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An amperometric sensor whose active layer is derived from a tetra core-substituted organic semiconductor, naphthalene diimide (NDI-CN4), has been evaluated for ammonia sensing at room temperature against the NDI devoid of core-substitution effects.

The optoelectronic properties of functional π-conjugated organic materials are affected by their ability to self-assemble within thin films of devices. There are limited reports that demonstrate the positive impact of self-assembly on the photovoltaic performance of organic solar cells. Here, we demonstrate that hydrogen-bonded supramolecular arrays of a cyanopyridone-based oligothiophene donor, CP6, show notable improvement in photovoltaic performance upon self-assembly into a nanofibrous network. The honeycomb-like blend network exhibited higher hole mobility, leading to efficient charge generation and transport. The photovoltaic performance of CP6 was superior to that of two structural analogues, CP5 and CP1, and was attributed to the enhanced capability of CP6 to self-assemble into a film morphology favorable for BHJ devices. The BHJ devices comprising CP6 and the conventional fullerene acceptor (PC71BM) exhibited an efficiency of 7.26%, which is greater than that of CP5 (5.19%) and CP1 (3.11%) and is among the best-performing, cyanopyridone-based oligothiophene donors described to date.

The development of perovskite solar cells (PSCs) as an efficient and cost-effective alternative to traditional approaches to solar energy transduction has received much recent attention, and there has been considerable progress made with reported power conversion efficiencies now surpassing 25%. This development is encouraging and is a result of intensive research on device design, factors affecting long-term stability of PSCs, and systematic material development in which electron transport layer (ETL) materials play a crucial role to afford high-performance PSC devices. ETL materials, including (6-(1,10-phenanthrolin-3-yl)naphthalen-2-yl)diphenylphosphine oxide (Phen-NaDPO), and n-type materials based on the naphthalene diimide (NDI) structure, appear to be amongst the most promising materials to date. This article provides an up-to-date review on organic n-type ETL materials, both polymeric and small molecules, based on NDI format, detailing reports of structures with key relevant parameters, such as the efficiency and stability of PSCs. The review is written from a perspective of organic chemistry and we believe this will provide fundamental advice on the future design of new ETL materials based on NDIs that will afford more efficient and stable PSCs.

Photocatalytic nitrogen reduction reaction (NRR) is a promising, green route to chemically reducing N2 into NH3 under ambient conditions, correlating to the N2 fixation process of nitrogenase enzymes. To achieve high-yield NRR with sunlight as the driving force, high-performance photocatalysts are essential. One-dimensional silicon nanowires (1D SiNWs) are a great photoelectric candidate, but inactive for NRR due to their inability to capture N2. In this study, we proposed SiNWs doped by p-block elements (B, C, P) to tune the affinity to N2 and demonstrated that two-coordinated boron (B2C) offers an ultra-low overpotential (η) of 0.34 V to catalyze full NRR, which is even much lower than that of flat benchmark Ru(0001) catalysts (η = 0.92 V). Moreover, aspects including suppressed hydrogen evolution reaction (HER), high-spin ground state of the B2C site, and decreased band gap after B-doping ensure the high selectivity and photocatalytic activity. Finally, this work not only shows the potential use of metal-free p-block element-based catalysts, but also would facilitate the development of 1D nanomaterials towards efficient reduction of N2 into NH3.

Electroreduction of N2 is a highly promising route for NH3 production. The lack of efficient catalysts that can activate and then reduce N2 into NH3 limits this as a pragmatic application. In this work, a 2D layered group IV-V material, silicon phosphide (SiP), is evaluated as a suitable substrate for the electrochemical nitrogen reduction reaction (ENRR). To capture N2, one phosphorus (P) defect was introduced on the plane of SiP. DFT calculations found that the defective SiP monolayer (D1-SiP, which is defined by the P-defect on SiP) exhibits enormous prospects towards the ENRR because of enhanced electron conductivity, good activation on N2, lower limiting potential (UL = -0.87 V) through the enzymatic pathway, smooth charge transfer between the catalyst and the reaction species, and robust thermal stability. Importantly, D1-SiP demonstrates the suppressed activities on producing of H2 and N2H4 side-products. This research demonstrates the potential of 2D metal-free Si-based catalysts for nitrogen fixation and further enriches the study of group IV-V materials for the ENRR.

