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The generation, manipulation and detection of spin-polarized electrons in nanostructures define the main challenges of spin-based electronics 1 . Amongst the different approaches for spin generation and manipulation, spin-orbit coupling, which couples the spin of an electron to its momentum, is attracting considerable interest. In a spin-orbit-coupled system a nonzero spincurrent is predicted in a direction perpendicular to the applied electric field, giving rise to a "spin Hall effect" 2,3,4 . Consistent with this effect, electrically-induced spin polarization was recently detected by optical techniques at the edges of a semiconductor channel 5 and in two-dimensional electron gases in semiconductor heterostructures 6,7 . Here we report electrical measurements of the spin-Hall effect in a diffusive metallic conductor, using a ferromagnetic electrode in combination with a tunnel barrier to inject a spin-polarized current. In our devices, we observe an induced voltage that results exclusively from the conversion of the injected spin current into charge imbalance through the spin Hall effect. Such a voltage is proportional to the component of the injected spins that is perpendicular to the plane defined by the spin current direction and the voltage probes. These experiments reveal opportunities for efficient spin detection without the need for magnetic materials, which could lead to useful spintronics devices that integrate information processing and data storage.The spin Hall effect (SHE), which was first described by Dyakonov and Perel 2,3 and more recently by Hirsch 4 , was proposed to occur in paramagnetic materials as a consequence of the spin-orbit interaction. In analogy to the standard Hall effect, the SHE refers to the generation of a pure spin current transverse to an applied electric field that results in an accompanying spin imbalance in the system. These early theoretical studies considered an extrinsic 2,3,4,8 SHE originating from an asymmetric scattering for spin-up and spin-down electrons. It was pointed out that, after scattering off an impurity, there is a spin-dependent probability difference in the electron trajectories which generates the spin imbalance. In the recently introduced intrinsic 9,10 SHE, spin imbalance is expected to occur even in the absence of scattering as a result of the band structure.Several experimental schemes have been proposed to electrically detect the extrinsic SHE in metals 4,8,11,12 . However, these schemes are difficult to implement. Spinrelated phenomena such as anisotropic magnetoresistance (AMR) in ferromagnetic (FM) electrodes, spin dependent interface scattering, or standard and anomalous Hall effects could render the SHE signal unobservable. We use the measurement scheme in Fig. 1 to study the SHE isolated from such spurious phenomena.It is natural to expect that, if a charge-current induces a transverse spin-imbalance through the spin-

Nanosize pores can turn semimetallic graphene into a semiconductor and, from being impermeable, into the most efficient molecular-sieve membrane. However, scaling the pores down to the nanometer, while fulfilling the tight structural constraints imposed by applications, represents an enormous challenge for present top-down strategies. Here we report a bottom-up method to synthesize nanoporous graphene comprising an ordered array of pores separated by ribbons, which can be tuned down to the 1-nanometer range. The size, density, morphology, and chemical composition of the pores are defined with atomic precision by the design of the molecular precursors. Our electronic characterization further reveals a highly anisotropic electronic structure, where orthogonal one-dimensional electronic bands with an energy gap of ∼1 electron volt coexist with confined pore states, making the nanoporous graphene a highly versatile semiconductor for simultaneous sieving and electrical sensing of molecular species.