5.4 Lighting applications

1MSc: f-Elements, Prof. J.-C. Bünzli, 2008

5.4 Lighting applications

Chapter 5 Selected applications


Producing white light: trichromatic stimuli

There are three “prime”colors corresponding to thethree spectral responses ofhuman vision

400 500 600 nm

80

40

60

20

0

-20

CRI / %

400 500 600 nm

Color rendering index obtainedby mixing the three prime colors

EuIII

TbIII

(EuII)



x

y

Trichromatic diagram

Xx

X Y Z=

+ +

Yy

X Y Z=

+ +

780

380

780

380

780

380

( )

( )

(

1d( ( )

(

)

( )

( )

)

)1

( d)

1d

x

y

XK

YK

ZK

z

P

P

P

= ⋅ ⋅ ⋅ λ

= ⋅ ⋅ ⋅ λ

= ⋅

ρ λ

⋅ ⋅ λ

ρ λ

ρ λ

λ λ

λ

λ

λ

λ

∫

∫

∫780

380( )() ) d(K P y= ⋅ ⋅ ⋅ λλ ρ λλ∫

EmissionReflectanceTrichromatic stimuli



Coating

W filament

V

Filling gas: Ar UV (254 nm)

e-

Hg

UV photons excite phosphor-containing coating leading to a white

emission thanks to an appropriate blend of phosphors

(Courtesy of P. Ceintrey, Rhodia Electronics & Catalysis)



Year Phosphor

1960 Ca5(PO4)3Cl:Sb3+,Mn2+ (white)

1974 BaMg2Al16O27:Eu2+ CeMgAl10O19:Tb3+ Y2O3:Eu3+

1990 BaMgAl10O17:Eu2+

(Sr,Ca)5(PO4)3Cl:Eu2+

(La,Ce)PO4:Tb3+

CeMgAl10O19:Tb3+

(Gd,Ce)MgB5O10:Tb3+

Y2O3:Eu3+

2005 BaMgAl10O17:Eu2+ (La,Ce)PO4:Tb3+ Y2O3:Eu3+

Major phosphors used by lighting industry



5D0→7F1LMCT

f-f transitions

Absorption spectrum

Y2O3 features metal ion sites with Oh symmetry, e.d. transitionsare therefore forbidden

230 280 330 380 430 480 530 580 630 680 730

λ /nm

Emission spectrum

Y2O3:Eu3+Y2O3:Eu3+

Hg 254 nm



LaPO4 : Ce,TbLaPO4 : Ce,Tb

240 290 340 390 440 490 540 590 640 690

λ (nm)

Absorption spectrum

4f-5dtransition Emission spectrum

Hg 254 nmCe3+→Tb3+

transfer



SynthesisMain difficulty is to reach adequate particle size

Example: red phosphor


2 m Volu

me (

%)

0

2

4

6

8

0.01 0.1 1 10 100

Particle diameter /µm

2.68 m



Green phosphor is obtained by co-precipitationleading to incorporation of Ce3+ and Tb3+ in theLaPO4 lattice; allows control of morphology, particle sizeand oxidation state of Ce and Tb.


After flux additionPrecursor

10 m 3 m



Blue phosphorSr4Al4O25:EuII

200 300 400 500 600 nm

excitationEmission(d-f transition)

Hg 254 nm



80

60

40

20

0600 700500400

P /W·nm-1·lm-1

J.M.P.J. Verstegen et al., J. Electrochem. Soc. 1974, 121, 1627

Spectral distributionof a luminescent lampwith the followingphosphors:

BaMg2Al16O27:EuII

CeMgAl11O19:TbIII

Y2O3:EuIII



19951970Hg

Fluorescent lampIncandescent lamp

Light Emitting Diodes

* Heat loss: 100 W gives only 18 W for lighting

* Elimination of heat loss but* 55% of energy is lost during conversion of UV excitation into visible photons

Energy saving

* 35% of energy is lost during conversion of UV excitation into visible photons

The future of lighting


18 % 25-30 % 60-70 %



Eliminating mercury from lamps: quantum cutting

6G J

6P J

8S7/27FJ

a

a

5DJ01

2

3

Eu Gd

b

b 200 nm

Ardischarge190 nm

Ardischarge190 nm



UV

5.5 Security inks

Euro bills



The euro isprotected by theluminescencefrom europium:red from EuIII

Europium wasdiscovered byEugène A. Demarçayin 1901 in Paris

560 580 600 620 640 660 680 700 720λ / nm

5D0 7FJ

EuIII2

J =

0 13 4


370.5 nm

λexc


λexc= 375 nm

450 500 550 600 650 700

λ/nm

Possibly EuII ?



5.6 Luminescent chemical sensors

The specific spectroscopic properties of LnIII ions makethem ideal luminescent probes:

- easily recognizable line-like spectra- long lifetimes of excited states- large Stokes’ shift upon ligand excitation

Time-resolved luminescence allows high signal-to-noiseratios, henceforth high sensitivity

Lanthanide-containing luminescent probes can be used as:- structural probe (site symmetry)- analytical probes (mainly for bio-analyses)- imaging probe for medical diagnosis (tumor imaging)



Time-resolved luminescence:an essential tool

Detection limits

Ion lexc /103 lem/nm /s Q Det. lim.