Cyanopyridone-based oligothiophene donors with both hydrophobic and hydrophilic characters have been evaluated as active layers within simple capacitive devices for humidity sensing at room temperature. Surface studies using atomic force microscopy revealed a self-assembled nanofibrous network with a thin needle-like structure for the terminal hydroxy example (CP6), devoid in the methyl example (CP1). The sensing performance of each sensor was investigated over a broad range of relative humidity levels as a function of capacitance at room temperature. The sensor CP6 demonstrated favourable features such as high sensitivity (12.2 pF/%RH), quick response/recovery (13 s/20.7 s), wide working range of relative humidity (10%–95% RH), low hysteresis (0.57%), outstanding recyclability, and excellent long-term stability. From the results obtained, hydrophilicity and hydrogen bonding appear to play a vital role in enhancing humidity sensing performance, leading to possible new design directions for simple organic semiconductor-based sensors.

It is challenging to identify effective electrocatalysts for nitrogen reduction in order to advance electrochemical nitrogen fixation under ambient conditions using methods that are powered by renewable energy. Silicon carbide was investigated computationally as a metal-free, surface-derived catalyst for the electrocatalytic nitrogen reduction reaction. As demonstrated by first-principle calculations, Si-terminated and C-terminated surfaces, with the Si and C as active sites, are all reactive for dinitrogen capture and activation, resembling the catalytic behavior of popular B-based electrocatalysts, but the latter (C-terminated) offers an ultralow over-potential of 0.39 V, which is lower than most metals and alloys, while retarding hydrogen evolution. This research enriches the design of catalysts for dinitrogen fixation under ambient conditions, and also highlights a new direction for Si-based materials for nitrogen reduction.

A spiro[fluorene-9,9′-xanthene], often described as a “low-cost spiro,” has been functionalized with terminal diketopyrrolopyrrole units to generate a promising, three-dimensional non-fullerene acceptor. The new acceptor, coded as SFX1, was readily synthesized using the Suzuki cross-coupling reaction and was sufficiently soluble in a variety of commonly used, film-processing solvents such as chlorobenzene and o-dichlorobenzene. SFX1 displayed promising optoelectronic properties and the HOMO/LUMO energy levels complementary to the commercially available and commonly used donor polymers P3HT and PTB7. The joining of two high-potential building blocks – the spiro[fluorene-9,9′-xanthene] and diketopyrrolopyrrole – demonstrates a new strategy where the device performance [D : A 1 : 1.2 = 9.42% (D = PTB7)] validates its use as a potential, three-dimensional non-fullerene acceptor.

A significant challenge of liquid phase exfoliation (LPE) of graphite to yield graphene resides in the fact that most conventional solvents used are high boiling points and thus extremely difficult to eliminate, especially during processing of graphene into composites or films. Here, we advance the ability to produce high yield graphene in a low boiling point organic solvent, chloroform, using core-substituted naphthalene diimides (cNDIs). Through the use of cNDIs it is possible to obtain high graphene concentrations of up to 0.13 mg/mL in chloroform. This yield represents a 69% improvement from graphene yields previously obtained in chloroform using unsubstituted NDIs. Characterisation of the products by UV-Vis, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) support the use of cNDIs as an appropriate exfoliating agent in chloroform.

This review focuses on describing all known synthetic strategies leading to core-annulation of naphthalene diimides (NDIs). Strategies presented involve the formation of four-, five- and six-membered ring annulations bearing different heteroatomic and carbocyclic derivatives, including annulenes. The core-annulation method opens the possibility for obtaining designer molecules with tuneable electronic characteristics such as a reduced energy band gap, and enhanced intermolecular overlap of π-systems that improve electronic coupling between molecules-which is highly desirable for charge transport properties summarised in the final pages for applications in electronic devices such as organic field-effect transistors (OFETs) and organic photovoltaic (OPV) cells. Molecular recognition in pH and fluoride sensing, or as a DNA probe, are some of additional applications of core-annulated NDIs presented here. Additionally, recent advances in core modification of NDIs are presented, opening an entire new chemical avenue to be explored. Finally, the outlook on the future prospect of annulated NDIs in various applications is summarised.

Naphthalene diimides (NDIs) are shown to arrange spontaneously co-facially with cucurbit[8]uril (CB[8]) in an aqueous environment through purely non-covalent interactions. The resultant 2 : 2 supramolecular complex of NDI and CB[8] is highly fluorescent (>30 times more than the constituent NDIs) due to the formation of NDI-NDI excimers within the supramolecular complex.

