Photoluminescence of graphene quantum-dot can be sensitively tuned by size, edge configurations, shape, chemical functionalities, defects, heteroatom-doping and hybridization states.

Field trials in Europe with Miscanthus over the past 25 years have demonstrated that interspecies hybrids such as M. 9 giganteus (M 9 g) combine both high yield potentials and low inputs in a wide range of soils and climates. Miscanthus hybrids are expected to play a major role in the provision of perennial lignocellulosic biomass across much of Europe as part of a lower carbon economy. However, even with favourable policies in some European countries, uptake has been slow. M 9 g, as a sterile clone, can only be propagated vegetatively, which leads to high establishment costs and low multiplication rates. Consequently, a decade ago, a strategic decision to develop rapidly multiplied seeded hybrids was taken. To make progress on this goal, we have (1) harnessed Correspondence: John Clifton-

Silver nanocrystals have been grown on Xe buffer layers at 50 K. These 3D nanocrystals are delivered to Si(111)-͑7 3 7͒ surfaces when the Xe layer is desorbed, but the density observed on the surface depends strongly on the buffer layer thickness. This dependence reflects an unusual desorption-assisted coalescence process. The results suggest that buffer-layer-assisted growth can be used to prepare nanocrystals of different sizes for a wide variety of materials and substrates. [S0031-9007(98)05945-6]

Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output–input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed‐based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass‐scale deployment of PBCs.