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Supporting Information

Efficient photosensitized oxygenations in phase

contact enhanced microreactors

Chan Pil Park, Ram Awatar Maurya, Jang Han Lee, and Dong-Pyo Kim*

General experimental conditions: SU-8-100 photoresist and SU-8 developer were obtained from MicroChem

(Newton, MA, USA), while Sylgard 184 silicone elastomer (dimethyl siloxane oligomer) and curing agent (dimethyl,

methylhydrogen siloxane, crosslinking agent) were purchased from Dow Corning (Midland, MI, USA). Polyvinylsilazane

(PVSZ, KION VL-20®) was purchased from Clarient (USA), other chemicals and organic solvents were purchased from

Aldrich and Alfa Aesar, used without further purification. white 16 W LED (FAWOO, LH16-AFE39S, Korea) has a emission

spectrum in the broad range of 440-630 nm. 1H NMR and 13C NMR spectra were recorded on a JNM-AL 400. Proton chemical

shifts are reported in ppm ( δ ) relative to TMS with the solvent resonance employed as the internal standard (CDCl3, δ 7.26

ppm). Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet

and doublet dt = doublet and triplet, m = multiplet), coupling constants (Hz) and integration. Carbon chemical shifts are

reported in ppm from TMS with the solvent resonance as the internal standard (CDCl3, δ 77.0 ppm). GC spectrum was recored

by Agilent 5975C GC/MSD System (Agilent Tech., USA/Germany).

Fabrication of a PVSZ shielded dual-channel microreactor (Dual-channel) Preparation of silicon masters for fabrication of gas channle and liquid channel: silicon wafer was spin-coated with a UV-

curable SU-8-100 to get the 200 μm layer. After a softbake at 110 oC, the silicon wafer was exposed to UV-light through a

specially designed photomask, and postbaked at 110 oC. Subsequently, the wafer was developed using SU-8 developer, and

cleaned.

Preparation of PDMS chip for gas channle and liquid channel: mixture containing the silicon elastomer and the curing

agent (10: 1 weight ratio) was poured onto the silicon master and baked for 4 h at 60 oC. After peeling off from the silicon

master, the inlets and outlet of the microfluidic device were punched.

Preparation of the Dual-channel: PDMS pre-polymer was spin-coated on the petri dish to get the 45 μm thin layer, it was

baked for 3h at 60 oC. The PDMS chip with gas channel was bonded to PDMS thin layer coated on petri dish after both

surfaces were treated by oxygen plasma for 1 min, the PDMS chip covered with thin layer was heated up in an oven at 60 °C

Supplementary Material (ESI) for Lab on a ChipThis journal is © The Royal Society of Chemistry 2011

for 2 h. The PDMS replica for liquid channel were treated by oxygen plasma to form a silicate layer with hydroxyl groups on

the surface. Polyvinylsilazane (PVSZ, KION VL-20®) prepolymer was then spin-coated at 1000 rpm for 40 s to become 15 μm

thickness. We controlled the coated thickness from 10 to 40 μm with a variation of rpm. The polymer coated on the PDMS slab

was gently wiped out with a glass slide to remove the polymer from convex surface. After 30 min exposure to UV light (λ =

250-400 nm), the modified PDMS block were baked at 120 oC for 4 h. The PDMS block with liquid channel was bonded to the

gas channel PDMS covered with thin layer after treatment with oxygen plasma for 1 min, the device with dual-channel for

liquid- and gas-flow was heated up in an oven for 12 h at 110 °C to achieve higher bonding strength.

Solvent resistance and optical transmittance of PVSZ shielded PDMS chip Solvent resistance aganist organic solvents: The PDMS chips with PVSZ shileded channel and unshielded channel were

bonded with glass after treatment with oxygen plasma for 1min, they were heated up in an oven for 12 h at 110 °C to achieve

higher bonding strength. 3 organic solutions of rhodamine B (acetic acid, t-butanol, and acetonitrile) were injected into the

unshielded PDMS channel and PVSZ shielded PDMS channel with the rate of 1 μL/min. All solutions in unshielded PDMS

channel were diffused into the wall of PDMS channel within 30 hours while the slutions in PVSZ shielded channel were

prevented from the diffusion for a longer time. Moreover, acetonitrile solution was not diffused into the PVSZ shielded

channel even after 7 days. Swelling images in unshielded PDMS and PVSZ shielded chip were collected in Figure 1S.