We report for the first-time the development of capacitive type humidity sensors employing naphthalene diimide derivatives (NDI) as sensing layer. Three different naphthalene diimide derivatives bearing imide side chains of different hydrophilicity were designed, synthesised and characterised. X-ray diffraction and thermogravimetric analyses gave useful information about structural and thermal behaviour of the newly developed materials, indicating their crystallinity and stability. Atomic force microscopy analysis revealed a variety of morphologies in thin films as a result of the structural properties of the NDIs. Devices bearing NDI layers were fabricated on ceramic substrates with gold interdigitated electrodes spaced 200 µm apart. Humidity sensing performance, as a change in capacitance, was studied upon exposure to a wide range of relative humidity levels (0–95%) at ambient temperature. Importantly, an increase in the capacitance of the sensors was recorded with an increase in relative humidity. The developed sensors exhibited high sensitivity, good long-term stability, excellent reproducibility, and low hysteresis. The sensor performance was also tested against different operating frequencies (250 Hz–2 kHz) to improve linearity, illustrating directions for optimised performance. These results confirm that sensors based on NDIs possess better sensing performance to other types of reported capacitive humidity sensors.

This review provides an update on advances in the area of electrical mode sensors using organic small molecule n-type semiconductors based on perylene. Among small organic molecules, perylene diimides (PDIs) are an important class of materials due to their outstanding thermal, chemical, electronic, and optical properties, all of which make them promising candidates for a wide range of organic electronic devices including sensors, organic solar cells, organic field-effect transistors, and organic light-emitting diodes. This is mainly due to their electron-withdrawing nature and significant charge transfer properties. Perylene-based sensors of this type show high sensing performance towards various analytes, particularly reducing gases like ammonia and hydrazine, but there are several issues that need to be addressed including the selectivity towards a specific gas, the effect of relative humidity, and operating temperature. In this review, we focus on the strategies and design principles applied to the gas-sensing performance of PDI-based devices, including resistive sensors, amperometric sensors, and operating at room temperature. The device properties and sensing mechanisms for different analytes, focusing on hydrazine and ammonia, are studied in detail, and some future research perspectives are discussed for this promising field. We hope the discussed results and examples inspire new forms of molecular engineering and begin to open opportunities for other rylene diimide classes to be applied as active materials.

Crown ethers are effective at binding cations and through substitution onto the core of photoactive naphthalene diimide molecules (NDIs), cation binding can be detected via changes in UV-visible absorption and/or fluorescence emission. In this work, two new NDI-crown ether cation sensors (aza-15-crown-5 ether NDI, 5, and aza-18-crown-6 ether NDI, 6) have been synthesised and changes in UV-visible and fluorescence spectra upon addition of various cations investigated. A substantial blue shift in the UV-visible absorption of 75 nm was observed for 6 with a 1 : 1 addition of Na+ or K+, providing a clear colourimetric readout, however, no significant spectral changes were observed for 5 with the cations trialled at this level of analyte. Calcium cations do, however, elicit a response from 5 at substantially higher molar ratios, with some perturbation of the absorption spectrum observable, and an approximately six-fold increase in fluorescence emission. Theoretical calculations indicate that for 6, K+ and Na+ bind to the ether oxygens resulting in a blue shift similar to that observed experimentally. Ca2+ however, was found to bind quite differently with 5via both the ether oxygens and the carbonyl group on the NDI. This observation highlights how small structural changes can lead to different and unexpected behaviour and that investigation of underlying binding mechanisms is important to inform the rational design of future systems.

This work reports synthesis, thin film characterizations, and study of an organic semiconductor 2-aminoanthraquinone (AAq) for humidity and temperature sensing applications. The morphological and phase studies of AAq thin films are carried out by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD) analysis. To study the sensing properties of AAq, a surface type Au/AAq/Au sensor is fabricated by thermally depositing a 60 nm layer of AAq at a pressure of ~10&minus, 5 mbar on a pre-patterned gold (Au) electrodes with inter-electrode gap of 45 &micro, m. To measure sensing capability of the Au/AAq/Au device, the variations in its capacitance and resistance are studied as a function of humidity and temperature. The Au/AAq/Au device measures and exhibits a linear change in capacitance and resistance when relative humidity (%RH) and temperature are varied. The AAq is a hydrophobic material which makes it one of the best candidates to be used as an active material in humidity sensors, on the other hand, its high melting point (575 K) is another appealing property that enables it for its potential applications in temperature sensors.

