although the following detailed description contains many specifics for the purposes of illustration , anyone of ordinary skill in the art will readily appreciate that many variations and alterations to the following exemplary details are within the scope of the invention . accordingly , the following preferred embodiment of the invention is set forth without any loss of generality to , and without imposing limitations upon , the claimed invention . the present invention is directed to modifying catalytic behavior of nanocrystals by proximity of other nanocrystals . the present invention relies on the changes of a nanocrystal &# 39 ; s electronic properties due to electron transfer with a nearby nanocrystal . in particular , the electron transfer from a nanocrystal with a high fermi level , referred to as a “ donor ”, to one with a lower fermi level , referred to as an “ acceptor ”, alters the electronic structure of both nanocrystals . for some reactions and catalysts , the catalytic behavior would be improved by changing ( raising or lowering ) the fermi level , or by raising or lowering or broadening or narrowing the catalyst d - band . therefore , according to the current invention , the method of placing at least two nanocrystals of different energy levels enables tuning of the energy levels to attain desired levels , such as a desired fermi level . in nanocrystals , the ionization potential ( ip ) or highest occupied molecular orbital ( homo ), may be the quantity of interest rather than the fermi level , however , for simplicity , we discuss merely the fermi level here . since the proximate nanocrystals must have different energy levels , particularly fermi levels , for electron transfer to occur , the proximate nanocrystals of a preferred embodiment generally have differences in elemental compositions , sizes , morphologies , or any combination thereof . some exemplary donor materials can include but are not limited to fe , co , au , pt , pd , zr , ag , ni , cu , and ru . some exemplary acceptor materials can include but are not limited to fe , co , au , pt , pd , zr , ag , ni , cu , and ru . oxides and doped oxide materials may also be used as donor and / or acceptor materials . in one embodiment , the donor and acceptor nanocrystals are placed approximately 0 . 5 to 10 nm apart , or a distance up to 10 nm to achieve electron transfer via tunneling . preferably , a vacuum or a material ( e . g . an organic ligand , a polymer , and an inorganic thin film ) is placed between the donor and acceptor . some exemplary organic ligands can include but are not limited to cyclopentadienyl , acetylacetonate , aminidate , oleic acid , oligo -( phenylene vinylene ), thiol , dithiocarbamate , trioctylphosphine oxide , p - sulfonatocalix ( n ) arene , polydimethylaminoethyl methacrylate , alkyl phosphine , and alkyl amine . further some exemplary polymers can include but are not limited to polyethylene , hydrogenated polynorbornene , pmma , pvc , meh - ppv , peo , polystyrene , and lipids . additionally , some exemplary inorganic thin films can include but are not limited to oxides , sulfides , selenides , nitrides , oxynitrides , arsenides , phosphides , si , and ge . in one embodiment , one or both of the donor and acceptor nanocrystals can be replaced by a thin film or by a bulk material , where the thin film has a thickness in a range of a sub - monolayer to 200 nm , and the bulk material has a thickness in a range of 3 nm to 500 μm . the present invention is preferably applied to the following reactions : catalytic reactions for fuel cells , ammonia synthesis , no reduction , methanation , methonal production , ethanol production , hydrocarbon synthesis , o 2 reduction , hydrogen production ( e . g . water - gas shift reactions ), hydrogenation and dehydrogenation , acid production ( e . g . formic acid ), and citral hydrogenation . it is noted that the present invention can be applied to any catalytic reaction and not limited to the above - listed reactions . in one embodiment , an electric field is disposed between the donor and acceptor , which aids the catalytic reaction . “ band bending ” is a process by which an electric dipole and an electric field are created , typically occurs as a result of electron transfer . the electric field may be used to enhance the catalytic behavior , particularly if the product , reactant , and / or intermediate states of the molecules undergoing the catalytic reaction are charged , polar , or polarizable . alternatively , if the donor and acceptor are not allowed to equilibrate ( i . e . the fermi levels cannot achieve the same value ), an electric field may remain as the driving force for the polarization that is restricted or not allowed to occur . this remaining electric field may also be used to aid the catalytic reaction . in addition to or in replacement of improving catalytic performance , certain embodiments of the present invention are directed to modifying the electronic properties of a nanocrystal to decrease the susceptibility of a catalyst to be poisoned by a strongly - adhered adsorbate . modified materials , particularly nanocrystals , according to the present invention can have many advantages over existing materials . the advantages include improved catalytic performance , such as increased energy efficiency and lifetime of catalytic systems , reduced cost , and reduced susceptibility to poisoning . referring now to the figures , fig1 a - 1 b show a computer simulation of charge transfer between pt qd &# 39 ; s , where positive values denote more e − density . the simulation provides similar and different pt catalysts disposed proximal to each other , where fig1 a shows two pt 39 particles placed separated by approximately 8 å , where some bonding occurs , and fig1 b shows one pt 68 particle and one pt 39 particle placed approximately 6 . 