TECHNOLOGY FOCUS - IMAGING AND COMMUNICATION - Preferred Method: The method (M1) further involves evaporating a portion of solvent to achieve a desired particle concentration and solvent composition. In the method (M2), the step of dispersing of the nanoparticles involves: first dispersing the nanoparticles in the first solvent to form a preliminary dispersion; adding the second solvent to the preliminary dispersion; and evaporating solvent to achieve the desired nanoparticle concentration. In the method (M3), the printing at a second time forms a deposit of the silicon ink that overlaps with the first silicon nanoparticle deposit while having a pattern that also deposits the silicon nanoparticle ink at locations distinct from the first silicon nanoparticle deposit. Preferred Ink: In the method (M1), the ink comprises (wt.%): elemental silicon nanoparticles (5), the first solvent (0.25-15) and the second solvent (65-94.75).    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Dispersion: The dispersion comprises elemental silicon/germanium nanoparticles (3-25 wt.%). The dispersion comprises (wt.%): elemental silicon nanoparticles (5), alcohol (5-65) and polar aprotic solvent (10-85). The dispersion comprises (wt.%): elemental silicon nanoparticles (5), alcohol (0.25-10) having a boiling point of not greater than 160 degrees C, and liquid (65-94.75) having a boiling point of 175 degrees C. The dispersion comprises alcohol (0.5-30 wt.%) having a boiling point of not greater than 160 degrees C and a viscosity of 10-800 cP. Preferred Method: In the method (P1), the reactant flow comprises a silicone precursor and where the product particles comprise elemental silicon. In the method (P1), the product elementary silicon particles have an average primary particle diameter of not greater than 50 nm. Preferred Components: The elemental silicon/germanium nanoparticles have an average primary particle diameter of not greater than 15 nanometers. The elemental silicon/germanium nanoparticles have a dopant concentration of at least 0.5 atomic percent. The elemental silicon/germanium nanoparticles have a dopant concentration of 1x 10-7 to 5x 10-3 atomic percent. The dopant is phosphorus or boron. The nanoparticles comprise not greater than 1 part per million of iron.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Apparatus: In the apparatus (A1), at least a portion of the interior of the reaction chamber, at least a portion of the nozzle exposed to the interior of the reaction chamber or reactant flow and/or at least a portion of the collection system exposed to flow from the reaction chamber, is coated with a polymer and/or ceramic material such that flow within apparatus has reduced exposure to metal contaminants from the apparatus. In the apparatus (A1), the interior of the reaction chamber is coated with polytetrafluoroethylene. Preferred Components: In the laser pyrolysis apparatus (A1), the light beam is configured such that flow from the reactant channel essentially completely flows through the light beam. The nozzle further comprises an entrainment channel surrounding the outer inert gas channel, where the entrainment channel is operably connected to an inert gas source. The inner inert gas channel, the intermediate reactant channel and the outer inert gas channel comprise approximately concentric cylindrical elements. The reactant channel has an inner diameter of 0.05 inches (1.27 mm) to 3 inches (76.2 mm), where the walls of the reactant channel have a thickness of 0.0025 inches (0.0635 mm) to 0.050 inches (1.27 mm). Tubes forming each channel comprise a hub, where the respective support hubs engage with a seal to form the nozzle with access ports through the hubs to the respective channels. The reactant reservoir comprises a gaseous silicon precursor and a dopant precursor. The nozzle comprises a reactant channel having a width and a length, at least quench gas channels oriented to provide flow along the length of the reactant channel and at least one entrainment gas channels oriented along the length of the inert gas channels, where the quench gas channels and the entrainment gas channels are operably connected to an inert gas source and the reactant channel is operably connected to the reactant delivery system and where the entrainment inlets have an area at least 25% larger than the area of the quench gas channels. The reactant channel is rectangular and is oriented such that a line along the propagation direction of the light beam is approximately perpendicular to the long dimension of the reactant channel. The reactant channel has an annular opening, where the quench gas channels comprises an central circular inlet positioned within the annular reactant inlet and an annular inlet surrounding the annular reactant inlet, and where the entrainment inlet is annular and positioned around the annular quench gas inlet.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The second solvent comprises N-methyl pyrrolidone, ethylene glycol, propylene glycol, terpinol, 2-(2-ethoxyethoxy)ethanol (Carbitol) and/or butyl cellosolve. The first solvent comprises isopropyl alcohol, acetone, dimethylformamide and/or cyclohexanone. The alcohol in the ink comprises isopropanol, ethylene glycol and/or propylene glycol. The polar aprotic solvent comprises N-methyl pyrrolidone, dimethylformamide, dimethylsulfoxide, methylethylketone, acetonitrile and/or ethylacetate. In the method (M1), the first solvent (preferably alcohol) has a boiling point of 55-160 degrees C and the second solvent has a boiling point of 175 degrees C. EXAMPLE - Preparation of Si nanoparticles by using laser pyrolysis was carried out as follows: The phosphine (PH3) gas was mixed with inert argon at a mole ratio of 91% Ar to 9% PH3. The silane precursor was mixed with the blend of Ar and phosphine precursor at a pressure of 500-650 torr to obtain highly doped Si nanoparticles. An ink was formulated with a concentration of 12 wt.% of obtained undoped Si particles having average particle size of 26 nm (BET surface area corresponding to 28 run particles) in a solvent of 1 part by weight propylene glycol and 7 parts by weight N-methyl pyrrolidone. The ink had a viscosity of 13.7 cP and a surface tension of 44 D/cm.