The replacement of the imide oxygen atoms with sulfur atoms in the naphthalene diimide (NDI) framework is an attractive strategy for tuning of the electronic properties of such molecules. Here we report the synthesis and characterization of the full series of six thionated NDI molecules with branched side chains. In order to provide a direct comparison with the unthionated parent molecule, a top-gate, bottom contact geometry is adopted, with work function-modified gold electrodes facilitating electron injection. The highest electron mobility was observed for the S2-cis molecule, with a mobility of 0.20 cm2/Vs compared to 0.068 cm2/Vs for the parent molecule. Mobilities slightly lower than that achieved for the S2-cis molecule were also achieved for the S2-trans and S3 derivatives, with the S1, S4 and S2-cis imide derivatives showing mobilities lower than the parent molecule. The thin film microstructure of these molecules has also been explored using a combination of grazing-incidence wide-angle X-ray scattering and near-edge X-ray absorption fine-structure spectroscopy. The performance and microstructure of thin films deposited either by spin-coating or blade coating are also compared.

The electrochemical nitrogen reduction reaction (NRR) is regarded as the most promising alternative to the traditional Haber-Bosch route in current context of developing sustainable and green technologies. However, challenges around low kinetics and low selectivity of NRR are significant barriers for this enticing goal. Different from the transition metal-based NRR catalysts that are prevalent in artificial nitrogen fixation, here, novel p-block non-transition metal catalysts, constructed from an Al-doped phosphorene monolayer, are reported for electrochemical NRR through the density functional theory (DFT) calculations for the first time. We surmised the empty sp3-orbital of doped Al with sp3 hybridization can act as strong Lewis acid sites for N2 adsorption and activation. Among investigated concept-models, Al2@P (-para) exhibits a high activity with an ultra-low limiting potential (UL) of −0.31 V, significantly exceeding the benchmark stepped Ru(0001) surface (UL = −0.98 V), which originates from the strong Lewis acid property of Al sites, good activation on adsorbed N2, and improved redox capacity by 2D phosphorene electron reservoir. Additionally, Al2@P (-para) demonstrates high NRR selectivity and thermal stability under ambient conditions. This research offers a new way of designing effective catalysts and will further boost the study of p-block elements for NRR.

We report fabrication and characterisation of humidity and ammonia sensors based on a nanoporous naphthalene diimide (NDI) thin layer, the active material coded as NDI-1, operating at room temperature. A thin layer of NDI-1 as an organic semiconducting sensing material was deposited onto the interdigitated electrodes using the spin-coating technique. Surface morphology investigations of the thin film using atomic force microscopy and scanning electronic microscopy revealed a uniform nanoporous surface. Structural and thermal behaviour studies of the NDI-1 using X-ray diffraction and thermogravimetric analyses confirmed the crystallinity and thermal stability, respectively. The capacitive type NDI-1 humidity sensor displayed a sensitivity of 10.13 pF/%RH, quick response and recovery (20.1/6.28 s), low hysteresis (0.72%), long-term stability and more importantly, a wide working range of relative humidity (10–95%) at 250 Hz. Interestingly, the developed sensor was sensitive enough to monitor respiration rate and demonstrated an excellent non-contact skin humidity sensing performance. The amperometric response of the sensor towards ammonia was also investigated. An increase in the sensor current was recorded when exposed to different ammonia concentrations (25, 37.5 and 50 ppm). The sensor showed high selectivity and good sensitivity (27.7%) towards 50 ppm ammonia with 200 s and 350 s response and recovery times, respectively.

The positive impact of self-assembly on the photovoltaic properties of a donor-π-acceptor oligothiophene molecule coded as CP3, which contains a barbituric acid as a terminal acceptor unit and triphenylamine as donor, enabling hydrogen-bonded spherulites to assemble in its films is described. The hydrogen-bonded supramolecular array of barbiturated-oligothiophene molecules were directly visualized by scanning electron microscopy. Bulk-heterojunction solar cells comprising CP3 and the fullerene PC61BM show a power conversion efficiency of 6.31%, which is markedly higher than a structural analogue CP4, which comprises a N-ethylrhodanine terminal acceptor unit incapable of participating in the same degree of self-assembly, supporting the impact of self-assembly in BHJ devices.

Through the molecular engineering of cyanopyrid-2,6-dione functionality, herein we report the design and synthesis of a novel, small molecule electron donor, (Z)-5-((5'-(4-(diphenylamino)phenyl)-[2,2′-bithiophen]-5-yl)methylene)-1-(4-(hexyloxy)phenyl)-4-methyl-2,6-dioxo-1,2,5,6-tetrahydropyridine-3-carbonitrile (coded as CP2), which exhibits improved optoelectronic and photovoltaic properties when compared with its structural analogue (E)-5-((5'-(4-(diphenylamino)phenyl)-[2,2′-bithiophen]-5-yl)methylene)-1-(2-ethylhexyl)-4-methyl-2,6-dioxo-1,2,5,6-tetrahydropyridine-3-carbonitrile (coded as CP1). The molecular engineering helps to achieve more desirable energy levels together with bathochromic shift in the absorption spectrum, which improves the short-circuit current density. A high conversion efficiency of 6.28% was obtained in simple devices (CP2: PC61BM 1: 1) which is one of the best results in the current literature for cyanopyrid-2,6-dione-based small molecule donors.

