₂ /Epoxide Copolymer

Pentyl valerate biofuel from γ-valerolactone in one-pot process: Insights on the key role of acid sites of the catalytic support

In this work the acid-catalysed reactions involved in the one-pot production of pentyl valerate (PV) from γ-valerolactone (GVL) and pentanol in liquid phase at 523 K, 10 bar of N 2 over acidic catalysts was studied. Two consecutive acid-catalysed reactions must be performed: (1) nucleophilic addition of pentanol (PL) to GVL to form 4-hydroxy pentyl valerate (HPV) and (2) HPV dehydration into pentyl 2-pentenoate (PP), avoiding the undesirable formation of 4-pentoxy pentyl valerate (PPV). It was found that the support activity and selectivity strongly depended on: (i) the nature; (ii) strength; (iii) density of acid sites and (iv) the textural properties of the acid support. Solids containing predominantly Lewis acid sites, such as ZnO/SiO 2 , γ-Al 2 O 3 and NaY zeolite promote mainly a strong GVL adsorption leading to a relatively high missing carbon balance. Catalysts having mainly surface Brønsted acid sites of medium–high strength, such as HPA/SiO 2 , showed a very high activity and selectivity to PP but deactivated dramatically. Zeolites containing at least 40% of Brønsted acidity and strong acid sites promoted remarkably the undesirable intramolecular dehydration of pentanol into pentenes. SiO 2 -Al 2 O 3 , exhibiting a B/(L + B) ratio of 0.21 and a wide strength of acid sites, was more selective to PP than to PPV though the missing carbon balance was high. By calorimetric adsorption and temperature-programmed oxidation adsorption enthalpies of 61.9 and 59.1 Kcal/mol for GVL and PL were obtained, respectively. Besides, by temperature-programmed desorption experiments it was determined that GVL adsorption is irreversible on SiO 2 -Al 2 O 3 , whereas in the case of PL is partially reversible. The effect of the calcination temperature on the product distribution and evolution of the missing carbon balance was also studied over SiO 2 -Al 2 O 3 . These results contribute to the future design of more efficient bifunctional catalytic systems for biofuel production.

The Grotthuss mechanism for bifunctional proton transfer in poly(benzimidazole).

Poly(benzimidazole) (PBI) has received considerable attention as an effective high-temperature polymer electrolyte membrane for fuel cells. In this work, the Grotthuss mechanism for bifunctional proton transfer in PBI membranes was studied using density functional theory and transition state theory. This study focused on the reaction paths and kinetics for bifunctional proton transfer scenarios in neutral ([PBI]2), single (H+[PBI]2) and double-protonated (H2+[PBI]2) dimers. The theoretical results showed that the energy barriers and strength for H-bonds are sensitive to the local dielectric environment. For [PBI]2 with ε = 1, the uphill potential energy curve is attributed to extraordinarily strong ion-pair H-bonds in the transition structure, regarded as a ‘dipolar energy trap’. For ε = 23, the ion-pair charges are partially neutralized, leading to a reduction in the electrostatic attraction in the transition structure. The dipolar energy trap appears to prohibit interconversion between the precursor, transition and proton-transferred structures, which rules out the possibility for [PBI]2 to be involved in the Grotthuss mechanism. For H+[PBI]2 and H2+[PBI]2 with ε = 1, the interconversion involves a low energy barrier, and the increase in the energy barrier for ε = 23 can be attributed to an increase in the strength of the protonated H-bonds in the transition structure: the local dielectric environment enhances the donor–acceptor interaction of the protonated H-bonds. Analysis of the rate constants confirmed that the quantum effect is not negligible for the N–H+ … N H-bond especially at low temperatures. Agreement between the theoretical and experimental data leads to the conclusion that the concerted bifunctional proton transfer in H2+[PBI]2 in a high local dielectric environment is ‘the rate-determining scenario’. Therefore, a low local dielectric environment can be one of the required conditions for effective proton conduction in acid-doped PBI membranes. These theoretical results provide insights into the Grotthuss mechanism, which can be used as guidelines for understanding the fundamentals of proton transfers in other bifunctional H-bond systems.

