Opportunity of Patterning in Chemistry

Patterning offers an efficient way to quantitatively enhance and enlarge material properties and functionalities, offering unprecedented opportunities for innovation in various scientific domains. By precisely controlling the spatial arrangement of materials at the micro- and nanoscale, patterning enables the exploitation of inherent material properties in novel ways. In addition, it generates new properties, leading to the development of advanced devices and applications. This article highlights the significant contributions of spatially controlled patterning in chemistry, particularly in generating new functional properties and devices, discussing some representative articles. Examples include the use of unconventional patterning techniques for surface functionalization, as well as the application of spatial confinement in improving material properties and controlling crystallization processes. Furthermore, the discussion extends to creating new devices, such as optical storage media and sensors, through spatial organization of materials.

Atomic Vacancies in Transition Metal Dichalcogenides: Properties, Fabrication, and Limits

Structural defects, such as heteroatoms or atomic vacancies, are always present in materials and significantly affect their physical properties, in both positive or unwanted ways. Interestingly, defects generate an impressive range of functionalities in many materials, such as catalysis, electrical and thermal conductivity tuning, thermoelectricity, enhanced ion storage, magnetism, and others. These properties enable the use of defective materials in a great variety of technological applications. Here we review the principal properties generated by atomic vacancies in 2D compounds and thin films of transition metal dichalcogenides and the most consolidated methods for their formation and engineering. Eventually, we critically analysed the most important advantages, the limits and the current open challenges.

Pentacoordinate Cobalt(II) Single Ion Magnets with Pendant Alkyl Chains: Shall We Go for Chloride or Bromide?

Four pentacoordinate complexes 1-4 of the type [Co(L1)X2] and [Co(L2)X2] (where L1=2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 1 and 2, L2=2,6-bis(1-dodecyl-1H-benzimidazol -2-yl)-pyridine for 3 and 4; X = Cl- for 1 and 3, X...

Combined wet lithography and fractional precipitation as a tool for fabrication of spatially controlled nanostructures of poly(3-hexylthiophene) ordered aggregates

Herein, we propose an easy and practical method for the fabrication of highly ordered supramolecular structures. The proposed approach combines fractional precipitation and wet lithography, to obtain a spatially-defined pattern of submicrometric structures with a high molecular order of poly(3-hexylthiophene). The process is demonstrated by XRD, confocal and time-resolved spectroscopy and by the performance of an effective field effect transistor.

Control of polymorphism in thiophene derivatives by sublimation-aided nanostructuring

Here we applied the concept of “sublimation-aided nanostructuring” to control the polymorphism of a model material.

AC parallel local oxidation of silicon

Here, we present a suitable advancement of parallel local oxidation nanolithography, demonstrating its feasibility in alternate current mode (AC-PLON). For demonstration, we fabricated model structures consisting of an array of parallel nanostripes of electrochemical SiO _x with a controlled roughness. Besides, we proved the repeatability of AC-PLON and its integrability with conventional parallel local oxidation nanolithography.

Naked-Eye Heterogeneous Sensing of Fluoride Ions by Co-Polymeric Nanosponge Systems Comprising Aromatic-Imide-Functionalized Nanocellulose and Branched Polyethyleneimine

Heterogeneous colorimetric sensors for fluoride ions were obtained by cross-linking TEMPO-oxidized cellulose nanofibers (TOCNF) with chemically modified branched polyethyleneimine 25 kDa (bPEI). Functionalization of bPEI primary amino groups with aromatic anhydrides led to the formation of the corresponding mono- and bis-imides on the grafted polymers (f-bPEI). A microwave-assisted procedure allowed the optimization of the synthetic protocol by reducing reaction time from 17 h to 30 minutes. Hydrogels obtained by mixing different ratios of TOCNF, bPEI and f-bPEI were lyophilized and thermally treated at about 100 °C to promote the formation of amide bonds between the amino groups of poly-cationic polymers and the carboxylic groups of cellulose nanofibers. This approach generated a series of cellulose nanosponges S1-S3 which were characterized by FT-IR and by solid state ¹³ C CPMAS NMR. These sponge materials can act as colorimetric sensors for the selective naked-eye recognition of fluoride ions over chloride, phosphate and acetate ions at concentrations of up to 0.05 M in DMSO. Moreover, when the sponges were functionalized with perylene tetracarboxylic diimide, successful naked-eye detection was achieved with only 0.02 % w/w of chromophore units per gram of material.