Parent isoquinoline diimide (IQDI) and phthalazine diimide (PTDI), as two new heterocyclic analogues of naphthalene diimides (NDIs), have been synthesized through an oxidative strategy in 35-79 % yield. X-ray crystallography has been used to support the formation of IQDI, which also show fluorescence quantum yields of 3.5 %. The electrochemical and electrical properties of these molecules have been studied. The electrochemical results show an interesting trend in first reduction potential PTDI

Dimers and trimers of a fluorenone-appended porphyrin were prepared via Lindsey optimized Sonogashira coupling reaction. The photophysical properties of the oligomers were investigated upon excitation of the fluorenone arms which act as donors. The emission profiles of the covalently linked porphyrins suggest that the diphenylacetylene bonds are vital for efficient intramolecular energy transfer between the porphyrin units. Additionally, higher fluorescence quantum yields were recorded for the oligomers than for the individual units.

Transforming the naphthalene diimide (NDI) core into unusual aromatic systems has large potential for applications in which current NDI-based systems show promise. Treatment of N,N-dialkylNDIs under mild oxidizing conditions with ruthenium(III) chloride and sodium periodate affords the corresponding 1,4-diones in good yield. Interestingly, while aliphatic substituents at the N-imide positions allowed oxidation to take place easily, the presence of neutral, electron-rich or electron-deficient phenyl groups retarded the oxidation process under these reaction conditions. The chemistry of the 1,4-dione is then explored through reduction and condensation reactions. In two examples, reaction of the 1,4-dione with diamines gives an unusual, ring-contracted product 20, which has a high quantum yield. Additionally, the 1,4-dione can be converted into larger heterocycles such as 21 and 22 featuring an isoquinoline core. The 1,4-diones and their products have been investigated by spectroscopy, cyclic voltammetry, theoretical studies, and X-ray crystallography. The results obtained demonstrate the potential of the 1,4-dione to serve as an invaluable precursor for NDI-based research.

Carbon-based electrocatalysts for nitrogen fixation under ambient conditions has attracted tremendous attention but still encounter great challenges of low Faradic efficiency (FE) and a sluggish kinetics. Inspired by intrinsic defects (vacancies, edges and dislocation) on graphene showing activity towards oxygen reduction reaction (ORR) and nitrogen reduction reaction (NRR), here, two commonly exposed surfaces of diamond carbon, i.e., C(111) & C(110), were calculated for electrocatalytic nitrogen reduction reaction (eNRR) by the density functional theory (DFT) method, and calculations show that, compared with C(110), C(111) could be highly promising towards eNRR with a low over-potential (η) of 0.57 V (ΔGmax = 0.73 eV, η = 0.57 V), which are distinctly less than that (ΔGmax = 1.08 eV, η = 0.92 V) of flat benchmark Ru(0001) catalysts. Importantly, these two surfaces are shown to exhibit the suppression of hydrogen evolution reaction (HER). This work is the first reported indication that the low-coordinated carbons (LCCs) on sp3-hybridized diamond-carbon framework are active for eNRR, which gives a brand-new direction of designing/synthesizing sp3-configured diamond-carbon-composited catalysts for eNRR.

New D-π-spacer-A model compound dye sensitizers (or dyes) are developed using digital structures for organic dyes sensitized solar cells (DSSCs) applications. Based on our previous studies, the model D-π-spacer-A dyes contain building blocks of a di(p-carboxy)-phenylamine as the electron donor and a perylene monoimide as the electron acceptor. The new D-π-spacer-A dyes are constructed through variations of a set of three model π-spacer units, fluorene, 3,4-ethylenedioxythiophene and thiophene. The new dyes are presented by digital structures of π(ijk) in a digital control Π-matrix. If the chromophore database of the π-units is arranged in a defined manner, the new dyes are therefore designed through selecting of the set of three integers (ijk). Properties such as the UV-vis spectra which are calculated using the time-dependent density functional theory (TD-DFT) determine if the new compounds are suitable for organic solar cell purposes. The same strategy can be applied to donors and acceptors in the D-π-spacer-A model compound in order to robust design and build new organic dyes for DSSCs. The digital structures of the organic compounds enhance the machine driven structure-property relationship establishment once the database is sufficiently comprehensive. The present study demonstrates that new compounds obtained through mixing the π-spacer units of fluorene, 3,4-ethylenedioxythiophene and thiophene, e.g. π121 and π211, result in better dyes in DSSC applications. The concise digital structures of the new dyes are able to achieve a more robust design of the organic dyes and other materials.