Bifunctional ultraviolet light-emitting/detecting device based on a SnO2 microwire/p-GaN heterojunction

SnO 2 has attracted considerable attention due to its wide bandgap, large exciton binding energy, and outstanding electrical and optoelectronic features. Owing to the lack of reliable and reproducible p-type SnO 2 , many challenges on developing SnO 2 -based optoelectronic devices and their practical applications still remain. Herein, single-crystal SnO 2 microwires (MWs) are acquired via the self-catalyzed approach. As a strategic alternative, n - SnO 2 MW/p-GaN heterojunction was constructed, which exhibited selectable dual-functionalities of light-emitting and photodetection when operated by applying an appropriate voltage. The device illustrated a distinct near-ultraviolet light-emission peaking at ∼ 395.0 nm and a linewidth ∼ 50 nm . Significantly, the device characteristics, in terms of the main peak positions and linewidth, are nearly invariant as functions of various injection current, suggesting that quantum-confined Stark effect is essentially absent. Meanwhile, the identical n - SnO 2 MW/p-GaN heterojunction can also achieve photovoltaic-type light detection. The device can steadily feature ultraviolet photodetecting ability, including the ultraviolet/visible rejection ratio ( R 360 nm / R 400 nm ) ∼ 1.5 × 10 3 , high photodark current ratio of 10 5 , fast response speed of 9.2/51 ms, maximum responsivity of 1.5 A/W, and detectivity of 1.3 × 10 13 Jones under 360 nm light at − 3 V bias. Therefore, the bifunctional device not only displays distinct near-ultraviolet light emission, but also has the ability of high-sensitive ultraviolet photodetection. The novel design of n - SnO 2 MW/p-GaN heterojunction bifunctional systems is expected to open doors to practical application of SnO 2 microstructures/nanostructures for large-scale device miniaturization, integration and multifunction in next-generation high-performance photoelectronic devices.

Direct Synthesis of Dimethyl Ether on Bifunctional Catalysts Based on Cu–ZnO(Al) and Supported H3PW12O40: Effect of Physical Mixing on Bifunctional Interactions and Activity

We studied different preparation methods to synthesize a series of bifunctional hybrid catalytic systems for the direct synthesis of DME from syngas. The objective was to optimize the contact and interaction between the methanol synthesis catalyst and the methanol dehydration catalyst (Cu/ZnO/Al2O3 and H3PW12O40 supported on TiO2, respectively) by using different mixing methods (simple mixing, mixing–milling, suspension, and mixing–pressing). It has been found that the close contact between methanol synthesis and acidic functions is highly dependent on the degree of mixing of the two catalysts. In this respect, the hybrid catalyst prepared by mixing–pressing, which represents the closest contact, shows the strongest alterations in both catalytic functions. These modifications are associated with a decrease in copper surface area and a decrease in strong acid sites caused by the physical blocking of active sites or by cation exchange of the Cu2+/Zn2+ species from Cu–ZnO(Al) and the H+ from the H3PW12O40 units. The activity results demonstrated that the mixing–pressing method leading to a closer contact between the two catalytic functions led to a very low dimethyl ether time yield compared to the other bifunctional catalysts prepared by less severe mixing methods (19.4 vs 205–335 μmol/min·gcat). This work clearly indicates the importance of the mixing method in the synthesis of the hybrid catalyst to optimize the distance and interaction between the metal and acid sites.

Bifunctional Palladium-Ceria Catalysts for Hydrogen Oxidation Reaction

In recent years, anion exchange membrane fuel cells (AEMFCs) have drawn much attention as the next-generation cost-effective fuel cells. A major challenge for the AEMFCs is the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline solution, which could be a major hinderance to developing high-performance AEMFC catalysts. Here, we explore the HOR mechanism for palladium-ceria anode catalysts using first-principles theory. This combination of materials has been shown to display excellent HOR performance experimentally. The computations are carried out for multiple palladium concentrations on ceria surfaces. The reaction pathway for HOR is investigated via the Tafel reaction for the dissociation of hydrogen molecules and Volmer reaction for the formation of water molecules. Our findings show that palladium-ceria bifunctional systems have improved HOR activity compared to their individual components. Specifically, an enhanced catalytic activity is predicted for 10 at. % palladium on ceria. We explain this behavior using multiple activity descriptors including hydrogen, OH, and H2O binding energies, and hybridization and charge transfer between the catalyst, the substrate, and adsorbents. The results suggest that the high HOR activity can be attributed to the delicate balance between the H and OH interactions with the palladium-ceria support as well as the interaction between the individual components that make up the heterostructure. The detailed first-principles analysis provides invaluable insights toward electronic, atomistic, and molecular mechanisms of HOR and paves the way for the development of catalysts that use significantly reduced amounts of precious metals. Sahoo et al., ACS Catal. 11, 2561 (2021).