5 å apart , where e − transfer occurs to the pt 68 particle . here , it is shown that the charge transferred charge sits on the edges of the qd &# 39 ; s . further , this simulation shows that pt catalyst behavior is modified by changing the particle size and the type of particles disposed nearby . pt is the most used catalyst for oxygen reduction , an important step in fuel cells . while pt ( and alloys that mostly contain pt ) is the best catalyst for that reaction , it is not ideal — it binds oxygen too strongly . as can be seen in fig2 a - 2 b , this simulation shows that pt catalyst behavior is modified and the method of the current invention changes the activity of the pt to make it bind oxygen more weakly . fig2 a - 2 b shows a comparison of density of states between a single pt 68 and pt 39 | pt 68 , demonstrating the changed electronic structure of pt 68 in the presence of a second qcs . fig2 b shows the effect of modified catalytic activity on o 2 adsorption by adjacent qcs of different energy levels according to the present invention . the interaction energy of oxygen with pt qcs can be tuned by altering the environment of the catalyst nanocrystal . fig3 a - 3 c show a computer simulation of a pt quantum well disposed proximal to a pt atom . fig3 a shows the simulation geometry ( periodic boundary conditions are used ). fig3 b shows how , compared to an isolated qw and isolated atom , the combined system has a difference in density of states ( dos ) near the fermi energy ( ε f ). the donor / acceptor system has shifted to higher dos just above the fermi level and lower dos just below ε f . this will impact catalytic activity . fig3 c , shows a charge difference map , where polarization is evident . the atom becomes relatively positive by 0 . 044e , and the qw becomes relatively negative by 0 . 016e , where overall , the charge transfer from the atom to the well is of 0 . 060e − . fig4 a shows that the symmetric system of two qcs of the same size and material does not develop an electron transfer . fig4 b shows the charge delocalized over adjacent qds and the polarization that results from highest occupied molecular orbital ( homo ) mismatch of the donor / acceptor according to the present invention . fig4 c shows o 2 bonding energy to au qd donor / acceptor pairs . table 1 below shows a comparison of qcs distance [ a ], o - o length [ å ], and adsorption energy [ ev ] for different au xx structures and o 2 molecules . fig5 a - 5 b show how wavefunction overlap depends on qd spacing , where larger polarization occurs when wavefunctions do not overlap according to the present invention . charge transfer from a donor qcs to an acceptor qcs is demonstrated in the result of this calculation of differently sized au qcs . fig6 shows a schematic drawing of energy levels in two different media separated by an insulator or vacuum according to the present invention . electron tunneling may occur through the insulator or vacuum from a higher energy level to a lower energy level . by the mechanism of electron tunneling , the donor and acceptor qcs of the present invention may transfer charge and become polarized , thereby altering chemical reactivity . fig7 shows a chart of different matrix / substrate interactions with nanocrystal catalysts according to the present invention . in this calculation , the catalyst support is mgo , and the donor and acceptor catalyst particles are differently sized au qcs . we see that the presence of the support , in this case , has relatively little effect on the electronic structure of the catalyst ( see the homo and lumo levels of au 14 with and without the presence of mgo ). however , the donor and acceptor still exchange charge through the mgo matrix , thereby altering chemical reactivity and catalytic performance . while the previous figures have shown charge transfer between donor and acceptor , this result shows that a material may be placed in between the donor and acceptor catalyst and still allow the desired electronic structure modification . the present invention has now been described in accordance with several exemplary embodiments , which are intended to be illustrative in all aspects , rather than restrictive . thus , the present invention is capable of many variations in detailed implementation , which may be derived from the description contained herein by a person of ordinary skill in the art . for example , there may be more than one donor qcs or more than one acceptor qcs . the donor and acceptor may be of different sizes , morphologies , materials , or any combinations of those traits . all such variations are considered to be within the scope and spirit of the present invention as defined by the following claims and their legal equivalents .