sd card and dust sensor

#include <SPI.h>
#include <SD.h>

/*
Standalone Sketch to use with a Arduino UNO and a
Sharp Optical Dust Sensor GP2Y1010AU0F
*/

int measurePin = 0; //Connect dust sensor to Arduino A0 pin
int ledPower = 2; //Connect 3 led driver pins of dust sensor to Arduino D2

int samplingTime = 280;
int deltaTime = 40;
int sleepTime = 9680;

float voMeasured = 0;
float calcVoltage = 0;
float dustDensity = 0;

void setup(){
Serial.begin(9600);
pinMode(ledPower,OUTPUT);
}

void loop(){
digitalWrite(ledPower,LOW); // power on the LED
delayMicroseconds(samplingTime);

voMeasured = analogRead(measurePin); // read the dust value

delayMicroseconds(deltaTime);
digitalWrite(ledPower,HIGH); // turn the LED off
delayMicroseconds(sleepTime);

// 0 - 5V mapped to 0 - 1023 integer values
// recover voltage
calcVoltage = voMeasured * (5.0 / 1024.0);

// linear eqaution taken from Monitoring your Air Quality
// Chris Nafis (c) 2012
dustDensity = 0.17 * calcVoltage - 0.1;

Serial.print("Raw Signal Value (0-1023): ");
Serial.print(voMeasured);

Serial.print(" - Voltage: ");
Serial.print(calcVoltage);

Serial.print(" - Dust Density: “);
Serial.println(dustDensity); // unit: mg/m3
/*file write init /
File dataFile = SD.open(“data.txt”, FILE_WRITE);
/

파일 쓰기 프로세스
*/
if (dataFile) {
dataFile.print(” - Dust Density: ");
dataFile.println(dustDensity); // unit: mg/m3
dataFile.close();
}
// if the file isn’t open, pop up an error:
else {
Serial.println(“error opening data.txt”);
}
delay(1000);
}

data not found

data not found

What does that mean? Nothing in your code prints that.