In this work, we report on the thermally induced phase behavior and crystalline structures of a series of solution-processable naphthalene diimide (NDI)-based molecules with alkyl side chains of varying length and branching. Taking advantage of synchrotron-based in situ grazing-incidence wide-angle x-ray scattering, the most kinetically favorable thin film crystalline structures of each molecule at room temperature and at elevated temperatures were resolved. The extracted unit cell parameters of the kinetically favorable crystal structures as a function of temperature were used to quantify the anisotropic thermal expansion coefficients along the three principal crystallographic directions. In particular, it is found that long alkyl side chains can effectively suppress crystalline polymorphism and enhance thermal reversibility. The acquired knowledge regarding the thermally induced phase transitions of thin films based on NDI-based small molecules with varying solubilizing side chains serves as guidance for further molecular design and synthesis of high performance $n$-type small molecules.

The development of brightly emissive compounds is of great research and commercial interest, with established and emerging applications across chemistry, biology, physics, medicine and engineering. Among the many types of molecules available, naphthalene diimides have been widely used for both fundamental photophysical studies and in practical applications that utilise fluorescence as an information readout. The monomeric naphthalene diimide is weakly fluorescent, however through various methods of core-derivatisation, it can be developed to be highly fluorescent and further functionalised to add utility. In this review, we highlight recent advances made in naphthalene diimide chemistry that have led to development of molecules with improved optical properties, and the design strategies utilised to produce bright fluorescence emission as small molecules or in supramolecular architectures.

A systematic investigation of the effect that simple substituents attached to the phenolic ring have on the stability and adsorption properties of the porous crystals of parent Sn(IV) porphyrin diphenolates is made. A family of three dimensional honey-comb-like supramolecular porous materials (SPMs) was obtained by crystallisation of three different discrete porphyrin diphenolates Sn(IV)tTTP(o-cresol)2 (1), Sn(IV)tTTP(o-bromo)2 (2), Sn(IV)tTTP(m-nitro)2 (3). Their structures and crystalline integrity were studied using single crystal X-ray diffraction and powder X-ray diffraction techniques, respectively. Vapor adsorption measurements on Sn(IV)tTTP(o-cresol)2 revealed a guest uptake capacity. Gas adsorption investigations of these materials demonstrates that this class of SPMs retains high thermal stability and permanent porosity with functional groups lining the pores, which makes this Sn(IV) porphyrin diphenolates family a potential candidate for building high thermal stability SPMs.

Two pendant-type naphthalene diimide (NDI) polymers bearing a polynorbornene backbone were prepared and their electrochemical properties explored. The NDI-based polymers displayed reversible redox responses in 1 M LiClO4 γ-butyrolactone electrolyte. Polymer 1, bearing a N-methyl group, exhibited remarkable charge-storage capabilities which demonstrated its potential usefulness as an organic cathode-active material in rechargeable devices with excellent performances such as large charge capacity, high rate capability, and charge-discharge cyclability.

Three robust molecular porous materials (MPMs) constructed from Sn(IV)TTP(bisphenolates) were reported. They all possess 1D hourglass-shaped channels within their crystal structures. Functionalisation of the channel lining through judicial choice of substituted phenol was demonstrated, which also allowed for a change in the pore diameter. TGA investigations revealed that these novel supramolecular systems are thermally stable over 550 K.

Symmetrically and dissymmetrically core-substituted amino naphthalene diimides (cNDIs) with water-soluble substituents have been synthesised. The compounds display characteristic steady-state optical properties absorbing and emitting light in the visible part of the electromagnetic spectrum. Time-resolved fluorescence studies reveal long emission lifetimes of ∼10 ns in chloroform, ∼8 ns in methanol and ∼4 ns in water. Suitability for use in biophysical applications is demonstrated by encapsulation into reverse micelles and liposomes. Fluorescence lifetime is shown to indicate cavity size in the reverse micelles and fluorescence correlation spectroscopy measurements of cNDI loaded liposomes successfully determined diffusion coefficients and hydrodynamic radii of the liposomes.

