光學(xué)性能對(duì)粒子尺寸的依賴性是量子點(diǎn)獨(dú)特的和最具吸引力的功能。例如，通過控制粒子的大小，CdSe量子點(diǎn)的發(fā)射光波長(zhǎng)在整個(gè)可見光范圍內(nèi)連續(xù)可調(diào)。然而，二元素量子點(diǎn)，如CdSe量子點(diǎn)，有兩個(gè)缺點(diǎn)。，其表面缺陷形成表面陷阱態(tài)，使發(fā)光效率和穩(wěn)定性降低。通過在量子點(diǎn)表面包附ZnS，形成Core-shell結(jié)構(gòu)可以降低面缺陷，但CdSe和ZnS晶格失配，在很大程度上影響其發(fā)光效率和光學(xué)穩(wěn)定性。第二，量子點(diǎn)的消光系數(shù)同粒子的體積成正比例關(guān)系。標(biāo)記6nm（紅光）CdSe量子點(diǎn)的物質(zhì)發(fā)射光強(qiáng)度是2nm（綠光）量子點(diǎn)的三十倍，這會(huì)引起檢測(cè)靈敏度的差異。
不同于二元素量子點(diǎn)，星爍納米研發(fā)的梯度合金CdSe量子點(diǎn)， 在發(fā)光核和ZnS殼中加入三元合金過渡組分，因而帶來了以下幾個(gè)優(yōu)點(diǎn)：
1、通過調(diào)整合金元素組成控制其光學(xué)性能，制備體積一致但發(fā)光頻率不同的量子點(diǎn)，從而降低由于應(yīng)用不同顏色量子點(diǎn)引起的檢測(cè)靈敏度上的差異； 
2、合金量子點(diǎn)晶格力度強(qiáng)，性能穩(wěn)定；
3、實(shí)現(xiàn)晶格的逐步過渡，有效降低量子點(diǎn)晶格缺陷造成的內(nèi)部壓力，從而使量子點(diǎn)具有較高的發(fā)光效率和穩(wěn)定性。

Size-dependent fluorescence property is probably the most unique and attractive feature of QDs. For instance, through controlling the particle size from 2-6 nm, the emission from CdSe QDs can be continuously tuned to from green to red that covers entire visible wavelength range. However, there are two issues associated with the fabrication and application of binary QDs such as CdSe. First, the formation of defects and surface-trap states results in the low luminescence efficiency and stability deficits. Although this problem can be minimized through nanocrystal surface-passivation with high bandgap inorganic material such as the most commonly used ZnS, the largely lattice mismatch between the core nanocrystal and passivation shell layer usually degrade the optical properties. Second, the extinction coefficient of QDs is also size-dependent – proportional to the volume of the particle. This means species labeled with 6 nm CdSe QDs will emit red light that is ~30 times stronger than the green light from a species that labeled with 2 nm green emitting QDs. 
Unlike binary QDs, the GA_CdSe/ZnS QDs we developed are tuned to have different emissions by changing their composition in both CdSe core and ZnS shells. This allows the preparation of GA QDs with the approximately the same particle sizes (hence the same absorption and emission intensity) but different emission wavelength. Subsequently, this will enable the measurement of each of the species with the equal sensitivity. Our GA_QDs possess higher and more stable PL emission due to larger particle size, higher crystalline, hardened lattice structure, lower inter-diffusion, and spatial compositional fluctuation.