This special issue contains a selection of papers presented at the Molecular Materials Meeting (M3) in Singapore. Inaugurated in January 2011, M3 was organized by Singapore's A*STAR Institute of Materials Research and Engineering. Focusing on understanding materials at the molecular level and harnessing their properties for innovative solutions to today's technological challenges, this conference brought out the ‘big ideas’ from its international participation of prominent scientists

The synthesis by atom-transfer radical polymerization, physical properties, and applications of amphiphilic block copolymers based on hydrophilic poly(ethylene oxide) or hydrophobic poly(propylene oxide) are reviewed. The focus is on complex copolymer architectures and recent developments in post-polymerization techniques, e.g., ‘click’ chemistry, to introduce broad functionalities. Examples are outlined including stimuli responsiveness, cell membrane penetrating ability, and formation of multi-compartmentalized micelles.

Highly crystalline poly(2,5-dimethoxyaniline) (PDMA) nanoplates were synthesized by oxidative polymerization of 2,5-dimethoxyaniline (DMA) using a low concentration of poly(styrenesulfonate) (PSS) as dopant acid. The extended conformation of PSS/DMA salts in dilute solution acts as a soft-template and guides the formation of the PDMA nanoplate. The plate-like geometry with several nanometre thickness and single crystal-like structure of PDMA mean that it has the potential for application in nanoelectronic devices.

Multicolour tetraphenylethene derivatives with aggregation-induced emission characteristics were designed and synthesized. These molecules can serve as efficient emitters for light-emitting devices as well as excellent cell staining agents for selectively illuminating the cytoplasm and vesicles of living cells.

Two dendrimers, D1 and D2 based on cationic iridium complexes are developed to have strong phosphorescence solvatochromism in different solvents and achieve efficient energy transfer from the dendrons to the core in the solid state. Both exhibited good optical properties for organic electronics.

Manganese compounds immobilized in Nafion on a fluorine-doped tin oxide electrode surface and illuminated in the presence of an applied potential yield a photocurrent assigned to the oxidation of solvent water. Manganese coordination complexes are rapidly photodecomposed under these conditions, leading to the formation of MnO₂ nanoparticles that are active for water oxidation catalysis.

Nanopore measurement of gold nanoparticles (AuNP) aggregation induced by peptide nucleic acid (PNA). 2D scatter plot of relative particle size distribution (y-axis) and peak duration distribution (x-axis) of the AuNP solution in the presence of 20-mer PNA at increasing concentrations of (A) 0, (B) 5, (C) 10, and (D) 25 nM. The measurements were conducted upon addition of PNA into AuNP solution.

Photocatalytically active epitaxial anatase TiO₂ was grown on SrTiO₃ single crystal substrates by liquid phase deposition at 50°C. The film consisted of nanosized crystallites with a void fraction of 31 %. This contributed to the cracking of thicker films due to the generation of capillary stresses in the nanosized pores during drying.

Treatment of the silanetetrabenzoic acid Si(p-C₆H₄CO₂ H)₄ (L-H₄) with M(NO₃)₂ (M = Mg, Co, or Ca) affords the metal-organic framework materials [Mg₃(LH)₂(EtOH)₂(H₂O)]·(EtOH)_4.5(H₂O)_0.25, [Co₃(LH)₂(EtOH)₂(H₂O)]·(EtOH)₃), and [Ca₃(LH)₂(EtOH)₄]·(EtOH)₆ respectively. Each structure contains layers of trinuclear metal based nodes, which are further coordinated by carboxylic acid groups to give a 3-D structure.

Poly(l-glutamate)-block-poly(2-(diethylamino)ethyl methacrylate) forms 180 nm positively charged vesicles at low pH and 100 nm negatively charged vesicles at high pH. The block copolymer forms complexes with DNA, and in-vitro studies at physiological pH using neuroblastoma cells did not show substantial gene expression.

Mass sensitive sensors have been designed to differentiate between different growing stages of yeast cells. Moreover, the viability of cells was detected by using a grid electrode on quartz crystal microbalances. Using this method allows differentiation of artificial bacteria cells between different strains.

Poly(N-isopropylacrylamide) brushes with variable grafting densities were synthesized via surface-initiated atom-transfer radical polymerization. Stabilities of polymer brushes with different initiators under cell culture conditions were monitored. In situ ellipsometry demonstrated the reversible swelling and collapse of brushes at different temperatures. Surface cultures of the cells MC-3T3 were employed for cell attachment studies and showed adhesion and proliferation on the brushes at T>lower critical solution temperature (LCST), and detachment at T<LCST. Adhesion as a function of brush structure is discussed.

The cubic hyperpolarizabilities of the zero-generation dendrimers 1–3 and related first generation dendrimers have been assessed over the spectral range 520–1600 nm using the Z-scan technique and ~150 fs pulses. The complexes exhibit self-defocusing behaviour and two-photon absorption at short wavelengths, and three-photon absorption at longer wavelengths.

The classical physical chemistry subject of volumes of mixing and de-mixing is revisited in a dynamic way using time-resolved pump-probe temperature-jump interferometry to determine how long it takes for a mixture of triethylamine and water to de-mix. It is shown that it takes ~150 ns for small phase domains to form that should have the expected equilibrium mole fractions of each component.

Dye-sensitized solar cells (DSSC) based on TiO₂ nanorod photoelectrodes are fabricated to achieve an energy conversion efficiency of 6.44 % under illumination with air mass 1.5 (100 mW cm^–2) simulated sunlight, which demonstrates the potential of electrospun TiO₂ nanofibres as efficient photoelectrode material for low-cost DSSC.

Surface plasmon resonance and gold nanoparticles (AuNP) have been used to detect oestrogen receptors (ERα and ERβ) interactions with their response elements. The AuNP-based colorimetric assay principle has also validated that protein-DNA complexes are able to provide more electrosteric forces than protein without forming a complex, using ERβ and AuNP of a range of particle sizes (10, 20, and 50 nm).

Secondary ion mass spectrometry was used to analyze a number of individual polyelectrolyte multilayer capsules and to determine the amount of loaded horseradish peroxidase. Distribution of a payload among the capsules in a batch was analyzed depending on loading method.

Adding the ability to control the temperature of the substrate in scanning tunneling microscopy experiments at the solution/solid interface results in unprecedented control over the energetics of the surface-confined molecular self-assembly. The first results from this new technique demonstrate the increased depth of understanding that we can expect as this relatively simple experimental modification is more routinely implemented.