Electron transfer (ET) is a key chemical reaction in nature and has been extensively studied in bulk systems, but remains challenging to investigate at the single-molecule level. A previously reported naphthalene diimide (NDI)-based system (Higginbotham et al., Chem. Commun. 2013, 49, 5061–5063) displays delayed fluorescence with good quantum yield (~0.5) and long-lived (nanoseconds) prompt and delayed fluorescence lifetimes, providing an opportunity to interrogate the underlying ET processes in single molecules. Time-resolved single-molecule fluorescence measurements enabled forward and reverse ET rate constants to be calculated for 45 individual molecules embedded in poly(methylmethacrylate) (PMMA) film. Interpretation of the results within the framework of Marcus–Hush theory for ET demonstrates that variation in both the electronic coupling and the driving force for ET is occurring from molecule to molecule within the PMMA film and over time for individual molecules.

A superhydrophobic cotton fabric exhibiting photocatalytic self-cleaning properties under visible-light was prepared by step-wise deposition of anatase TiO2, meso-tetra(4-carboxyphenyl)porphyrin (TCPP) and trimethoxy(octadecyl)silane (OTMS). The modified cotton fabrics not only exhibited excellent superhydrophobicity with a water contact angle of 156°, but also showed significant photocatalytic degradation of methylene blue under visible-light irradiation. The fabrics were characterized by FESEM, XRD, NMR and UV-Vis spectroscopy. Textiles with dual functionality of superhydrophobicity and visible-light photocatalysis are promising for a wide range of self-cleaning applications.

Photocatalytic degradation of organic contaminants by self-cleaning textiles is an efficient method to create green environment and minimise energy consumption. In this work, the concept of dye-sensitised self-cleaning textiles has been introduced by incorporating monolayers of meso-tetra(4-carboxyphenyl)porphyrin (TCPP) on the surface of titania-coated cotton against methylene blue. Different complexes of TCPP (M = 2H, Fe, Co, Zn, Cu) have been trialled and evaluated for photocatalytic activity and stability. Cotton fabrics coated with TCPP show superior photochemical activity as compared to TiO2-coated fabrics under visible-light irradiation. The free base derivative availed the highest photocatalytic efficiency when compared to the metal complexes with Cu∼Fe > Co > Zn. In terms of stability, meso-tetra(4-car-boxyphenyl)porphyrinato copper(II) showed significant stabilisation under photocatalytic conditions when compared to the metal-free porphyrin and other metal complexes (Cu ≫ Co > 2H > Zn∼Fe). Porphyrins offer great potential in visible-light self-cleaning applications.

The synthesis and spectroscopic properties of a dissymmetrically core-extended naphthalene diimides derived from o-phenylenediamine and cyanoethene dithiolate were explored. The push-pull nature of the peripheral substituents allows these naphthalene diimide dyes and their progenitors to display interesting photophysical and electrochemical properties, with the target system acting as a highly reversible and quantitative molecular switch with clear absorption and emission readouts based on chemical oxidation and reduction processes.

Here we study the effect of side chain length and type on the microstructure and organic field-effect transistor (OFET) performance of solution-processed naphthalene diimide (NDI) thin films. Linear side chains with four (C4), five (C5), six (C6), eight (C8) and twelve (C12) carbon atoms are studied along with a branched ethylhexyl (EH) side chain. Interestingly, mobilities of up to ~0.2 cm2/Vs are achieved for short (C4) and long (C12) side chains with linear chains of intermediate length and the branched side chain producing lower mobilities. The observed mobility trends are explained in terms of the competing influence of changes in crystal packing and changes in thin film morphology with changes in side chain length. Shorter side chains produce changes in the lateral stacking of NDI units which promote higher mobility while longer side chains produce solution-processed thin films with higher film quality evidenced by larger domain sizes and lower orientational disorder. Side chain length is also found to strongly modulate the molecular orientation of the NDI core, with high edge-on orientations observed for long chains, and tilted orientations for short chains. Thin film microstructure is investigated using a range of techniques including atomic force microscopy, grazing incidence wide-angle X-ray scattering and near-edge X-ray absorption fine-structure spectroscopy.

Water-soluble naphthalene diimide based fluorescent chemosensor, N1, was designed for Cu2+ recognition. The sensor exhibited significant fluorescence modulation and chromogenic change with high Cu2+ sensitivity and selectivity over interfering metal ions. The sensor was able to efficiently monitor Cu2+ in 100% aqueous buffer solution with a low detection limit of 0.7 ppb which is much lower than the recommended value in drinking water by the United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO). The complex formation of N1 with Cu2+ was found to be 1:1 N1-Cu2+ by Job’s plot analysis. Furthermore, the sensor was highly tolerant to interference from a matrix of real samples such as drinking water and human liver carcinoma cell line.