SERS study on the aggregation mechanisms resulting from the orientation of dipyridinic derivatives on gold nanoparticles

In this work, was studied the adsorption and orientation of three dipyridinic derivatives 9,10-bis-((E)-2-(pyridin-4-yl)vinyl)anthracene (DPAC), 1,4-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-T) and 2,6-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-L) on gold nanoparticles, using Surface Enhanced Raman Scattering (SERS). Systematic modification in the shapes of the bifunctional systems (Cross-shape, T-shape and Linear-shape) shows changes significant in the preferential orientation of these analytes on the nanostructured gold surface. Additional data from UV–vis measurements and TEM images are in agreement with the Reaction Limited Colloid Aggregation (RLCA) mechanisms for DPAC and DPNA-T and Diffusion Limited Colloid Aggregation (DLCA) mechanisms for DPNA-L, showing that for the same analyte concentration, the aggregation mechanism depends on the molecular shape. These results allow us to rationalize the fundamental aspects involved in the development of devices based on plasmonic resonance with potential applications in the field of molecular electronics.

Selective catalytic hydrogenation of biomass derived furans to secondary alcohols using Pt/polyoxometalate catalysts under mild reaction conditions

AbstractPromising bifunctional catalyst systems composed of platinum and polyoxometalates (POMs) were applied successfully for the selective catalytic hydrogenation of 2,5‐dimethylfuran (DMF) to 2‐hexanol under mild conditions. Pt(acac)2 was found to be the most active Pt precursor for the ring opening of DMF, and the Keggin‐type POM K3[PW12O40] was identified as the most promoting acidic support for 2‐hexanol formation at 80 °C and 10 bar H2 pressure using n‐decane as a carrier liquid. It was revealed that modifications in the synthetic procedure of the Pt/K3[PW12O40] catalytic system allowed its catalytic performance to be enhanced. Thus, a higher yield of 2‐hexanol (72.5%) was achieved compared to that (49%) obtained using a commercial Pt/C catalyst with the same Pt loading. The Wells–Dawson‐type POM containing catalyst Pt/K6[α‐P2W18O62] was found to be selective for 2‐hexanon formation (56.4% yield) under identical reaction conditions. Furthermore, furan and 2‐methylfuran were also selectively hydrogenated to 1‐butanol (59.7% yield) and 1/2‐pentanol (44.3% yield), respectively, under the applied reaction conditions. Moreover, using analytical tools like N2‐physisorption, NH3‐TPD, inductively coupled plasma optical emission spectroscopy (ICP‐OES), CO chemisorption, and transmission electron microscopy (TEM), revealed that the higher total acid site density of the K3[PW12O40] enhances C=O hydrogenation and overcomes the rate‐limiting step of 2‐hexanone hydrogenation to 2‐hexanol. This demonstrates the high performance of the bi‐functional catalyst system Pt/K3[PW12O40] towards ring opening of various furans and the very high selectivity towards alcohol formation. This approach opens new interesting valorization pathways for several furanic compounds with respect to sustainable alcohol formation. © 2021 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Asymmetric Dehydrative Allylation Using Soft Ruthenium and Hard Brønsted Acid Combined Catalyst.

Asymmetric Pd-catalyzed Tsuji-Trost-type allylation is an important catalytic reaction toward chiral natural and unnatural product syntheses. We successfully modified a desalt-type reaction using allyl ester or halide to a dehydrative one using allylic alcohol via the establishment of two redox-mediated donor acceptor bifunctional catalyst systems. These systems were cationic CpRu-Cl-Napy-PyCOOH and cationic CpRu-Naph-diPIM-dioxo-iPr/p-TsOH and were designed on the basis of the soft ruthenium and hard Brønsted acid combined catalyst concept. The complementary use of the two chiral catalysts for dehydrative asymmetric allylation expands the application scope facilitating the utilization of both aliphatic and aromatic allylic alcohols with various nucleophiles in the substrate. In this account, the design, synthesis, and application of these catalysts were reported.

Temperature-Sensitive Lipid-Coated Carbon Nanotubes for Synergistic Photothermal Therapy and Gene Therapy.