A) PVSZ shielded chip


B) Unshielded PDMS chip

Figure 1S. Swelling resistance against organic solvents.

Duarbility of the Dual-channel microreactor with PVSZ coated channel and PDMS mambrane: In dual-channel

micorreactor with PVSZ shield channel, a bottom part of the upper channel, which is the upper surface of the middle PDMS

membrane layer, was not coated with PVSZ polymer to allow an oxygen diffusion. However, proper flow rate of oxygen

prevented the swelling apprearance through the uncoated membrane. Figure 2S shows the clear diffenrence in swelling aspect

with diffent flow rate of oxygen (20 μL/min and 40 μL/min). The enough O2 injection rate (over than 60 μL/min for the certain

prevetntion) from the lower gas channel to the upper solution channel supported the membrane and the arrangement, did not

lead to any deformation under continuous running of 30 hours.

O2 injection rate = 40 μL/min O2 injection rate = 20 μL/min

Figure 2S. Swelling aspects in mixing zone after continuous running of 30 hours under 2 different

injection rates of oxygen.

Optical transmittance: the optical transmittances of PDMS, glass, and PVSZ coated PDMS chip (PDMS-Kion; 10 μm PVSZ

thickness) were compared across the UV-Visible range, the results are depicted in Figure 3S. The PVSZ coated chip show a

good transmittance of over 90 % in the measured range.


Figure 3S. Transmittance data of the glass, PDMS, and PVSZ shielded PDMS (PDMS-Kion).

The contact area to volume ratios in two microreactors and batch system : The contact

area to volume ratio is directly connected with the reactor volume and design, we calculated the ratios of three reacion systems.

Because the lengths of each drops in the Mono-channel system were various depended on its position, we calculated the

average length of 10 drops selected from inlet, middle, outlet part. Even though the contact angle of soution to channel surface

was not 90o, we assuemed vertical contact between gas and liquid for simple calculation. In the batch system, we also

simplified the contact area by assuming a condition of no stirring and no bubbling.

• Volume of reactor= 38.9 μL

• Area of cross section = Volume / channel length = 43222 μm2

• Contact area (red surface) = 90 cm × 220 μm

• Contact area to volume ratio = (90 cm × 220 μm) / 38.9 μL

= 220 μm / area of cross section = 50.9 cm-1

• Area of cross section = 43222 μm2

• Contact area (red surface) = 2 × 43222 μm2

• Volume of each drop = 1340 μm × 43222 μm2

• Contact area to volume ratio = (2 × 43222 μm2) / (1340 μm × 43222 μm2)

= 2 / 1340 μm = 14.9 cm-1

• Volume for solution = 20 mL

• Contact area (red surface) = π × (2.2 cm)2 = 15.20 cm2

• Contact area to volume ratio = (15.20 cm2) / 20 mL = 0.76 cm-1

Figure 4S. The contact area to volume ratios in two microreactors and batch system.


Dual-channel microreactor as an approach for scale-up process: It has the upper liquid

channel with 285 μL volume and the contact area of 12.2 cm-1, the calculated contact area-to-volume ratio was 42.8 cm-1.

Figure 5S. The Dual-channel microreactor for scale-up process.