Thin films of meso-tetra(4-carboxyphenyl)porphyrin with different metal centres (MTCPP, M = Fe, Co and Zn) in combination with anatase TiO2 have been formed on cotton fabric. Their self-cleaning properties have been evaluated by conducting the photocatalytic degradation of methylene blue under visible-light irradiation. All MTCPP/TiO2-coated cotton fabrics showed superior self-cleaning performance as compared to the bare TiO2-coated cotton. Among the three metal porphyrins, FeTCPP showed the highest photocatalytic activity with complete degradation of methylene blue in 180 min. The fabrics were characterized by FESEM, XRD, UV–vis and fluorescence spectroscopy.

A simple one pot hydrothermal procedure for the synthesis of cobalt selenide (CoSe) decorated reduced graphene oxide (rGO) is reported along with the application of this hybrid material as a new electrocatalyst for glucose oxidation. In alkaline media, glassy carbon electrodes modified with CoSe–rGO composite dispersed in chitosan display excellent reproducibility for the determination of glucose along with a high sensitivity of 480 μA mM−1 cm−2, a linear dynamic range of up to 10 mM, a lower limit of detection of 2.5 μM and an exceptionally high maximum current density of 5.41 ± 0.03 mA cm−2. Bulk electrolysis measurements carried out with the CoSe–rGO/chitosan modified glassy carbon plate revealed that the oxidation of glucose can proceed beyond the formation of gluconolactone with formate detected by 1H-NMR and CO2 detected by gas chromatography; the latter result showing the ability to achieve complete oxidation of glucose. Studies with ascorbic and uric acid showed that their interference with respect to glucose measurement either is negligible or can be overcome.

Naphthalene diimides undergo single electron reduction processes either chemically or electrochemically at modest potential to yield the corresponding radical anion in high yield. The diimide radical anion has well-behaved properties, including stability, excellent photophysical behaviour and well-structured EPR signals. These properties, combined with the vast array of functionality now possible on the core represent strong candidates for pragmatic photovoltaic devices. This chapter describes the development of naphthalene diimides in photovoltaic systems supported by a theoretical basis for energy and electron transfer mechanisms.

Bioanodes for fuel cell applications require highly efficient oxidation reactions to achieve a sufficiently large current density. In this study, gold nanoparticles have been synthesized using branched polyethylenimine (bPEI), a well-known polymer that forms a hydrogel in water, as the stabilizer. Primary amine groups available in bPEI provide active sites for further conjugation with ferrocene propionic acid via the 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling reaction, with the enzyme glucose oxidase, using glutaraldehyde as linkers. This composite material was then used for the fabrication of glucose oxidase electrodes by drop casting of aqueous solutions onto glassy carbon electrodes. The three-dimensional structure offered by the new hydrogel facilitates communication between the enzyme and the electrode through the redox mediator ferrocene. This allows the glucose oxidase electrode to exhibit excellent activity towards electrocatalytic oxidation of glucose in phosphate buffer solutions at pH 7 with a maximum current density of approximately 800 μA cm−2, one of the highest values reported so far for redox hydrogel based glucose oxidase electrodes. Over a wide glucose concentration range, the enzyme response follows that predicted by the Michaelis-Menten equation with a Michaelis constant of 8.4 mM. In the sensing context, this electrode also exhibits a wide linear dynamic glucose concentration range of 0.5–10 mM with a limit of detection of 0.04 mM.

Solutions of carboxymethyl sago pulp (CMSP) of various degree of substitution were irradiated with electron beam of various radiation doses. The gelation dose (Dg) and po/qo ratio (po is degradation density, qo is crosslinking density) is dependent on CMSP concentration and degree of substitution. In the range of concentrations of 10% to 80% (w/v) CMSP with degree of substitutions of 0.4, 0.6, and 0.8, the po/qo ratio decreases with increasing %CMSP showing that crosslinking processes are dominating and increasing the gel network of the CMSP hydrogel. The fourier transform infrared spectra of CMSP hydrogels of degree of substitutions of 0.4, 0.6, and 0.8 with percentage of gel fractions 25, 35, and ≥ 40 show differences in the intensity of the absorption bands at 1020–1100, 1326, and 1422 cm−1 with different degree of substitutions and percentage of gel fraction (%GF) that correspond to different extents of chain scission and crosslinking. The swelling behavior in water shows that CMSP hydrogels could absorb 3500–5300% of water by 1 g of CMSP hydrogel. The ability to absorb water increases with the decrease of degree of substitution and %GF of the CMSP hydrogels. It is also observed that the optimum pH for swelling CMSP hydrogel is at pH 7. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013