Eu 340 36 613 730 0.69 0.05 pM

Sm 340 36 643 50 0.02 3.5 pM

UV pulse

2-4 ms

Backgroundluminescence

Eu emission

measurement

time

Iem



LnIII luminescence as signaling method

h

hh

h

an

+

an

a) Direct binding of the analyte modifies the LnIII inner co-ordination sphere

Here, water molecules are expelled, lifting theluminescence quenching.


J.-C. Bünzli & C. Piguet, Chem. Soc. Rev. 2005, 34, 1048


an

h h an

b) Binding of the analyte to a ligand modifies its energy- transfer properties

Here, binding of the analyte results in a quenching of themetal-centered luminescence.Alternatively, luminescence can be activated by such abinding.



an

h

h

h

anh

c) Binding of the analyte to a ligand initiates an energy- transfer process to the metal ion

Note: in bio-analyses, specific biochemical reactionsare usually used to render the analysis target specific.



a) Modification of inner coordination sphere: anion analysis

N NN N

P

O

Eu

OTf2

OTf2

OH2 In acetonitrile:

Q = 2.6 %= 0.86 ms

N NN N

P

O

Eu

O

OTf2

O

O

N Q = 30 % = 1.45 msKassoc = 106

L. J. Charbonnière et al., J. Am. Chem. Soc.2002, 124, 7779

OTf = CF3SO3

-



Supramolecular pH sensor

D. Parker et al, J. Am. Chem. Soc. 2001, 123, 7601

O

HO

O

N

NN

N N

HO

O OH

H

S

R

O

O

pH sensor

NN

SO2R

H3O+

NN

H

SO2R

(H2O)

-H3O+

modulateselectron densityof N-atom

pH range5 – 7.5



4 5 6 7 8 9 10 11

6

7

8

9

10

11

pH

EuIII

Luminescence

Supramolecular pH sensor

Chapter 2 Physico-chemical properties


electronic relays

A.P. de Silva et al., Chem. Commun. 1997, 1891

Ln binding unit

EuEu

logK = 4.8 (MeOH)

N N

N

OMeO O OMe

N

N

b) Removal of a quenching process

OO

N

O OO

OO

N

O OO

OO

N

O OO

K+ receptor


OO

N

OOO

OO

N

OOO

OO

N

OOO

K+ receptor

N

N



UV-irradiation

EuEuIIIIII EuEuIIIILuminescence quenchedby PET process Q = 2.6% in MeOH

O

ON

OO

ON N

N

N

O

O

OO

O

OMeO O OMe

EuEu

O

ON

OO

ON N

N

N

O

O

OO

O

OMeO O OMe

EuEu



KK KK

EuEu

UV-irradiation

light emissionQ = 47 % in MeOH

logK = 4.3 (MeOH)

O

ON

OO

ON N

N

N

O

O

OO

O

OMeO O OMe




-CD coupled to dtpaweak Tb emission in H2O

Strong Tb emission in H2Odue to efficient energy transferfrom host

Nocera et al., Coord. Chem. Rev. 1998, 171, 115

TbTb

N

ON

N

NO

N

O

O

OO

O

H

H

TbOH2OH2

c) Initiating an energy transfer process

TbTb

N

ON

N

NO

N

O

O

OO

O

H

H

TbOH2OH2



0

10

20

30

40

0 5 10 15 20

c / ppm

Irel

Supramolecular PAH sensor

Tb luminescenceenhancement

TbTb

N

ON

N

NO

N

O

O

OO

O

H

H

TbOH2OH2



kisc = 5.2·108 s-1

ket = 8.3·104 s-1

E /

103

cm

-1

0

34.9

22.9

20.4

SS00

SS11

33TT

Tb3+

5D4

7FJ

kr = 1.7·104 s-1

Nocera et al., Coord. Chem. Rev. 1998, 171, 115

Supramolecular PAH sensor

TbTb

N

ON

N

NO

N

O

O

OO

O

H

H

TbOH2OH2



Supramolecular PAH sensor (2)

Enhancement of the Tbluminescence in de-oxygenatedsolution by supramolecularfixation of naphtalene

D. Parker et al., J. C. S., Perkin Trans. 2, 2000, 1329

Large associationconstant: logK = 4

permethylated -CD

OO

O

O

O

N

NN

N N

OO

H

(OMe)6

(OMe)7 (OMe)7

Tb

OH2sensitised Tb3+ emission



0 2 4 6 8 10 12

0.2

0.4

0.6

0.8

1.0

1.2

Supramolecular Supramolecular PAH sensor (2)PAH sensor (2)

c-1 / 104 M-1

(I -

I0)-1

Benesi-Hildebrand analysis

logKnapht = 4OO

O

O

O

N

NN

N N

OO

H

(OMe)6

(OMe)7(OMe)7

Tb

OH2

D. Parker et al., J. C. S., Perkin Trans. 2, 2000, 1329


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5.4 Lighting applications

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