The reaction volume (solution volume) in the Mono-channel reaction (Table 1, entry

2 and 5) : In the Mono-channel reaction, the reactor are filled with solution and gaseous oxygen which supply an oxygen to

solution and also prevent a merging of each solution drops. For comparison the productivity between the Mono-channel and

the Dual-channel in entry 2 and entry 5 of Table 1, we calculated the real reaction volume in the Mono-channel reaction with

reactor volume of 38.9 μL. The injected amounts of oxygen were assumed from result of Figure 3 in manuscript, 12.8 μL

solution in the 0.35 M concentration required 105 μL oxygen to complete the reaction, it also means that a reaction in 0.1 M

concentration needs 30 μL oxygen. Even though the length of oygen bubbles from inlet to outlet was not linearly decreased

which means the continuoux consuming of oxygen during the reaction, we assumed the linear decresing in the length to

simplify the calculation.

• 0.35 M reaction

• Total channel length: 900 mm

• Drop length (average): 1.34 mm

• Total length of solution phase (mm): 1.34 × (n +1)

• Total length of gas phase (mm) = [12.06 + (12.06 – a) + (12.06 – 2a) + ........ + {12.06 - (n - 2)a} + {12.06 - (n - 1)a}


+ (12.06 – n × a)] = 12.06 × (n +1) – {a + 2a + 3a + ....... + (n -2)a + (n - 1)a + na}

= 12.06 × (n +1) – a × n × (n +1) / 2 = 12.06 × (n +1) – 12.06 × (n + 1) / 2 = 12.06 × (n + 1) / 2

• Gas length + solution length = 1.34 × (n +1) + 12.06 × (n + 1) / 2 = (n + 1) × (1.34 + 12.06 / 2) = 900 mm

• Total drops in microreactor (n + 1) = 122

• Total length of solution phase = 122 × 1.34 mm = 163.5 mm

• Total length of gas phase = 122 × 12.06 / 2 = 735.5 mm

• Solution volume to reactor volume ratio = 18.2 %

B) 0.1 M reaction

• Total channel length: 900 mm

• Drop length (average): 1.34 mm

• Total length of solution phase (mm): 1.34 × (n +1)

• Total length of gas phase (mm) = [3.45 + (3.45 – a) + (3.45 – 2a) + ........ + {3.45 - (n - 2)a} + {3.45 - (n - 1)a} + (3.45 – n × a)]

= 3.45 × (n +1) – {a + 2a + 3a + ....... + (n -2 )a + (n - 1)a + na} = 3.45 × (n +1) – a × n × (n +1) / 2

= 3.45 × (n +1) – 3.45 × (n + 1) / 2 = 3.45 × (n + 1) / 2

• Gas length + solution length = 1.34 × (n +1) + 3.45 × (n + 1) / 2 = (n + 1) × (1.34 + 3.45 / 2) = 900 mm

• Total drops in microreactor (n + 1) = 294

• Total length of solution phase = 294 × 1.34 mm = 393 mm

• Total length of gas phase = 294 × 3.45 / 2 = 507 mm

• Solution volume to reactor volume ratio = 44 %

Figure 6S. The comparison of solution volume in the Mono-channel reaction under different

concentrations of substrate.

Photosensitized oxygenation of (-)-citronellol in batch system (general procedure in

batch reaction for photosensitized oxygenation): a solution of (-)-citronellol (7 mmol) and methylene

blue (0.07 mmol) in acetonitrile (20 mL) were loaded into a 50 mL round bottom glass at 5 oC, and treated with oxygen

bubbling for 20 min, before continuous bubbling and irradiation with the white 16 W LED lamp as close as possible. The ratio

of mixture products was analyzed with 1H NMR instrument using an internal standard after NaBH4 treatment of crude mixture

in CH3OH (Scheme 1S).


OHOH

OH OHOOH

OOH

OH OH

2 3 2S 3S

NaBH4

MeOH

1 : 1.5

Scheme 1S

1H NMR (CDCl3, 400 MHz) �8.20 (bs, 1H, OH), 7.90 (bs, 1H, OH), 5.73 (dt, J = 15.85, 7.07 Hz, 1H, CH2CH=CH of 2S), 5.57 (d, J = 15.85 Hz, 1H, CH2CH=CH of 2S), 5.12-5.01 (m, 2H =CH2 of 3S), 4.31-4.20 (m, 1H, CHOH of 3S), 3.75-3.63 (m, 4H, CH2OH of 2S & 3S), 2.09-1.93 (m, 2H, CH2CHOH of 3S), 1.73-1.25 (m, 12H, CH2CHCH2 and OH of 2S & 3S), 1.60 (s, 3H, CH3C= of 3S), 1.33 (s, 6H, (CH3)2C of 2S ), 0.93-0.90 (m, 6H CH3CH of 2S & 3S).

