Luminescence spectral properties of CdS nanoparticles

• US 6,660,379 B1
• Filed: 07/25/2001
• Issued: 12/09/2003
• Est. Priority Date: 02/05/1999
• Status: Expired due to Fees

• Current Assignee: University of Maryland Baltimore County (University of Maryland)
• Original Assignee: University of Maryland Baltimore County (University of Maryland)
• Inventors: Gryczynski, Zygmunt, Gryczynski, Ignacy, Lakowicz, Joseph R.
• Primary Examiner(s): KILIMAN, LESZEK B
• Application Number:
  US09/890,042
• Time in Patent Office: 867 Days
• Field of Search: 428/402, 428/403, 428/407, 252/500, 252/501.1, 252/518, 313/502, 313/503
• US Class Current: 428/402
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/565 with zinc cadmium
• CPC Class Codes: C12Q 1/6816 characterised by the detection means C12Q1/6804 takes precedence
• CPC Class Codes: G01N 33/588 with semiconductor nanocrystal label, e.g. quantum dots
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

The steady state and time resolved luminescence spectral properties of two types of novel CdS nanoparticles and nanoparticles are described. CdS nanoparticles formed in the presence of an amine-terminated dendrimer show blue emission. The emission wavelength of these nanoparticles depended on the excitation wavelength. The CdS/dendrimer nanoparticles display polarized emission with the anisotropy rising progressively from 340 to 420 nm excitation, reaching a maximal anisotropy value in excess of 0.3. A new constant positive polarized emission from luminescent nanoparticles is also described. Polyphosphate-stabilized CdS nanoparticles are described that display a longer wavelength red emission maximum than bulk CdS and display a zero anisotropy for all excitation wavelengths. Both nanoparticles display strongly heterogeneous intensity decays with mean decay times of 93 ns and 10 μs for the blue and red emitting particles, respectively. Both types of nanoparticles were several times more photostable upon continous illumination than fluorescein. In spite of the long decay times the nanoparticles are mostly insensitive to dissolved oxygen but are quenched by iodide. These nanoparticles can provide a new class of luminophores for use in chemical sensing, DNA sequencing, high throughput screening and other applications.

Claims

1. A fluorescent nanoparticle comprising

cadmium sulfide;

and

at least one dendrimer.

2. A fluorescent nanoparticle of claim 1 wherein said at least one dendrimer is selected from the group consisting of amine-terminated dendrimer, poly(amidoamine) dendrimer, poly(amidoamino-organosilicon) dendrimer having hydrophilic domains and hydrophobic domains, star polymers, self-assemblying polymers, and zeolites.

3. A fluorescent powder comprising:

a plurality of the fluorescent nanoparticles of claim 1 wherein said fluorescent nanoparticles have an average critical dimension ranging from approximately 2 nm to approximately 5 nm and wherein the majority of the plurality of said fluorescent nanoparticles have a size distribution within approximately +/−

15% of the average critical dimension.

4. A fluorescent power of claim 3 wherein said at least one dendrimer is selected from the group comprising amine-terminated dendrimer, poly(amidoamine) dendrimer, poly(amidoamino-organosilicon) dendrimer having hydrophilic domains and hydrophobic domains, star polymers, self-assemblying polymers, and zeolites.

5. A process for making the fluorescent nanoparticle of claim 1 comprising

mixing a Cd(NO₃)₂.4H₂O methanol solution with a molar equivalent methanol solution of dendrimer;

and

adding Na₂S while in deoxygenated environment.

6. The fluorescent nanoparticle of claim 1, wherein the fluorescent nanoparticle has a wavelength emission of at least 500 nm and a decay lifetime of at least 30 ns.

7. A sensor for the measuring of the concentration of an analyte or the absence of an analyte in a sample, said sensor comprising:

a signal emitting probe further comprising a fluorescent nanoparticle of claim 1;

a light source;

a light filter;

a fluorescent light detector;

a fluorescence measurement system; and

a data analysis system wherein said data analysis system converts the measured fluorescence of a signal to a concentration for an analyte.

8. A fluorescent nanoparticle comprising

cadmium sulfide;

and

polyphosphate.

9. A fluorescent powder comprising:

a plurality of the fluorescent nanoparticles of claim 8 wherein said fluorescent nanoparticles have an average critical dimension ranging from approximately 2 nm to approximately 5 nm and wherein the majority of the plurality of said fluorescent nanoparticles have a size distribution within approximately +/−

15% of the average critical dimension.

10. A process for making a fluorescent nanoparticle of claim 8 comprising:

mixing a Cd(NO₃)₂.4H₂O methanol solution with a molar equivalent methanol solution of Na₆(PO₃)₆; and

adding Na₂S while in deoxygenated environment.

11. The fluorescent nanoparticle of claim 8, wherein the fluorescent nanoparticle has a wavelength emission of at least 500 nm and a decay lifetime of at least 30 ns.

12. A sensor for the measuring of the concentration of an analyte or the absence of an analyte in a sample, said sensor comprising:

a signal emitting probe further comprising a fluorescent nanoparticle of claim 8;

a light source;

a light filter;

a fluorescent light detector;

a fluorescence measurement system; and

a data analysis system wherein said data analysis system converts the measured fluorescence of a signal to a concentration for an analyte.