Multifunctional self-assembled monolayers via microcontact printing and degas-driven flow guided patterning

Soft lithography-based patterning techniques have been developed to investigate biological and chemical phenomena. Until now, micropatterning with various materials required multiple procedural steps such as repeating layer-by-layer patterning, aligning of stamps, and incubating printed inks. Herein, we describe a facile micropatterning method for producing chemically well-defined surface architectures by combining microcontact (µCP) and microfluidic vacuum-assisted degas-driven flow guided patterning (DFGP) with a poly(dimethylsiloxane) (PDMS) stamp. To demonstrate our concept, we fabricated a bi-composite micropatterned surface with different functional molecular inks such as fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) and polyethylene glycol (PEG)-silane for a biomolecule array, and 3-aminopropyltriethoxysilane (APTES) and PEG-silane pattern for a self-assembled colloid gold nanoparticle monolayer. With a certain composition of molecular inks for the patterning, bi-composite surface patterns could be produced by this µCP-DFGP approach without any supplementary process. This patterning approach can be used in microfabrication and highly applicable to biomolecules and nanoparticles that spread as a monolayer.

Spatial control of chirality in supramolecular aggregates

Chirality is one of the most intriguing properties of matter related to a molecule’s lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic.

Luminescent films for chemo- and biosensing

Luminescent films have received great interest for chemo-/bio-sensing applications due to their distinct advantages over solution-based probes, such as good stability and portability, tunable shape and size, non-invasion, real-time detection, extensive suitability in gas/vapor sensing, and recycling. On the other hand, they can achieve selective and sensitive detection of chemical/biological species using special luminophores with a recognition moiety or the assembly of common luminophores and functional materials. Nowadays, the extensively used assembly techniques include drop-casting/spin-coating, Langmuir-Blodgett (LB), self-assembled monolayers (SAMs), layer-by-layer (LBL), and electrospinning. Therefore, this review summarizes the recent advances in luminescent films with these assembly techniques and their applications in chemo-/bio-sensing. We mainly focused on the discussion of the relationship between the sensing properties of the films and their architecture. Furthermore, we discussed some critical challenges existing in this field and possible solutions that have been or are being developed to overcome these challenges.

Self-protective action in multicomponent fluorescent self-assembled monolayers

We report on the fabrication of self-protective self-assembled monolayers constituted by a highly fluorescent component and a linear alkyl chain.

Organic Materials for Time-Temperature Integrator Devices

Time-temperature integrators (TTIs) are devices capable of recording the thermal history of a system. They have an enormous impact in the food and pharmaceutical industries. TTIs exploit several irreversible thermally activated transitions such as recrystallization, dewetting, smoothening, chemical decomposition, and polymorphic transitions, usually considered drawbacks for many technological applications. The aim of this article is to sensitize research groups working in organic synthesis and surface science toward TTI devices, enlarging the prospects of many new materials. We reviewed the principal applications highlighting the need and criticisms of TTIs, which offer a new opportunity for the development of many materials.

Additive, modular functionalization of reactive self-assembled monolayers: toward the fabrication of multilevel optical storage media

We report a novel strategy based on iterative microcontact printing, which provides additive, modular functionalization of reactive SAMs by different functional molecules. We demonstrate that after printing the molecules form an interpenetrating network at the SAM surface preserving their individual properties. We exploited the process by fabricating new optical storage media that consist of a multilevel TAG.

APTES mediated modular modification of regenerated silk fibroin in a water solution

Chemical modification of regenerated silk fibroin was achieved by exploiting (3-aminopropyl)triethoxysilane acting simultaneously as solvent, carrier in water, grafter of an hydrophobic fluorescent molecule and reinforcing agent.