Photosensitized oxygenation of (-)-citronellol in Mono-channel: in one gas-tight Hamilton

syringe was placed a solution of (-)-citronellol (3.5 mmol) in acetonitrile (3 mL), and in another syringe was placed a solution

of methylene blue (0.035 mmol) in acetonitrile (7 mL). Oxygen gas was placed in the third syringe. The reaction streams were

introduced to the three-inlets of the mono-channel microreactor through a 10 cm segment of polytetrafluoroethylene (PTFE)

tubing. The injection rates of reagent and sensitizer varied, and that of the gas also varied in irradiation of 16 W LED light. The

reaction result was collected in a vial through the segment of PTFE tubing. The ratio of mixture products was analyzed with 1H

NMR instrument after NaBH4 treatment of crude mixture in CH3OH.

Photosensitized oxygenation of (-)-citronellol in the Dual-channel (general procedure

in Dual-channel for photosensitized oxygenation): a solution of (-)-citronellol (3.5 mmol) in

acetonitrile (3 mL) was loaded into a gas-tight Hamilton syringe and delivered into upper channel or the microreactor. In the

same manner, a solution of methylene blue (0.035 mmol) in acetonitrile (7 mL) and oxygen respectively delivered into upper

and down channel of the microreactor in irradiation of 16 W LED light. With a variation in flow rates of two solution and

oxygen, the reaction solutions were collected in brown glass vial. The ratio of mixture products was analyzed with 1H NMR

instrument after NaBH4 treatment of crude mixture in CH3OH.

Photosenxitized oxygenation of α-terpinene to ascaridole in batch system: a reaction

procedure followed the general procedure in batch reaction for photosensitized oxygenation. The conversion was analysized by

GC/MS instrument, yield was measured by 1H NMR spectroscopy.

OHOH

OH OH

2S 3S


1H NMR (CDCl3, 400 MHz) δ 6.4 (d, J = 8.0 Hz, 1H, CH), 6.41 (d, J = 8.0 Hz, 1H, CH), 2.03-2.06 (m, 2H,

CH2CH2), 2.02 (hept, J = 6.0 Hz, 1H, CH(CH3)2), 1.49-1.56 (m, 2H, CH2CH2), 1.37 (s, 3H, CH3), 0.99 (d, J =

6.0 Hz, 6H, CH(CH3)2).

Photosensitized oxygenation of α-terpinene to ascaridole in the Dual-channel: a reaction

procedure followed the general procedure in Dual-channel for photosensitized oxygenation. The conversions were analysized

by GC/MS instrument, yield was measured by 1H NMR spectroscopy.

Photosensitized oxygenation of allylic alcohols in the Dual-channel: a reaction procedure

followed the general procedure in Dual-channel for photosensitized oxygenation.

1H NMR (CDCl3, 400 MHz) δ 5.07-5.03 (m, 2H, CH2C=), 4.56-4.50 (m, 1H, CHOOH), 3.76 (d, J = 6.58 Hz,

2H, CH2OH), 1.78 (s, 3H, CH3C=).

Anti: 1H NMR (CDCl3, 400 MHz) δ 5.10-5.03 (m, 2H, CH2=), 4.25 (d, J = 4.56 Hz, 1H, CHOOH), 3.94 (dq,

J = 4.56, 6.48 Hz, 1H, CHOH), 1.74 (s, 3H, CH3C=), 1.14 (d, J = 6.45 Hz, 3H, CH3CH).

OHOOH

OHOOH

anti

OO


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