The combination of photothermal therapy (PTT) and gene therapy (GT) shows great potential to achieve synergistic anti-tumor activity. However, the lack of a controlled release of genes from carriers remains a severe hindrance. Herein, peptide lipid (PL) and sucrose laurate (SL) were used to coat single-walled carbon nanotubes (SCNTs) and multi-walled carbon nanotubes (MCNTs) to form bifunctional delivery systems (denoted SCNT-PS and MCNT-PS, respectively) with excellent temperature-sensitivity and photothermal performance. CNT/siRNA suppressed tumor growth by silencing survivin expression while exhibiting photothermal effects under near-infrared (NIR) light. SCNT-PS/siRNA showed very high anti-tumor activity, resulting in the complete inhibition of some tumors. It was highly efficient for systemic delivery to tumor sites and to facilitate siRNA release owing to the phase transition of the temperature-sensitive lipids, due to PL and SL coating. Thus, SCNT-PS/siRNA is a promising anti-tumor nanocarrier for combined PTT and GT.

Reliability Analysis of Accelerated Destructive Degradation Testing Data for Bi-Functional DC Motor Systems

An accelerated degradation test (ADT) has become a popular method to accelerate degradation mechanisms by stressing products beyond their normal use conditions. The components of an automobile are degraded over time or cycle due to their constant exposure to friction or wear. Sometimes, the performance degradation can be measured only by destructive inspection such as operating torques of return-springs in a bi-functional DC motor system. Plastic deformation of the return-spring causes the degradation of actuating forces for shield movement, resulting in deterioration of the shield moving speed in a headlight system. We suggest a step-by-step procedure for a reliability analysis for a bi-functional DC motor in a headlight system, based mainly on accelerated destructive degradation test (ADDT) data. We also propose nonlinear degradation models to describe the ADDT data of the return-springs. Exposure effects of high temperatures on the return-springs are quantitatively modeled through the ADDT models. We compare the estimation results from both the closed-form expression and Monte Carlo simulation to predict the failure–time distribution at normal use conditions, showing that the lifetime estimation results from the closed-form formulation are more conservative.

Bifunctional Cobalt-Containing Catalytic Systems Based on SAPO-11 Molecular Sieves in Fischer–Tropsch Synthesis of Fuels

The study investigated, for the first time with respect to Fischer–Tropsch synthesis of fuels, cobalt-containing catalytic systems based on SAPO-11 molecular sieves with differing secondary porous structure characteristics. Various methods, such as XRD, low-temperature nitrogen adsorption/desorption, SEM, TEM, H2-TPD, and NH3-TPD, were used to characterize the prepared catalysts, which were subsequently examined in hydrocarbon synthesis at 2.0 MPa, 240°C, and gas WHSV = 1000 h–1. The study demonstrated good prospects for micro/mesoporous-structured SAPO-11 as an acid catalyst component for fuel production.

Synthesis, characterization and surface enhanced Raman spectroscopy study of a new family of different substituted cruciform molecular systems deposited on gold nanoparticles

AbstractIn this work, the adsorption and orientation on gold nanoparticles (AuNps) of a new family of cruciform systems consisting of thiophene rings and imino groups were studied. The structural modification and its influence on the adsorbate‐substrate interaction were evaluated by UV–Vis spectroscopy and Surface Enhanced Raman Spectroscopy (SERS). The absence of SERS spectrum for (N,N′‐bis(4‐(trifluoromethyl)benzylidene)‐2,5‐di (thiophene‐2‐yl)‐1,4‐diaminobenzene) CFF shows that the inclusion of a trifluoromethyl group (‐CF3) on the benzylidene fragment limits the interaction of the CFF system with the gold substrate, in contrast, to that obtained for (N, N′‐dibenzylidene‐2,5‐di (thiophene‐2‐yl) ‐1,4‐diaminobenzene) 2‐CF and (N, N′‐bis (4‐methoxybenzylidene) ‐2,5‐di (thiophene‐2yl) ‐1,4‐diaminobenzene) CMF, where the adsorption took place preferentially through the thiophene rings, resulting in partial quinoidization. On the other hand, the interaction for compound (N, N′‐bis (4‐methylenepyridinyl) ‐2,5‐di (thiophene‐2‐yl) ‐1,4‐diaminobenzene) CPy with the surface was conducted by means of the pyridinic fragments. The systematic modification of the bifunctional cruciform systems, with groups of different nature, makes it possible to rationalize the structural aspects that directly influence the adsorbate‐substrate interaction and molecular orientation on gold substrates. These structural parameters are the basis to the development of stable molecular assemblies, which can act as basic building blocks in the manufacture of molecular switches.