Solid nanoarchitecture – Cu(ii) solution: dynamics of the chemical communication

The response of a porphyrin nanoarchitecture, covalently supported on quartz, was investigated upon the external chemical Cu(ii) stimulus. The overall structure behaves as a ternary optical system.

Synthesis and structure–property investigation of multi-arm oligothiophenes

A series of soluble 3D-oligothiophenes with different conjugation lengths are synthesized and characterized. Physical properties and formation of charge transfer complexes of oligothiophenes with Hg(ii) ions and TCNQ are investigated.

Photoinduced self-assembly of carboxylic acid-terminated lamellar silsesquioxane: highly functional films for attaching and patterning amino-based ligands

A facile procedure for immobilizing and photopatterning amino ligands onto a multilayer cross-linked COOH-functionalized organosilica film is described. Key features include high functionality, robustness and no restriction on the substrate.

A time-temperature integrator based on fluorescent and polymorphic compounds

Despite the variety of functional properties of molecular materials, which make them of interest for a number of technologies, their tendency to form inhomogeneous aggregates in thin films and to self-organize in polymorphs are considered drawbacks for practical applications. Here, we report on the use of polymorphic molecular fluorescent thin films as time temperature integrators, a class of devices that monitor the thermal history of a product. The device is fabricated by patterning the fluorescent model compound thieno(bis)imide-oligothiophene. The fluorescence colour of the pattern changes as a consequence of an irreversible phase variation driven by temperature, and reveals the temperature at which the pattern was exposed. The experimental results are quantitatively analysed in the range 20–200°C and interpreted considering a polymorph recrystallization in the thin film. Noteworthy, the reported method is of general validity and can be extended to every compound featuring irreversible temperature-dependent change of fluorescence.

Optical properties of hybrid T3Pyr/SiO2/3C-SiC nanowires

A new class of nanostructured hybrid materials is developed by direct grafting of a model thiophene-based organic dye on the surface of 3C-SiC/SiO2 core/shell nanowires. TEM-EDX analysis reveals that the carbon distribution is more spread than it would be, considering only the SiC core size, suggesting a main contribution from C of the oligothiophene framework. Further, the sulfur signal found along the treated wires is not detected in the as-grown samples. In addition, the fluorescent spectra are similar for the functionalized nanostructures and T3Pyr in solution, confirming homogeneous molecule grafting on the nanowire surface. Chemical and luminescence characterizations confirm a homogeneous functionalization of the nanowires. In particular, the fluorophore retains its optical properties after functionalization.

Selective growth of α-sexithiophene by using silicon oxides patterns

A process for fabricating ordered organic films on large area is presented. The process allows growing sexithiophene ultra-thin films at precise locations on patterned Si/SiO(x) substrates by driving the orientation of growth. This process combines the parallel local anodic oxidation of Si/SiO(x) substrates with the selective arrangement of molecular ultra-thin film. The former is used to fabricate silicon oxide arrays of parallel lines of 400 nm in width over an area of 1 cm(2). Selective growth arises from the interplay between kinetic growth parameters and preferential interactions with the patterned surface. The result is an ultra-thin film of organic molecules that is conformal to the features of the fabricated motives.

One-step substrate nanofabrication and patterning of nanoparticles by lithographically controlled etching

We propose an integrated top-down and bottom-up approach to single-step nanofabrication of complex nanostructures made of different materials. The process, termed lithographically controlled etching (LCE), starts with a drop of an etching solution cast on the surface to be patterned. By placing a polymeric mold on the substrate, the stamp protrusions come into contact with the surface, thus protecting it, whereas the surface beneath the mold recesses is exposed to a thin layer of etching solution, allowing the surface to be etched. By dispersing nanoparticles into the etching solution, these can be deposited and self-organize in the recesses on the substrate as these are excavated. We demonstrate here the fabrication of complex structures and nanowires 30 nm wide. Moreover, by exploiting capillary forces, it is possible to deposit nanoparticles at precise positions with respect to optically addressable microstructures, thus realizing a multiscale functional pattern.